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In animals, it has been shown that different cell types maintain different concentrations of magnesium. It seems likely that the same is true for plants. This suggests that different cell types may regulate influx and efflux of magnesium in different ways based on their unique metabolic needs. Interstitial and systemic concentrations of free magnesium must be delicately maintained by the combined processes of buffering (binding of ions to proteins and other molecules) and muffling (the transport of ions to storage or extracellular spaces).
In plants, and more recently in animals, magnesium has been recognized as an important signaling ion, both activating and mediating many biochemical reactions. The best example of this is perhaps the regulation of carbon fixation in chloroplasts in the Calvin cycle.
Magnesium is very important in cellular function. Deficiency of the nutrient causes disease of the affected organism. In single-cell organisms such as bacteria and yeast, low levels of magnesium manifests in greatly reduced growth rates. In magnesium transport knockout strains of bacteria, healthy rates are maintained only with exposure to very high external concentrations of the ion. In yeast, mitochondrial magnesium deficiency also leads to disease.
Plants deficient in magnesium show stress responses. The first observable signs of both magnesium starvation and overexposure in plants is a decrease in the rate of photosynthesis. This is due to the central position of the Mg ion in the chlorophyll molecule. The later effects of magnesium deficiency on plants are a significant reduction in growth and reproductive viability. Magnesium can also be toxic to plants, although this is typically seen only in drought conditions.
In animals, magnesium deficiency (hypomagnesemia) is seen when the environmental availability of magnesium is low. In ruminant animals, particularly vulnerable to magnesium availability in pasture grasses, the condition is known as grass tetany. Hypomagnesemia is identified by a loss of balance due to muscle weakness. A number of genetically attributable hypomagnesemia disorders have also been identified in humans.
Overexposure to magnesium may be toxic to individual cells, though these effects have been difficult to show experimentally. Hypermagnesemia, an overabundance of magnesium in the blood, is usually caused by loss of kidney function. Healthy animals rapidly excrete excess magnesium in the urine and stool. Urinary magnesium is called magnesuria. Characteristic concentrations of magnesium in model organisms are: in E. coli 30-100mM (bound), 0.01-1mM (free), in budding yeast 50mM, in mammalian cell 10mM (bound), 0.5mM (free) and in blood plasma 1mM. | 1 | Applied and Interdisciplinary Chemistry |
Atmospheric curium compounds are poorly soluble in common solvents and mostly adhere to soil particles. Soil analysis revealed about 4,000 times higher concentration of curium at the sandy soil particles than in water present in the soil pores. An even higher ratio of about 18,000 was measured in loam soils. | 0 | Theoretical and Fundamental Chemistry |
The Stork quinine synthesis starts from chiral (S)-4-vinylbutyrolactone 1. The compound is obtained by chiral resolution and in fact, in the subsequent steps all stereogenic centers are put in place by chiral induction: the sequence does not contain asymmetric steps.
The lactone is ring-opened with diethylamine to amide 2 and its hydroxyl group is protected as a tert-butyldimethyl silyl ether (TBS) in 3. The C5 and C6 atoms are added as tert-butyldiphenylsilyl (TBDPS) protected iodoethanol in a nucleophilic substitution of acidic C4 with lithium diisopropylamide (LDA) at −78 °C to 4 with correct stereochemistry. Removal of the silyl protecting group with p-toluenesulfonic acid to alcohol 4b and ring-closure by azeotropic distillation returns the compound to lactone 5 (direct alkylation of 1 met with undisclosed problems).
The lactone is then reduced to the lactol 5b with diisobutylaluminum hydride and its liberated aldehyde reacts in a Wittig reaction with methoxymethylenetriphenylphosphine (delivering the C8 atom) to form enol ether 6. The hydroxyl group is replaced in a Mitsunobu reaction by an azide group with diphenylphosphoryl azide in 7 and acid hydrolysis yields the azido aldehyde 8.
The methyl group in 6-methoxy-4-methylquinoline 9 is sufficiently acidic for nucleophilic addition of its anion (by reaction with LDA) to the aldehyde group in 8 to form 10 as a mixture of epimers. This is of no consequence for stereocontrol because in the next step the alcohol is oxidized in a Swern oxidation to ketone 11. A Staudinger reaction with triphenylphosphine closes the ring between the ketone and the azide to the tetrahydropyridine 12. The imine group in this compound is reduced to the amine 13 with sodium borohydride with the correct stereospecificity. The silyl protecting group is removed with hydrogen fluoride to alcohol 14 and then activated as a mesyl leaving group by reaction with mesyl chloride in pyridine which enables the third ring closure to 15. In the final step the C9 hydroxyl group was introduced by oxidation with sodium hydride, dimethylsulfoxide and oxygen with quinine to epiquinine ratio of 14:1. | 0 | Theoretical and Fundamental Chemistry |
This class is defined by loss of two beta-strands and additional N-terminal strands. Both namesakes of this superfamily, myosin and kinesin, have shifted to use ATP. | 1 | Applied and Interdisciplinary Chemistry |
* The Genesis Account: A theological, historical, and scientific commentary on Genesis 1-11, 2015, Creation Book Publishers
* Christianity for Skeptics, 2012, with Steve Kumar (first author), Creation Book Publishers
* The Greatest Hoax on Earth? Refuting Dawkins on Evolution, 2010, Creation Book Publishers
* By Design: Evidence for natures Intelligent Designer—the God of the Bible', 2008, Creation Book Publishers ABN: 978-0-949906-72-4
* Refuting Compromise: A Biblical and Scientific Refutation of Progressive Creationism, 2004, Creation Book Publishers
* The Revised & Expanded Answers Book, 2003, with Carl Wieland and David Catchpoole, edited by Don Batten,
* Refuting Evolution 2, 2002/2011, Creation Book Publishers
* Refuting Evolution, 1999–2010, Creation Book Publishers | 0 | Theoretical and Fundamental Chemistry |
Time-domain thermoreflectance is a method by which the thermal properties of a material can be measured, most importantly thermal conductivity. This method can be applied most notably to thin film materials (up to hundreds of nanometers thick), which have properties that vary greatly when compared to the same materials in bulk. The idea behind this technique is that once a material is heated up, the change in the reflectance of the surface can be utilized to derive the thermal properties. The reflectivity is measured with respect to time, and the data received can be matched to a model with coefficients that correspond to thermal properties. | 0 | Theoretical and Fundamental Chemistry |
Berthelot's reagent has been used in a range of situations. It is often used in colorimetric methods, through an AutoAnalyzer, spectrophotometer, or multiwell plate spectrophotometer. The reagent lacks sensitivity in situations where there may be amines as well as ammonia, however this can be overcome in part by the use of 2-phenylphenol to replace phenol. An ion selective electrode, or distillation/titration method can often be used in cases where Berthelot chemistry is ineffective.
Berthelot chemistry has also been adapted for the analysis of nitrite and nitrate in soil and water after conversion, typically by reduction with Devarda's alloy, of these species to ammonium. | 0 | Theoretical and Fundamental Chemistry |
There are several types of screen media manufactured with different types of material that use the two common types of screen media attachment systems, tensioned and modular. | 1 | Applied and Interdisciplinary Chemistry |
The CEBR manifesto states: "The UK has suffered from too many boom and bust infrastructure projects. A steady, planned, rolling programme will reduce costs, speed up journey times, create more seats on more reliable trains and ultimately reduce ticket prices." The group staged a protest on top of Snowdon in 2018. In July 2019, the final report of the rail decarbonisation project was published by the group. | 1 | Applied and Interdisciplinary Chemistry |
In crystals, the electronic energy spectrum has a band structure . Near the minimum of an isotropic energy band, electron energy can be expanded in powers of as where is the electron effective mass. It can be shown that it satisfies the equation
Here the sum runs over all bands with . Therefore, the ratio of the free electron mass to its effective mass in a crystal can be considered as the oscillator strength for the transition of an electron from the quantum state at the bottom of the band into the same state. | 0 | Theoretical and Fundamental Chemistry |
The van Deemter equation in chromatography, named for Jan van Deemter, relates the variance per unit length of a separation column to the linear mobile phase velocity by considering physical, kinetic, and thermodynamic properties of a separation. These properties include pathways within the column, diffusion (axial and longitudinal), and mass transfer kinetics between stationary and mobile phases. In liquid chromatography, the mobile phase velocity is taken as the exit velocity, that is, the ratio of the flow rate in ml/second to the cross-sectional area of the ‘column-exit flow path.’ For a packed column, the cross-sectional area of the column exit flow path is usually taken as 0.6 times the cross-sectional area of the column. Alternatively, the linear velocity can be taken as the ratio of the column length to the dead time. If the mobile phase is a gas, then the pressure correction must be applied. The variance per unit length of the column is taken as the ratio of the column length to the column efficiency in theoretical plates. The van Deemter equation is a hyperbolic function that predicts that there is an optimum velocity at which there will be the minimum variance per unit column length and, thence, a maximum efficiency. The van Deemter equation was the result of the first application of rate theory to the chromatography elution process. | 0 | Theoretical and Fundamental Chemistry |
Additionally, sea foam is a habitat for a number of marine microorganisms. Some research has shown the presence of various microphytoplanktonic, nanophytoplanktonic, and diatom groups in seafoam; the phytoplankton groups appeared in significantly higher abundance than in sea surface film and the top pelagic zone | 0 | Theoretical and Fundamental Chemistry |
To reconcile the evidence from both mutational pressures and selection, the prevailing hypothesis for codon bias can be explained by the mutation-selection-drift balance model. This hypothesis states that selection favors major codons over minor codons, but minor codons are able to persist due to mutation pressure and genetic drift. It also suggests that selection is generally weak, but that selection intensity scales to higher expression and more functional constraints of coding sequences. | 1 | Applied and Interdisciplinary Chemistry |
Bimetal strips are used in miniature circuit breakers to protect circuits from excess current. A coil of wire is used to heat a bimetal strip, which bends and operates a linkage that unlatches a spring-operated contact. This interrupts the circuit and can be reset when the bimetal strip has cooled down.
Bimetal strips are also used in time-delay relays, gas oven safety valves, thermal flashers for older turn signal lamps, and fluorescent lamp starters. In some devices, the current running directly through the bimetal strip is sufficient to heat it and operate contacts directly. It has also been used in mechanical PWM voltage regulators for automotive uses. | 1 | Applied and Interdisciplinary Chemistry |
Dimethyldioctadecylammonium bromide (also dioctadecyldimethylammonium bromide or DODAB) is a double-chained quaternary ammonium surfactant that forms unilamellar vesicles (ULVs) in water. Among various preparation methods, the ‘‘hot-water” method offers a simple procedure to prepare DODAB cationic vesicles by simply dissolving the DODAB in hot water above 50 °C, i.e., chain melting (main) transition, Tm.
In general, the DSC thermograms of the unsonicated DODAB dispersions are dominated by two endotherms; the pre- (35–36 °C) and main transition (42.7–45 °C) peaks. Moreover, in literature reported the presence of a third
endotherm (post transition) at 52.2 °C.
The main transition (Tm) is ascribed to gel to liquid-crystalline phase transition in which the alkyl chains transform from solidlike to liquid-like state.
The 10 mM DODAB is a critical concentration, below which the dispersions consist of large polydispersed unilamellar vesicles (ULVs) that exhibit a local (chain melting) transition at 43 °C, beyond which a structural transition occurs: ULVs --> MLVs (multilamellar vesicles) as indicated by the sudden increase in the dynamic moduli. However, above 10 mM DODAB, the dispersions are mostly formed by ULVs in coexistence with lamellar fragments resulting in a network that shows a rheogram similar to that of hexagonal liquid-crystalline phase. | 0 | Theoretical and Fundamental Chemistry |
Some authorities have recommended producing methanol instead of traditional transportation fuels. It is a liquid at normal temperatures and can be toxic if ingested. Methanol has a higher octane rating than gasoline but a lower energy density, and can be mixed with other fuels or used on its own. It may also be used in the production of more complex hydrocarbons and polymers. Direct methanol fuel cells have been developed by Caltech's Jet Propulsion Laboratory to convert methanol and oxygen into electricity. It is possible to convert methanol into gasoline, jet fuel or other hydrocarbons, but that requires additional energy and more complex production facilities. Methanol is slightly more corrosive than traditional fuels, requiring automobile modifications on the order of US$100 each to use it.
In 2016, a method using carbon spikes, copper nanoparticles and nitrogen that converts carbon dioxide to ethanol was developed. | 0 | Theoretical and Fundamental Chemistry |
The α-carbon is important for enol- and enolate-based carbonyl chemistry as well. Chemical transformations affected by the conversion to either an enolate or an enol, in general, lead to the α-carbon acting as a nucleophile, becoming, for example, alkylated in the presence of primary haloalkane. An exception is in reaction with silyl chlorides, bromides, and iodides, where the oxygen acts as the nucleophile to produce silyl enol ether. | 0 | Theoretical and Fundamental Chemistry |
Bragg diffraction occurs when radiation of a wavelength comparable to atomic spacings is scattered in a specular fashion (mirror-like reflection) by planes of atoms in a crystalline material, and undergoes constructive interference. When the scattered waves are incident at a specific angle, they remain in phase and constructively interfere. The glancing angle (see figure on the right, and note that this differs from the convention in Snells law where is measured from the surface normal), the wavelength , and the "grating constant" of the crystal are connected by the relation:where is the diffraction order ( is first order, is second order, is third order). This equation, Braggs law, describes the condition on θ for constructive interference.
A map of the intensities of the scattered waves as a function of their angle is called a diffraction pattern. Strong intensities known as Bragg peaks are obtained in the diffraction pattern when the scattering angles satisfy Bragg condition. This is a special case of the more general Laue equations, and the Laue equations can be shown to reduce to the Bragg condition with additional assumptions. | 0 | Theoretical and Fundamental Chemistry |
The beginning of the 1990s saw Brill accorded the Archaeological Institute of Americas Pomerance Award for scientific contributions to archaeology; however the decade mostly reflects Brills continuing dedication to Asian glasses and the study of the Silk Road (Archaeological Institute of America 2009). In Scientific Research in Early Chinese Glass, Brill reflected that in comparison to the knowledge of glassmaking in the West, ‘little is known about Chinese glass and about the role it played in the overall unfolding of glass history on a worldwide basis’ (1991, vii). One reason for this is that glass was never produced in the East in such great quantities as it was in the West but also that archaeological Chinese glasses are often prone to problems (Brill 1991). The difficulties of analysing Chinese glasses were reflected later in the publication where, following the chemical investigation of 71 samples, Brill found that identifying the ‘basic formulation’, or ‘any of the primary batch materials’ of the glasses was still almost impossible (Brill et al. 1991). Brill had greater success in differentiating between Chinese glass samples when using lead isotope analysis, a method that has proven effective in the first instance of identifying Chinese glass as the leads used here are different from those anywhere else in the world (Brill, Barnes et al. 1991). Brill found his Chinese samples to fall into two distinct groups, possessing on one hand the highest, and on the other the lowest, lead isotope ratios he had ever encountered (Brill, Barnes et al. 1991). As such, he was able to show that despite the striking similarity in the glasses’ chemical composition and appearance, the ores from which their leads were sourced must have been from very geologically-different mines (Brill, Barnes et al. 1991).
Brill conducted further investigations of ancient Asian glasses for the Nara Symposium on the Silk Roads maritime route in 1991, ‘to demonstrate [...] that chemical analyses can be useful for learning how glass was traded along the Desert, Steppe, and Maritime Routes of the Silk Road’ (1993a, 71), as well as providing a more technical discussion on glass and glassmaking in China for the Glass Art Societys Toledo Conference in 1993 (Brill 1993b). Further lead isotope analysis, this time on Chinese and central Asian pigments, was conducted with a larger team for the Getty's Conservation of Ancient Sites on the Silk Road, which saw Brill et al. launching studies that held incredible potential for understanding ‘chronological or stylistic differences among Buddhist cave paintings’, or ‘distinguish[ing] between original and repainted parts of individual works’ (1993, 371). | 0 | Theoretical and Fundamental Chemistry |
Another idea proposed was that ERVs from the same family played a role in recruiting multiple genes into the same network of regulation. It was found that MER41 elements provided addition redundant regulatory enhancement to the genes located near STAT1 binding sites. | 1 | Applied and Interdisciplinary Chemistry |
Ambergris is found in lumps of various shapes and sizes, usually weighing from to or more. When initially expelled by or removed from the whale, the fatty precursor of ambergris is pale white in color (sometimes streaked with black), soft, with a strong fecal smell. Following months to years of photodegradation and oxidation in the ocean, this precursor gradually hardens, developing a dark grey or black color, a crusty and waxy texture, and a peculiar odor that is at once sweet, earthy, marine, and animalic. Its scent has been generally described as a vastly richer and smoother version of isopropanol without its stinging harshness. In this developed condition, ambergris has a specific gravity ranging from 0.780 to 0.926 (meaning it floats in water). It melts at about to a fatty, yellow resinous liquid; and at it is volatilised into a white vapor. It is soluble in ether, and in volatile and fixed oils. | 1 | Applied and Interdisciplinary Chemistry |
In one large-scale application, para-xylene is converted to terephthalic acid. The major application of ortho-xylene is as a precursor to phthalate esters, used as plasticizer. Meta-xylene is converted to isophthalic acid derivatives, which are components of alkyd resins. | 1 | Applied and Interdisciplinary Chemistry |
Research on accurately modeling rates of mutation has been conducted for many years. A recent paper by Ziheng Yang and Rasmus Nielsen compared various methods and developed a new modeling method. They found that the new method was preferable for its smaller biases, which make it useful for large scale screening, but that the maximum-likelihood model was preferable in most scenarios because of its simplicity, and its flexibility in comparing multiple sequences while taking into account phylogeny.
Further research by Yang and Nielsen found that nonsynonymous to synonymous substitution ratios varied across loci in differing evolutionary lineages. During their study of nuclear loci of primates, even-toed ungulates, and rodents, they found that the ratio varied significantly at 22 of the 48 loci studied. This result provides strong evidence against a strictly neutral theory of molecular evolution, which states that mutations are mostly neutral or deleterious, and provides support for theories that include advantageous mutations. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, alkynylation is an addition reaction in which a terminal alkyne () is added to a carbonyl group () to form an α-alkynyl alcohol ().
When the acetylide is formed from acetylene (), the reaction gives an α-ethynyl alcohol. This process is often referred to as ethynylation. Such processes often involve metal acetylide intermediates. | 0 | Theoretical and Fundamental Chemistry |
Table 1: Reaction times and yield vary on the substrate. The β-glucopyranoside was found to be the best substrate for the Tipson–Cohen reaction as the reaction time and yield were much superior that any other substrate proposed in the study.
Substrates possess benzylidene protecting groups at C-4 and C-6, OMe groups at anomeric position and OTs groups at C-2 and C-3. Reaction temperature 95–100 ˚C | 0 | Theoretical and Fundamental Chemistry |
If protein specific labelling is applied, MDS allows membrane proteins to be sized. This is particularly useful as it is an area where other biophysical techniques can struggle - for example dynamic light scattering (DLS) is of limited use, since free detergent molecules may also scatter light and affect the results.
Furthermore, as the size reported is an average of all detectable species present there is no bias towards large species, as is found in DLS measurements.
Another key advantage is that results can be obtained with very small quantities of material which may be particularly important where samples are scarce or expensive.
With commercially available MDS instruments, testing is very simple and there is no need to input test parameters or sample conditions. This makes it a very repeatable method of testing as most of the functions such as flow rates, detector settings etc. are automated by the instrument rather than set by the operator.
In addition to size, MDS is able to calculate concentration so two parameters can be assessed in one test.
Finally the method does not require calibration, as it relies on a ratio-metric measurement to determine diffusion rate. | 1 | Applied and Interdisciplinary Chemistry |
There are two main types of vibrations: free and forced. Free vibrations are the natural or normal modes of vibration for a substance. Forced vibrations are caused by some sort of excitation to make the analyte resonate beyond its normal modes. ARS employs forced vibrations upon the analyte unlike most commonly used techniques which use free vibrations to measure the analyte. ARS excites multiple normal modes by sweeping the excitation frequency of an analyte with no internal vibrations to obtain a resonance spectrum. These resonance frequencies greatly depend on the type of analyte being measured and also depend greatly on the physical properties of the analyte itself (mass, shape, size, etc.). The physical properties will greatly influence the range of frequencies produced by the resonating analyte. In general small analytes have megahertz frequencies while larger analytes can be only a few hundred hertz. The more complex the analyte the more complex the resonance spectrum. | 0 | Theoretical and Fundamental Chemistry |
The columns used in FPLC are large [mm id] tubes that contain small [µ] particles or gel beads that are known as stationary phase. The chromatographic bed is composed by the gel beads inside the column and the sample is introduced into the injector and carried into the column by the flowing solvent. As a result of different components adhering to or diffusing through the gel, the sample mixture gets separated.
Columns used with an FPLC can separate macromolecules based on size (size-exclusion chromatography), charge distribution (ion exchange), hydrophobicity, reverse-phase or biorecognition (as with affinity chromatography). For easy use, a wide range of pre-packed columns for techniques such as ion exchange, gel filtration (size exclusion), hydrophobic interaction, and affinity chromatography are available. FPLC differs from HPLC in that the columns used for FPLC can only be used up to maximum pressure of 3-4 MPa (435-580 psi). Thus, if the pressure of HPLC can be limited, each FPLC column may also be used in an HPLC machine. | 0 | Theoretical and Fundamental Chemistry |
Neurotrophin-3, or NT-3, is a neurotrophic factor, in the NGF-family of neurotrophins. It is a protein growth factor that has activity on certain neurons of the peripheral and central nervous system; it helps to support the survival and differentiation of existing neurons, and encourages the growth and differentiation of new neurons and synapses. NT-3 is the third neurotrophic factor to be characterized, after NGF and BDNF.
NT-3 is unique among the neurotrophins in the number of neurons it has potential to stimulate, given its ability to activate two of the receptor tyrosine kinase neurotrophin receptors (TrkC and TrkB). Mice born without the ability to make NT-3 have loss of proprioceptive and subsets of mechanoreceptive sensory neurons. | 1 | Applied and Interdisciplinary Chemistry |
The CO compensation point (Γ) is the CO concentration at which the rate of photosynthesis exactly matches the rate of respiration. There is a significant difference in Γ between plants and plants: on land, the typical value for Γ in a plant ranges from 40–100 μmol/mol, while in plants the values are lower at 3–10 μmol/mol. Plants with a weaker CCM, such as C2 photosynthesis, may display an intermediate value at 25 μmol/mol.
The μmol/mol unit may alternatively be expressed as the partial pressure of CO in pascals; for atmospheric conditions, 1μmol/mol = 1 ppm ≈ 0.1 Pa. For modeling of photosynthesis, the more important variable is the CO compensation point in the absence of mitochondrial respiration, also known as the CO photocompensation point (Γ*), the biochemical CO compensation point of Rubisco. It may be measured by whole-leaf isotopic gas exchange, or be estimated in the Laisk method using an intermediate "apparent" value of C* with correction. C* approximates Γ* in the absence of carbon refixation, i.e. carbon fixation from photorespiration products. In plants, both values are lower than their counterparts. In C2 plants that operate by refixation, only C* is significantly lower.
As it is not yet common to routinely change the concentration of air, the concentration points are largely theoretical derived from modeling and extrapolation, though they do hold up well in these applications. Both Γ and Γ* are linearly related to the partial pressure of oxygen (p(O)) due to the side reaction of Rubisco. Γ is also related to temperature due to the temperature-dependence of respiration rates. It is also related to irradiation, as light is required to produce RuBP (ribulose-1,5-bisphosphate), the electron acceptor for Rubisco. At normal irradiation, there would almost always be enough RuBP; but at low irradiation, lack of RuBP decreases the photosynthetic activity and therefore affects Γ. | 0 | Theoretical and Fundamental Chemistry |
For organic compounds, the length of the C-O bond does not vary widely from 120 picometers. Inorganic carbonyls have shorter C-O distances: CO, 113; CO, 116; and COCl, 116 pm.
The carbonyl carbon is typically electrophilic. A qualitative order of electrophilicity is RCHO (aldehydes) > RCO (ketones) > RCOR' (esters) > RCONH (amides). A variety of nucleophiles attack, breaking the carbon-oxygen double bond.
Interactions between carbonyl groups and other substituents were found in a study of collagen. Substituents can affect carbonyl groups by addition or subtraction of electron density by means of a sigma bond. ΔHσ values are much greater when the substituents on the carbonyl group are more electronegative than carbon.
The polarity of C=O bond also enhances the acidity of any adjacent C-H bonds. Due to the positive charge on carbon and the negative charge on oxygen, carbonyl groups are subject to additions and/or nucleophilic attacks. A variety of nucleophiles attack, breaking the carbon-oxygen double bond, and leading to addition-elimination reactions. Nucleophiliic reactivity is often proportional to the basicity of the nucleophile and as nucleophilicity increases, the stability within a carbonyl compound decreases. The pK values of acetaldehyde and acetone are 16.7 and 19 respectively, | 0 | Theoretical and Fundamental Chemistry |
The PageRank algorithm has several applications in biochemistry. ("PageRank" is an algorithm used in Google Search for ranking websites in their results, but it has been adopted for other purposes also. According to Google, PageRank works by "counting the number and quality of links to a page to determine a rough estimate of how important the website is," the underlying assumption being that more important websites are likely to receive more links from other websites.) | 1 | Applied and Interdisciplinary Chemistry |
Most radiometers for remote sensing (RS) acquire multispectral images. Dividing the spectrum into many bands, multispectral is the opposite of panchromatic, which records only the total intensity of radiation falling on each pixel. Usually, Earth observation satellites have three or more radiometers. Each acquires one digital image (in remote sensing, called a scene) in a small spectral band. The bands are grouped into wavelength regions based on the origin of the light and the interests of the researchers. | 0 | Theoretical and Fundamental Chemistry |
* sulphurated hydrogene
**therapeutic application of H2S for gastrointestinal disorders dates as early as 1806
*hepatic air | 1 | Applied and Interdisciplinary Chemistry |
Wood's notation takes the form
where M is the chemical symbol of the substrate, A is the chemical symbol of the overlayer, are the Miller indices of the surface plane, R and correspond to the rotational difference between the substrate and overlayer vectors, and the vector magnitudes shown are those of the substrate ( subscripts) and of the overlayer ( subscripts). This notation can only describe commensurate overlayers however, while matrix notation can describe both. | 0 | Theoretical and Fundamental Chemistry |
Decorin is an example of a proteoglycan which functions as a myokine. Kanzleiter et al have established that this myokine is secreted during muscular contraction against resistance, and plays a role in muscle growth. They reported on July 1, 2014: "The small leucine-rich proteoglycan decorin has been described as a myokine for some time. However, its regulation and impact on skeletal muscle (had) not been investigated in detail. In (our recent) study, we report decorin to be differentially expressed and released in response to muscle contraction using different approaches. Decorin is released from contracting human myotubes, and circulating decorin levels are increased in response to acute resistance exercise in humans. Moreover, decorin expression in skeletal muscle is increased in humans and mice after chronic training. Because decorin directly binds myostatin, a potent inhibitor of muscle growth, we investigated a potential function of decorin in the regulation of skeletal muscle growth. In vivo overexpression of decorin in murine skeletal muscle promoted expression of the pro-myogenic factor Mighty, which is negatively regulated by myostatin. We also found Myod1 and follistatin to be increased in response to decorin overexpression. Moreover, muscle-specific ubiquitin ligases atrogin1 and MuRF1, which are involved in atrophic pathways, were reduced by decorin overexpression. In summary, our findings suggest that decorin secreted from myotubes in response to exercise is involved in the regulation of muscle hypertrophy and hence could play a role in exercise-related restructuring processes of skeletal muscle." | 1 | Applied and Interdisciplinary Chemistry |
In many nonlinear field theories like general relativity or Yang–Mills theories, the basic field equations are highly nonlinear and exact solutions are only known for ‘sufficiently symmetric’ distributions of matter (e.g. rotationally or axially symmetric configurations). Time-translation symmetry is guaranteed only in spacetimes where the metric is static: that is, where there is a coordinate system in which the metric coefficients contain no time variable. Many general relativity systems are not static in any frame of reference so no conserved energy can be defined. | 0 | Theoretical and Fundamental Chemistry |
The 1st group of anions consist of CO, HCO, CHCOO, S, SO, Thiosulfate| and NO. The reagent for Group 1 anions is dilute hydrochloric acid (HCl) or dilute sulfuric acid (HSO).
* Carbonates give a brisk effervescence with dilute HSO due to the release of CO, a colorless gas which turns limewater milky due to formation of CaCO (carbonatation). The milkiness disappears on passing an excess of the gas through the lime water, due to formation of Ca(HCO).
* Acetates give the vinegar-like smell of CHCOOH when treated with dilute HSO and heated. A blood red colouration is produced upon addition of yellow FeCl, due to formation of iron(III) acetate.
* Sulfides give the rotten egg smell of HS when treated with dilute HSO. The presence of sulfide is confirmed by adding lead(II) acetate paper, which turns black due to the formation of PbS. Sulfides also turn solutions of red sodium nitroprusside purple.
* Sulfites produce SO gas, which smells of burning sulfur, when treated with dilute acid. They turn acidified KCrO from orange to green.
* Thiosulfates produce SO gas when treated with dilute acid. In addition, they form a cloudy precipitate of sulfur.
* Nitrites give reddish-brown fumes of NO when treated with dilute HSO. These fumes cause a solution of potassium iodide (KI) and starch to turn blue. | 0 | Theoretical and Fundamental Chemistry |
A total of 64 experiments were performed in which the actual Faraday efficiency was measured. The results were analyzed twice; once with the popular assumption that the Faraday efficiency is 100%, and, again, taking into account the measured Faraday efficiency in each experiment. The average Faraday efficiency measured in these experiments was 78%. | 0 | Theoretical and Fundamental Chemistry |
Mycosubtilin is a heptapeptide, cyclized in a ring with a β-amino fatty acid. The peptide sequence is composed of -Asn--Tyr--Asn--Gln--Pro--Ser--Asn. | 0 | Theoretical and Fundamental Chemistry |
Specific temperature at a specific pressure at which large groups of micelles begin to precipitate out into a quasi-separate phase. As temperature is raised above the cloud point this causes the distinct surfactant phase to form densely packed micelle groups known as aggregates. The phase separation is a reversible separation controlled by enthalpy (promotes aggregation/separation) above the cloud point, and entropy (promotes miscibility of micelles in water) below the cloud point. The cloud point is the equilibrium between the two free energies. | 0 | Theoretical and Fundamental Chemistry |
*1966: published Physical Methods in Inorganic Chemistry
*1966: published Prerequisites for College Chemistry
*1969: won the ACS Award in Inorganic Chemistry
*1970: co-authored Acids and Bases with N A Matwiyoff
*1970: co-authored Core Experiments in General Chemistry with T L Brown
*1971: published Qualitative Concepts from Quantum Chemistry
*1973: awarded the Guggenheim Fellowship for Chemistry
*1974: published Principles of Chemistry with Practical Perspectives
*1979: published General Chemistry Problem Solving I
*1986: established the Florida Catalysis Conference Foundation, Inc.
*1994: published Applications of Electrostatic-Covalent Models in Chemistry
Professor Drago established the Drago Distinguished Professor position at the University of Florida, and an annual Drago Chemistry Award at Ithaca College. | 0 | Theoretical and Fundamental Chemistry |
Compared to traditional inhibitors, PROTACs display multiple benefits that make them desirable drug candidates. Due to their catalytic mechanism, PROTACs can be administered at lower doses compared to their inhibitor analogues. Some PROTACs have been shown to be more selective than their inhibitor analogues, reducing off-target effects. PROTACs have the ability to target previously undruggable proteins, as they do not need to target catalytic pockets. This also helps prevent mutation-driven drug resistance often found with enzymatic inhibitors. | 1 | Applied and Interdisciplinary Chemistry |
The study of protein folding began in 1910 with a famous paper by Harriette Chick and C. J. Martin, in which they showed that the flocculation of a protein was composed of two distinct processes: the precipitation of a protein from solution was preceded by another process called denaturation, in which the protein became much less soluble, lost its enzymatic activity and became more chemically reactive. In the mid-1920s, Tim Anson and Alfred Mirsky proposed that denaturation was a reversible process, a correct hypothesis that was initially lampooned by some scientists as "unboiling the egg". Anson also suggested that denaturation was a two-state ("all-or-none") process, in which one fundamental molecular transition resulted in the drastic changes in solubility, enzymatic activity and chemical reactivity; he further noted that the free energy changes upon denaturation were much smaller than those typically involved in chemical reactions. In 1929, Hsien Wu hypothesized that denaturation was protein unfolding, a purely conformational change that resulted in the exposure of amino acid side chains to the solvent. According to this (correct) hypothesis, exposure of aliphatic and reactive side chains to solvent rendered the protein less soluble and more reactive, whereas the loss of a specific conformation caused the loss of enzymatic activity. Although considered plausible, Wu's hypothesis was not immediately accepted, since so little was known of protein structure and enzymology and other factors could account for the changes in solubility, enzymatic activity and chemical reactivity. In the early 1960s, Chris Anfinsen showed that the folding of ribonuclease A was fully reversible with no external cofactors needed, verifying the "thermodynamic hypothesis" of protein folding that the folded state represents the global minimum of free energy for the protein.
The hypothesis of protein folding was followed by research into the physical interactions that stabilize folded protein structures. The crucial role of hydrophobic interactions was hypothesized by Dorothy Wrinch and Irving Langmuir, as a mechanism that might stabilize her cyclol structures. Although supported by J. D. Bernal and others, this (correct) hypothesis was rejected along with the cyclol hypothesis, which was disproven in the 1930s by Linus Pauling (among others). Instead, Pauling championed the idea that protein structure was stabilized mainly by hydrogen bonds, an idea advanced initially by William Astbury (1933). Remarkably, Paulings incorrect theory about H-bonds resulted in his correct' models for the secondary structure elements of proteins, the alpha helix and the beta sheet. The hydrophobic interaction was restored to its correct prominence by a famous article in 1959 by Walter Kauzmann on denaturation, based partly on work by Kaj Linderstrøm-Lang. The ionic nature of proteins was demonstrated by Bjerrum, Weber and Arne Tiselius, but Linderstrom-Lang showed that the charges were generally accessible to solvent and not bound to each other (1949).
The secondary and low-resolution tertiary structure of globular proteins was investigated initially by hydrodynamic methods, such as analytical ultracentrifugation and flow birefringence. Spectroscopic methods to probe protein structure (such as circular dichroism, fluorescence, near-ultraviolet and infrared absorbance) were developed in the 1950s. The first atomic-resolution structures of proteins were solved by X-ray crystallography in the 1960s and by NMR in the 1980s. , the Protein Data Bank has over 150,000 atomic-resolution structures of proteins. In more recent times, cryo-electron microscopy of large macromolecular assemblies has achieved atomic resolution, and computational protein structure prediction of small protein domains is approaching atomic resolution. | 1 | Applied and Interdisciplinary Chemistry |
Valvular heart disease is a major cause of death globally. Both mechanical valves and fixed biological xenograft or homografts used clinically have many drawbacks. One study focused on fibrin-based heart valves to assess structure and mechanical durability on sheep revealed promising potential for patient originated valve replacements. From autologous arterial-derived cells and fibrin scaffold, tissue engineered heart valves are formed, then mechanically conditioned and transplanted into the pulmonary trunk of the same animals. The preliminary result are potentially hopeful towards autologous heart valve production. | 1 | Applied and Interdisciplinary Chemistry |
Transcription-mediated amplification (TMA) is an isothermal (performed at constant temperature), single-tube nucleic acid amplification system utilizing two enzymes, RNA polymerase and reverse transcriptase.
"Amplification" means creating many more copies of a strand of nucleic acid than was present at first, in order to readily detect it or test it. Rapidly amplifying the target RNA/DNA allows a lab to simultaneously detect multiple pathogenic organisms in a single tube. TMA technology allows a clinical laboratory to perform nucleic acid test (NAT) assays for blood screening with fewer steps, less processing time, and faster results.
It is used in molecular biology, forensics, and medicine for the rapid identification and diagnosis of pathogenic organisms.
In contrast to similar techniques such as polymerase chain reaction and ligase chain reaction, this method involves RNA transcription (via RNA polymerase) and DNA synthesis (via reverse transcriptase) to produce an RNA amplicon (the source or product of amplification) from a target nucleic acid. This technique can be used to target both RNA and DNA.
Transcription-mediated amplification has several advantages compared to other amplification methods including:
* TMA is isothermal; a water bath or heat block is used instead of a thermal cycler.
* TMA produces RNA amplicon rather than DNA amplicon. Since RNA is more labile in a laboratory environment, this reduces the possibility of carry-over contamination.
* TMA produces 100–1000 copies per cycle (PCR and LCR exponentially doubles each cycle). This results in a 10 billion fold increase of DNA (or RNA) copies within about 15–30 minutes. | 1 | Applied and Interdisciplinary Chemistry |
For the governing equations of compressible flow, each equation, starting with the conservation of mass, is filtered. This gives:
which results in an additional sub-filter term. However, it is desirable to avoid having to model the sub-filter scales of the mass conservation equation. For this reason, Favre proposed a density-weighted filtering operation, called Favre filtering, defined for an arbitrary quantity as:
which, in the limit of incompressibility, becomes the normal filtering operation. This makes the conservation of mass equation:
This concept can then be extended to write the Favre-filtered momentum equation for compressible flow. Following Vreman:
where is the shear stress tensor, given for a Newtonian fluid by:
and the term represents a sub-filter viscous contribution from evaluating the viscosity using the Favre-filtered temperature . The subgrid stress tensor for the Favre-filtered momentum field is given by
By analogy, the Leonard decomposition may also be written for the residual stress tensor for a filtered triple product . The triple product can be rewritten using the Favre filtering operator as , which is an unclosed term (it requires knowledge of the fields and , when only the fields and are known). It can be broken up in a manner analogous to above, which results in a sub-filter stress tensor . This sub-filter term can be split up into contributions from three types of interactions: the Leondard tensor , representing interactions among resolved scales; the Clark tensor , representing interactions between resolved and unresolved scales; and the Reynolds tensor , which represents interactions among unresolved scales. | 1 | Applied and Interdisciplinary Chemistry |
Estimation of V̇O max from a timed one-mile track walk in decimal minutes (, e.g.: 20:35 would be specified as 20.58), sex, age in years, body weight in pounds (, lbs), and 60-second heart rate in beats-per-minute (, bpm) at the end of the mile. The constant is 6.3150 for males, 0 for females. | 1 | Applied and Interdisciplinary Chemistry |
Birds not usually considered predators of mice do take voles; examples include gulls (Larus sp.), northern shrikes (Larius borealis), black-billed magpies (Pica hudsonica), common ravens (Corvus corax), American crows (C. brachyrhynchos), great blue herons (Ardea herodias), and American bitterns (Botaurus lentiginosus).
Major mammalian predators include the badger (Taxidea taxus), striped skunk (Mephitis mephitis), weasels (Mustela and Neogale sp.), martens (Martes americana and M. caurina), domestic dogs (Canis familiaris), domestic cats (Felis catus) and mountain lions (Puma concolor). Other animals reported to have ingested voles include trout (Salmo sp.), Pacific giant salamanders (Dicampton ensatus), garter snakes (Thamnophis sp.), yellow-bellied racers (Coluber constrictor flaviventris), gopher snakes (Pituophis melanoleucas), plains rattlesnakes (Crotalus viridis), and rubber boas (Charina bottae).
In northern prairie wetlands, meadow voles are a large portion of the diets of red foxes (Vulpes vulpes), American mink (Neogale vison), short-eared owls (Asio flammeus), and northern harriers (Circus cyaneus). Voles are frequently taken by racers (Coluber sp.) since both often use the same burrows. | 1 | Applied and Interdisciplinary Chemistry |
Sulfur has four stable isotopes, with the following abundances: S (0.9502), S (0.0075), S (0.0421) and S (0.0002). These abundances are compared to those found in Cañon Diablo troilite. Variations in sulfur isotope ratios are used to study the origin of sulfur in an orebody and the temperature of formation of sulfur–bearing minerals as well as a biosignature that can reveal presence of sulfate reducing microbes. | 0 | Theoretical and Fundamental Chemistry |
A dendrimer is a highly branched macromolecule with a spherical shape. The surface of the particle may be functionalized in many ways and many of the properties of the resulting construct are determined by its surface.
In particular it is possible to construct a cationic dendrimer, i.e. one with a positive surface charge. When in the presence of genetic material such as DNA or RNA, charge complementarity leads to a temporary association of the nucleic acid with the cationic dendrimer. On reaching its destination the dendrimer-nucleic acid complex is then taken into the cell via endocytosis.
In recent years the benchmark for transfection agents has been cationic lipids. Limitations of these competing reagents have been reported to include: the lack of ability to transfect some cell types, the lack of robust active targeting capabilities, incompatibility with animal models, and toxicity. Dendrimers offer robust covalent construction and extreme control over molecule structure, and therefore size. Together these give compelling advantages compared to existing approaches.
Producing dendrimers has historically been a slow and expensive process consisting of numerous slow reactions, an obstacle that severely curtailed their commercial development. The Michigan-based company Dendritic Nanotechnologies discovered a method to produce dendrimers using kinetically driven chemistry, a process that not only reduced cost by a magnitude of three, but also cut reaction time from over a month to several days. These new "Priostar" dendrimers can be specifically constructed to carry a DNA or RNA payload that transfects cells at a high efficiency with little or no toxicity. | 1 | Applied and Interdisciplinary Chemistry |
S1 end mapping - S1 nuclease - satellite DNA - screening - SDS-PAGE - secondary structure - selection - selenium responsive proteins - sense strand - sequence - sequence motif - sequence polymorphism - sequence-tagged site - sequential epitope - severe combined immunodeficiency - sex chromosome - sex-linked - Shine-Dalgarno sequence - shotgun cloning - shotgun cloning or sequencing - shotgun sequencing - shuttle vector - Siah interacting protein N-terminal domain - sickle-cell disease - side chain - sigma factor - signal peptidase - signal sequence - silent mutation - single nucleotide polymorphism - siRNA - site-directed mutagenesis - site-specific recombination - Slc22a21 - slot blot - SNP - Slc22a21 - SMCR2 - snRNA - snRNP - solution hybridization - somatic cells - Southern blot - southwestern blot - SP6 RNA polymerase - SpAB protein domain - spectral karyotype - splicing - Simple Sequence Repeats (SSR) - SPR domain - SQ2397 - SRG1 RNA - ST7-AS2 - ST7-OT3 - stable transfection - start codon - stem-loop - sticky end - stomoxyn - stop codon - streptavidin - stringency - structural motif - sub-cloning - substitution - succinate—citramalate CoA-transferase - suicide gene - sulfate-transporting ATPase - supercoil - SurE, survival protein E - Syb-prII-1 - syndrome - | 1 | Applied and Interdisciplinary Chemistry |
Tissue engineering emerged during the 1990s as a potentially powerful option for regenerating tissue and research initiatives were established in various cities in the US and in European countries including the UK, Italy, Germany and Switzerland, and also in Japan. Soon fledgling societies were formed in these countries in order to represent these new sciences, notably the European Tissue Engineering Society (ETES) and, in the US, the Tissue Engineering Society (TES), soon to become the Tissue Engineering Society international (TESi) and the Regenerative Medicine Society (RMS).
Because of the overlap between the activities of these societies and the increasing globalization of science and medicine, considerations of a merger between TESI and ETES and RMS were initiated in 2004 and agreement was reached during 2005 about the formation of the consolidated society, the Tissue Engineering and Regenerative Medicine International Society (TERMIS). Election of officers for TERMIS took place in September 2005, and the by-laws were approved by the Board.
Rapid progress in the organization of TERMIS took place during late 2005 and 2006. The SYIS, Student and Young Investigator Section was established in January 2006, website and newsletter launched and membership dues procedures put in place. | 1 | Applied and Interdisciplinary Chemistry |
The NeSSI Technology Development Roadmap groups the technology into three generations, which are backward compatible. Generation I is a commercial product and proven in numerous industrial and laboratory applications. Generation II products have been proven in the laboratory but have yet to be commercialized. Generation III (microanalytical) is in development. | 1 | Applied and Interdisciplinary Chemistry |
1,3-Propanedithiol is the chemical compound with the formula HSCHCHCHSH. This dithiol is a useful reagent in organic synthesis. This liquid, which is readily available commercially, has an intense stench. | 0 | Theoretical and Fundamental Chemistry |
Silver-coated mirrors are optimum for use as steering mirrors for infrared pulses around 800 nm. Their reflectivity is higher than gold and much higher than aluminum at that wavelength. | 0 | Theoretical and Fundamental Chemistry |
In laboratory settings, ELISA and immunodiffusion assays are most commonly used to detect levels of Anti-Ro/SSA antibodies in patient sera.
Antibodies specific to Ro52 are difficult to detect via laboratory testing. Their low detectability may be attributed to several factors: the antibodies are precipitin negative, lack antinuclear antibody (ANA) specific fluorescence staining patterns, and have a low signature in ELISA assays. Furthermore, Ro52 can be masked by Anti-Ro60 antibodies in lab tests that simultaneously assess the two antibodies. | 1 | Applied and Interdisciplinary Chemistry |
Consider the scattering of a beam of wavelength by an assembly of particles or atoms stationary at positions . Assume that the scattering is weak, so that the amplitude of the incident beam is constant throughout the sample volume (Born approximation), and absorption, refraction and multiple scattering can be neglected (kinematic diffraction). The direction of any scattered wave is defined by its scattering vector . , where and ( ) are the scattered and incident beam wavevectors, and is the angle between them. For elastic scattering, and , limiting the possible range of (see Ewald sphere). The amplitude and phase of this scattered wave will be the vector sum of the scattered waves from all the atoms
For an assembly of atoms, is the atomic form factor of the -th atom. The scattered intensity is obtained by multiplying this function by its complex conjugate
The structure factor is defined as this intensity normalized by
If all the atoms are identical, then Equation () becomes and so
Another useful simplification is if the material is isotropic, like a powder or a simple liquid. In that case, the intensity depends on and . In three dimensions, Equation () then simplifies to the Debye scattering equation:
An alternative derivation gives good insight, but uses Fourier transforms and convolution. To be general, consider a scalar (real) quantity defined in a volume ; this may correspond, for instance, to a mass or charge distribution or to the refractive index of an inhomogeneous medium. If the scalar function is integrable, we can write its Fourier transform as . In the Born approximation the amplitude of the scattered wave corresponding to the scattering vector is proportional to the Fourier transform . When the system under study is composed of a number of identical constituents (atoms, molecules, colloidal particles, etc.) each of which has a distribution of mass or charge then the total distribution can be considered the convolution of this function with a set of delta functions.
with the particle positions as before. Using the property that the Fourier transform of a convolution product is simply the product of the Fourier transforms of the two factors, we have , so that:
This is clearly the same as Equation () with all particles identical, except that here is shown explicitly as a function of .
In general, the particle positions are not fixed and the measurement takes place over a finite exposure time and with a macroscopic sample (much larger than the interparticle distance). The experimentally accessible intensity is thus an averaged one ; we need not specify whether denotes a time or ensemble average. To take this into account we can rewrite Equation () as: | 0 | Theoretical and Fundamental Chemistry |
Nucleophilic substitution reactions occur when a nucleophilic molecule attacks a positive or partially positive electrophilic center by breaking and creating a new bond. S1 and S2 are two different mechanisms for nucleophilic substitution, and S1 involves a carbocation intermediate. In S1, a leaving group is broken off to create a carbocation reaction intermediate. Then, a nucleophile attacks and forms a new bond with the carbocation intermediate to form the final, substituted product, as shown in the reaction of 2-bromo-2-methylpropane to form 2-methyl-2-propanol.
In this reaction, is the formed carbocation intermediate to form the alcohol product. | 0 | Theoretical and Fundamental Chemistry |
Transition metal carbyne complexes are organometallic compounds with a triple bond between carbon and the transition metal. This triple bond consists of a σ-bond and two π-bonds. The HOMO of the carbyne ligand interacts with the LUMO of the metal to create the σ-bond. The two π-bonds are formed when the two HOMO orbitals of the metal back-donate to the LUMO of the carbyne. They are also called metal alkylidynes—the carbon is a carbyne ligand. Such compounds are useful in organic synthesis of alkynes and nitriles. They have been the focus on much fundamental research. | 0 | Theoretical and Fundamental Chemistry |
The largest implication that arises from resonance fluorescence is that for future technologies. Resonance fluorescence is used primarily in the coherent control of atoms. By coupling a two-level atom, such as a quantum dot, to an electric field in the form of a laser, you are able to effectively create a qubit. The qubit states correspond to the excited and the ground state of the two-level atoms. Manipulation of the electromagnetic field allows for effective control of the dynamics of the atom. These can then be used to created quantum computers. The largest barriers that still stand in the way of this being achievable are failures in truly controlling the atom. For instance true control of spontaneous decay and decoherence of the field pose large problems that must be overcome before two-level atoms can truly be used as qubits. | 0 | Theoretical and Fundamental Chemistry |
The transcription, a complete set of general transcription factors and RNA polymerase need to be assembled at the core promoter to form the ~2.5 million Dalton preinitiation complex. For example, for promoters that contain a TATA box near the TSS, the recognition of TATA box by the TBP subunit of TFIID initiates the assembly of a transcription complex. The next proteins to enter are TFIIA and TFIIB, which stabilize the DNA-TFIID complex and recruit Pol II in association with TFIIF and additional transcription factors. TFIIB serves as the bridge between the TATA-bound TBP and the RNA polymerase. It also helps to place the active centre of the polymerase in the correct position to initiate transcription. One of the last transcription factors to be recruited to the preinitiation complex is TFIIH, which plays an important role in promoter melting and escape. | 1 | Applied and Interdisciplinary Chemistry |
The GFP was created in 1970 by the polymer physicist André Kovacs and the chemist Georges Champetier, one of the first researchers in France to study polymer science.
The statutes of the GFP set out the following goals:
* the advancement and dissemination of studies on macromolecular substances,
* the grouping of researchers studying polymers in order to promote exchanges of ideas and facilitate knowledge of scientific and technical progress in this field,
* the development of relationships between basic research and its applications.
The GFP is based in Strasbourg, where in 1954 the physicist Charles Sadron founded the first CNRS laboratory dedicated to polymer science, which became the Institut Charles Sadron in 1985. Its first general meeting was held on November 26–27, 1970 in Paris. Its first committee comprised Georges Champetier (President), Charles Sadron and René Riou (Vice-presidents), André Kovacs (Secretary general) and Constant Wippler (Treasurer). Since its founding, the presidency of the GFP has alternated between researchers based in academia and industry, while the secretary has always been a member of the Institut Charles Sadron (originally the CRM). | 1 | Applied and Interdisciplinary Chemistry |
The Tn5 transposon system is a model system for the study of transposition and for the application of transposon mutagenesis. Tn5 is a bacterial composite transposon in which genes (the original system containing antibiotic resistance genes) are flanked by two nearly identical insertion sequences, named IS50R and IS50L corresponding to the right and left sides of the transposon respectively. The IS50R sequence codes for two proteins, Tnp and Inh. These two proteins are identical in sequence, save for the fact that Inh is lacking the 55 N-terminal amino acids. Tnp codes for a transposase for the entire system, and Inh encodes an inhibitor of transposase. The DNA-binding domain of Tnp resides in the 55 N-terminal amino acids, and so these residues are essential for function. The IS50R and IS50L sequences are both flanked by 19-base pair elements on the inside and outside ends of the transposon, labelled IE and OE respectively. Mutation of these regions results in an inability of transposase genes to bind to the sequences. The binding interactions between transposase and these sequences is very complicated, and is affected by DNA methylation and other epigenetic marks. In addition, other proteins seem to be able to bind with and affect the transposition of the IS50 elements, such as DnaA.
The most likely pathway of Tn 5 transposition is the common pathway for all transposon systems. It begins with Tnp binding the OE and IE sequences of each IS50 sequence. The two ends are brought together, and through oligomerization of DNA, the sequence is cut out of the chromosome. After introducing 9-base pair 5 ends in target DNA, the transposon and its incorporated genes are inserted into the target DNA, duplicating the regions on either end of the transposon. Genes of interest can be genetically engineered into the transposon system between the IS50 sequences. By placing the transposon under the control of a host promoter, the genes will be expressed. Incorporated genes usually include, in addition to the gene of interest, a selectable marker to identify transformants, a eukaryotic promoter/terminator (if expressing in a eukaryote), and 3 UTR sequences to separate genes in a polycistronic stretch of sequence. | 1 | Applied and Interdisciplinary Chemistry |
Conventional radioisotope thermoelectric generators (RTGs) used to power spacecraft use a radioactive material whose radiation is used to heat a block of material and then converted to electricity using a thermocouple. Thermocouples are very inefficient and their replacement with TPV could offer significant improvements in efficiency and thus require a smaller and lighter RTG for any given mission. Experimental systems developed by Emcore (a multi-junction solar cell provider), Creare, Oak Ridge and NASA's Glenn Research Center demonstrated 15 to 20% efficiency. A similar concept was developed by the University of Houston which reached 30% efficiency, a 3 to 4-fold improvement over existing systems. | 0 | Theoretical and Fundamental Chemistry |
Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay.
Nuclear fission was discovered on 19 December 1938 in Berlin by German chemists Otto Hahn and Fritz Strassmann. Physicists Lise Meitner and her nephew Otto Robert Frisch explained it theoretically in January 1939. Frisch named the process "fission" by analogy with biological fission of living cells. In their second publication on nuclear fission in February 1939, Hahn and Strassmann predicted the existence and liberation of additional neutrons during the fission process, opening up the possibility of a nuclear chain reaction.
For heavy nuclides, it is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments (heating the bulk material where fission takes place). Like nuclear fusion, for fission to produce energy, the total binding energy of the resulting elements must be greater than that of the starting element.
Fission is a form of nuclear transmutation because the resulting fragments (or daughter atoms) are not the same element as the original parent atom. The two (or more) nuclei produced are most often of comparable but slightly different sizes, typically with a mass ratio of products of about 3 to 2, for common fissile isotopes. Most fissions are binary fissions (producing two charged fragments), but occasionally (2 to 4 times per 1000 events), three positively charged fragments are produced, in a ternary fission. The smallest of these fragments in ternary processes ranges in size from a proton to an argon nucleus.
Apart from fission induced by a neutron, harnessed and exploited by humans, a natural form of spontaneous radioactive decay (not requiring a neutron) is also referred to as fission, and occurs especially in very high-mass-number isotopes. Spontaneous fission was discovered in 1940 by Flyorov, Petrzhak, and Kurchatov in Moscow, in an experiment intended to confirm that, without bombardment by neutrons, the fission rate of uranium was negligible, as predicted by Niels Bohr; it was not negligible.
The unpredictable composition of the products (which vary in a broad probabilistic and somewhat chaotic manner) distinguishes fission from purely quantum tunneling processes such as proton emission, alpha decay, and cluster decay, which give the same products each time. Nuclear fission produces energy for nuclear power and drives the explosion of nuclear weapons. Both uses are possible because certain substances called nuclear fuels undergo fission when struck by fission neutrons, and in turn emit neutrons when they break apart. This makes a self-sustaining nuclear chain reaction possible, releasing energy at a controlled rate in a nuclear reactor or at a very rapid, uncontrolled rate in a nuclear weapon.
The amount of free energy released in the fission of an equivalent amount of is a million times more than that released in the combustion of methane or from hydrogen fuel cells.
The products of nuclear fission, however, are on average far more radioactive than the heavy elements which are normally fissioned as fuel, and remain so for significant amounts of time, giving rise to a nuclear waste problem. However, the seven long-lived fission products make up only a small fraction of fission products. Neutron absorption which does not lead to fission produces Plutonium (from ) and minor actinides (from both and ) whose radiotoxicity is far higher than that of the long lived fission products. Concerns over nuclear waste accumulation and the destructive potential of nuclear weapons are a counterbalance to the peaceful desire to use fission as an energy source. The thorium fuel cycle produces virtually no plutonium and much less minor actinides, but - or rather its decay products - are a major gamma ray emitter. All actinides are fertile or fissile and fast breeder reactors can fission them all albeit only in certain configurations. Nuclear reprocessing aims to recover usable material from spent nuclear fuel to both enable uranium (and thorium) supplies to last longer and to reduce the amount of "waste". The industry term for a process that fissions all or nearly all actinides is a "closed fuel cycle". | 0 | Theoretical and Fundamental Chemistry |
The squat effect is the hydrodynamic phenomenon by which a vessel moving through shallow water creates an area of reduced pressure that causes the ship to increase its draft and thereby be closer to the seabed than would otherwise be expected. This phenomenon is caused by the water flow which accelerates as it passes between the hull and the seabed in confined waters, the increase in water velocity causing a resultant reduction in pressure. Squat effect from a combination of vertical sinkage and a change of trim may cause the vessel to dip towards the stern or towards the bow. This is understood to be a function of the Block coefficient of the vessel concerned, finer lined vessels Cb <0.7 squatting by the stern and vessels with a Cb >0.7 squatting by the head or bow.
Squat effect is approximately proportional to the square of the speed of the ship. Thus, by reducing speed by half, the squat effect is reduced by a factor of four. Squat effect is usually felt more when the depth/draft ratio is less than four or when sailing close to a bank. It can lead to unexpected groundings and handling difficulties. There are indications of squat which mariners and ship pilots should be aware of such as vibration, poor helm response, shearing off course, change of trim and a change in wash.
Squat effect is included by navigators in under keel clearance calculations. | 1 | Applied and Interdisciplinary Chemistry |
Nutrients enter freshwater or marine environments as surface runoff from agricultural pollution and urban runoff from fertilized lawns, golf courses and other landscaped properties; and from sewage treatment plants that lack nutrient control systems. Additional nutrients are introduced from atmospheric pollution. Coastal areas worldwide, especially wetlands and estuaries, coral reefs and swamps, are prone to being overloaded with those nutrients. Most of the large cities along the Mediterranean Sea, for example, discharge all of their sewage into the sea untreated. The same is true for most coastal developing countries, while in parts of the developing world, as much as 70% of wastewater from large cities may re-enter water systems without being treated.
Residual nutrients in treated wastewater can also accumulate in downstream source water areas and fuel eutrophication, which leads progressively to a cyanobacteria-dominated system characterized by seasonal HABs. As more wastewater treatment infrastructure is built, more treated wastewater is returned to the natural water system, leading to a significant increase in these residual nutrients.
Residual nutrients combine with nutrients from other sources to increase the sediment nutrient stockpile that is the driving force behind phase shifts to entrenched eutrophic conditions.
This contributes to the ongoing degradation of dams, lakes, rivers, and reservoirs - source water areas that are starting to become known as ecological infrastructure, placing increasing pressure on wastewater treatment works and water purification plants. Such pressures, in turn, intensify seasonal HABs. | 0 | Theoretical and Fundamental Chemistry |
VAMAS6 - vanillin synthase - VanY protein domain - Var1 protein domain - vax2os1 - vector - VEK-30 protein domain - vinorine hydroxylase - vitamin B12-transporting ATPase - vitamin D binding protein domain III - vitelline membrane outer layer protein I (VMO-I) - | 1 | Applied and Interdisciplinary Chemistry |
A bevel protractor is a graduated circular protractor with one pivoted arm; used for measuring or marking off angles. Sometimes Vernier scales are attached to give more precise readings. It has wide application in architectural and mechanical drawing, although its use is decreasing with the availability of modern drawing software or CAD.
Universal bevel protractors are also used by toolmakers; as they measure angles by mechanical contact they are classed as mechanical protractors.
The bevel protractor is used to establish and test angles to very close tolerances. It reads to 5 arcminutes (5′ or °) and can measure angles from 0° to 360°.
The bevel protractor consists of a beam, a graduated dial, and a blade which is connected to a swivel plate (with Vernier scale) by a thumb nut and clamp. When the edges of the beam and blade are parallel, a small mark on the swivel plate coincides with the zero line on the graduated dial. To measure an angle between the beam and the blade of 90° or less, the reading may be obtained directly from the graduation number on the dial indicated by the mark on the swivel plate. To measure an angle of over 90°, subtract the number of degrees as indicated on the dial from 180°, as the dial is graduated from opposite zero marks to 90° each way.
Since the spaces, both on the main scale and the Vernier scale, are numbered both to the right and the left from zero, any angle can be measured. The readings can be taken either to the right or to the left, according to the direction in which the zero on the main scale is moved. | 0 | Theoretical and Fundamental Chemistry |
An early application of a DNA database was the compilation of a Mitochondrial DNA Concordance, prepared by Kevin W. P. Miller and John L. Dawson at the University of Cambridge from 1996 to 1999 from data collected as part of Millers PhD thesis. There are now several DNA databases in existence around the world. Some are private, but most of the largest databases are government-controlled. The United States maintains the largest DNA database, with the Combined DNA Index System (CODIS) holding over 13 million records as of May 2018. The United Kingdom maintains the National DNA Database (NDNAD), which is of similar size, despite the UKs smaller population. The size of this database, and its rate of growth, are giving concern to civil liberties groups in the UK, where police have wide-ranging powers to take samples and retain them even in the event of acquittal. The Conservative–Liberal Democrat coalition partially addressed these concerns with part 1 of the Protection of Freedoms Act 2012, under which DNA samples must be deleted if suspects are acquitted or not charged, except in relation to certain (mostly serious or sexual) offenses. Public discourse around the introduction of advanced forensic techniques (such as genetic genealogy using public genealogy databases and DNA phenotyping approaches) has been limited, disjointed, unfocused, and raises issues of privacy and consent that may warrant the establishment of additional legal protections.
The U.S. Patriot Act of the United States provides a means for the U.S. government to get DNA samples from suspected terrorists. DNA information from crimes is collected and deposited into the CODIS database, which is maintained by the FBI. CODIS enables law enforcement officials to test DNA samples from crimes for matches within the database, providing a means of finding specific biological profiles associated with collected DNA evidence.
When a match is made from a national DNA databank to link a crime scene to an offender having provided a DNA sample to a database, that link is often referred to as a cold hit. A cold hit is of value in referring the police agency to a specific suspect but is of less evidential value than a DNA match made from outside the DNA Databank.
FBI agents cannot legally store DNA of a person not convicted of a crime. DNA collected from a suspect not later convicted must be disposed of and not entered into the database. In 1998, a man residing in the UK was arrested on accusation of burglary. His DNA was taken and tested, and he was later released. Nine months later, this man's DNA was accidentally and illegally entered in the DNA database. New DNA is automatically compared to the DNA found at cold cases and, in this case, this man was found to be a match to DNA found at a rape and assault case one year earlier. The government then prosecuted him for these crimes. During the trial the DNA match was requested to be removed from the evidence because it had been illegally entered into the database. The request was carried out.
The DNA of the perpetrator, collected from victims of rape, can be stored for years until a match is found. In 2014, to address this problem, Congress extended a bill that helps states deal with "a backlog" of evidence.
PIDS(Plant international DNA-fingerprinting system) is an open source web server and free software based plant international DNA fingerprinting system.
It manages huge amount of microsatellite DNA fingerprint data, performs genetic studies, and automates collection, storage and maintenance while decreasing human error and increasing efficiency.
The system may be tailored to specific laboratory needs, making it a valuable tool for plant breeders, forensic science, and human fingerprint recognition.
It keeps track of experiments, standardizes data and promotes inter-database communication.
It also helps with the regulation of variety quality, the preservation of variety rights and the use of molecular markers in breeding by providing location statistics, merging, comparison and genetic analysis function. | 1 | Applied and Interdisciplinary Chemistry |
Solid-state NMR techniques have the potential to yield detailed information about the dynamics of individual amino acid residues within a membrane protein. However, the techniques can require large amounts (100–200 mg) of isotopically labeled proteins and are most informative when applied to small proteins where spectroscopic assignments are possible. | 1 | Applied and Interdisciplinary Chemistry |
Significant are also the extensions of the polaron concept: acoustic polaron, piezoelectric polaron, electronic polaron, bound polaron, trapped polaron, spin polaron, molecular polaron, solvated polarons, polaronic exciton, Jahn-Teller polaron, small polaron, bipolarons and many-polaron systems. These extensions of the concept are invoked, e. g., to study the properties of conjugated polymers, colossal magnetoresistance perovskites, high- superconductors, layered MgB superconductors, fullerenes, quasi-1D conductors, semiconductor nanostructures.
The possibility that polarons and bipolarons play a role in high- superconductors has renewed interest in the physical properties of many-polaron systems and, in particular, in their optical properties. Theoretical treatments have been extended from one-polaron to many-polaron systems.
A new aspect of the polaron concept has been investigated for semiconductor nanostructures: the exciton-phonon states are not factorizable into an adiabatic product Ansatz, so that a non-adiabatic treatment is needed. The non-adiabaticity of the exciton-phonon systems leads to a strong enhancement of the phonon-assisted transition probabilities (as compared to those treated adiabatically) and to multiphonon optical spectra that are considerably different from the Franck–Condon progression even for small values of the electron-phonon coupling constant as is the case for typical semiconductor nanostructures.
In biophysics Davydov soliton is a propagating along the protein α-helix self-trapped amide I excitation that is a solution of the Davydov Hamiltonian. The mathematical techniques that are used to analyze Davydovs soliton are similar to some that have been developed in polaron theory. In this context the Davydov soliton corresponds to a polaron that is (i) large so the continuum limit approximation in justified, (ii) acoustic because the self-localization arises from interactions with acoustic modes of the lattice, and (iii) weakly coupled' because the anharmonic energy is small compared with the phonon bandwidth.
It has been shown that the system of an impurity in a Bose–Einstein condensate is also a member of the polaron family. This allows the hitherto inaccessible strong coupling regime to be studied, since the interaction strengths can be externally tuned through the use of a Feshbach resonance. This was recently realized experimentally by two research groups.
The existence of the polaron in a Bose–Einstein condensate was demonstrated for both attractive and repulsive interactions, including the strong coupling regime and dynamically observed. | 0 | Theoretical and Fundamental Chemistry |
Mapping the relative orientation of crystalline grains and/or phases helps understand material texture at the micro and nano scales. In a transmission electron microscope, this is accomplished by recording a diffraction pattern at a large number of points (pixels) over a region of the crystalline specimen. By comparing the recorded patterns to a database of known patterns (either previously indexed experimental patterns or simulated patterns), the relative orientation of grains in the field of view can be determined.
Because this process is highly automated, the quality of the recorded diffraction patterns is crucial to the software's ability to accurately compare and assign orientations to each pixel. Thus, the advantages of PED are well-suited for use with this scanning technique. By instead recording a PED pattern at each pixel, dynamical effects are reduced, and the patterns are more easily compared to simulated data, improving the accuracy of the automated phase/orientation assignment. | 0 | Theoretical and Fundamental Chemistry |
In physics, optical depth or optical thickness is the natural logarithm of the ratio of incident to transmitted radiant power through a material.
Thus, the larger the optical depth, the smaller the amount of transmitted radiant power through the material.
Spectral optical depth or spectral optical thickness is the natural logarithm of the ratio of incident to transmitted spectral radiant power through a material. Optical depth is dimensionless, and in particular is not a length, though it is a monotonically increasing function of optical path length, and approaches zero as the path length approaches zero. The use of the term "optical density" for optical depth is discouraged.
In chemistry, a closely related quantity called "absorbance" or "decadic absorbance" is used instead of optical depth: the common logarithm of the ratio of incident to transmitted radiant power through a material. It is the optical depth divided by , because of the different logarithm bases used. | 0 | Theoretical and Fundamental Chemistry |
The term "biotoxin" is sometimes used to explicitly confirm the biological origin as opposed to environmental or anthropogenic origins. Biotoxins can be classified by their mechanism of delivery as poisons (passively transferred via ingestion, inhalation, or absorption across the skin), toxungens (actively transferred to the target's surface by spitting, spraying, or smearing), or venoms (delivered through a wound generated by a bite, sting, or other such action). They can also be classified by their source, such as fungal biotoxins, microbial toxins, plant biotoxins, or animal biotoxins.
Toxins produced by microorganisms are important virulence determinants responsible for microbial pathogenicity and/or evasion of the host immune response.
Biotoxins vary greatly in purpose and mechanism, and can be highly complex (the venom of the cone snail can contain over 100 unique peptides, which target specific nerve channels or receptors).
Biotoxins in nature have two primary functions:
* Predation, such as in the spider, snake, scorpion, jellyfish, and wasp
* Defense as in the bee, ant, termite, honey bee, wasp, poison dart frog and plants producing toxins
** The toxins used as defense in species among the poison dart frog can also be used for medicinal purposes
Some of the more well known types of biotoxins include:
* Cyanotoxins, produced by cyanobacteria
* Dinotoxins, produced by dinoflagellates
* Necrotoxins cause necrosis (i.e., death) in the cells they encounter. Necrotoxins spread through the bloodstream. In humans, skin and muscle tissues are most sensitive to necrotoxins. Organisms that possess necrotoxins include:
** The brown recluse or "fiddle back" spider
** Most rattlesnakes and vipers produce phospholipase and various trypsin-like serine proteases
** Puff adder
** Necrotizing fasciitis (caused by the "flesh eating" bacterium Streptococcus pyogenes) – produces a pore forming toxin
* Neurotoxins primarily affect the nervous systems of animals. The group neurotoxins generally consists of ion channel toxins that disrupt ion channel conductance. Organisms that possess neurotoxins include:
** The black widow spider.
** Most scorpions
** The box jellyfish
** Elapid snakes
** The cone snail
** The Blue-ringed octopus
** Venomous fish
** Frogs
** Palythoa coral
** Various different types of algae, cyanobacteria and dinoflagellates
* Myotoxins are small, basic peptides found in snake and lizard venoms, They cause muscle tissue damage by a non-enzymatic receptor based mechanism. Organisms that possess myotoxins include:
** rattlesnakes
** Mexican beaded lizard
* Cytotoxins are toxic at the level of individual cells, either in a non-specific fashion or only in certain types of living cells:
** Ricin, from castor beans
** Apitoxin, from honey bees
** T-2 mycotoxin, from certain toxic mushrooms
** Cardiotoxin III, from Chinese cobra
** Hemotoxin, from vipers | 1 | Applied and Interdisciplinary Chemistry |
Nano-particles can self-assemble on solid surfaces after external forces (like magnetic and electric) are applied. Templates made of microstructures, like carbon nanotubes or block polymers, can also be used to assist in self-assembly. They cause directed self-assembly (DSA), in which active sites are embedded to selectively induce nanoparticle deposition. Such templates are objects onto which different particles can be arranged into a structure with a morphology similar to that of the template. Carbon nanotubes (microstructures), single molecules, or block copolymers are common templates. Nanoparticles are often shown to self-assemble within distances of nanometers and micrometers, but block copolymer templates can be used to form well-defined self-assemblies over macroscopic distances. By incorporating active sites to the surfaces of nanotubes and polymers, the functionalization of these templates can be transformed to favor self-assembly of specified nanoparticles. | 0 | Theoretical and Fundamental Chemistry |
Many isotopes of chemical elements can be used for NMR analysis.
Commonly used nuclei:
* , the most commonly used spin- nucleus in NMR investigation, has been studied using many forms of NMR. Hydrogen is highly abundant, especially in biological systems. It is the nucleus most sensitive to NMR signal (apart from , which is not commonly used due to its instability and radioactivity). Proton NMR produces narrow chemical shift with sharp signals. Fast acquisition of quantitative results (peak integrals in stoichiometric ratio) is possible due to short relaxation time. The signal has been the sole diagnostic nucleus used for clinical magnetic resonance imaging (MRI).
* , a spin-1 nucleus commonly utilized as signal-free medium in the form of deuterated solvents during proton NMR, to avoid signal interference from hydrogen-containing solvents in measurement of solutes. Also used in determining the behavior of lipids in lipid membranes and other solids or liquid crystals as it is a relatively non-perturbing label which can selectively replace . Alternatively, can be detected in media specially labeled with . Deuterium resonance is commonly used in high-resolution NMR spectroscopy to monitor drifts in the magnetic field strength (lock) and to monitor the homogeneity of the external magnetic field.
* , is very sensitive to NMR. There is a very low percentage in natural helium, and subsequently has to be purified from . It is used mainly in studies of endohedral fullerenes, where its chemical inertness is beneficial to ascertaining the structure of the entrapping fullerene.
* , more sensitive than , yields sharper signals. The nuclear spin of B is 3 and that of B is . Quartz tubes must be used because borosilicate glass interferes with measurement.
* spin-, is widely used, despite its relative paucity in naturally occurring carbon (approximately 1.1%). It is stable to nuclear decay. Since there is a low percentage in natural carbon, spectrum acquisition on samples which have not been experimentally enriched in takes a long time. Frequently used for labeling of compounds in synthetic and metabolic studies. Has low sensitivity and moderately wide chemical shift range, yields sharp signals. Low percentage makes it useful by preventing spin-spin couplings and makes the spectrum appear less crowded. Slow relaxation means that spectra are not integrable unless long acquisition times are used.
* , spin-1, medium sensitivity nucleus with wide chemical shift range. Its large quadrupole moment interferes in acquisition of high resolution spectra, limiting usefulness to smaller molecules and functional groups with a high degree of symmetry such as the headgroups of lipids.
* , spin-, relatively commonly used. Can be used for isotopically labeling compounds. Very insensitive but yields sharp signals. Low percentage in natural nitrogen together with low sensitivity requires high concentrations or expensive isotope enrichment.
* , spin-, low sensitivity and very low natural abundance (0.037%), wide chemical shift range (up to 2000 ppm). Quadrupole moment causing line broadening. Used in metabolic and biochemical studies in studies of chemical equilibria.
* , spin-, relatively commonly measured. Sensitive, yields sharp signals, has a wide chemical shift range.
* , spin-, 100% of natural phosphorus. Medium sensitivity, wide chemical shift range, yields sharp lines. Spectra tend to have a moderate amount of noise. Used in biochemical studies and in coordination chemistry with phosphorus-containing ligands.
* and , spin-, broad signal. is significantly more sensitive, preferred over despite its slightly broader signal. Organic chlorides yield very broad signals. Its use is limited to inorganic and ionic chlorides and very small organic molecules.
* , spin-, relatively small quadrupole moment, moderately sensitive, very low natural abundance. Used in biochemistry to study calcium binding to DNA, proteins, etc.
* , used in studies of catalysts and complexes.
Other nuclei (usually used in the studies of their complexes and chemical bonding, or to detect presence of the element): | 0 | Theoretical and Fundamental Chemistry |
* Palladium precatalyst species are activated under reaction conditions to form a reactive Pd compound, A. The exact identity of the catalytic species depends strongly upon reaction conditions. With simple phosphines, such as PPh (n=2), and in case of bulky phosphines (i.e., ) it was demonstrated that monoligated species (n=1) are formed. Furthermore, some results point to the formation of anionic palladium species, [LPdCl] , which could be the real catalysts in the presence of anions and halides.
* The active Pd catalyst is involved in the oxidative addition step with the aryl or vinyl halide substrate to produce Pd species B. Similar to the above discussion, its structure depends on the employed ligands. This step is believed to be the rate-limiting step of the reaction.
* Complex B reacts with copper acetylide, complex F, in a transmetallation step, yielding complex C and regenerating the copper catalyst.
* The structure of complex C depends on the properties of the ligands. For the facile reductive elimination to occur, the substrate motifs need to be in close vicinity, i.e. cis-orientation, so there can be trans-cis isomerisation involved. In reductive elimination the product tolane is expelled from the complex and the active Pd catalytic species is regenerated. | 0 | Theoretical and Fundamental Chemistry |
β-catenin destabilization by ethanol is one of two known pathways whereby alcohol exposure induces fetal alcohol syndrome (the other is ethanol-induced folate deficiency). Ethanol leads to β-catenin destabilization via a G-protein-dependent pathway, wherein activated Phospholipase Cβ hydrolyzes phosphatidylinositol-(4,5)-bisphosphate to diacylglycerol and inositol-(1,4,5)-trisphosphate. Soluble inositol-(1,4,5)-trisphosphate triggers calcium to be released from the endoplasmic reticulum. This sudden increase in cytoplasmic calcium activates Ca2+/calmodulin-dependent protein kinase (CaMKII). Activated CaMKII destabilizes β-catenin via a poorly characterized mechanism, but which likely involves β-catenin phosphorylation by CaMKII. The β-catenin transcriptional program (which is required for normal neural crest cell development) is thereby suppressed, resulting in premature neural crest cell apoptosis (cell death). | 1 | Applied and Interdisciplinary Chemistry |
Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of microorganisms that may deplete the water of oxygen. Although eutrophication is a natural process, manmade or cultural eutrophication is far more common and is a rapid process caused by a variety of polluting inputs including poorly treated sewage, industrial wastewater, and fertilizer runoff. Such nutrient pollution usually causes algal blooms and bacterial growth, resulting in the depletion of dissolved oxygen in water and causing substantial environmental degradation.
Approaches for prevention and reversal of eutrophication include minimizing point source pollution from sewage and agriculture as well as other nonpoint pollution sources. Additionally, the introducution of bacteria and algae-inhibiting organisms such as shellfish and seaweed can also help reduce nitrogen pollution, which in turn controls the growth of cyanobacteria, the main source of harmful algae blooms. | 1 | Applied and Interdisciplinary Chemistry |
Theories about the origin of life require knowledge of chemical pathways that permit formation of lifes key building blocks under plausible prebiotic conditions. The RNA world hypothesis holds that in the primordial soup there existed free-floating ribonucleotides, the fundamental molecules that combine in series to form RNA. Complex molecules like RNA must have arisen from small molecules whose reactivity was governed by physico-chemical processes. RNA is composed of purine and pyrimidine nucleotides, both of which are necessary for reliable information transfer, and thus Darwinian evolution. Becker et al. showed how pyrimidine nucleosides can be synthesized from small molecules and ribose, driven solely by wet-dry cycles. Purine nucleosides can be synthesized by a similar pathway. 5-mono- and di-phosphates also form selectively from phosphate-containing minerals, allowing concurrent formation of polyribonucleotides with both the purine and pyrimidine bases. Thus a reaction network towards the purine and pyrimidine RNA building blocks can be established starting from simple atmospheric or volcanic molecules. | 1 | Applied and Interdisciplinary Chemistry |
A hemichrome (FeIII) is a form of low-spin methemoglobin (metHb).
Hemichromes, which precede the denaturation processes of hemoglobin (Hb), are mainly produced by partially denaturated hemoglobins and form histidine complexes.
Hemichromes are usually associated with blood disorders. | 1 | Applied and Interdisciplinary Chemistry |
RNA is a very similar molecule to DNA, with only two significant chemical differences (the backbone of RNA uses ribose instead of deoxyribose and its nucleobases include uracil instead of thymine). The overall structure of RNA and DNA are immensely similar—one strand of DNA and one of RNA can bind to form a double helical structure. This makes the storage of information in RNA possible in a very similar way to the storage of information in DNA. However, RNA is less stable, being more prone to hydrolysis due to the presence of a hydroxyl group at the ribose 2' position. | 0 | Theoretical and Fundamental Chemistry |
The decline of filter-feeding shellfish populations, such as oysters, likely contribute to HAB occurrence. As such, numerous research projects are assessing the potential of restored shellfish populations to reduce HAB occurrence. | 0 | Theoretical and Fundamental Chemistry |
Major developments: Bayonets spread across Eurasia. A paper cartridge is introduced by Gustavus Adolphus. Rifles are used for war by Denmark. A ship of the line carrying 60 to 120 cannons appears in Europe. Samuel Pepys' diary mentions a machine gun like pistol. The "true" flintlock replaces the snaphance flintlock in Europe by the end of the 17th century. Both China and Japan reject the flintlock and the Mughal Empire only uses it in limited quantities. Gunpowder is used for mining in Europe. | 1 | Applied and Interdisciplinary Chemistry |
The anaerobic aspect of this process, the process carried out without oxygen, is performed by anaerobic microorganisms degrading organic substances in the wastewater. An integral process within this part of the separation is hydrolysis, which decomposes the organic compounds into much simpler compounds which can then be passed through microbial cells. This is the first of a four-step process to complete the transformation of organic matter to biogases:
# Hydrolysis: Specifically, enzymatic hydrolysis is used to release proteins from the microorganisms. These processes subsequently break down complex compounds, such as lipids, proteins, and polysaccharides, which have a large molecular mass, to simple compounds such as:
#* Lipids → fatty acids and glycerol
#* Proteins → amino acids
#* Polysaccharides → glucose, fructose, and galactose
# Acidogenesis: Takes the products of hydrolysis, mentioned above, and utilizes acidogenic bacteria to transform them into:
#* Short-chain fatty acids: lactic acid, propionic acid, and butyric acids
#* Ethanol
#* Hydrogen gas
#* Carbon dioxide
# Acetogenesis: Anaerobic bacteria are used to convert the products of acidogenesis to:
#* Acetic acid
#* Hydrogen gas
#* Carbon dioxide
#* Small organic molecules
# Methanogenesis: In the final step, methanogenic bacteria transform the aforementioned intermediate products into biogas(methane and carbon dioxide).
This process has to be carried out under a specific range of temperatures and pH. Most of the time, an anaerobic process will be slowed down if the temperature of the process goes below 35 °C (mesophilic and thermophilic conditions). Since a distinguishing characteristic of anaerobic processes is their slow development, many other factors can further slow down this process such as the organic matter composition, nutrient concentration, and the presence of toxic substances. All of these factors can fully veer the treatment off its course if not analyzed properly. | 1 | Applied and Interdisciplinary Chemistry |
The following processes for the regeneration of HCl from spent pickle liquors have been adopted by the ferrous metals processing industry: | 0 | Theoretical and Fundamental Chemistry |
MALDI-TOF spectra are often used for the identification of microorganisms such as bacteria or fungi. A portion of a colony of the microbe in question is placed onto the sample target and overlaid with matrix. The mass spectra of expressed proteins generated are analyzed by dedicated software and compared with stored profiles for species determination in what is known as biotyping. It offers benefits to other immunological or biochemical procedures and has become a common method for species identification in clinical microbiological laboratories. Benefits of high resolution MALDI-MS performed on a Fourier transform ion cyclotron resonance mass spectrometry (also known as FT-MS) have been demonstrated for typing and subtyping viruses though single ion detection known as proteotyping, with a particular focus on influenza viruses.
One main advantage over other microbiological identification methods is its ability to rapidly and reliably identify, at low cost, a wide variety of microorganisms directly from the selective medium used to isolate them. The absence of the need to purify the suspect or "presumptive" colony allows for a much faster turn-around times. For example, it has been demonstrated that MALDI-TOF can be used to detect bacteria directly from blood cultures.
Another advantage is the potential to predict antibiotic susceptibility of bacteria. A single mass spectral peak can predict methicillin resistance of Staphylococcus aureus. MALDI can also detect carbapenemase of carbapenem-resistant enterobacteriaceae, including Acinetobacter baumannii and Klebsiella pneumoniae. However, most proteins that mediate antibiotic resistance are larger than MALDI-TOFs 2000–20,000 Da range for protein peak interpretation and only occasionally, as in the 2011 Klebsiella pneumoniae' carbapenemase (KPC) outbreak at the NIH, a correlation between a peak and resistance conferring protein can be made. | 1 | Applied and Interdisciplinary Chemistry |
CS was discovered by Béla Lengyel, who assigned it an unsymmetrical structure. Later, infrared and Raman spectroscopy showed that the structure is symmetrical with a D point group symmetry, i.e. S=C=C=C=S. This compound is analogous to carbon suboxide whose structure is O=C=C=C=O.
Lengyel first synthesized this compound by passing carbon disulfide (CS) vapor through an electric arc with carbon electrodes. This treatment produced a black solution that after filtration and evaporation gave a cherry-red liquid. He determined the molecular mass by cryoscopy. Later preparations of CS include thermolysis of a stream of CS in a quartz tube heated to 900 to 1100 °C as well as flash vacuum pyrolysis (FVP) of 1,2-dithiole-3-thiones. | 0 | Theoretical and Fundamental Chemistry |
Organic molecules containing knots may fall into the categories of slipknots or pseudo-knots. They are not considered mathematical knots because they are not a closed curve, but rather a knot that exists within an otherwise linear chain, with termini at each end. Knotted proteins are thought to form molecular knots during their tertiary structure folding process, and knotted nucleic acids generally form molecular knots during genomic replication and transcription, though details of knotting mechanism continue to be disputed and ambiguous. Molecular simulations are fundamental to the research on molecular knotting mechanisms.
Knotted DNA was found first by Liu et al. in 1981, in single-stranded, circular, bacterial DNA, though double-stranded circular DNA has been found to also form knots. Naturally knotted RNA has not yet been reported.
A number of proteins containing naturally occurring molecular knots have been identified. The knot types found to be naturally occurring in proteins are the and knots, as identified in the KnotProt database of known knotted proteins. | 0 | Theoretical and Fundamental Chemistry |
Synthesis of molecules in a combinatorial fashion can quickly lead to large numbers of molecules. For example, a molecule with three points of diversity (R, R, and R) can generate possible structures, where , , and are the numbers of different substituents utilized.
The basic principle of combinatorial chemistry is to prepare libraries of a very large number of compounds then identify the useful components of the libraries.
Although combinatorial chemistry has only really been taken up by industry since the 1990s, its roots can be seen as far back as the 1960s when a researcher at Rockefeller University, Bruce Merrifield, started investigating the solid-phase synthesis of peptides.
In its modern form, combinatorial chemistry has probably had its biggest impact in the pharmaceutical industry. Researchers attempting to optimize the activity profile of a compound create a library of many different but related compounds. Advances in robotics have led to an industrial approach to combinatorial synthesis, enabling companies to routinely produce over 100,000 new and unique compounds per year.
In order to handle the vast number of structural possibilities, researchers often create a virtual library, a computational enumeration of all possible structures of a given pharmacophore with all available reactants. Such a library can consist of thousands to millions of virtual compounds. The researcher will select a subset of the virtual library for actual synthesis, based upon various calculations and criteria (see ADME, computational chemistry, and QSAR). | 1 | Applied and Interdisciplinary Chemistry |
Studying the decomposition of double salts of aryldiazonium halides with mercury halides by copper powder, in 1929 Nesmeyanov proposed a new method for obtaining arylmercury halides. Later, the diazo method was extended to the synthesis of organometallic compounds of thallium, germanium, tin, lead, arsenic, antimony, and bismuth. The features of the diazo method, which distinguish it from direct metalation methods, are the possibility of obtaining organometallic compounds with different functional groups in the carbon radical and the possibility of selectively introducing a metal atom into a certain position. In 1935 – 1948, Nesmeyanov, together with K. A. Kocheshkov, obtained organic derivatives of tin, lead, antimony and other metals. Due to mutual transitions from organic derivatives of some elements to organic compounds of other elements, organometallic compounds obtained by the diazo method have found new applications in synthesis. | 0 | Theoretical and Fundamental Chemistry |
For Schottky diodes, majority carrier traps are observed by the application of a reverse bias pulse, while minority carrier traps can be observed when the reverse bias voltage pulses are replaced with light pulses with the photon energy from the above semiconductor bandgap spectral range. This method is called Minority Carrier Transient Spectroscopy (MCTS). The minority carrier traps can be also observed for the p-n junctions by application of forward bias pulses, which inject minority carriers into the space charge region. In DLTS plots the minority carrier spectra usually are depicted with an opposite sign of amplitude in respect to the majority carrier trap spectra. | 0 | Theoretical and Fundamental Chemistry |
Usually, the amine reacts as the nucleophile with another organic compound acting as the electrophile. This sense of reactivity may be reversed for some electron-deficient amines, including oxaziridines, hydroxylamines, oximes, and other N–O substrates. When the amine is used as an electrophile, the reaction is called electrophilic amination. Electron-rich organic substrates that may be used as nucleophiles for this process include carbanions and enolates. | 0 | Theoretical and Fundamental Chemistry |
S-Methylcysteine is the amino acid with the nominal formula CHSCHCH(NH)COH. It is the S-methylated derivative of cysteine. This amino acid occurs widely in plants, including many edible vegetables. | 1 | Applied and Interdisciplinary Chemistry |
80 people who got a good score will join the Summer School 1, which is usually held far away from Seoul. In the school, students learn basic chemistry for two weeks and there isn't any experiment classes. When the school is almost finished, students take an exam. One person gets a Best Graduation, 24 people get a Merit, and some of the rest get an Honorable Mention. 25 people-Best Graduation and Merit-can join the Winter School 1 without Test 2. In 2018, the Summer School will be held at Daegu Gyeongbuk Institute of Science and Technology. | 1 | Applied and Interdisciplinary Chemistry |
The Oligomer Restriction method was beset by a number of problems:
* It could be applied only to the small set of DNA polymorphisms which alter a restriction site, and only to those sites for which sequence information was known. Many of the known RFLP assays detected polymorphisms which were far away from their probe locations.
* It is difficult to label oligonucleotides to a level high enough to use them as probes for genomic DNA. This problem also plagued the development of ASO probes.
* It is difficult to design oligonucleotides and use them in a way that they become hybridization probes for just a single site within a genome. Binding to non-specific locations can often obscure the effect of the probe at the target location.
* Not all restriction enzymes have the desired specificity for their recognition sequence. Some can recognize and cut single-stranded DNA, and some show a low level of cleavage for mismatched sites. Even a small amount of non-specific cleavage can swamp the weak signal expected from the target sequence.
* It was difficult to design an OR method that included controls for both of the alleles being tested. In part 2 of the simplified example described above, the probe was not cleaved when hybridized to a mutant target. But the same (non-) result would occur for the large excess of unhybridized probe, as well as if any problem occurred preventing the complete digestion by restriction enzyme. In the actual method reported, a second non-polymorphic restriction site was used to cut all of the hybridized probe, and a second unlabeled oligonucleotide was used to block the unhybridized probe. These controls would not have been available for other targets. | 1 | Applied and Interdisciplinary Chemistry |
Consider the series of delta functions given by
The Patterson function is given by the following series of delta functions and unit step functions | 0 | Theoretical and Fundamental Chemistry |
Hydrolysis is the reverse reaction of formation with regeneration of the carbonyl compound.
In the Shapiro reaction tosylhydrazones are used as a leaving group in elimination reactions. This reaction requires a strong base. If sodium methoxide is used as the base the reaction is called a Bamford–Stevens reaction. Tosylhydrazones can be reduced to the corresponding alkanes with reagents such as sodium borohydride and borane.
Tosylhydrazone salts can react with metals to form metal carbenes and used in cyclopropanations and epoxidations. An example of a transition metal-catalyzed cyclopropanation is a synthesis of tranylcypromine, in which the sodium salt of benzaldehyde tosylhydrazone is converted to a rhodium metal carbene through the diazo intermediate.
Tosylhydrazones are also starting materials for certain cross-coupling reactions. In the first report on this reaction type the coupling partners were a tosylhydrazone, an aryl halide with catalyst system dibenzylideneacetone / XPhos. As part of the catalytic cycle the diazo intermediateformed by decomposition of the tosylhydrazone forms a palladium-carbene complex with the oxidative addition complex of palladium with the aryl halide.
Using this powerful method it is possible to access bioactive compounds. | 0 | Theoretical and Fundamental Chemistry |
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