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Variations of the steroid 21-hydroxylase can be found in all vertebrates.
Cyp21 first emerged in chordates before the speciation between basal chordates and vertebrates. The sea lamprey, an early jawless fish species that originated over 500 million years ago, provides valuable insights into the evolution and emergence of Cyp21. Sea lampreys lack the 11β-hydroxylase enzyme responsible for converting 11-deoxycortisol to cortisol as observed in mammals. Instead, they rely on 11-deoxycortisol, a product of a reaction catalyzed by CYP21, as their primary glucocorticoid hormone with mineralocorticoid properties. This suggests the presence of a complex and highly specific corticosteroid signaling pathway that emerged at least half a billion years ago during early vertebrate evolution.
In vertebrates, such as fish, amphibians, reptiles, birds, and mammals, Cyp21 participates in the biosynthesis of glucocorticoids and mineralocorticoids, therefore, Cyp21 is essential for the regulation of stress response, electrolyte balance and blood pressure, immune system, and metabolism in vertebrates.
Cyp21 is relatively conserved among mammals, and shows some variations in its structure, expression, and regulation. Rhesus macaques and orangutans possess two copies of Cyp21, while chimpanzees have three, still, a pseudogene (CYP21A1P) is only present in humans among primates. | 1 | Biochemistry |
A neurochemical is a small organic molecule or peptide that participates in neural activity. The science of neurochemistry studies the functions of neurochemicals. | 1 | Biochemistry |
Liver of sulfur was once used to counteract poisoning with several metals, including arsenic, copper, lead, and antimony. A lump was dissolved in warm water and the patient was instructed to drink the solution three or four times over the course of an hour. At one time sulfurated potash was used to combat arthritis. It eventually fell into disfavor for medical purposes because sulfides and polysulfides were discovered to be toxic in their own right. | 7 | Physical Chemistry |
DNA has a negative charge and so will move to the positive electrode in an electric field. A gel is a molecular mesh, with holes roughly the same size as the diameter of the DNA string. When an electric field is applied, the DNA will begin to move through the gel, at a speed roughly inversely proportional to the length of the DNA molecule (shorter lengths of DNA travel faster) — this is the basis for size dependent separation in standard electrophoresis.
In TGGE there is also a temperature gradient across the gel. At room temperature, the DNA will exist stably in a double-stranded form. As the temperature is increased, the strands begin to separate (melting), and the speed at which they move through the gel decreases drastically. Critically, the temperature at which melting occurs depends on the sequence (GC basepairs are more stable than AT due to stacking interactions, not due to the difference in hydrogen bonds (there are three hydrogen bonds between a cytosine and guanine base pair, but only two between adenine and thymine)), so TGGE provides a "sequence dependent, size independent method" for separating DNA molecules. TGGE separates molecules and gives additional information about melting behavior and stability (Biometra, 2000). | 1 | Biochemistry |
The action potential in a normal skeletal muscle cell is similar to the action potential in neurons. Action potentials result from the depolarization of the cell membrane (the sarcolemma), which opens voltage-sensitive sodium channels; these become inactivated and the membrane is repolarized through the outward current of potassium ions. The resting potential prior to the action potential is typically −90mV, somewhat more negative than typical neurons. The muscle action potential lasts roughly 2–4 ms, the absolute refractory period is roughly 1–3 ms, and the conduction velocity along the muscle is roughly 5 m/s. The action potential releases calcium ions that free up the tropomyosin and allow the muscle to contract. Muscle action potentials are provoked by the arrival of a pre-synaptic neuronal action potential at the neuromuscular junction, which is a common target for neurotoxins. | 7 | Physical Chemistry |
Thyroid hormone increases the number of beta-adrenergic receptors available for epinephrine at the latters target cell, thereby increasing epinephrines effect on that cell. Specially in cardiac cell. Without the thyroid hormone, epinephrine would have only a weak effect.
Cortisol is required for the response of vascular and bronchial smooth muscle to catecholamines. Cortisol is also required for the lipolytic effect of catecholamines, ACTH, and growth hormone on fat cells. Cortisol is also required for the calorigenic effects of glucagon and catecholamines.
The effects of a hormone in the body depend on its concentration. Permissive actions of glucocorticoids like cortisol generally occur at low concentrations. Abnormally high amounts of a hormone can result in atypical effects. Glucocorticoids function by attaching to cytoplasmic receptors to either enhance or suppress changes in the transcription of DNA and thus the synthesis of proteins. Glucocorticoids also inhibit the secretion of cytokines via post-translational modification effects. | 1 | Biochemistry |
As a student, Eötvös started to research surface tension and developed a new method for its determination. The Eötvös rule was first found phenomenologically and published in 1886. In 1893 William Ramsay and Shields showed an improved version considering that the line normally passes the temperature axis 6 K before the critical point. John Lennard-Jones and Corner published (1940) a derivation of the equation by means of statistical mechanics. In 1945 E. A. Guggenheim gave a further improved variant of the equation. | 7 | Physical Chemistry |
MCT2 transporters within the peroxisome function to transport pyruvate into the peroxisome where it is reduced by peroxisomal LDH (pLDH) to lactate. In turn, NADH is converted to NAD+, regenerating this necessary component for subsequent β-oxidation. Lactate is then shuttled out of the peroxisome via MCT2, where it is oxidized by cytoplasmic LDH (cLDH) to pyruvate, generating NADH for energy use and completing the cycle (see figure). | 1 | Biochemistry |
Two drops of iron(III) chloride are added to a test tube with distilled water. After mixing, it is divided into two parts. Add one millilitre of gastric juice in one test tube and the same volume of distilled water in the other test tube, which is acting as a control. The test tube with the gastric juice turns yellow in the presence of lactic acid due to the formation of ferric lactate. | 3 | Analytical Chemistry |
This type of equipment has an eccentric drive or weights that causes the shaker to travel in an orbital path. The material rolls over the screen and falls with the induction of gravity and directional shifts. Rubber balls and trays provide an additional mechanical means to cause the material to fall through. The balls also provide a throwing action for the material to find an open slot to fall through.
The shaker is set a shallow angle relative to the horizontal level plane. Usually, no more than 2 to 5 degrees relative to the horizontal level plane.
These types of shakers are used for very clean cuts. Generally, a final material cut will not contain any oversize or any fines contamination.
These shakers are designed for the highest attainable quality at the cost of a reduced feed rate. | 8 | Metallurgy |
FS 49 C2 acts similarly to an inert gas. It absorbs the heat produced from the combustion process. This mechanism is consistent with the observation that the fire heat release rate does not decrease until sufficient gas is released.
The difference from inert gases and FS 49 C2 is that it takes less gas to suppress a fire, and therefore gas storage takes less space, depending on the storage pressure. Savings may vary between a 50-90%. | 2 | Environmental Chemistry |
* 2012 – Pearson Education RACI Centenary of Federation Chemistry Educator of the Year Award
* 2011 – Vice-Chancellor's Award for Outstanding Teaching
* 2011 – Australian Learning and Teaching Council Citation for Teaching Excellence
* 2010 – Vice-Chancellor's Award for Support of the Student Experience
* 2008 – NSW and ACT Young Tall Poppy Science Award
* 2007 – RACI Athel Beckwith Lectureship
* 2006 – RACI Nyholm Lectureship | 0 | Organic Chemistry |
There were various iron-making ventures during the 19th Century, and steel was made but only on a very small scale.
The first commercial scale production of steel in Australia was by William Sandford Limited at the Eskbank Ironworks at Lithgow, New South Wales, in 1901. The plant became Australias first integrated iron and steel works in 1907. It was later expanded by Charles Hoskins. The first steel rails rolled in Australia were rolled there in 1911. Between 1928 and 1932, the operations at Lithgow were transferred, under the management of Cecil Hoskins, to a new plant at Port Kembla, still the site of most of Australias steel production today.
The Minister for Public Works, Arthur Hill Griffith, had consistently advocated for the greater industrialization of Newcastle, then, under William Holman, personally negotiated the establishment of a steelworks with G. D. Delprat of BHP. Griffith was also the architect of the Walsh Island establishment.
In 1915, BHP ventured into steel manufacturing with its Newcastle Steelworks, which was closed in 1999. The long products side of the steel business was spun off to form OneSteel in 2000. BHPs decision to move from mining ore to open a steelworks at Newcastle was precipitated by the technical limitations in recovering value from mining the lower-lying sulphide ores. The discovery of Iron Knob and Iron Monarch near the western shore of the Spencer Gulf in South Australia combined with the development by the BHP metallurgist, Archibald Drummond Carmichael, of a technique for separating zinc sulphides from the accompanying earth and rock led BHP to implement the startlingly simple and cheap process for liberating vast amounts of valuable metals out of sulphide ores, including huge heaps of tailings and slimes up to' high. | 8 | Metallurgy |
The starting material for this route is a β-(Δ-cyclopentenyl)-ethane derivative with a good leaving group on the terminal carbon of the ethane group. Electron density from the π bond of the alkene moiety is donated into the σ* anti-bond between the terminal carbon and the leaving group (see Figure 8c).
For example, the major product of the acetolysis of β-(Δ-cyclopentenyl)-ethyl nosylate (p-nitrobenzenesulfonate) is 2-exo-norbornyl acetate. The dearth of β-(Δ-cyclopentenyl)-ethyl acetate present after the reaction is explained by the greater stability of the norbornyl system over the decorated cyclopentenyl system.
This route is only effective if the cyclopentenyl olefin is isolated from any larger π-bonded system. The reaction rate significantly decreases if the involved double bond forms a six-membered aromatic ring as it does in 2-indanylethyl nosylate. Alkyl substitutions on the olefins have been seen to increase the reaction rate by stabilizing the resulting carbocation. | 7 | Physical Chemistry |
Alpine lakes located in the Central Pyrenees region of northeast Spain are unaffected by anthropogenic factors making these oligotrophic lakes ideal indicators for sediment input and environmental change. Dissolved organic matter and nutrients from dust transport can aid bacteria with growth and production in low nutrient waters. Within the collected samples of one study, a high diversity of airborne microorganisms were detected and had strong similarities to Mauritian soils despite Saharan dust storms occurring at the time of detection. | 7 | Physical Chemistry |
Iron can also enter cells via CD44 in complexes bound to hyaluronic acid during epithelial–mesenchymal transition (EMT). In this process, epithelial cells transform into mesenchymal cells with detachment from the basement membrane, to which they’re normally anchored, paving the way for the newly differentiated motile mesenchymal cells to begin migration away from the epithelial layer.
While EMT plays a crucial role in physiological processes like implantation, where it enables the embryo to invade the endometrium to facilitate placental attachment, its dysregulation can also fuel the malignant spread of tumors empowering them to invade surrounding tissues and establish distant colonies (metastasis).
Malignant cells often exhibit a heightened demand for iron, fueling their transition towards a more invasive mesenchymal state. This iron is necessary for the expression of mesenchymal genes, like those encoding transforming growth factor beta (TGF-β), crucial for EMT. Notably, iron’s unique ability to catalyze protein and DNA demethylation plays a vital role in this gene expression process.
Conventional iron uptake pathways, such as those using the transferrin receptor 1 (TfR1), often prove insufficient to meet these elevated iron demands in cancer cells. As a result, various cytokines and growth factors trigger the upregulation of CD44, a surface molecule capable of internalizing iron bound to the hyaluronan complex. This alternative pathway, relying on CD44-mediated endocytosis, becomes the dominant iron uptake mechanism compared to the traditional TfR1-dependent route. | 1 | Biochemistry |
The simplest mathematical model to explain the Vroman Effect is the Langmuir model using the Langmuir isotherm. More complex models include the Fruendlich isotherm and other modifications to the Langmuir model. This model explains the kinetics between reversible adsorption and desorption, assuming the adsorbate behaves as an ideal gas at isothermal conditions. | 7 | Physical Chemistry |
The receptor-based approach is used in exposure science. It starts by looking at different contaminants and concentrations that reach people. An exposure analyst can use direct or indirect measurements to determine if a person has been in contact with a specific contaminant or has been exposed to a specific risk (e.g. accident). Once a contaminant has been proved to reach people, exposure analysts work backwards to determine its source. After the identification of the source, it is important to find out the most efficient way to reduce adverse health effects. If the contaminant reaches a person, it is very hard to reduce the associated adverse effects. Therefore, it is very important to reduce exposure in order to diminish the risk of adverse health effects. It is highly important to use both regulatory and non-regulatory approaches in order to decrease peoples exposure to contaminants. In many cases, it is better to change peoples activities in order to reduce their exposures rather than regulating a source of contaminants.
The receptor-based approach can be opposed to the source-based approach. This approach begins by looking at different sources of contaminants such as industries and power plants. Then, it is important to find out if the contaminant of interest has reached a receptor (usually humans). With this approach, it is very hard to prove that a pollutant from a source has reached a target. | 2 | Environmental Chemistry |
In order to combat the potential global warming effects of F-gases, and as part of the EU's Kyoto protocol commitments, in 2006 the European Union passed two pieces of legislation controlling their use: the [http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2006:161:0001:0011:EN:PDF F-gas Regulation (EC) No 842/2006] and the Mobile Air Conditioning Directive [http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2006:161:0012:0018:en:PDF Directive 2006/40/EC]. The F-gas Regulation adopts an approach based on containment and recovery of F-gases as well as imposing obligations on reporting, training and labeling on those using F-gases.
On 26 September 2011, the Commission issued a [http://ec.europa.eu/clima/policies/f-gas/docs/report_en.pdf report] on the application, effects and adequacy of the Regulation, drawing from the results of an analytical [http://ec.europa.eu/clima/policies/f-gas/docs/2011_study_en.pdf study] it commissioned from German environmental research institute, Öko-Recherche. A further [https://web.archive.org/web/20130720143224/http://www.epeeglobal.org/epeedocs/internet/docs/ERIE__Armines_study_-_Executive_Summary_-_October_2011_5889.pdf study], conducted by the Armines Centre energétique et procédés and by Energy Research Innovation Engineering (ERIE) found that emissions reductions of up to 60% can be achieved by improving containment measures and accelerating the changeover from high GWP refrigerants to ones with lower GWP.
On 7 November 2012, the European Commission published the [http://ec.europa.eu/clima/policies/f-gas/legislation/docs/com_2012_643_en.pdf proposal] to revise the F-gas Regulation. In December 2013, the European Parliament and the Council of the EU agreed the [http://www.eu2013.lt/en/news/pressreleases/member-states-approve-the-agreement-by-the-co-legislators-on-the-regulation-on-reduction-of-emissions-of-fluorinated-greenhouse-gases-f-gases- text of the revised regulation], which shall be applied from 1 January 2015. | 2 | Environmental Chemistry |
Gene therapy encapsulates many forms of adding different nucleic acids to a cell. Gene augmentation adds a new protein coding gene to a cell. One form of gene augmentiation is gene replacement therapy, a treatment for monogenic recessive disorders where a single gene is not functional an additional functional gene is added. For diseases caused by multiple genes or a dominant gene, gene silencing or gene editing approaches are more appropriate but gene addition, a form of gene augmentation where new gene is added, may improve a cells function without modifying the genes that cause a disorder. | 1 | Biochemistry |
* Antirrhinin (cyanidin-3-rutinoside or 3-C-R), found in black raspberry
* Cyanidin-3-xylosylrutinoside, found in black raspberry
* Cyanidin-3,4′-di-O-β-glucopyranoside, found in red onion
* Cyanidin-4′-O-β-glucoside, found in red onion
* Chrysanthemin (cyanidin-3-O-glucoside), found in blackcurrant pomace
* Ideain (cyanidin 3-O-galactoside), found in Vaccinium species
* Cyanin (cyanidin-3,5-O-diglucoside), found in red wine | 3 | Analytical Chemistry |
When sequencing RNA other than mRNA, the library preparation is modified. The cellular RNA is selected based on the desired size range. For small RNA targets, such as miRNA, the RNA is isolated through size selection. This can be performed with a size exclusion gel, through size selection magnetic beads, or with a commercially developed kit. Once isolated, linkers are added to the 3 and 5 end then purified. The final step is cDNA generation through reverse transcription. | 1 | Biochemistry |
Post-treatment disinfection provides secondary protection against compromised membranes and downstream problems. Disinfection by means of ultraviolet (UV) lamps (sometimes called germicidal or bactericidal) may be employed to sterilize pathogens that evade the RO process. Chlorination or chloramination (chlorine and ammonia) protects against pathogens that may have lodged in the distribution system downstream. | 3 | Analytical Chemistry |
Selection favors different traits in captive populations than it does in wild populations, so this may result in adaptations that are beneficial in captivity but are deleterious in the wild. This reduces the success of re-introductions, so it is important to manage captive populations in order to reduce adaptations to captivity. Adaptations to captivity can be reduced by minimizing the number of generations in captivity and by maximizing the number of migrants from wild populations. Minimizing selection on captive populations by creating an environment that is similar to their natural environment is another method of reducing adaptations to captivity, but it is important to find a balance between an environment that minimizes adaptation to captivity and an environment that permits adequate reproduction. Adaptations to captivity can also be reduced by managing the captive population as a series of population fragments. In this management strategy, the captive population is split into several sub-populations or fragments which are maintained separately. Smaller populations have lower adaptive potentials, so the population fragments are less likely to accumulate adaptations associated with captivity. The fragments are maintained separately until inbreeding becomes a concern. Immigrants are then exchanged between the fragments to reduce inbreeding, and then the fragments are managed separately again. | 1 | Biochemistry |
Alternatives for normally occupied areas include (PFC-410 or CEA-410), CF (PFC-218 or CEA-308), HCFC Blend A (NAF S-III), HFC-23 (FE 13), HFC-227ea (FM 200), IG-01 (argon), IG-55 (argonite), HFC-125, or HFC-134a. For normally unoccupied areas, the alternatives include carbon dioxide, powdered Aerosol C, CFI, HCFC-22, HCFC-124, HFC-125, HFC-134a, gelled halocarbon/dry chemical suspension (PGA), blend of inert gas, high expansion foam systems and powdered aerosol (FS 0140), and IG-541 (Inergen).
Perfluorocarbons, i.e., PFCs such as CF, have very long atmospheric lifetimes and very high global warming potentials. Hydrochlorofluorocarbons, i.e., HCFCs including HCFC containing NAF S-III, contain chlorine and are stratospheric ozone layer depleters, although less so than Halon 1301. Their selection for usage as Halon replacements should consider those factors, and is restricted in some countries. | 2 | Environmental Chemistry |
Impurities usually enter the solder reservoir by dissolving the metals present in the assemblies being soldered. Dissolving of process equipment is not common as the materials are usually chosen to be insoluble in solder.
* Aluminium – little solubility, causes sluggishness of solder and dull gritty appearance due to formation of oxides. Addition of antimony to solders forms Al-Sb intermetallics that are segregated into dross. Promotes embrittlement.
* Antimony – added intentionally, up to 0.3% improves wetting, larger amounts slowly degrade wetting. Increases melting point.
* Arsenic – forms thin intermetallics with adverse effects on mechanical properties, causes dewetting of brass surfaces
* Cadmium – causes sluggishness of solder, forms oxides and tarnishes
* Copper – most common contaminant, forms needle-shaped intermetallics, causes sluggishness of solders, grittiness of alloys, decreased wetting
* Gold – easily dissolves, forms brittle intermetallics, contamination above 0.5% causes sluggishness and decreases wetting. Lowers melting point of tin-based solders. Higher-tin alloys can absorb more gold without embrittlement.
* Iron – forms intermetallics, causes grittiness, but rate of dissolution is very low; readily dissolves in lead-tin above 427 °C.
* Lead – causes Restriction of Hazardous Substances Directive compliance problems at above 0.1%.
* Nickel – causes grittiness, very little solubility in Sn-Pb
* Phosphorus – forms tin and lead phosphides, causes grittiness and dewetting, present in electroless nickel plating
* Silver – often added intentionally, in high amounts forms intermetallics that cause grittiness and formation of pimples on the solder surface, potential for embrittlement
* Sulfur – forms lead and tin sulfides, causes dewetting
* Zinc – in melt forms excessive dross, in solidified joints rapidly oxidizes on the surface; zinc oxide is insoluble in fluxes, impairing repairability; copper and nickel barrier layers may be needed when soldering brass to prevent zinc migration to the surface; potential for embrittlement
Board finishes vs wave soldering bath impurities buildup:
* HASL, lead-free (Hot Air Level): usually virtually pure tin. Does not contaminate high-tin baths.
* HASL, leaded: some lead dissolves into the bath
* ENIG (Electroless Nickel Immersion Gold): typically 100-200 microinches of nickel with 3-5 microinches of gold on top. Some gold dissolves into the bath, but limits exceeding buildup is rare.
* Immersion silver: typically 10–15 microinches of silver. Some dissolves into the bath, limits exceeding buildup is rare.
* Immersion tin: does not contaminate high-tin baths.
* OSP (Organic solderability preservative): usually imidazole-class compounds forming a thin layer on the copper surface. Copper readily dissolves in high-tin baths. | 8 | Metallurgy |
Ethers feature bent linkages. In dimethyl ether, the bond angle is 111° and C–O distances are 141 pm. The barrier to rotation about the C–O bonds is low. The bonding of oxygen in ethers, alcohols, and water is similar. In the language of valence bond theory, the hybridization at oxygen is sp.
Oxygen is more electronegative than carbon, thus the alpha hydrogens of ethers are more acidic than those of simple hydrocarbons. They are far less acidic than alpha hydrogens of carbonyl groups (such as in ketones or aldehydes), however.
Ethers can be symmetrical of the type ROR or unsymmetrical of the type ROR'. Examples of the former are dimethyl ether, diethyl ether, dipropyl ether etc. Illustrative unsymmetrical ethers are anisole (methoxybenzene) and dimethoxyethane. | 0 | Organic Chemistry |
A breakthrough curve in adsorption is the course of the effluent adsorptive concentration at the outlet of a fixed bed adsorber. Breakthrough curves are important for adsorptive separation technologies and for the characterization of porous materials. | 7 | Physical Chemistry |
Carbon sequestration is part of the natural carbon cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of Earth.
Carbon dioxide is naturally captured from the atmosphere through biological, chemical or physical processes, and stored in long-term reservoirs.
Forests, kelp beds, and other forms of plant life absorb carbon dioxide from the air as they grow, and bind it into biomass. However, these biological stores are considered volatile carbon sinks as the long-term sequestration cannot be guaranteed. Events such as wildfires or disease, economic pressures and changing political priorities can result in the sequestered carbon being released back into the atmosphere. | 5 | Photochemistry |
The magnetostriction effect describes a property of ferromagnetic materials which causes them to change their shape when subjected to a magnetic field. Joule first reported observing the change in the length of ferromagnetic rods in 1842. | 7 | Physical Chemistry |
Bacteria can use several different electron donors. When organic matter is the electron source, the donor may be NADH or succinate, in which case electrons enter the electron transport chain via NADH dehydrogenase (similar to Complex I in mitochondria) or succinate dehydrogenase (similar to Complex II). Other dehydrogenases may be used to process different energy sources: formate dehydrogenase, lactate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, H dehydrogenase (hydrogenase), electron transport chain. Some dehydrogenases are also proton pumps, while others funnel electrons into the quinone pool. Most dehydrogenases show induced expression in the bacterial cell in response to metabolic needs triggered by the environment in which the cells grow. In the case of lactate dehydrogenase in E. coli, the enzyme is used aerobically and in combination with other dehydrogenases. It is inducible and is expressed when the concentration of DL-lactate in the cell is high. | 1 | Biochemistry |
Nagai continued his studies at Tokyo Imperial University and became the first doctor of pharmacy in Japan. He was sent under government sponsorship to Prussia in 1871 to study at the University of Berlin. He was the only civilian in a group of military students sent to study in Great Britain and France, and he traveled by way of the United States and Great Britain. While in Berlin, he resided at the home of Japanese diplomat Aoki Shūzō. He was influenced by the lectures of von Hofmann, and received a doctorate with a study on eugenol while working as an assistant at von Hofmann's laboratory. He decided to take up organic chemistry in 1873.
Nagai returned to Japan in 1883 to take up a position at the Tokyo Imperial University, and became Professor of Chemistry and Pharmacy there in 1893. His research centered on the chemical analysis of various Japanese and Chinese traditional herbal medicines.
While in Germany, Nagai married Therese Schumacher, the daughter of a wealthy lumber and mining magnate. On their return to Japan, she became a professor of German language at Japan Women's University, and was active in introducing German foods and culture to Japan. In 1923, Nagai and his wife hosted Albert Einstein and his wife during their visit to Japan.
His son, Alexander Nagai, served as a diplomat at the Embassy of Japan in Berlin until the end of World War II.
As first president of the Pharmaceutical Society of Japan (PSJ, founded in 1880); Nagai had an important impact on the propagation of chemistry and pharmaceutical sciences in an industrializing Japan. | 0 | Organic Chemistry |
Thiophosphates (or phosphorothioates, PS) are chemical compounds and anions with the general chemical formula (x = 0, 1, 2, or 3) and related derivatives where organic groups are attached to one or more O or S. Thiophosphates feature tetrahedral phosphorus(V) centers. | 0 | Organic Chemistry |
In the absence of an effective enantiomeric environment (precursor, chiral catalyst, or kinetic resolution), separation of a racemic mixture into its enantiomeric components is impossible, although certain racemic mixtures spontaneously crystallize in the form of a racemic conglomerate, in which crystals of the enantiomers are physically segregated and may be separated mechanically. However, most racemates form crystals containing both enantiomers in a 1:1 ratio.
In his pioneering work, Louis Pasteur was able to isolate the isomers of sodium ammonium tartrate because the individual enantiomers crystallize separately from solution. To be sure, equal amounts of the enantiomorphic crystals are produced, but the two kinds of crystals can be separated with tweezers. This behavior is unusual. A less common method is by enantiomer self-disproportionation.
The second strategy is asymmetric synthesis: the use of various techniques to prepare the desired compound in high enantiomeric excess. Techniques encompassed include the use of chiral starting materials (chiral pool synthesis), the use of chiral auxiliaries and chiral catalysts, and the application of asymmetric induction. The use of enzymes (biocatalysis) may also produce the desired compound.
A third strategy is Enantioconvergent synthesis, the synthesis of one enantiomer from a racemic precursor, utilizing both enantiomers. By making use of a chiral catalyist, both enantiomers of the reactant result in a single enantiomer of product.
Enantiomers may not be isolable if there is an accessible pathway for racemization (interconversion between enantiomorphs to yield a racemic mixture) at a given temperature and timescale. For example, amines with three distinct substituents are chiral, but with few exceptions (e.g. substituted N-chloroaziridines), they rapidly undergo "umbrella inversion" at room temperature, leading to racemization. If the racemization is fast enough, the molecule can often be treated as an achiral, averaged structure. | 4 | Stereochemistry |
In 2006 Goossen et al. proposed a reaction to synthesize biaryl compounds via catalytic decarboxylative cross coupling.
The mechanism involves two overlapping cycles, one using a copper halide and the other using palladium. The decarboxylation step occurs between the substituted benzoic acid and copper halide to form the intermediate aryl copper species. The palladium initially undergoes oxidative addition from the aryl halide to form a Pd(II) aryl complex. After both of these initial steps, the substituted aryl copper undergoes trans-metalation with the palladium complex. This step forms the copper halide, which then undergoes anion exchange with the substituted benzoic acid to reform the aryl copper intermediate, continuing the catalytic cycle. The other complex formed in the trans-metalation step is a bis-aryl palladium(II), which then undergoes reductive elimination to form the desired bis-aryl species as well as the starting Pd(0) complex, thus completing the catalytic cycle. | 0 | Organic Chemistry |
To overcome problems associated with oligonucleotide quality several elaborate strategies have been developed, employing either separately prepared fishing oligonucleotides, mismatch binding enzymes of the mutS family or specific endonucleases from bacteria or phages. Nevertheless, all these strategies increase time and costs for gene synthesis based on the annealing of chemically synthesized oligonucleotides.
Massively parallel sequencing has also been used as a tool to screen complex oligonucleotide libraries and enable the retrieval of accurate molecules. In one approach, oligonucleotides are sequenced on the 454 pyrosequencing platform and a robotic system images and picks individual beads corresponding to accurate sequence. In another approach, a complex oligonucleotide library is modified with unique flanking tags before massively parallel sequencing. Tag-directed primers then enable the retrieval of molecules with desired sequences by dial-out PCR.
Increasingly, genes are ordered in sets including functionally related genes or multiple sequence variants on a single gene. Virtually all of the therapeutic proteins in development, such as monoclonal antibodies, are optimised by testing many gene variants for improved function or expression. | 1 | Biochemistry |
Once the function of the mutated protein has been determined it is possible to sequence/purify/clone the regions flanking the insertion by the following methods: | 1 | Biochemistry |
Tailings do not have to be stored in ponds or sent as slurries into oceans, rivers or streams. There is a growing use of the practice of dewatering tailings using vacuum or pressure filters so the tailings can then be stacked. This saves water which potentially reduces the impacts on the environment in terms of a reduction in the potential seepage rates, space used, leaves the tailings in a dense and stable arrangement and eliminates the long-term liability that ponds leave after mining is finished. However although there are potential merits to dry stacked tailings these systems are often cost prohibitive due to increased capital cost to purchase and install the filter systems and the increase in operating costs (generally associated electricity consumption and consumables such as filter cloth) of such systems. | 8 | Metallurgy |
Although as a general rule, dietary supplement labeling and marketing are not allowed to make disease prevention or treatment claims, the FDA has for some foods and dietary supplements reviewed the science, concluded that there is significant scientific agreement, and published specifically worded allowed health claims. An initial ruling allowing a health claim for calcium dietary supplements and osteoporosis was later amended to include calcium and vitamin D supplements, effective January 1, 2010. Examples of allowed wording are shown below. In order to qualify for the calcium health claim, a dietary supplement must contain at least 20% of the Reference Dietary Intake, which for calcium means at least 260 mg/serving.
*"Adequate calcium throughout life, as part of a well-balanced diet, may reduce the risk of osteoporosis."
*"Adequate calcium as part of a healthful diet, along with physical activity, may reduce the risk of osteoporosis in later life."
*"Adequate calcium and vitamin D throughout life, as part of a well-balanced diet, may reduce the risk of osteoporosis."
*"Adequate calcium and vitamin D as part of a healthful diet, along with physical activity, may reduce the risk of osteoporosis in later life."
In 2005 the FDA approved a Qualified Health Claim for calcium and hypertension, with suggested wording "Some scientific evidence suggests that calcium supplements may reduce the risk of hypertension. However, FDA has determined that the evidence is inconsistent and not conclusive." Evidence for pregnancy-induced hypertension and preeclampsia was considered inconclusive. The same year the FDA approved a QHC for calcium and colon cancer, with suggested wording "Some evidence suggests that calcium supplements may reduce the risk of colon/rectal cancer, however, FDA has determined that this evidence is limited and not conclusive." Evidence for breast cancer and prostate cancer was considered inconclusive. Proposals for QHCs for calcium as protective against kidney stones or against menstrual disorders or pain were rejected.
The European Food Safety Authority (EFSA) concluded that "Calcium contributes to the normal development of bones." The EFSA rejected a claim that a cause-and-effect relationship existed between the dietary intake of calcium and potassium and maintenance of normal acid-base balance. The EFSA also rejected claims for calcium and nails, hair, blood lipids, premenstrual syndrome and body weight maintenance. | 1 | Biochemistry |
The spectral absorption is equal to the emissivity ; this relation is known as Kirchhoff's law of thermal radiation. An object is called a black body if this holds for all frequencies, and the following formula applies:
If objects appear white (reflective in the visual spectrum), they are not necessarily equally reflective (and thus non-emissive) in the thermal infrared – see the diagram at the left. Most household radiators are painted white, which is sensible given that they are not hot enough to radiate any significant amount of heat, and are not designed as thermal radiators at all – instead, they are actually convectors, and painting them matt black would make little difference to their efficacy. Acrylic and urethane based white paints have 93% blackbody radiation efficiency at room temperature (meaning the term "black body" does not always correspond to the visually perceived color of an object). These materials that do not follow the "black color = high emissivity/absorptivity" caveat will most likely have functional spectral emissivity/absorptivity dependence.
Only truly gray systems (relative equivalent emissivity/absorptivity and no directional transmissivity dependence in all control volume bodies considered) can achieve reasonable steady-state heat flux estimates through the Stefan-Boltzmann law. Encountering this "ideally calculable" situation is almost impossible (although common engineering procedures surrender the dependency of these unknown variables and "assume" this to be the case). Optimistically, these "gray" approximations will get close to real solutions, as most divergence from Stefan-Boltzmann solutions is very small (especially in most standard temperature and pressure lab controlled environments). | 7 | Physical Chemistry |
C5a is a powerful inflammatory mediator, and seems to be a key factor in the development of pathology of many inflammatory diseases involving the complement system such as sepsis, rheumatoid arthritis, inflammatory bowel disease, systemic lupus erythemotosis, psoriasis. The inhibitor of C5a that can block its effects would be helpful in medical applications.
Another candidate is PMX53 or PMX205 that is highly specific for CD88 and effectively reduces inflammatory response. C5a has been identified as a key mediator of neutrophil dysfunction in sepsis, with antibody blockade of C5a improving outcomes in experimental models. This has also been shown in humans, with C5a-mediated neutrophil dysfunction predicting subsequent nosocomial infection and death from sepsis. Recent data demonstrates that C5a not only impairs phagocytosis by neutrophils but also impairs phagosomal maturation, inducing a marked alteration in the neutrophil phosphoproteomic response to bacterial targets. C5a binding to C5aR1 and C5aR2 (C5L2) mediates the formation of neutrophil extracellular traps and release of cytotoxic histones to the extracellular space, which is believed to act as a pathogenetic process of acute respiratory distress syndrome (ARDS) and promote tumor growth and metastasis. | 1 | Biochemistry |
The Toda oscillator is a dynamical system of any origin, which can be described with dependent coordinate and independent coordinate , characterized in that the evolution along independent coordinate can be approximated with equation
where
, and prime denotes the derivative. | 7 | Physical Chemistry |
Using the definition above for and , the first and second derivatives can be expressed in terms of the Faddeeva function as
and
respectively.
Often, one or multiple Voigt profiles and/or their respective derivatives need to be fitted to a measured signal by means of non-linear least squares, e.g., in spectroscopy. Then, further partial derivatives can be utilised to accelerate computations. Instead of approximating the Jacobian matrix with respect to the parameters , , and with the aid of finite differences, the corresponding analytical expressions can be applied. With and , these are given by:
for the original voigt profile ;
for the first order partial derivative ; and
for the second order partial derivative . Since and play a relatively similar role in the calculation of , their respective partial derivatives also look quite similar in terms of their structure, although they result in totally different derivative profiles. Indeed, the partial derivatives with respect to and show more similarity since both are width parameters. All these derivatives involve only simple operations (multiplications and additions) because the computationally expensive and are readily obtained when computing . Such a reuse of previous calculations allows for a derivation at minimum costs. This is not the case for finite difference gradient approximation as it requires the evaluation of for each gradient respectively. | 7 | Physical Chemistry |
The 5′ UTR begins at the transcription start site and ends one nucleotide (nt) before the initiation sequence (usually AUG) of the coding region. In prokaryotes, the length of the 5′ UTR tends to be 3–10 nucleotides long, while in eukaryotes it tends to be anywhere from 100 to several thousand nucleotides long. For example, the ste11 transcript in Schizosaccharomyces pombe has a 2273 nucleotide 5′ UTR while the lac operon in Escherichia coli only has seven nucleotides in its 5′ UTR. The differing sizes are likely due to the complexity of the eukaryotic regulation which the 5′ UTR holds as well as the larger pre-initiation complex that must form to begin translation.
The 5′ UTR can also be completely missing, in the case of leaderless mRNAs. Ribosomes of all three domains of life accept and translate such mRNAs. Such sequences are naturally found in all three domains of life. Humans have many pressure-related genes under a 2–3 nucleotide leader. Mammals also have other types of ultra-short leaders like the TISU sequence. | 1 | Biochemistry |
Miray Bekbölet is a Turkish environmental chemist researching oxidation techniques, photocatalytic and photolytic reactions, adsorption/bio-oxidation processes in aquatic systems, and drinking water quality. She is a professor of environmental chemistry at the Boğaziçi University Institute of Environmental Sciences. | 5 | Photochemistry |
It has been used to produce smoke screens since it produces a heavy, white smoke that has little tendency to rise. "Tickle" was the standard means of producing on-set smoke effects for motion pictures, before being phased out in the 1980s due to concerns about hydrated HCl's effects on the respiratory system. | 0 | Organic Chemistry |
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into oxides of nitrogen. Most commercially available nitric acid has a concentration of 68% in water. When the solution contains more than 86% , it is referred to as fuming nitric acid. Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as red fuming nitric acid at concentrations above 86%, or white fuming nitric acid at concentrations above 95%.
Nitric acid is the primary reagent used for nitration – the addition of a nitro group, typically to an organic molecule. While some resulting nitro compounds are shock- and thermally-sensitive explosives, a few are stable enough to be used in munitions and demolition, while others are still more stable and used as pigments in inks and dyes. Nitric acid is also commonly used as a strong oxidizing agent. | 3 | Analytical Chemistry |
Non-classical ions differ from traditional cations in their electronic structure: though chemical bonds are typically depicted as the sharing of electrons between two atoms, stable non-classical ions can contain three or more atoms that share a single pair of electrons. In 1939, Thomas Nevell and others attempted to elucidate the mechanism for transforming camphene hydrochloride into isobornyl chloride. In one of the proposed reaction mechanisms depicted in the paper, the positive charge of an intermediate cation was not assigned to a single atom but rather to the structure as a whole. This was later cited by opponents of the non-classical description as the first time that a non-classical ion was invoked. However, the term "non-classical ion" did not explicitly appear in the chemistry literature until over a decade later, when it was used to label delocalized bonding in a pyramidal, butyl cation.
The term synartetic ion was also invoked to describe delocalized bonding in stable carbocations before the term non-classical ion was in widespread use. The first users of this term commented on the striking similarity between bonding in these types of cations and bonding in borohydrides. | 7 | Physical Chemistry |
* King Chandra and the Mehrauli Pillar, M.C. Joshi, S.K. Gupta and Shankar Goyal, Eds., Kusumanjali Publications, Meerut, 1989.
* The Rustless Wonder – A Study of the Iron Pillar at Delhi, T.R. Anantharaman, Vigyan Prasar New Delhi, 1996.
* Delhi Iron Pillar: New Insights. R. Balasubramaniam, Aryan Books International, Delhi, and Indian Institute of Advanced Study, Shimla, 2002, Hardbound, . [http://www.infinityfoundation.com/mandala/t_rv/t_rv_agraw_delhi_frameset.htm] [http://home.iitk.ac.in/~bala/journalpaper/journal/index.htm]
* The Delhi Iron Pillar: Its Art, Metallurgy and Inscriptions, M.C. Joshi, S.K. Gupta and Shankar Goyal, Eds., Kusumanjali Publications, Meerut, 1996.
* The World Heritage Complex of the Qutub, R. Balasubramaniam, Aryan Books International, New Delhi, 2005, Hardbound, .
* "Delhi Iron Pillar" (in two parts), R. Balasubramaniam, IIM Metal News Volume 7, No. 2, April 2004, pp. 11–17 and IIM Metal News Volume 7, No. 3, June 2004, pp. 5–13. [http://home.iitk.ac.in/%7Ebala/journalpaper/popart_6_7/metalnews_2004.pdf]
* [http://home.iitk.ac.in/%7Ebala/journalpaper/journal/journalpaper_20.pdf New Insights on the 1600-Year Old Corrosion Resistant Delhi Iron Pillar], R. Balasubramaniam, Indian Journal of History of Science 36 (2001) 1–49.
* The Early use of Iron in India, Dilip K. Chakrabarti, Oxford University Press, New Delhi, 1992, . | 8 | Metallurgy |
Transferrins are glycoproteins that are often found in biological fluids of vertebrates. When a transferrin protein loaded with iron encounters a transferrin receptor on the surface of a cell, e.g., erythroid precursors in the bone marrow, it binds to it and is transported into the cell in a vesicle by receptor-mediated endocytosis. The pH of the vesicle is reduced by hydrogen ion pumps ( ATPases) to about 5.5, causing transferrin to release its iron ions. Iron release rate is dependent on several factors including pH levels, interactions between lobes, temperature, salt, and chelator. The receptor with its ligand bound transferrin is then transported through the endocytic cycle back to the cell surface, ready for another round of iron uptake.
Each transferrin molecule has the ability to carry two iron ions in the ferric form (). | 1 | Biochemistry |
Ethylene binds to it specific transmembrane receptor present on the cell membrane of endoplasmic reticulum. There are different ethylene receptor isoforms. Five isoforms are known in Arabidopsis thaliana which are named ethylene response/receptor 1 (ETR1), ethylene response sensor 1 (ERS1), ETR2, ERS2, and ethylene insensitive 4 (EIN4). The ETR1 is similar (conserved sequence) in different plants but with slight amino acid differences. A. thaliana receptors are classified into two subfamilies based on genetic relationship and common structural features, namely subfamily 1 that includes ETR1 and ERS1, and subfamily 2 that consists of ETR2, ERS2, and EIN4. In tomato there are seven types of ethylene receptors named SlETR1, SlETR2, SlETR3, SlETR4, SlETR5, SlETR6, and SlETR7 (Sl for Solanum lycopersicum, the scientific of tomato).
All ethylene receptors have similar organisation: a short N-terminal domain, three conserved transmembrane domains towards the N-terminus, followed by a GAF domain of unknown function, and then signal output motifs in the C-terminal region. The N-terminus is exposed on the lumen of the endoplasmic reticulum, and the C-terminus that is exposed to the cytoplasm of the cell. The N-terminus contains the sites for binding of ethylene, dimerization and membrane localization. Two similar receptors combine to form a homodimer through a disulfide bridge forming a cysteine-cysteine interaction. However, the main membrane localization is done by the transmembrane domain, which can also bind ethylene with the help of copper as a cofactor. Copper ion is supplied by a transmembrane protein responsive-to-antagonist 1 (RAN1) from antioxidant protein 1 (ATX1) via tiplin, or directly by copper transport protein.
Although the receptors are functionally active as dimers, only one copper ion binds to such dimer, indicating that one receptor dimer binds only one ethylene molecule. Mutations in the binding sites stop ethylene binding and also make plants insensitive to ethylene. Cys-65 in the protein helix 2 is particularly important as the binding site of copper ion as mutation in it stops copper and ethylene binding. The C-terminus is basically a bacterial two-component system with kinase activity and response regulator. ETR1 has histidine kinase activity, whereas ETR2, ERS2, and EIN4 have serine/threonine kinase activity, and ERS1 has both. The histidine kinase in ETR1 is not required for ethylene signaling. | 1 | Biochemistry |
Surface bodies of water provide environments able to dry out and be rewetted. Continued wet-dry cycles allow the concentration of prebiotic compounds and condensation reactions to polymerise macromolecules. Moreover, lake and ponds on land allow for detrital input from the weathering of continental rocks which contain apatite, the most common source of phosphates needed for nucleotide backbones. The amount of exposed continental crust in the Hadean is unknown, but models of early ocean depths and rates of ocean island and continental crust growth make it plausible that there was exposed land. Another line of evidence for a surface start to life is the requirement for UV for organism function. UV is necessary for the formation of the U+C nucleotide base pair by partial hydrolysis and nucleobase loss. Simultaneously, UV can be harmful and sterilising to life, especially for simple early lifeforms with little ability to repair radiation damage. Radiation levels from a young Sun were likely greater, and, with no ozone layer, harmful shortwave UV rays would reach the surface of Earth. For life to begin, a shielded environment with influx from UV-exposed sources is necessary to both benefit and protect from UV. Shielding under ice, liquid water, mineral surfaces (e.g. clay) or regolith is possible in a range of surface water settings. While deep sea vents may have input from raining down of surface exposed materials, the likelihood of concentration is lessened by the ocean's open system. | 9 | Geochemistry |
In terms of flowering time in long day conditions, all mutants made the observed flowering late, with PRR7 significantly more late in comparison to the other mutants. All double mutants with PRR7 saw much later flowering time than the PRR5/PRR9 mutant. | 1 | Biochemistry |
The first study reporting molecular delivery using ultrasound was a 1987 in vitro study attempting to transfer plasmid DNA to cultured mouse fibroblast cells using sonoporation. This successful plasmid DNA transfection conferring G418 antibiotic resistance ultimately led to further in vitro studies that hinted at the potential for sonoporation transfection of plasmid DNA and siRNA in vivo. | 1 | Biochemistry |
The Thyrotroph Thyroid Hormone Sensitivity Index (abbreviated TTSI, also referred to as Thyrotroph T4 Resistance Index or TT4RI) is a calculated structure parameter of thyroid homeostasis. It was originally developed to deliver a method for fast screening for resistance to thyroid hormone. Today it is also used to get an estimate for the set point of thyroid homeostasis, especially to assess dynamic thyrotropic adaptation of the anterior pituitary gland, including non-thyroidal illnesses. | 1 | Biochemistry |
The Governing Board of the Eastern Analytical Symposium presents awards each year for outstanding contributions and achievements in general analytical chemistry and in five specific areas of analysis. The award inscriptions read, "In Recognition of Outstanding Achievements in the Field of -----".
*Analytical Chemistry
*Magnetic Resonance
*Vibrational spectroscopy
*Chemometrics
*Mass Spectrometry
*Separation Science or Chromatography
The Governing Board each year also honors a Young Investigator who is making an impact on the field of analytical chemistry. The [http://easinc.org/wordpress/?page_id=2142 2017 Awardee] will be Prof. Dwight R. Stoll.
In addition to the EAS Awards, awards presented by sponsoring organizations at the Symposium include:
* The Benedetti-Pichler Award of the American Microchemical Society
* The Ernst Abbe Award of the New York Microscopical Society
* The Gold Medal of the New York Society for Applied Spectroscopy
From 2012 to 2014, an award was also presented to a New Faculty active in NMR.
Past award recipients can be found [https://eas.org/2021/?page_id=811 here]. | 7 | Physical Chemistry |
Magnetation is the processing of iron ore tailings, the waste product of iron ore mines, to recover hematite. Crushed mine tailings are mixed with water to create a slurry; the slurry is then pumped through magnetic separation chambers to extract hematite. Commercial interest in this process stems from the possibility of extracting additional iron from tailings supplied by existing mines, increasing their yield. | 8 | Metallurgy |
Experimentation with respiratory oxidase inhibitors (for instance, cyanide) on unicellular algae has revealed interactive pathways to be present between chloroplasts and mitochondria. Metabolic pathways responsible for photosynthesis are present in chloroplasts, whereas respiratory metabolic pathways are present in mitochondria. In these pathways, metabolic carriers (like phosphate) exchange NAD(P)H molecules between photosynthetic and respiratory ETCs. Evidence using mass spectrometry on algae and photosynthetic mutants of Chlamydomonas, discovered that oxygen molecules were also being exchanged between photosynthetic and chlororespiratory ETCs. The mutant Chlamydomonas alga species, lacks photosystems one and two (PS I and PS II), so when the alga underwent flash-induced PS I activity, it resulted in no effect on mitochondrial pathways of respiration. Instead, this flash-induced PS I activity caused an exchange between photosynthetic and chlororespiratory ETCs, which was observed using polarography. This flash of PS I activity is triggered by an over-reduction of the PQ pool and/or lack of the pyridine nucleotide in the thylakoid membrane. A reduction in such molecules then stimulates NADPH and PTOX molecules to trigger chlororespiratory pathways.
Furthermore, in the absence of light (and thus photosynthesis), chlororespiration plays an integral role in enabling metabolic pathways to compensate for chemical energy synthesis. This is achieved through the oxidation of stromal compounds, which increases the PQ pool and allows for the chlororespiratory ETC to take place. | 1 | Biochemistry |
One of the drawbacks of using a separating funnel is emulsions can form easily, and can take a long time to separate once formed. They are often formed while liquids are being mixed in the separating funnel. This can occur when small droplets are suspended in an aqueous solution. If an emulsion is formed, one technique used to separate the liquids is to slowly swirl the solution in the separating funnel. If the emulsion is not separated by this process, a small amount of saturated saline solution is added ("salting out").
Research is being done on alternative, more efficient techniques, mostly utilizing stir bars (stirrer bars) to decrease or even eliminate the chance of emulsification, thus decreasing the amount of waiting time. | 3 | Analytical Chemistry |
Certain kinds of IVF have been shown to lead to distortions in the sex ratio at birth. Intracytoplasmic sperm injection (ICSI), which was first applied in 1991, leads to slightly more female births (51.3% female). Blastocyst transfer, which was first applied in 1984, leads to significantly more male births (56.1% male). Standard IVF done at the second or third day leads to a normal sex ratio.
Epigenetic modifications caused by extended culture leading to the death of more female embryos has been theorised as the reason why blastocyst transfer leads to a higher male sex ratio; however, adding retinoic acid to the culture can bring this ratio back to normal. A second theory is that the male-biased sex ratio may due to a higher rate of selection of male embryos. Male embryos develop faster in vitro, and thus may appear more viable for transfer. | 1 | Biochemistry |
It monitors background radiation in the UK. Workers exposed to radiation include workers in dental radiography and nuclear power stations; exposure to radiation for workers in the UK must be ALARP. It offers 3-day training courses around twice a month, at a national level, for workers exposed to radiation.
It produces reports on environmental background radiation in England. It works with the ICRP, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), and the International Atomic Energy Agency (IAEA). Inside the UK, it works with the Scottish Environment Protection Agency (SEPA) and the Environment Agency (EA). | 2 | Environmental Chemistry |
A blotting matrix, in molecular biology and genetics, is the substrate onto which macromolecules, such as proteins, are transferred in a blot method. The matrices are generally chemically modified paper filters or microporous membrane filters. In a dot blot, macromolecules are applied directly to the matrix. Macromolecules can also be separated and transferred via gel electrophoresis.
One of the most common blotting matrices for protein analysis is nitrocellulose, which has a high affinity for proteins due to hydrophobic interactions. However, proteins with low molecular weight have a small affinity for nitrocellulose, limiting potential applications. This defect may be remedied by glutaraldehyde, which can covalently bond proteins to nitrocellulose. Another matrix is cellulose paper modified with diazophenylthiother, which can also facilitate covalent bonding of proteins. Nylon membranes are also used for protein blotting, although they may result in the binding of anionic dyes such as Coomassie blue and Amido black. Polyvinylidene fluoride membranes are also commonly used, due to their hydrophobicity. | 1 | Biochemistry |
Mixed liquor suspended solids (MLSS) is the concentration of suspended solids, in an aeration tank during the activated sludge process, which occurs during the treatment of waste water. The units MLSS is primarily measured in milligram per litre (mg/L), but for activated sludge its mostly measured in gram per litre [g/L] which is equal to kilogram per cubic metre [kg/m3]. Mixed liquor is a combination of raw or unsettled wastewater or pre-settled wastewater and activated sludge within an aeration tank. MLSS consists mostly of microorganisms and non-biodegradable suspended matter. MLSS is an important part of the activated sludge process to ensure that there is a sufficient quantity of active biomass available to consume the applied quantity of organic pollutant at any time. This is known as the food to microorganism ratio, more commonly notated as the F/M ratio. By maintaining this ratio at the appropriate level the biomass will consume high percentages of the food. This minimizes the loss of residual food in the treated effluent. In simple terms, the more the biomass consumes the lower the biochemical oxygen demand (BOD) will be in the discharge. It is important that MLSS removes COD and BOD in order to purify water for clean surface waters, and subsequently clean drinking water and hygiene. Raw sewage enters in the water treatment process with a concentration of sometimes several hundred mg/L of BOD. Upon being treated by screening, pre-settling, activated sludge processes or other methods of treatment, the concentration of BOD in water can be lowered to less than 2 mg/L, which is considered to be clean, safe to discharge to surface waters or to reuse water.
The total weight of MLSS within an aeration tank can be calculated by multiplying the concentration of MLSS (kg/m3) in the aeration tank by the tank volume (m3). | 3 | Analytical Chemistry |
The term "virokine" was coined by National Institutes of Health virologist Bernard Moss. The early 1990s saw several reports of virally encoded proteins with sequence homology to immune proteins, followed by reports of the cowpox and vaccinia viruses directly interfering with key immune regulator IL1B. The first identified virokine was an epidermal growth factor-like protein found in myxoma viruses.
Much of the early work on virokines involved vaccinia virus, which was discovered to secrete proteins that promote proliferation of neighboring cells and block complement immune activity leading to inflammation. | 1 | Biochemistry |
This family of clusters includes the nido cages . Relatively little work has been devoted to these compounds. Pentaborane[9] reacts with acetylene to give nido-1,2-. Upon treatment with sodium hydride, latter forms the salt [1,2-. | 7 | Physical Chemistry |
pK values of amino acid side chains play an important role in defining the pH-dependent characteristics of a protein. The pH-dependence of the activity displayed by enzymes and the pH-dependence of protein stability, for example, are properties that are determined by the pK values of amino acid side chains.
The pK values of an amino acid side chain in solution is typically inferred from the pK values of model compounds (compounds that are similar to the side chains of amino acids). See Amino acid for the pK values of all amino acid side chains inferred in such a way. There are also numerous experimental studies that have yielded such values, for example by use of NMR spectroscopy.
The table below lists the model pK values that are often used in a protein pK calculation, and contains a third column based on protein studies. | 7 | Physical Chemistry |
Molecular Physics is a peer-reviewed scientific journal covering research on the interface between chemistry and physics, in particular chemical physics and physical chemistry. It covers both theoretical and experimental molecular science, including electronic structure, molecular dynamics, spectroscopy, reaction kinetics, statistical mechanics, condensed matter and surface science. The journal was established in 1958 and is published by Taylor & Francis. According to the Journal Citation Reports, the journal has a 2021 impact factor of 1.937.
The current editor-in-chief is Professor George Jackson (Imperial College London). A reprint of the first editorial and a full list of editors since its establishment can be found in the issue celebrating 50 years of the journal. | 7 | Physical Chemistry |
Later in the 20th century several British pathologists, Mikey Rochman, Francis Camps, Sydney Smith and Keith Simpson pioneered new forensic science methods. Alec Jeffreys pioneered the use of DNA profiling in forensic science in 1984. He realized the scope of DNA fingerprinting, which uses variations in the genetic code to identify individuals. The method has since become important in forensic science to assist police detective work, and it has also proved useful in resolving paternity and immigration disputes. DNA fingerprinting was first used as a police forensic test to identify the rapist and killer of two teenagers, Lynda Mann and Dawn Ashworth, who were both murdered in Narborough, Leicestershire, in 1983 and 1986 respectively. Colin Pitchfork was identified and convicted of murder after samples taken from him matched semen samples taken from the two dead girls.
Forensic science has been fostered by a number of national and international forensic science learned bodies including the American Academy of Forensic Sciences (founded 1948), publishers of the Journal of Forensic Sciences; the Canadian Society of Forensic Science (founded 1953), publishers of the Journal of the Canadian Society of Forensic Science; the Chartered Society of Forensic Sciences, (founded 1959), then known as the Forensic Science Society, publisher of Science & Justice; the British Academy of Forensic Sciences (founded 1960), publishers of Medicine, Science and the Law; the Australian Academy of Forensic Sciences (founded 1967), publishers of the Australian Journal of Forensic Sciences; and the European Network of Forensic Science Institutes (founded 1995). | 3 | Analytical Chemistry |
The NMDA receptor (NMDAR) does not, in resting or near-resting membrane potential conditions, contribute significant current to the EPSP. Following the presynaptic release of the glutamate that binds to and opens the AMPAR, the NMDAR also binds this glutamate and opens. However, current does not flow through the NMDAR ion channel because it is instantaneously blocked by a magnesium ion (Mg) that binds to a site "inside" the open pore of the NMDAR channel. Magnesium has access to this binding site only when the NMDAR channel is opened by glutamate binding, a so-called open channel block. | 1 | Biochemistry |
Perilipin expression is elevated in obese animals and humans. Polymorphisms in the human perilipin (PLIN) gene have been associated with variance in body-weight regulation and may be a genetic influence on obesity risk in humans.
This protein can be modified by O-linked acetylglucosamine (O-GlNac) moieties and the enzyme that intervenes is O-GlcNAc transferase (OGT). An abundance of OGT obstructs lipolysis and benefits diet-induced obesity and whole-body insulin resistance. Studies also propose that an overexpression of adipose O-GlcNAc signaling is a molecular expression of obesity and diabetes in humans. | 1 | Biochemistry |
In the medical field, experiments are done to test for the uses of cell-cell fusogens in axonal nerve repairs and to determine their usefulness with other nerve cells. The current method for nerve repair is suturing the cut ends of nerves. This has a long recovery process, with a low functionality rate for the repaired nerves. When considering cell-cell fusogens as a potential answer, researchers divided these fusogens into two groups based on fusion mechanisms: cell aggregation and membrane modification. One fusogen PEG was found to fit in both groups. It was this fusogen that made restoring nerve cells in humans possible. Once operations were within a certain time frame (12 hours for human nerve repair and 24 hours for sciatic rat treatments), patient recovery was almost successful. With this research, there is potential for repairing human nerve grafts. Some potential uses of cell-cell fusogens studied are cancer vaccines and the regeneration of damaged cells. Additionally, any peripheral nerve in the body could be repaired, and transferred tissues could work as soon as the senses return. Finally, any surgery done on nerves could be repaired as well, thus resulting in a quicker recovery. | 1 | Biochemistry |
For a system undergoing a reversible reaction described by the general chemical equation
a thermodynamic equilibrium constant, denoted by , is defined to be the value of the reaction quotient Q when forward and reverse reactions occur at the same rate. At chemical equilibrium, the chemical composition of the mixture does not change with time, and the Gibbs free energy change for the reaction is zero. If the composition of a mixture at equilibrium is changed by addition of some reagent, a new equilibrium position will be reached, given enough time. An equilibrium constant is related to the composition of the mixture at equilibrium by
where {X} denotes the thermodynamic activity of reagent X at equilibrium, [X] the numerical value of the corresponding concentration in moles per liter, and γ the corresponding activity coefficient. If X is a gas, instead of [X] the numerical value of the partial pressure in bar is used. If it can be assumed that the quotient of activity coefficients, , is constant over a range of experimental conditions, such as pH, then an equilibrium constant can be derived as a quotient of concentrations.
An equilibrium constant is related to the standard Gibbs free energy change of reaction by
where R is the universal gas constant, T is the absolute temperature (in kelvins must be a pure number and cannot have a dimension, since logarithms can only be taken of pure numbers. must also be a pure number. On the other hand, the reaction quotient at equilibrium
does have the dimension of concentration raised to some power (see , below). Such reaction quotients are often referred to, in the biochemical literature, as equilibrium constants.
For an equilibrium mixture of gases, an equilibrium constant can be defined in terms of partial pressure or fugacity.
An equilibrium constant is related to the forward and backward rate constants, k and k of the reactions involved in reaching equilibrium: | 7 | Physical Chemistry |
In chemistry, a Zintl phase is a product of a reaction between a group 1 (alkali metal) or group 2 (alkaline earth metal) and main group metal or metalloid (from groups 13, 14, 15, or 16). It is characterized by intermediate metallic/ionic bonding. Zintl phases are a subgroup of brittle, high-melting intermetallic compounds that are diamagnetic or exhibit temperature-independent paramagnetism and are poor conductors or semiconductors.
This type of solid is named after German chemist Eduard Zintl who investigated them in the 1930s. The term "Zintl Phases" was first used by Laves in 1941. In his early studies, Zintl noted that there was an atomic volume contraction upon the formation of these products and realized that this could indicate cation formation. He suggested that the structures of these phases were ionic, with complete electron transfer from the more electropositive metal to the more electronegative main group element. The structure of the anion within the phase is then considered on the basis of the resulting electronic state. These ideas are further developed in the Zintl-Klemm-Busmann concept, where the polyanion structure should be similar to that of the isovalent element. Further, the anionic sublattice can be isolated as polyanions (Zintl ions) in solution and are the basis of a rich subfield of main group inorganic chemistry. | 7 | Physical Chemistry |
A study of non-medical use potential of eszopiclone found that in persons with a known history of non-medical benzodiazepine use, eszopiclone at doses of 6 and 12 mg produced effects similar to those of diazepam 20 mg. The study found that at these doses which are two or more times greater than the maximum recommended doses, a dose-related increase in reports of amnesia, sedation, sleepiness, and hallucinations was observed for both eszopiclone (Lunesta) as well as for diazepam (Valium). | 4 | Stereochemistry |
Transvection is an epigenetic phenomenon that results from an interaction between an allele on one chromosome and the corresponding allele on the homologous chromosome. Transvection can lead to either gene activation or repression. It can also occur between nonallelic regions of the genome as well as regions of the genome that are not transcribed.
The first observation of mitotic (i.e. non-meiotic) chromosome pairing was discovered via microscopy in 1908 by Nettie Stevens. Edward B. Lewis at Caltech discovered transvection at the bithorax complex in Drosophila in the 1950s. Since then, transvection has been observed at a number of additional loci in Drosophila, including the genes known as white, decapentaplegic, eyes absent, vestigial, and yellow.
As defined by Lewis, "Operationally, transvection is occurring if the phenotype of a given genotype can be altered solely by disruption of somatic (or meiotic) pairing. Such disruption can generally be accomplished by introduction of a heterozygous rearrangement that disrupts pairing in the relevant region but has no position effect of its own on the phenotype" (cited by Ting Wu and Jim Morris, 1999). Recently, pairing-mediated phenomena have been observed in species other than Drosophila, including mice, humans, plants, nematodes, insects, and fungi. In light of these findings, transvection may represent a potent and widespread form of gene regulation.
Transvection appears to be dependent upon chromosome pairing. In some cases, if one allele is placed on a different chromosome by a translocation, transvection does not occur. Transvection can sometimes be restored in a translocation homozygote, where both alleles may once again be able to pair. Restoration of phenotype has been observed at bithorax, decapentaplegic, eyes absent, and vestigial, and with transgenes of white. In some cases, transvection between two alleles leads to intragenic complementation while disruption of transvection disrupts the complementation.
Transvection is believed to occur through a variety of mechanisms. In one mechanism, the enhancers of one allele activate the promoter of a paired second allele. Other mechanisms include pairing-sensitive silencing and enhancer bypass of a chromatin insulator through pairing-mediated changes in gene structure.
The physiological relevance of transvection has recently been documented in the context of sex-biased gene expression. In Drosophila, transvection acts on the female X-linked gene yellow, which is homozygous in females (XX) versus hemizygous in males (XY). | 1 | Biochemistry |
In 1943, he defended his Ph.D. thesis on “Obtaining Hexamethylenetetramine (urotropine) from Natural Gas”. In 1945, the Synthesis of Additives Laboratory was organized in Azerbaijan Scientific-Research Institute of Oil-Processing. Guliyev headed this laboratory. As a result of experiments by him and his team, lubricating additives, Az.SRI depressor and Az.SRI -4 were applied in industry for the first time in the Soviet Union. In 1948 and 1951, Guliyev and his team of were awarded two Stalin Prizes (later renamed to The USSR State Prize) for these developments. | 0 | Organic Chemistry |
Ethyltolune describes organic compounds with the formula . Three isomers exist: 1,2- 1,3-, and 1,4-. All are colorless liquids, immiscible in water, with similar boiling points. They are classified are aromatic hydrocarbons. The ring bears two substituents: a methyl group and an ethyl group. | 0 | Organic Chemistry |
Static light scattering measures the product of weight-averaged molar mass and concentration of macromolecules in solution. Given a fixed total concentration of one or more species over the measurement time, the scattering signal is a direct measure of the weight-averaged molar mass of the solution, which will vary as complexes form or dissociate.
Hence the measurement quantifies the stoichiometry of the complexes as well as kinetics. Light scattering assays of protein kinetics is a very general technique that does not require an enzyme. | 1 | Biochemistry |
TEs are mutagens and due to the contribution to the formation of new cis-regulatory DNA elements that are connected to many transcription factors that are found in living cells; TEs can undergo many evolutionary mutations and alterations. These are often the causes of genetic disease, and gives the potential lethal effects of ectopic expression.
TEs can damage the genome of their host cell in different ways:
* A transposon or a retrotransposon that inserts itself into a functional gene can disable that gene.
* After a DNA transposon leaves a gene, the resulting gap may not be repaired correctly.
* Multiple copies of the same sequence, such as Alu sequences, can hinder precise chromosomal pairing during mitosis and meiosis, resulting in unequal crossovers, one of the main reasons for chromosome duplication.
TEs use a number of different mechanisms to cause genetic instability and disease in their host genomes.
* Expression of disease-causing, damaging proteins that inhibit normal cellular function.
** Many TEs contain promoters which drive transcription of their own transposase. These promoters can cause aberrant expression of linked genes, causing disease or mutant phenotypes. | 1 | Biochemistry |
Plants respond and adapt to environmental factors, such as light and mechanical stress from wind. Leaves need to support their own mass and align themselves in such a way as to optimize their exposure to the sun, generally more or less horizontally. However, horizontal alignment maximizes exposure to bending forces and failure from stresses such as wind, snow, hail, falling debris, animals, and abrasion from surrounding foliage and plant structures. Overall leaves are relatively flimsy with regard to other plant structures such as stems, branches and roots.
Both leaf blade and petiole structure influence the leaf's response to forces such as wind, allowing a degree of repositioning to minimize drag and damage, as opposed to resistance. Leaf movement like this may also increase turbulence of the air close to the surface of the leaf, which thins the boundary layer of air immediately adjacent to the surface, increasing the capacity for gas and heat exchange, as well as photosynthesis. Strong wind forces may result in diminished leaf number and surface area, which while reducing drag, involves a trade off of also reducing photosynthesis. Thus, leaf design may involve compromise between carbon gain, thermoregulation and water loss on the one hand, and the cost of sustaining both static and dynamic loads. In vascular plants, perpendicular forces are spread over a larger area and are relatively flexible in both bending and torsion, enabling elastic deforming without damage.
Many leaves rely on hydrostatic support arranged around a skeleton of vascular tissue for their strength, which depends on maintaining leaf water status. Both the mechanics and architecture of the leaf reflect the need for transportation and support. Read and Stokes (2006) consider two basic models, the "hydrostatic" and "I-beam leaf" form (see Fig 1). Hydrostatic leaves such as in Prostanthera lasianthos are large and thin, and may involve the need for multiple leaves rather single large leaves because of the amount of veins needed to support the periphery of large leaves. But large leaf size favors efficiency in photosynthesis and water conservation, involving further trade offs. On the other hand, I-beam leaves such as Banksia marginata involve specialized structures to stiffen them. These I-beams are formed from bundle sheath extensions of sclerenchyma meeting stiffened sub-epidermal layers. This shifts the balance from reliance on hydrostatic pressure to structural support, an obvious advantage where water is relatively scarce.
Long narrow leaves bend more easily than ovate leaf blades of the same area. Monocots typically have such linear leaves that maximize surface area while minimising self-shading. In these a high proportion of longitudinal main veins provide additional support. | 5 | Photochemistry |
Transcriptomics has been characterised by the development of new techniques which have redefined what is possible every decade or so and rendered previous technologies obsolete. The first attempt at capturing a partial human transcriptome was published in 1991 and reported 609 mRNA sequences from the human brain. In 2008, two human transcriptomes, composed of millions of transcript-derived sequences covering 16,000 genes, were published, and by 2015 transcriptomes had been published for hundreds of individuals. Transcriptomes of different disease states, tissues, or even single cells are now routinely generated. This explosion in transcriptomics has been driven by the rapid development of new technologies with improved sensitivity and economy. | 1 | Biochemistry |
Alfred G. Gilman and Martin Rodbell received the 1994 Nobel Prize in Medicine and Physiology for the discovery of the G Protein System. | 1 | Biochemistry |
The antenna complex is composed of molecules of chlorophyll and carotenoids mounted on two proteins. These pigment molecules transmit the resonance energy from photons when they become photoexcited. Antenna molecules can absorb all wavelengths of light within the visible spectrum. The number of these pigment molecules varies from organism to organism. For instance, the cyanobacterium Synechococcus elongatus (Thermosynechococcus elongatus) has about 100 chlorophylls and 20 carotenoids, whereas spinach chloroplasts have around 200 chlorophylls and 50 carotenoids. Located within the antenna complex of PSI are molecules of chlorophyll called P700 reaction centers. The energy passed around by antenna molecules is directed to the reaction center. There may be as many as 120 or as few as 25 chlorophyll molecules per P700. | 5 | Photochemistry |
After the successful operation of the BBOC at BRM, MIM Holdings Limited (“MIM”) decided to license the technology to other smelter and refinery operators. Early adopters included Hindustan Zinc Limited, which by 1995 had two 1 t BBOC plants operating in India, and ASARCO Inc., which was operating a 3 t BBOC furnace at its Omaha, Nebraska, refinery. | 8 | Metallurgy |
When a synonymous or silent mutation occurs, the change is often assumed to be neutral, meaning that it does not affect the fitness of the individual carrying the new gene to survive and reproduce.
Synonymous changes may not be neutral because certain codons are translated more efficiently (faster and/or more accurately) than others. For example, when a handful of synonymous changes in the fruit fly alcohol dehydrogenase gene were introduced, changing several codons to sub-optimal synonyms, production of the encoded enzyme was reduced and the adult flies showed lower ethanol tolerance.
Many organisms, from bacteria through animals, display biased use of certain synonymous codons. Such codon usage bias may arise for different reasons, some selective, and some neutral. In Saccharomyces cerevisiae synonymous codon usage has been shown to influence mRNA folding stability, with mRNA encoding different protein secondary structure preferring different codons.
Another reason why synonymous changes are not always neutral is the fact that exon sequences close to exon-intron borders function as RNA splicing signals. When the splicing signal is destroyed by a synonymous mutation, the exon does not appear in the final protein. This results in a truncated protein. One study found that about a quarter of synonymous variations affecting exon 12 of the cystic fibrosis transmembrane conductance regulator gene result in that exon being skipped. | 1 | Biochemistry |
PKR (encoded in humans by the gene EIF2AK2) activation is mainly dependent on the presence of double-stranded RNA during a viral infection. dsRNA causes PKR to form dimers, resulting in autophosphorylation and activation. Once activated, PKR will phosphorylate eIF2α which causes a cascade of events that result in viral and host protein synthesis being inhibited. Other stressors that cause the activation of PKR include oxidative stress, endoplasmic reticulum stress, growth factor deprivation and bacterial infection. Caspase activity early on in apoptosis has also been observed to trigger activation of PKR. However, these stressors differ in that they activate PKR without using dsRNA. | 1 | Biochemistry |
A point C on the screw axis satisfies the equation:
Solve this equation for C using Cayley's formula for a rotation matrix
where [B] is the skew-symmetric matrix constructed from Rodrigues' vector
such that
Use this form of the rotation A to obtain
which becomes
This equation can be solved for C on the screw axis P(t) to obtain,
The screw axis of this spatial displacement has the Plücker coordinates . | 3 | Analytical Chemistry |
A particularly interesting property of many catenanes is the ability of the rings to rotate with respect to one another. This motion can often be detected and measured by NMR spectroscopy, among other methods. When molecular recognition motifs exist in the finished catenane (usually those that were used to synthesize the catenane), the catenane can have one or more thermodynamically preferred positions of the rings with respect to each other (recognition sites). In the case where one recognition site is a switchable moiety, a mechanical molecular switch results. When a catenane is synthesized by coordination of the macrocycles around a metal ion, then removal and re-insertion of the metal ion can switch the free motion of the rings on and off.
If there are more than one recognition sites it is possible to observe different colors depending on the recognition site the ring occupies and thus it is possible to change the color of the catenane solution by changing the preferred recognition site. Switching between the two sites may be achieved by the use of chemical, electrochemical or even visible light based methods.
Catenanes have been synthesized incorporating many functional units, including redox-active groups (e.g. viologen, TTF=tetrathiafulvalene), photoisomerizable groups (e.g. azobenzene), fluorescent groups and chiral groups. Some such units have been used to create molecular switches as described above, as well as for the fabrication of molecular electronic devices and molecular sensors. | 6 | Supramolecular Chemistry |
Millesimal fineness is a system of denoting the purity of platinum, gold and silver alloys by parts per thousand of pure metal by mass in the alloy. For example, an alloy containing 75% gold is denoted as "750". Many European countries use decimal hallmark stamps (i.e., "585", "750", etc.) rather than "14 k", "18 k", etc., which is used in the United Kingdom and United States.
It is an extension of the older karat system of denoting the purity of gold by fractions of 24, such as "18 karat" for an alloy with 75% (18 parts per 24) pure gold by mass.
The millesimal fineness is usually rounded to a three figure number, particularly where used as a hallmark, and the fineness may vary slightly from the traditional versions of purity.
Here are the most common millesimal finenesses used for precious metals and the most common terms associated with them. | 8 | Metallurgy |
RNF123 was found to be an interacting protein of FAM227B through Affinity Capture – MS. RAB3A was found to be an interacting protein of FAM227B through tandem affinity purification. | 1 | Biochemistry |
The hyperbolic response between photosynthesis and irradiance, depicted by the PI curve, is important for assessing phytoplankton population dynamics, which influence many aspects of the marine environment. | 5 | Photochemistry |
As describes, the vertices of the Laves graph can be defined by selecting one out of every eight points in the three-dimensional integer lattice, and forming their nearest neighbor graph. Specifically, one chooses the points
and all the other points formed by adding multiples of four to these coordinates. The edges of the Laves graph connect pairs of points whose Euclidean distance from each other is the square root of two, , as the points of each pair differ by one unit in two coordinates, and are the same in the third coordinate. The edges meet at 120° angles at each vertex, in a flat plane. All pairs of vertices that are non-adjacent are farther apart, at a distance of at least from each other. The edges of the resulting geometric graph are diagonals of a subset of the faces of the regular skew polyhedron with six square faces per vertex, so the Laves graph is embedded in this skew polyhedron.
It is possible to choose a larger set of one out of every four points of the integer lattice, so that the graph of distance- pairs of this larger set forms two mirror-image copies of the Laves graph, disconnected from each other, with all other pairs of points farther than apart. | 3 | Analytical Chemistry |
Cocaine is a monoamine transporter blocker and, thus, an indirect agonist of dopamine receptors. Cocaine binds the dopamine transporter (DAT), blocking the protein's ability to uptake dopamine from the synaptic cleft and also blocking DAT from terminating dopamine signaling. Blockage of DAT increases the extracellular concentration of dopamine, therefore increasing the amount of dopamine receptor binding and signaling.
Dipyridamole inhibits reuptake of adenosine, resulting in greater extracellular concentrations of adenosine. Dipyridamole also inhibits the enzyme adenosine deaminase, the enzyme that catalyzes the breakdown of adenosine. | 1 | Biochemistry |
BSi dissolution is controlled by:
* Thermodynamics of solubility: Temperature (0 to 25 °C - 50x increase).
* Sinking rate: Food web structure—grazers, fecal pellets, discarded feeding structures, Aggregation - rapid transport.
* Bacterial degradation of organic matrix (Bidle and Azam, 1999). | 1 | Biochemistry |
SELDI technology was developed by T. William Hutchens and Tai-Tung Yip at Baylor College of Medicine in 1993. Hutchens and Yip attached single-stranded DNA to agarose beads and used the beads to capture lactoferrin, an iron-binding glycoprotein, from preterm infant urine. The beads were incubated in the sample and then removed, washed, and analyzed with a MALDI-MS probe tip. This research led to the idea that MALDI surfaces could be derivatized with SEAC devices; the technique was later described by Hutchens and Yip in 1998.
SELDI technology was first commercialized by Ciphergen Biosystems in 1997 as the ProteinChip system, and is now produced and marketed by Bio-Rad Laboratories. | 1 | Biochemistry |
Another application for duplex sequencing is in the detection of DNA/RNA copy numbers by estimating the relative frequency of variants. A method for counting PCR template molecules with application to next-generation sequencing is an example. | 1 | Biochemistry |
A variety of reasons for a Phase I study to be performed exist, the most common being:
* Purchase of real property by a person or entity not previously on title.
* Contemplation by a new lender to provide a loan on the subject real estate.
* Partnership buyout or principal redistribution of ownership.
* Application to a public agency for change of use or other discretionary land use permit.
* Existing property owner's desire to understand toxic history of the property.
* Compulsion by a regulatory agency who suspects toxic conditions on the site.
* Divestiture of properties. | 2 | Environmental Chemistry |
Isotopic labeling (or isotopic labelling) is a technique used to track the passage of an isotope (an atom with a detectable variation in neutron count) through chemical reaction, metabolic pathway, or a biological cell. The reactant is labeled by replacing one or more specific atoms with their isotopes. The reactant is then allowed to undergo the reaction. The position of the isotopes in the products is measured to determine the sequence the isotopic atom followed in the reaction or the cell's metabolic pathway. The nuclides used in isotopic labeling may be stable nuclides or radionuclides. In the latter case, the labeling is called radiolabeling.
In isotopic labeling, there are multiple ways to detect the presence of labeling isotopes; through their mass, vibrational mode, or radioactive decay. Mass spectrometry detects the difference in an isotopes mass, while infrared spectroscopy detects the difference in the isotopes vibrational modes. Nuclear magnetic resonance detects atoms with different gyromagnetic ratios. The radioactive decay can be detected through an ionization chamber or autoradiographs of gels.
An example of the use of isotopic labeling is the study of phenol (CHOH) in water by replacing common hydrogen (protium) with deuterium (deuterium labeling). Upon adding phenol to deuterated water (water containing DO in addition to the usual HO), the substitution of deuterium for the hydrogen is observed in phenol's hydroxyl group (resulting in CHOD), indicating that phenol readily undergoes hydrogen-exchange reactions with water. Only the hydroxyl group is affected, indicating that the other 5 hydrogen atoms do not participate in the exchange reactions. | 7 | Physical Chemistry |
Thymidine diphosphate glucose (often abbreviated dTDP-glucose or TDP-glucose) is a nucleotide-linked sugar consisting of deoxythymidine diphosphate linked to glucose. It is the starting compound for the syntheses of many deoxysugars. | 1 | Biochemistry |
Recently, functional experiments have revealed many novel functional roles of RNA modifications. Most of the RNA modifications are found on transfer-RNA and ribosomal-RNA, but also eukaryotic mRNA has been shown to be modified with multiple different modifications. 17 naturally occurring modifications on mRNA have been identified, from which the N6-methyladenosine is the most abundant and studied. mRNA modifications are linked to many functions in the cell. They ensure the correct maturation and function of the mRNA, but also at the same time act as part of cells immune system. Certain modifications like 2’O-methylated nucleotides has been associated with cells ability to distinguish own mRNA from foreign RNA. For example, mA has been predicted to affect protein translation and localization, mRNA stability, alternative polyA choice and stem cell pluripotency. Pseudouridylation of nonsense codons suppresses translation termination both in vitro and in vivo', suggesting that RNA modification may provide a new way to expand the genetic code. 5-methylcytosine on the other hand has been associated with mRNA transport from the nucleus to the cytoplasm and enhancement of translation. These functions of mC are not fully known and proven but one strong argument towards these functions in the cell is the observed localization of mC to translation initiation site. Importantly, many modification enzymes are dysregulated and genetically mutated in many disease types. For example, genetic mutations in pseudouridine synthases cause mitochondrial myopathy, sideroblastic anemia (MLASA) and dyskeratosis congenital.
Compared to the modifications identified from other RNA species like tRNA and rRNA, the amount of identified modifications on mRNA is very small. One of the biggest reasons why mRNA modifications are not so well known is missing research techniques. In addition to the lack of identified modifications, the knowledge of associated proteins is also behind other RNA species. Modifications are results of specific enzyme interactions with the RNA molecule. Considering mRNA modifications most of the known related enzymes are the writer enzymes that add the modification on the mRNA. The additional groups of enzymes readers and erasers are for most of the modifications either poorly known of not known at all. For these reasons there has been during the past decade huge interest in studying these modifications and their function. | 1 | Biochemistry |
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