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Plastoquinone (PQ) is a terpenoid-quinone (meroterpenoid) molecule involved in the electron transport chain in the light-dependent reactions of photosynthesis. The most common form of plastoquinone, known as PQ-A or PQ-9, is a 2,3-dimethyl-1,4-benzoquinone molecule with a side chain of nine isoprenyl units. There are other forms of plastoquinone, such as ones with shorter side chains like PQ-3 (which has 3 isoprenyl side units instead of 9) as well as analogs such as PQ-B, PQ-C, and PQ-D, which differ in their side chains. The benzoquinone and isoprenyl units are both nonpolar, anchoring the molecule within the inner section of a lipid bilayer, where the hydrophobic tails are usually found.
Plastoquinones are very structurally similar to ubiquinone, or coenzyme Q10, differing by the length of the isoprenyl side chain, replacement of the methoxy groups with methyl groups, and removal of the methyl group in the 2 position on the quinone. Like ubiquinone, it can come in several oxidation states: plastoquinone, plastosemiquinone (unstable), and plastoquinol, which differs from plastoquinone by having two hydroxyl groups instead of two carbonyl groups.
Plastoquinol, the reduced form, also functions as an antioxidant by reducing reactive oxygen species, some produced from the photosynthetic reactions, that could harm the cell membrane. One example of how it does this is by reacting with superoxides to form hydrogen peroxide and plastosemiquinone.
The prefix plasto- means either plastid or chloroplast, alluding to its location within the cell. | 5 | Photochemistry |
In crystallography, a lattice plane of a given Bravais lattice is any plane containing at least three noncollinear Bravais lattice points. Equivalently, a lattice plane is a plane whose intersections with the lattice (or any crystalline structure of that lattice) are periodic (i.e. are described by 2d Bravais lattices). A family of lattice planes is a collection of equally spaced parallel lattice planes that, taken together, intersect all lattice points. Every family of lattice planes can be described by a set of integer Miller indices that have no common divisors (i.e. are relative prime). Conversely, every set of Miller indices without common divisors defines a family of lattice planes. If, on the other hand, the Miller indices are not relative prime, the family of planes defined by them is not a family of lattice planes, because not every plane of the family then intersects lattice points.
Conversely, planes that are not lattice planes have aperiodic intersections with the lattice called quasicrystals; this is known as a "cut-and-project" construction of a quasicrystal (and is typically also generalized to higher dimensions). | 3 | Analytical Chemistry |
With her expertise on peptide synthesis, Photaki examined the biocatalytic properties and kinetics of enzyme active site analogues she prepared.
Another research topic she developed in the early part of her career was the chemical transformation of carbohydrates and glycosylated species, such as the stereoselective conversion of -glucosamine to -serinaldehyde which formed the basis of her doctoral thesis.
Finally, she examined some of the coordination complexes formed by histidine-containing peptides with , , and , and after the antitumour properties of platinum complexes were realised, she also worked on the peptide enzymatic reactions in the presence of amine complexes. | 0 | Organic Chemistry |
Chlorosome shape can vary between species, with some species containing ellipsoidal shaped chlorosomes and others containing conical or irregular shaped chlorosomes.
Inside green sulfur bacteria, the chlorosomes are attached to type-I reaction centers in the cell membrane via FMO-proteins and a chlorosome baseplate composed of CsmA proteins. Filamentous anoxygenic phototrophs of the phylum Chloroflexota lack the FMO complex, but instead use a protein complex called B808-866. Unlike the FMO proteins in green sulfur bacteria, B808-866 proteins are embedded in the cytoplasmic membrane and surround type-II reaction centers, providing the link between the reaction centers and the baseplate.
The composition of the chlorosomes is mostly bacteriochlorophyll (BChl) with small amounts of carotenoids and quinones surrounded by a galactolipid monolayer. In Chlorobi, chlorosome monolayers can contain up to eleven different proteins. The proteins of Chlorobi are the ones currently best understood in terms of structure and function. These proteins are named CsmA through CsmF, CsmH through CsmK, and CsmX. Other Csm proteins with different letter suffixes can be found in Chloroflexota and Ca. "Chloracidobacterium".
Within the chlorosome, the thousands of BChl pigment molecules have the ability to self assemble with each other, meaning they do not interact with protein scaffolding complexes for assembly. These pigments self assemble in lamellar structures about 10-30 nm wide. | 5 | Photochemistry |
Some reports have suggested that the extrinsic Fas pathway is sufficient to induce complete apoptosis in certain cell types through DISC assembly and subsequent caspase-8 activation. These cells are dubbed Type 1 cells and are characterized by the inability of anti-apoptotic members of the Bcl-2 family (namely Bcl-2 and Bcl-xL) to protect from Fas-mediated apoptosis. Characterized Type 1 cells include H9, CH1, SKW6.4 and SW480, all of which are lymphocyte lineages except the latter, which is a colon adenocarcinoma lineage. However, evidence for crosstalk between the extrinsic and intrinsic pathways exists in the Fas signal cascade.
In most cell types, caspase-8 catalyzes the cleavage of the pro-apoptotic BH3-only protein Bid into its truncated form, tBid. BH-3 only members of the Bcl-2 family exclusively engage anti-apoptotic members of the family (Bcl-2, Bcl-xL), allowing Bak and Bax to translocate to the outer mitochondrial membrane, thus permeabilizing it and facilitating release of pro-apoptotic proteins such as cytochrome c and Smac/DIABLO, an antagonist of inhibitors of apoptosis proteins (IAPs). | 1 | Biochemistry |
An easy way to produce fermented water is to obtain turbo yeast kits (contains Saccharomyces cerevisiae yeast strain, enzymes, vitamins, and minerals) that instructs on the package the quantity of white sugar, and tap water needed.
* Inverted sugar syrup
** Water
** Sugars in wine: White sugar (or crystallized sucrose) is cheap and common. Also, partial refined sugar like brown sugar should be avoided, for example molasses produces a distinct flavor in rum. Using plain sugar is beneficial over whole fruit; Methanol is a major occurrence in fruit spirits.
* Yeast in winemaking: The most common yeast associated with winemaking is Saccharomyces cerevisiae. Saccharomyces cerevisiae is excellent at producing ethanol. Yeast are dependent on a few nutrients (often included in yeast kit sanchets) to produce as much ethanol as possible, the most important ones are:
** Invertase is an enzyme that cleaves the glycosidic linkage between the glucose and fructose molecules in sucrose. This helps the yeast metabolize the sugars faster.
** Thiamine: Increases the resistance of the yeast Saccharomyces cerevisiae against oxidative, osmotic and thermal stress.
** Yeast assimilable nitrogen (YAN), is the combination of free amino nitrogen (FAN), ammonia (NH) and ammonium (NH) that is available for the wine yeast Saccharomyces cerevisiae to use during fermentation. Outside the sugars in wine, nitrogen is the most important nutrient needed to carry out a successful fermentation that doesn't end prior to the intended point of dryness or sees the development of off-odors and related wine faults. | 1 | Biochemistry |
:For a synthetic analogue see also 3,5-Difluoro-4-hydroxybenzylidene imidazolinone.
Mechanistically, the process involves base-mediated cyclization followed by dehydration and oxidation. In the reaction of 7a to 8 involves the formation of an enamine from the imine, while in the reaction of 7b to 9 a proton is abstracted. The formed HBI fluorophore is highlighted in green.
The reactions are catalyzed by residues Glu222 and Arg96. An analogous mechanism is also possible with threonine in place of Ser65. | 1 | Biochemistry |
In mirror writing a text is deliberately displayed as its mirror image, in order to be read through a mirror. For example, emergency vehicles such as ambulances or fire engines use mirror images in order to be read from a vehicle's rear-view mirror. Some movie theaters also use mirror writing in a Rear Window Captioning System used to assist individuals with hearing impairments in watching films. | 4 | Stereochemistry |
Polycrystalline silicon, or multicrystalline silicon (multi-Si) cells are made from cast square ingots—large blocks of molten silicon carefully cooled and solidified. They consist of small crystals giving the material its typical metal flake effect. Polysilicon cells are the most common type used in photovoltaics and are less expensive, but also less efficient, than those made from monocrystalline silicon. | 7 | Physical Chemistry |
To study charge transfer reactions of an ITIES, a four-electrode cell is used.
Two reference electrodes are used to control the polarisation of the interface, and two counter electrodes made of noble metals are used to pass the current. The aqueous supporting electrolyte must be hydrophilic, such as LiCl, and the organic electrolyte must be lipophilic, such as tetraheptylammonium tetra-pentafluorophenyl borate. | 7 | Physical Chemistry |
The Tsuji–Wilkinson decarbonylation proceeds under mild conditions and is highly stereospecific. In addition to aliphatic, aromatic, and α,β-unsaturated aldehydes, acyl nitriles and 1,2-diketones are also suitable substrates. Few methods exist for decarbonylation.
One illustrative application is the synthesis of the core nucleus of FR-900482. Note that the ester is unaffected by the rhodium reagent.
The Tsuji–Wilkinson decarbonylation is employed in the penultimate step of the synthesis of (–)-presilphiperfolan-8-ol. They comment “Of note in these final steps, separate reduction and oxidation steps proceeded in inferior yield in generating 38 (70% versus 93%), while the Rh(PPh)Cl operation proceeded smoothly when conducted on small scale (~15 mg). In total, the synthesis required 13 steps from commercial starting material, and ~15 mg of [(–)-presilphiperfolan-8-ol] has been prepared with spectral properties and optical rotations matching that of the natural isolate.” | 0 | Organic Chemistry |
The hydroformylation of alkenes to give aldehydes is an important industrial process. Almost 6 million tons of aldehydes are produced by this method annually.
Rhodium complexes containing diphosphine ligands are active hydroformylation catalysts.
The ratio of linear to branched aldehyde product depends on the structure of the catalyst.
One intermediate, [Rh(H)(alkene)(CO)L], exists in two different isomers, depending on the position of phosphine ligands (Figure 4).
Diphosphine ligands such as dppe, which has a bite angle of about 90°, span the equatorial and apical positions (AE isomer). Diphosphines with larger bite angles (above 120°) preferentially occupy a pair of equatorial positions (EE isomer). It is believed that the EE isomer favors formation of linear aldehydes, the desired product. In an effort to create rhodium complexes in which the phosphine ligands preferentially occupy the equatorial positions, the use of diphosphine ligands with wide bite angles such as BISBI (Figure 5) has been investigated.
With a bite angle of approximately 113°, BISBI spans sites on equatorial plane of the trigonal bipyramidal intermediate complex (Figure 6).
The structure of the intermediate [Rh(H)(diphosphine)(CO)] does not however determine the regioselectivity of the hydroformylation. Instead, the formation of the linear vs. branched aldehydes is determined upon formation of [Rh(H)(diphosphine)CO(alkene)] and the subsequent hydride migration step. The bite angle affect the steric crowding at the Rh atom that results from the interactions of the bulky backbone of the ligand with substrate. The wide bite angle that results from the backbone allows the five-coordinate [Rh(H)(diphosphine)CO(alkene)] intermediate to adopt a structure that relieves steric hindrance. Thus, BISBI occupies the equatorial positions, where it has the most space. This preference of a transition state that relieves steric hindrance favors the formation of the linear aldehyde. The regioselectivity is also controlled by the hydride migration, which is usually irreversible in the formation of linear aldehydes.
Furthermore, studies using Xantphos ligands (ligands with bulky backbones) in hydroformylation have indicated an increase in the rate of catalysis in metal complexes that contain diphosphine ligands with larger bite angles. The electronic effect of this increase in reaction rate is uncertain since it mainly depends on the bonding between the alkene and rhodium. Large bite angles promote alkene to rhodium electron donation, which results in an accumulation of electron density on the rhodium atom. This increased electron density would be available for π-donation into the anti-bonding orbitals of other ligands, which could weaken other M-L bonds within the catalyst, leading to higher rates.
The application of diphosphine ligands to catalysts is not limited to the process of hydroformylation. Hydrocyanation and hydrogenation reactions also implement phosphine-mediated catalysts. | 0 | Organic Chemistry |
Methane was typically measured using gas chromatography. Gas chromatography is a type of chromatography used for separating or analyzing chemical compounds. It is less expensive in general, compared to more advanced methods, but it is more time and labor-intensive.
Spectroscopic methods were the preferred method for atmospheric gas measurements due to its sensitivity and precision. Also, spectroscopic methods are the only way of remotely sensing the atmospheric gases. Infrared spectroscopy covers a large spectrum of techniques, one of which detects gases based on absorption spectroscopy. There are various methods for spectroscopic methods, including Differential optical absorption spectroscopy, Laser-induced fluorescence, and Fourier Transform Infrared.
In 2011, cavity ring-down spectroscopy was the most widely used IR absorption technique of detecting methane. It is a form of laser absorption spectroscopy which determines the mole fraction to the order of parts per trillion. | 2 | Environmental Chemistry |
Very high densities are required to thermalize the rotational transitions of HO, so it is difficult to detect far-infrared emission lines from a quiescent molecular cloud. Even at H densities of 10 cm, dust must be optically thick at infrared wavelengths. But the passage of a shock wave through a molecular cloud is precisely the process which can bring the molecular gas out of equilibrium with the dust, making observations of far-infrared emission lines possible. A moderately fast shock may produce a transient raise in the HO abundance relative to hydrogen. So, it is possible that far-infrared emission lines of HO can be a good diagnostic of shock conditions. | 2 | Environmental Chemistry |
The most basic mechanistic flow for RNA Silencing is as follows:
(For a more detailed explanation of the mechanism, refer to the RNAi:Cellular mechanism article.)
1: RNA with inverted repeats hairpin/panhandle constructs --> 2: dsRNA --> 3: miRNAs/siRNAs --> 4: RISC --> 5: Destruction of target mRNA
# It has been discovered that the best precursor to good RNA silencing is to have single stranded antisense RNA with inverted repeats which, in turn, build small hairpin RNA and panhandle constructs. The hairpin or panhandle constructs exist so that the RNA can remain independent and not anneal with other RNA strands.
# These small hairpin RNAs and/or panhandles then get transported from the nucleus to the cytosol through the nuclear export receptor called exportin-5, and then get transformed into a dsRNA, a double stranded RNA, which, like DNA, is a double stranded series of nucleotides. If the mechanism didn't use dsRNAs, but only single strands, there would be a higher chance for it to hybridize to other "good" mRNAs. As a double strand, it can be kept on call for when it is needed.
# The dsRNA then gets cut up by a Dicer into small (21-28 nt = nucleotides long) strands of miRNAs (microRNAs) or siRNAs (short interfering RNAs.) A Dicer is an endoribonuclease RNase, which is a complex of a protein mixed with strand(s) of RNA.
# Lastly, the double stranded miRNAs/siRNAs separate into single strands; the antisense RNA strand of the two will combine with another endoribonuclease enzyme complex called RISC (RNA-induced silencing complex), which includes the catalytic component Argonaute, and will guide the RISC to break up the "perfectly complementary" target mRNA or viral genomic RNA so that it can be destroyed.
# It means that based on a short sequence specific area, a corresponding mRNA will be cut. To make sure, it will be cut in many other places as well. (If the mechanism only worked with a long stretch, then there would be higher chance that it would not have time to match to its complementary long mRNA.) It has also been shown that the repeated-associated short interference RNAs (rasiRNA) have a role in guiding chromatin modification.
For an animated explanation of the mechanism of RNAi by Nature Reviews, see the External Links section below. | 1 | Biochemistry |
Paz-Pujalt was born August 9, 1954, in Arequipa, Peru. He is of Galician and Welsh descent on his fathers side and Catalan and Basque on his mothers. He graduated from San Andrés (Colegio), an Anglo Peruvian college preparatory school in Lima, Peru. He graduated with honors and received the Miller Prize for accomplishments in English. Paz-Pujalt did his undergraduate work at the University of Wisconsin-Eau Claire and completed his Ph.D. in physical chemistry at the University of Wisconsin–Milwaukee. His doctoral adviser was George Keulks. He was also mentored by the distinguished professor W. Keith Hall. During this time he studied surface science under Gert Ertl, winner of the Nobel Prize in Chemistry. Additionally, Paz-Pujalt has received numerous executive level diplomas from MIT and Wharton. | 7 | Physical Chemistry |
Serotonin syndrome may result from the combined use of dextromethorphan and serotonergic antidepressants such as selective serotonin reuptake inhibitor (SSRIs) or monoamine oxidase inhibitor (MAOIs). Further research is needed to determine whether doses of dextromethorphan beyond those normally used therapeutically are needed to produce this effect. In any case, dextromethorphan should not be taken with MAOIs due to the possibility of this complication. Serotonin syndrome is a potentially life-threatening condition that can occur rapidly, due to a buildup of an excessive amount of serotonin in the body.
Patients who are taking dextromethorphan should exercise caution when drinking grapefruit juice or eating grapefruit, as compounds in grapefruit affect a number of drugs, including dextromethorphan, through the inhibition of the cytochrome P450 system in the liver, and can lead to excessive accumulation of the drug which both increases and prolongs effects. Grapefruit and grapefruit juices (especially white grapefruit juice, but also including other citrus fruits such as bergamot and lime, as well as a number of noncitrus fruits) generally are recommended to be avoided while using dextromethorphan and numerous other medications. | 4 | Stereochemistry |
FK1012 is a dimer consisting of two molecules of tacrolimus (FK506) linked via their vinyl groups. It is used as a research tool in chemically induced dimerization applications. FK1012 is a chemical inducer of dimerization (CID) which makes the protein capable of dimerization or oligomerization of fusion proteins containing one or more FKBP12 domains. It is used in pharmacology to act as a mediator in the formation of FK506 dimer. FK506 binding proteins (FKBPs) do not normally form dimers but can be caused to dimerize in the presence of FK1012. Genetically engineered proteins based on FKBPs can be used to manipulate protein localization, signaling pathways and protein activation. | 1 | Biochemistry |
When the incident particle, such as an alpha particle or electron, is diffracted in the Coulomb potential of atoms and molecules, the elastic scattering process is called Rutherford scattering. In many electron diffraction techniques like reflection high energy electron diffraction (RHEED), transmission electron diffraction (TED), and gas electron diffraction (GED), where the incident electrons have sufficiently high energy (>10 keV), the elastic electron scattering becomes the main component of the scattering process and the scattering intensity is expressed as a function of the momentum transfer defined as the difference between the momentum vector of the incident electron and that of the scattered electron. | 7 | Physical Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2021 impact factor of 4.755. | 7 | Physical Chemistry |
In the A/B approach to cobyric acid, the Harvard A-D-component was coupled to the ETH B-C-component between rings D and C, and then closed to a corrin between rings A and B. Both these critical steps were accomplished by C,C-coupling via sulfide contraction, a new reaction type developed in the synthesis of the B-C-component at ETH. The A-D-component was synthesized at Harvard from a ring-A precursor (prepared from achiral starting materials), and a ring-D precursor prepared from (−)-camphor. A model A-D-component was used to explore the coupling conditions; this component differed from the A-D-component used in the final synthesis by having as the functional group at the ring-D f-side chain a methyl ester group (like all other side chains) instead of a nitrile group. | 0 | Organic Chemistry |
There is tenuous evidence that a virus common to peppers, the Pepper Mild Mottle Virus (PMMoV) may have moved on to infect humans. This is a rare and unlikely event as, to enter a cell and replicate, a virus must "bind to a receptor on its surface, and a plant virus would be highly unlikely to recognize a receptor on a human cell. One possibility is that the virus does not infect human cells directly. Instead, the naked viral RNA may alter the function of the cells through a mechanism similar to RNA interference, in which the presence of certain RNA sequences can turn genes on and off," according to Virologist Robert Garry. | 1 | Biochemistry |
A microchannel plate (MCP) is used to detect single particles (electrons, ions and neutrons) and photons (ultraviolet radiation and X-rays). It is closely related to an electron multiplier, as both intensify single particles or photons by the multiplication of electrons via secondary emission. Because a microchannel plate detector has many separate channels, it can provide spatial resolution. | 7 | Physical Chemistry |
Conventional cytogenetic testing cannot offer the gene-level resolution required to predict the outcome of a pregnancy and whole genome deep sequencing is not practical for routine prenatal diagnosis. Whole-genome jumping library could complement conventional prenatal testing. This novel method was successfully applied to identify a case of CHARGE syndrome. | 1 | Biochemistry |
In aluminium alloys containing magnesium, magnesium oxides (MgO), cuboids (MgAlO-cuboid) and metallurgical spinel (MgAlO-spinel) can form. They result from the reaction between magnesium and oxygen in the melt. More of them will form with time and temperature.
Spinel can be highly detrimental because of its big size and high hardness. | 8 | Metallurgy |
Deep-sea hydrothermal vents, emitting hot acidic or alkaline water, would have created external proton gradients. These provided energy that primordial organisms could have exploited. To keep the flows separate, such an organism could have wedged itself in the rock of the hydrothermal vent, exposed to the hydrothermal flow on one side and the more alkaline water on the other. As long as the organism's membrane (or passive ion channels within it) is permeable to protons, the mechanism can function without ion pumps. Such a proto-organism could then have evolved further mechanisms such as ion pumps and ATP synthase. | 1 | Biochemistry |
Rats that were given a diet containing ptaquiloside for a prolonged period developed tumors in both the ileum and urinary bladder. Prakash, Smith and co-workers showed that ptaquiloside-induced carcinogenesis was initiated by the activation of the H-ras oncogene. Other non-ruminants such as pig, rabbit, and guinea pig, also develop syndromes after ingestion of ptaquiloside, which include haematuria, tumors and organ abnormities (see the diagram). | 0 | Organic Chemistry |
In some cases, the FEN1 lasts for only a short period of time and disengages from the replication complex. This causes a delay in the cleavage that the flaps displaced by Pol δ become long. When the RPA reaches a long enough length, it can bind stably. When the RPA bound flaps are refactorized to FEN1 cleavage the require another nuclease for processing, this has been identified as an alternate nuclease, DNA2. DNA2 has defects in the DEN1 overexpression. The DNA2 showed to work with FEN1 to process long flaps. DNA2 can dissociate the RPA from a long flap, it does this by using a mechanism like the FEN1. It binds the flap and threads the 5’ end of the flap. The nuclease cleaves the flap making it too short to bind to the RPA, the flap being too short means it is available for FEN1 and ligation. This is known as the long flap method. DNA2 can act as FEN1 as a backup for nuclease activity but it is not an efficient process. | 1 | Biochemistry |
AB chromosome translocation analyses place on short arm of chromosome 4 (4S; Simcox and Weber 1985 ). There is close linkage to other genes in the benzoxazinoid synthesis pathway [bx2, bx3, bx4, bx5 Frey et al. 1995, 1997 ). Gene bx1 is 2490 bp from bx2 (Frey et al. 1997 ); between umc123 and agrc94 on 4S (Melanson et al. 1997 ). Mapping probes: SSR p-umc1022 (Sharopova et al. 2002 ); Overgo (physical map probe) PCO06449 (Gardiner et al. 2004 ). | 1 | Biochemistry |
Flower visitors such as insects and bats detect floral scents thanks to chemoreceptors of variable specificity to a specific VOC. The fixation of a VOC on a chemoreceptor triggers the activation of an antennal glomerulus, further projecting on an olfactory receptor neuron and finally triggering a behavioral response after processing the information (see also Olfaction, Insect olfaction). The simultaneous perception of various VOCs may cause the activation of several glomeruli, but the output signal may not be additive due to synergistic or antagonistic mechanisms linked with inter-neuronal activity. Therefore, the perception of a VOC within a floral blend may trigger a different behavioral response than when perceived isolated. Similarly, the output signal is not proportional to the amount of VOCs, with some VOCs in low amounts in the floral blend having major effects on pollinator behavior. A good characterization of floral scent, both qualitative and quantitative, is necessary to understand and potentially predict flower visitors' behavior.
Flower visitors use floral scents to detect, recognize and locate their host species and even discriminate among flowers of the same plant. This is made possible by the high specificity of floral scent, where both diversity of VOCs and their relative amount may characterize the flowering species, an individual plant, a flower of the plant, and the distance of the plume from the source.
To make the best use of this specific information, flower visitors rely on long-term and short-term memory that allows them to efficiently choose their flowers. They learn to associate the floral scent of a plant with a reward such as nectar and pollen, and have different behavioral responses to known scents versus unknown ones. They are also able to react similarly to slightly different odor blends. | 1 | Biochemistry |
The unscaled elasticities can be depicted in matrix form, called the unscaled elasticity matrix, . Given a network with molecular species and reactions, the unscaled elasticity matrix is defined as:
Likewise, is it also possible to define the matrix of scaled elasticities: | 7 | Physical Chemistry |
When the adhesion is weaker than cohesion, which is quite common, the liquid particles escape the solution more easily that increases the vapor pressure and leads to a positive deviation.
If the deviation is large, then the vapor pressure curve shows a maximum at a particular composition and forms a positive azeotrope (low-boiling mixture). Some mixtures in which this happens are (1) ethanol and water, (2) benzene and methanol, (3) carbon disulfide and acetone, (4) chloroform and ethanol, and (5) glycine and water. When these pairs of components are mixed, the process is endothermic as weaker intermolecular interactions are formed so that ΔH is positive. | 7 | Physical Chemistry |
The MG-RAST pipeline incorporates a series of steps for quality control and artifacts removal, ensuring robust processing of metagenomic and metatranscriptome datasets. The initial stage involves trimming low-quality regions using SolexaQA and eliminating reads with inappropriate lengths. In the case of metagenome and metatranscriptome datasets, a dereplication step is introduced to enhance data processing efficiency.
The subsequent step employs DRISEE (Duplicate Read Inferred Sequencing Error Estimation) to evaluate sample sequencing errors by measuring Artificial Duplicate Reads (ADRs). This assessment contributes to enhancing the accuracy of downstream analyses.
Finally, the pipeline offers the option to screen reads using the Bowtie aligner. It identifies and removes reads that exhibit matches close to the genomes of model organisms, including fly, mouse, cow, and human. This step aids in refining the dataset by filtering out reads associated with potential contaminants or unintended sequences. | 1 | Biochemistry |
Coenzyme A is produced commercially via extraction from yeast, however this is an inefficient process (yields approximately 25 mg/kg) resulting in an expensive product. Various ways of producing CoA synthetically, or semi-synthetically have been investigated although none are currently operating at an industrial scale. | 1 | Biochemistry |
T. Ohta suggested that the concept of energy quality may be more intuitive if one considers examples where the form of energy remains constant but the amount of energy flowing, or transferred is varied. For instance if we consider only the inertial form of energy, then the energy quality of a moving body is higher when it moves with a greater velocity. If we consider only the heat form of energy, then a higher temperature has higher quality. And if we consider only the light form of energy then light with higher frequency has greater quality (Ohta 1994, p. 90). All these differences in energy quality are therefore easily measured with the appropriate scientific instrument. | 7 | Physical Chemistry |
Voltage gated ion channels respond to changes in the membrane potential. Voltage gated potassium, chloride and sodium channels are key components in the generation of the action potential as well as hyper-polarization. These channels work by selecting an ion based on electrostatic attraction or repulsion allowing the ion to bind to the channel. This releases the water molecule attached to the channel and the ion is passed through the pore. Voltage gated sodium channels open in response to a stimulus and close again. This means the channel either is open or not, there is no part way open. Sometimes the channel closes but is able to be reopened right away, known as channel gating, or it can be closed without being able to be reopened right away, known as channel inactivation.
At resting potential, both the voltage gated sodium and potassium channels are closed but as the cell membrane becomes depolarized the voltage gated sodium channels begin to open up and the neuron begins to depolarize, creating a current feedback loop known as the Hodgkin cycle. However, potassium ions naturally move out of the cell and if the original depolarization event was not significant enough then the neuron does not generate an action potential. If all the sodium channels are open, however, then the neuron becomes ten times more permeable to sodium than potassium, quickly depolarizing the cell to a peak of +40 mV. At this level the sodium channels begin to inactivate and voltage gated potassium channels begin to open. This combination of closed sodium channels and open potassium channels leads to the neuron re-polarizing and becoming negative again. The neuron continues to re-polarize until the cell reaches ~ –75 mV, which is the equilibrium potential of potassium ions. This is the point at which the neuron is hyperpolarized, between –70 mV and –75 mV. After hyperpolarization the potassium channels close and the natural permeability of the neuron to sodium and potassium allows the neuron to return to its resting potential of –70 mV. During the refractory period, which is after hyper-polarization but before the neuron has returned to its resting potential the neuron is capable of triggering an action potential due to the sodium channels ability to be opened, however, because the neuron is more negative it becomes more difficult to reach the action potential threshold.
HCN channels are activated by hyperpolarization.
Recent research has shown that neuronal refractory periods can exceed 20 milliseconds where the relation between hyperpolarization and the neuronal refractory was questioned. | 7 | Physical Chemistry |
Fluorobenzene is produced by thermal decomposition of benzenediazonium tetrafluoroborate. The conversion is called the Balz–Schiemann reaction.
The traditional Balz–Schiemann reaction has been the subject of many motivations, e.g. using hexafluorophosphate(V) () and hexafluoroantimonate(V) () in place of tetrafluoroborate (). The diazotization can be effected with nitrosonium salts such as nitrosonium hexafluoroantimonate(V) . | 0 | Organic Chemistry |
The second term on the right hand side of (3) is the structure factor.
For a given reciprocal lattice vector (corresponding to a family of lattice planes labeled by Miller indices ), the intensity of scattered particles is proportional to the square of the structure factor.
Buried in (6) are detailed aspects of the crystal structure that are worth distinguishing and discussing. | 7 | Physical Chemistry |
For example, consider the (linear) chemical system involving two chemical species and and the reaction . In this system, (species), (reactions). A state of the system is a vector , where are the number of molecules of and respectively. Let , so that the rate of reaction 1 (the only reaction) depends on the concentration of . The stoichiometry matrix is .
Then the master equation reads:
where is the shift caused by the action of the product of step operators, required to change state to a precursor state . | 7 | Physical Chemistry |
Various countries have tests for determining non-combustibility of materials. Most involve the heating of a specified quantity of the test specimen for a set duration. Usually, the material must not support combustion and must not lose more than a certain amount of mass. As a general rule of thumb, concrete, steel, and ceramics - in other words inorganic substances - pass these tests, so building codes list them as suitable and sometimes even mandate their use in certain applications. In Canada, for instance, firewalls must be made of concrete. | 7 | Physical Chemistry |
When there is enough matter in a region to allow molecular collisions to occur very much more often than absorption or emission of photons, for radiation one speaks of local thermodynamic equilibrium (LTE). In this case, Kirchhoff's law of equality of radiative absorptivity and emissivity holds.
Two bodies in radiative exchange equilibrium, each in its own local thermodynamic equilibrium, have the same temperature and their radiative exchange complies with the Stokes-Helmholtz reciprocity principle. | 7 | Physical Chemistry |
Veterans are presented with awards and are thanked for their service on formalities such as ceremonies which are plentiful and widely covered in the Iranian media, particularly on two annual national occasions, namely Disabled Veterans' Day in May and Sacred Defence Week (Sept. 20–27), which commemorates the commencement of the Iran–Iraq War.
According to the supreme leader of Iran, Ali Khamenei, "disabled war veterans are images of the war crimes of big powers who encouraged former Iraqi dictator Saddam Hussein to invade Iran." | 1 | Biochemistry |
Active esters are mainly used as acylating agents. They undergo the same reactions as their unactivated analogues but do so more rapidly. They are prone to hydrolysis, for example. Of great interest is the enhanced reactivity of active esters toward amines to give amides. | 0 | Organic Chemistry |
Inositol pentakisphosphate (abbreviated IP5) is a molecule derived from inositol tetrakisphosphate by adding a phosphate group with the help of Inositol-polyphosphate multikinase (IPMK). It is believed to be one of the many second messengers in the inositol phosphate family. It "is implicated in a wide array of biological and pathophysiological responses, including tumorigenesis, invasion and metastasis, therefore specific inhibitors of the kinase may prove useful in cancer therapy."
IP5 also plays a role in defense signaling in plants. It potentiates the interaction of the plant hormone JA-Ile by its receptor. | 1 | Biochemistry |
Each tablet contains 2, 4, or 8 mg of the tert-butylamine salt of perindopril. Perindopril is also available under the trade name Coversyl Plus, containing 4 mg of perindopril combined with 1.25 mg indapamide, a thiazide-like diuretic.
In Australia, each tablet contains 2.5, 5, or 10 mg of perindopril arginine. Perindopril is also available under the trade name Coversyl Plus, containing 5 mg of perindopril arginine combined with 1.25 mg indapamide and Coversyl Plus LD, containing 2.5 mg of perindopril arginine combined with 0.625 mg indapamide.
The efficacy and tolerability of a fixed-dose combination of 4 mg perindopril and 5 mg amlodipine, a calcium channel antagonist, has been confirmed in a prospective, observational multicenter trial of 1,250 hypertensive patients. A preparation of the two drugs is available commercially as Coveram. | 4 | Stereochemistry |
The idea of the creatine phosphate shuttle was suggested as an explanation for altered blood glucose levels in exercising diabetic patients. The change in blood glucose levels were very similar to the alterations that would occur if a diabetic patient would receive a shot of Insulin.It was then proposed that contraction of myofibrils during rigorous exercise freed creatine which imitated the effects of Insulin by consumption of ATP and releasing ADP. With the discovery of the mitochondrial isozyme of creatine kinase which participates in the shuttle, the other isozyme in the cytosol, Samuel Bessman further contributed to the creatine phosphate shuttle and proposed that the reversible properties of the creatine kinase enzyme was why exercise in diabetic patients can imitate the effects of Insulin. | 1 | Biochemistry |
Chemistry determines the optimum relationship between the fuel and the material, among other variables. The reverberatory furnace can be contrasted on the one hand with the blast furnace, in which fuel and material are mixed in a single chamber, and, on the other hand, with crucible, muffling, or retort furnaces, in which the subject material is isolated from the fuel and all of the products of combustion including gases and flying ash. There are, however, a great many furnace designs, and the terminology of metallurgy has not been very consistently defined, so it is difficult to categorically contradict other views.
The applications of these devices fall into two general categories, metallurgical melting furnaces, and lower temperature processing furnaces typically used for metallic ores and other minerals.
A reverberatory furnace is at a disadvantage from the standpoint of efficiency compared to a blast furnace due to the separation of the burning fuel and the subject material, and it is necessary to effectively utilize both reflected radiant heat and direct contact with the exhaust gases (convection) to maximize heat transfer. Historically these furnaces have used solid fuel, and bituminous coal has proven to be the best choice. The brightly visible flames, due to the substantial volatile component, give more radiant heat transfer than anthracite coal or charcoal.
Contact with the products of combustion, which may add undesirable elements to the subject material, is used to advantage in some processes. Control of the fuel/air balance can alter the exhaust gas chemistry toward either an oxidizing or a reducing mixture, and thus alter the chemistry of the material being processed. For example, cast iron can be puddled in an oxidizing atmosphere to convert it to the lower-carbon mild steel or bar iron. The Siemens-Martin oven in open hearth steelmaking is also a reverberatory furnace.
Reverberatory furnaces (in this context, usually called air furnaces) were formerly also used for melting brass, bronze, and pig iron for foundry work. They were also, for the first 75 years of the 20th century, the dominant smelting furnace used in copper production, treating either roasted calcine or raw copper sulfide concentrate. While they have been supplanted in this role, first by flash furnaces and more recently also by the Ausmelt and ISASMELT furnaces, they are very effective at producing slags with low copper losses. | 8 | Metallurgy |
The thermodynamic square is mostly used to compute the derivative of any thermodynamic potential of interest. Suppose for example one desires to compute the derivative of the internal energy . The following procedure should be considered:
# Place oneself in the thermodynamic potential of interest, namely (, , , ). In our example, that would be .
# The two opposite corners of the potential of interest represent the coefficients of the overall result. If the coefficient lies on the left hand side of the square, a negative sign should be added. In our example, an intermediate result would be .
# In the opposite corner of each coefficient, you will find the associated differential. In our example, the opposite corner to would be (volume) and the opposite corner for would be (entropy). In our example, an interim result would be: . Notice that the sign convention will affect only the coefficients, not the differentials.
# Finally, always add , where denotes the chemical potential. Therefore, we would have: .
The Gibbs–Duhem equation can be derived by using this technique. Notice though that the final addition of the differential of the chemical potential has to be generalized. | 7 | Physical Chemistry |
Deflocculation is the exact opposite of flocculation, also sometimes known as peptization. Sodium silicate (NaSiO) is a typical example. Usually in higher pH ranges in addition to low ionic strength of solutions and domination of monovalent metal cations the colloidal particles can be dispersed.
The additive that prevents the colloids from forming flocs is called a deflocculant. For deflocculation imparted through electrostatic barriers, the efficacy of a deflocculant can be gauged in terms of zeta potential. According to the Encyclopedic Dictionary of Polymers deflocculation is "a state or condition of a dispersion of a solid in a liquid in which each solid particle remains independent and unassociated with adjacent particles (much like emulsifier). A deflocculated suspension shows zero or very low yield value".
Deflocculation can be a problem in wastewater treatment plants as it commonly causes sludge settling problems and deterioration of the effluent quality. | 8 | Metallurgy |
London dispersion forces are the weakest type of non-covalent interaction. In organic molecules, however, the multitude of contacts can lead to larger contributions, particularly in the presence of heteroatoms. They are also known as "induced dipole-induced dipole interactions" and present between all molecules, even those which inherently do not have permanent dipoles. Dispersive interactions increase with the polarizability of interacting groups, but are weakened by solvents of increased polarizability. They are caused by the temporary repulsion of electrons away from the electrons of a neighboring molecule, leading to a partially positive dipole on one molecule and a partially negative dipole on another molecule. Hexane is a good example of a molecule with no polarity or highly electronegative atoms, yet is a liquid at room temperature due mainly to London dispersion forces. In this example, when one hexane molecule approaches another, a temporary, weak partially negative dipole on the incoming hexane can polarize the electron cloud of another, causing a partially positive dipole on that hexane molecule. In absence of solvents hydrocarbons such as hexane form crystals due to dispersive forces ; the sublimation heat of crystals is a measure of the dispersive interaction. While these interactions are short-lived and very weak, they can be responsible for why certain non-polar molecules are liquids at room temperature. | 6 | Supramolecular Chemistry |
Levosalbutamol's bronchodilator properties give it indications in treatment of COPD (chronic obstructive pulmonary disease, also known as chronic obstructive lung disease) and asthma. Like other bronchodilators, it acts by relaxing smooth muscle in the bronchial tubes, and thus shortening or reversing an acute "attack" of shortness of breath or difficulty breathing. Unlike some slower-acting bronchodilators, it is not indicated as a preventative of chronic bronchial constriction. | 4 | Stereochemistry |
The values of I, I, R, and R are dependent upon the physical size of the solar cell. In comparing otherwise identical cells, a cell with twice the junction area of another will, in principle, have double the I and I because it has twice the area where photocurrent is generated and across which diode current can flow. By the same argument, it will also have half the R of the series resistance related to vertical current flow; however, for large-area silicon solar cells, the scaling of the series resistance encountered by lateral current flow is not easily predictable since it will depend crucially on the grid design (it is not clear what "otherwise identical" means in this respect). Depending on the shunt type, the larger cell may also have half the R because it has twice the area where shunts may occur; on the other hand, if shunts occur mainly at the perimeter, then R will decrease according to the change in circumference, not area.
Since the changes in the currents are the dominating ones and are balancing each other, the open-circuit voltage is practically the same; V starts to depend on the cell size only if R becomes too low. To account for the dominance of the currents, the characteristic equation is frequently written in terms of current density, or current produced per unit cell area:
where
*J, current density (ampere/cm)
*J, photogenerated current density (ampere/cm)
*J, reverse saturation current density (ampere/cm)
*r, specific series resistance (Ω·cm)
*r, specific shunt resistance (Ω·cm).
This formulation has several advantages. One is that since cell characteristics are referenced to a common cross-sectional area they may be compared for cells of different physical dimensions. While this is of limited benefit in a manufacturing setting, where all cells tend to be the same size, it is useful in research and in comparing cells between manufacturers. Another advantage is that the density equation naturally scales the parameter values to similar orders of magnitude, which can make numerical extraction of them simpler and more accurate even with naive solution methods.
There are practical limitations of this formulation. For instance, certain parasitic effects grow in importance as cell sizes shrink and can affect the extracted parameter values. Recombination and contamination of the junction tend to be greatest at the perimeter of the cell, so very small cells may exhibit higher values of J or lower values of R than larger cells that are otherwise identical. In such cases, comparisons between cells must be made cautiously and with these effects in mind.
This approach should only be used for comparing solar cells with comparable layout. For instance, a comparison between primarily quadratical solar cells like typical crystalline silicon solar cells and narrow but long solar cells like typical thin film solar cells can lead to wrong assumptions caused by the different kinds of current paths and therefore the influence of, for instance, a distributed series resistance contribution to r. Macro-architecture of the solar cells could result in different surface areas being placed in any fixed volume - particularly for thin film solar cells and flexible solar cells which may allow for highly convoluted folded structures. If volume is the binding constraint, then efficiency density based on surface area may be of less relevance. | 7 | Physical Chemistry |
With the mass convergent evolution of the C-fixation pathway in a diversity of plant lineages, ancestral C-type RuBisCO evolved to have faster turnover of in exchange for lower specificity as a result of the greater localization of from the mesophyll cells into the bundle sheath cells. This was achieved through enhancement of conformational flexibility of the “open-closed” transition in the Calvin cycle. Laboratory-based phylogenetic studies have shown that this evolution was constrained by the trade-off between stability and activity brought about by the series of necessary mutations for C RuBisCO. Moreover, in order to sustain the destabilizing mutations, the evolution to C RuBisCO was preceded by a period in which mutations granted the enzyme increased stability, establishing a buffer to sustain and maintain the mutations required for C RuBisCO. To assist with this buffering process, the newly-evolved enzyme was found to have further developed a series of stabilizing mutations. While RuBisCO has always been accumulating new mutations, most of these mutations that have survived have not had significant effects on protein stability. The destabilizing C mutations on RuBisCO has been sustained by environmental pressures such as low concentrations, requiring a sacrifice of stability for new adaptive functions. | 5 | Photochemistry |
In electrochemistry, electrode potential is the voltage of a galvanic cell built from a standard reference electrode and another electrode to be characterized. By convention, the reference electrode is the standard hydrogen electrode (SHE). It is defined to have a potential of zero volts. It may also be defined as the potential difference between the charged metallic rods and salt solution.
The electrode potential has its origin in the potential difference developed at the interface between the electrode and the electrolyte. It is common, for instance, to speak of the electrode potential of the redox couple. | 7 | Physical Chemistry |
In 2004, Panek and his co-workers reported an approach which takes advantage of chiral crotylsilane-based C-C bond construction methodology to obtain the absolute stereochemistry of the three subunits of (+)-discodermolide. One of the key features of the Paterson approach is the utilization of hydrozirconation-cross-coupling methodology for the construction of C13-C14 (Z)-olefin. Acetate aldol reaction with high levels of 1,5-anti stereo induction and palladium-mediated sp2-sp3 cross coupling reaction are used to connect subunits. The Panek synthesis of (+)-discodermolide has an overall yield of 2.1% with a longest linear sequence of 27 steps and 42 total steps. | 0 | Organic Chemistry |
The Patterson power cell is an electrolysis device invented by chemist James A. Patterson, which he said created 200 times more energy than it used, and neutralizes radioactivity without emitting any harmful radiation. It is one of several cells that some observers classified as cold fusion; cells which were the subject of an intense scientific controversy in 1989, before being discredited in the eyes of mainstream science.
The Patterson power cell is given little credence by scientists. Physicist Robert L. Park describes the device as fringe science in his book Voodoo Science. | 7 | Physical Chemistry |
One model proposes that loss of the GTP-cap causes the GDP-containing protofilaments to shrink. Based on this GTP-cap model, catastrophe happens randomly. The model proposes that an increase in microtubule growth will correlate with a decrease in random catastrophe frequency or vice versa. The discovery of microtubule-associated proteins that change the rate of catastrophe while not impacting the rate of microtubule growth challenges this model of stochastic growth and shrinkage. | 1 | Biochemistry |
* Casting – molten metal is poured into a shaped mold. Variants of casting include sand casting, investment casting, also called the lost wax process, die casting, and continuous castings. Each of these forms has advantages for certain metals and applications considering factors like magnetism and corrosion.
* Forging – a red-hot billet is hammered into shape.
* Rolling – a billet is passed through successively narrower rollers to create a sheet.
* Extrusion – a hot and malleable metal is forced under pressure through a die, which shapes it before it cools.
* Machining – lathes, milling machines and drills cut the cold metal to shape.
* Sintering – a powdered metal is heated in a non-oxidizing environment after being compressed into a die.
* Fabrication – sheets of metal are cut with guillotines or gas cutters and bent and welded into structural shape.
* Laser cladding – metallic powder is blown through a movable laser beam (e.g. mounted on a NC 5-axis machine). The resulting melted metal reaches a substrate to form a melt pool. By moving the laser head, it is possible to stack the tracks and build up a three-dimensional piece.
* 3D printing – Sintering or melting amorphous powder metal in a 3D space to make any object to shape.
Cold-working processes, in which the product's shape is altered by rolling, fabrication or other processes, while the product is cold, can increase the strength of the product by a process called work hardening. Work hardening creates microscopic defects in the metal, which resist further changes of shape. | 8 | Metallurgy |
*Analysis of concentration
*Verifying the proper functioning of an analytical instrument or a sensor device such as an ion selective electrode
*Determining the basic effects of a control treatment (such as a dose-survival curve in clonogenic assay) | 1 | Biochemistry |
Kinetics for reductive elimination are hard to predict, but reactions that involve hydrides are particularly fast due to effects of orbital overlap in the transition state. | 0 | Organic Chemistry |
The types of gel most typically used are agarose and polyacrylamide gels. Each type of gel is well-suited to different types and sizes of the analyte. Polyacrylamide gels are usually used for proteins and have very high resolving power for small fragments of DNA (5-500 bp). Agarose gels, on the other hand, have lower resolving power for DNA but have a greater range of separation, and are therefore used for DNA fragments of usually 50–20,000 bp in size, but the resolution of over 6 Mb is possible with pulsed field gel electrophoresis (PFGE). Polyacrylamide gels are run in a vertical configuration while agarose gels are typically run horizontally in a submarine mode. They also differ in their casting methodology, as agarose sets thermally, while polyacrylamide forms in a chemical polymerization reaction. | 1 | Biochemistry |
Silicon-infiltrated carbon-carbon composite is used for high performance "ceramic" brake disks, as they are able to withstand extreme temperatures. The silicon reacts with the graphite in the carbon-carbon composite to become carbon-fiber-reinforced silicon carbide (C/SiC). These brake disks are used on some road-going sports cars, supercars, as well as other performance cars including the Porsche Carrera GT, the Bugatti Veyron, the Chevrolet Corvette ZR1, the McLaren P1, Bentley, Ferrari, Lamborghini and some specific high-performance Audi cars. Silicon carbide is also used in a sintered form for diesel particulate filters. It is also used as an oil additive to reduce friction, emissions, and harmonics. | 8 | Metallurgy |
Biodiesel production is the process of producing the biofuel, biodiesel, through the chemical reactions of transesterification and esterification. This process renders a product (chemistry) and by-products.
The fats and oils react with short-chain alcohols (typically methanol or ethanol). The alcohols used should be of low molecular weight. Ethanol is the most used because of its low cost, however, greater conversions into biodiesel can be reached using methanol. Although the transesterification reaction can be catalyzed by either acids or bases, the base-catalyzed reaction is more common. This path has lower reaction times and catalyst cost than those acid catalysis. However, alkaline catalysis has the disadvantage of high sensitivity to both water and free fatty acids present in the oils. | 0 | Organic Chemistry |
Not all atoms attract electrons with the same force. The amount of "pull" an atom exerts on its electrons is called its electronegativity. Atoms with high electronegativitiessuch as fluorine, oxygen, and nitrogenexert a greater pull on electrons than atoms with lower electronegativities such as alkali metals and alkaline earth metals. In a bond, this leads to unequal sharing of electrons between the atoms, as electrons will be drawn closer to the atom with the higher electronegativity.
Because electrons have a negative charge, the unequal sharing of electrons within a bond leads to the formation of an electric dipole: a separation of positive and negative electric charge. Because the amount of charge separated in such dipoles is usually smaller than a fundamental charge, they are called partial charges, denoted as δ+ (delta plus) and δ− (delta minus). These symbols were introduced by Sir Christopher Ingold and Edith Hilda (Usherwood) Ingold in 1926. The bond dipole moment is calculated by multiplying the amount of charge separated and the distance between the charges.
These dipoles within molecules can interact with dipoles in other molecules, creating dipole-dipole intermolecular forces. | 7 | Physical Chemistry |
Metabolic water refers to water created inside a living organism through metabolism, by oxidizing energy-containing substances in food and adipose tissue. Animal metabolism produces about 107–110 grams of water per 100 grams of fat, 41–42 grams of water per 100 g of protein, and 60 grams of water per 100 g of carbohydrate.
Some organisms, especially xerocoles — animals living in the desert — rely exclusively on metabolic water. Migratory birds must rely exclusively on metabolic water production while making non-stop flights, facilitated by the high metabolic rate during such flights. Humans, by contrast, obtain only about 8–10% of their water needs through metabolic water production.
In mammals, the water produced from metabolism of protein roughly equals the amount needed to excrete the urea which is a byproduct of the metabolism of protein. Birds, however, excrete uric acid and can have a net gain of water from the metabolism of protein. | 1 | Biochemistry |
Fineness of silver in Britain was traditionally expressed as the mass of silver expressed in troy ounces and pennyweights ( troy ounce) in one troy pound (12 troy ounces) of the resulting alloy. Britannia silver has a fineness of 11 ounces, 10 pennyweights, or about silver, whereas sterling silver has a fineness of 11 ounces, 2 pennyweights, or exactly silver. | 8 | Metallurgy |
Phosphorylation involves the transfer of phosphate groups from ATP to the enzyme, the energy for which comes from hydrolysing ATP into ADP or AMP. However, dephosphorylation releases phosphates into solution as free ions, because attaching them back to ATP would require energy input.
Cysteine-dependent phosphatases (CDPs) catalyse the hydrolysis of a phosphoester bond via a phospho-cysteine intermediate.
The free cysteine nucleophile forms a bond with the phosphorus atom of the phosphate moiety, and the P-O bond linking the phosphate group to the tyrosine is protonated, either by a suitably positioned acidic amino acid residue (Asp in the diagram below) or a water molecule. The phospho-cysteine intermediate is then hydrolysed by another water molecule, thus regenerating the active site for another dephosphorylation reaction.
Metallo-phosphatases (e.g. PP2C) co-ordinate 2 catalytically essential metal ions within their active site. There is currently some confusion of the identity of these metal ions, as successive attempts to identify them yield different answers. There is currently evidence that these metals could be Magnesium, Manganese, Iron, Zinc, or any combination thereof. It is thought that a hydroxyl ion bridging the two metal ions takes part in nucleophilic attack on the phosphorus ion. | 1 | Biochemistry |
In 2005, Dauphas was awarded Nier Prize of the Meteoritical Society which recognizes outstanding research in meteoritics and closely allied fields by young scientists. In 2007, he was awarded the David and Lucile Packard Foundation Fellowship, given to the most promising early-career scientists and engineers, across the US. He won the 2008 Houtermans Award, given by the European Association of Geochemistry for outstanding contributions to geochemistry. He was awarded the James B. Macelwane Medal of the American Geophysical Union (AGU) for "significant contributions to the geophysical sciences", and was selected as an AGU Fellow in 2011. In 2014, he became a Fellow of the Meteoritical Society. He was one of the finalists in 2017 for the Blavatnik National Awards.
In 2016, Dauphas received a named professorship from the University of Chicago as the Louis Block professor, Physical Sciences Division. In 2019, Dauphas was elected Geochemical Fellow of the Geochemical Society and the European Association of Geochemistry in recognition of his career contribution to the field of geochemistry. | 9 | Geochemistry |
A biaxial nematic is a spatially homogeneous liquid crystal with three distinct optical axes. This is to be contrasted to a simple nematic, which has a single preferred axis, around which the system is rotationally symmetric. The symmetry group of a biaxial nematic is i.e. that of a rectangular right parallelepiped, having 3 orthogonal axes and three orthogonal mirror planes. In a frame co-aligned with optical axes the second rank order parameter tensor of a biaxial nematic has the form
where is the standard nematic scalar order parameter and is a measure of the biaxiality.
The first report of a thermotropic biaxial nematic appeared in 2004 based on a boomerang shaped oxadiazole bent-core mesogen. The biaxial nematic phase for this particular compound only occurs at temperatures around 200 °C and is preceded by as yet unidentified smectic phases.
It is also found that this material can segregate into chiral domains of opposite handedness. For this to happen the boomerang shaped molecules adopt a helical superstructure.
In one azo bent-core mesogen a thermal transition is found from a uniaxial N to a biaxial nematic N mesophase, as predicted by theory and simulation. This transition is observed on heating from the N phase with Polarizing optical microscopy as a change in Schlieren texture and increased light transmittance and from x-ray diffraction as the splitting of the nematic reflection. The transition is a second order transition with low energy content and therefore not observed in differential scanning calorimetry. The positional order parameter for the uniaxial nematic phase is 0.75 to 1.5 times the mesogen length and for the biaxial nematic phase 2 to 3.3 times the mesogen length.
Another strategy towards biaxial nematics is the use of mixtures of classical rodlike mesogens and disklike discotic mesogens. The biaxial nematic phase is expected to be located below the minimum in the rod-disk phase diagram. In one study a miscible system of rods and disks is actually found although the biaxial nematic phase remains elusive. | 7 | Physical Chemistry |
From 1995 Murray worked at the Thomas J. Watson Research Center at IBM. From 2000 to 2006 he headed their Nanoscale Materials and Devices Department. In 2006 the University of Pennsylvania announced his appointment as the Richard Perry University Professor, with appointments in Chemistry and Materials Science, in the schools of Arts and Sciences, and Engineering and Applied Science. | 7 | Physical Chemistry |
Adsorption constants are equilibrium constants, therefore they obey the Van 't Hoff equation:
As can be seen in the formula, the variation of K must be isosteric, that is, at constant coverage.
If we start from the BET isotherm and assume that the entropy change is the same for liquefaction and adsorption, we obtain
that is to say, adsorption is more exothermic than liquefaction. | 7 | Physical Chemistry |
At the active site, a substrate binds to an enzyme to induce a chemical reaction. Substrates, transition states, and products can bind to the active site, as well as any competitive inhibitors. For example, in the context of protein function, the binding of calcium to troponin in muscle cells can induce a conformational change in troponin. This allows for tropomyosin to expose the actin-myosin binding site to which the myosin head binds to form a cross-bridge and induce a muscle contraction.
In the context of the blood, an example of competitive binding is carbon monoxide which competes with oxygen for the active site on heme. Carbon monoxide's high affinity may outcompete oxygen in the presence of low oxygen concentration. In these circumstances, the binding of carbon monoxide induces a conformation change that discourages heme from binding to oxygen, resulting in carbon monoxide poisoning. | 1 | Biochemistry |
There were four named penicillins at the time penicillin V was discovered (penicillins I, II, III, IV), however, Penicillin V was named "V" for Vertraulich (German for confidential); it was not named for the Roman numeral "5".
Penicillin VK is the potassium salt of penicillin V (K is the chemical symbol for potassium). | 4 | Stereochemistry |
Esketamine, sold under the brand names Spravato (for depression) and Ketanest (for anesthesia) among others, is the S(+) enantiomer of ketamine. It is a dissociative hallucinogen drug used as a general anesthetic and as an antidepressant for treatment of depression. Esketamine is the active enantiomer of ketamine in terms of NMDA receptor antagonism and is more potent than racemic ketamine.
It is specifically used as a therapy for treatment-resistant depression (TRD) and for major depressive disorder (MDD) with co-occurring suicidal ideation or behavior. Its efficacy for depression is modest and similar to that of other antidepressants. Esketamine is not used by infusion into a vein for anesthesia as it is only FDA approved for depression in the form of an intranasal spray (the parent compound Ketamine is most often administered intravenously) and under direct medical supervision as a nasal spray.
Adverse effects of esketamine include dissociation, dizziness, sedation, nausea, vomiting, vertigo, numbness, anxiety, lethargy, increased blood pressure, and feelings of drunkenness. Less often, esketamine can cause bladder problems. Esketamine acts primarily as a N-methyl--aspartate (NMDA) receptor antagonist but also has other actions.
In the form of racemic ketamine, esketamine was first synthesized in 1962 and introduced for medical use as an anesthetic in 1970. Enantiopure esketamine was introduced for medical use as an anesthetic in 1997 and as an antidepressant in 2019. It is used as an anesthetic in the European Union and as an antidepressant in the United States and Canada. Due to misuse liability as a dissociative hallucinogen, esketamine is a controlled substance. | 4 | Stereochemistry |
For a process that occurs at constant temperature and pressure, spontaneity can be determined using the change in Gibbs free energy, which is given by:
where the sign of ΔG depends on the signs of the changes in enthalpy (ΔH) and entropy (ΔS). If these two signs are the same (both positive or both negative), then the sign of ΔG will change from positive to negative (or vice versa) at the temperature
In cases where ΔG is:
* negative, the process is spontaneous and may proceed in the forward direction as written.
* positive, the process is non-spontaneous as written, but it may proceed spontaneously in the reverse direction.
* zero, the process is at equilibrium, with no net change taking place over time.
This set of rules can be used to determine four distinct cases by examining the signs of the ΔS and ΔH.
* When ΔS > 0 and ΔH < 0, the process is always spontaneous as written.
* When ΔS < 0 and ΔH > 0, the process is never spontaneous, but the reverse process is always spontaneous.
* When ΔS > 0 and ΔH > 0, the process will be spontaneous at high temperatures and non-spontaneous at low temperatures.
* When ΔS < 0 and ΔH < 0, the process will be spontaneous at low temperatures and non-spontaneous at high temperatures.
For the latter two cases, the temperature at which the spontaneity changes will be determined by the relative magnitudes of ΔS and ΔH. | 7 | Physical Chemistry |
In the iron–carbon system (i.e. plain-carbon steels and cast irons) it is a common constituent because ferrite can contain at most 0.02wt% of uncombined carbon. Therefore, in carbon steels and cast irons that are slowly cooled, a portion of the carbon is in the form of cementite. Cementite forms directly from the melt in the case of white cast iron. In carbon steel, cementite precipitates from austenite as austenite transforms to ferrite on slow cooling, or from martensite during tempering. An intimate mixture with ferrite, the other product of austenite, forms a lamellar structure called pearlite.
While cementite is thermodynamically unstable, eventually being converted to austenite (low carbon level) and graphite (high carbon level) at higher temperatures, it does not decompose on heating at temperatures below the eutectoid temperature (723 °C) on the metastable iron-carbon phase diagram.
Mechanical properties are as follows: room temperature microhardness 760–1350 HV; bending strength 4.6–8 GPa, Young's modulus 160–180 GPa, indentation fracture toughness 1.5–2.7 MPa√m. | 8 | Metallurgy |
*. For conservative case, this reduces to .
*. For conservative case, this reduces to .
*If the characteristic function is , where are two constants(have to satisfy ) and if is the nth moment of the H function, then we have
and | 7 | Physical Chemistry |
Many of the noble metals can act as catalysts. For example, platinum is used in catalytic converters, devices which convert toxic gases produced in car engines, such as the oxides of nitrogen, into non-polluting substances.
Gold has many industrial applications; it is used as a catalyst in hydrogenation and the water gas shift reaction. | 8 | Metallurgy |
Subject to any regulations restricting who can obtain donor sperm, donor sperm is available to all people who, for whatever reason, wish to have a child. These regulations vary significantly across jurisdictions, and some countries do not have any regulations. When an individual finds that they are barred from receiving donor sperm within their jurisdiction, they may travel to another jurisdiction to obtain sperm. Regulations change from time to time. In most jurisdictions, donor sperm is available to an individual if their partner is infertile or where they have a genetic disorder. However, the categories of individuals who may obtain donor sperm is expanding, with its availability to single persons and to same-sex couples becoming more common, and some sperm banks supply fertility centers which specialize in the treatment of such people.
Frozen vials of donor sperm may be shipped by the sperm bank to a recipient's home for self-insemination, or they may be shipped to a fertility clinic or physician for use in fertility treatments. The sperm bank will rely on the recipient woman or medical practitioner to report the outcome of any use of the sperm to the sperm bank. This enables a sperm bank to adhere to any national limits of pregnancy numbers. The sperm bank may also impose its own worldwide limit on numbers.
Sperm is introduced into the recipient by means of artificial insemination or by IVF. The most common technique is conventional artificial insemination which consists of a catheter to put the sperm into the vagina where it is deposited at the entrance to the cervix. In biological terms, this is much the same process as when semen is ejaculated from the penis during sexual intercourse. Owing to its simplicity, this method of insemination is commonly used for home and self inseminations principally by single women and lesbians. Other types of uses include intrauterine insemination (IUI) and deep intrauterine artificial insemination where washed sperm must be used. These methods of insemination are most commonly used in fertility centers and clinics mainly because they produce better pregnancy rates than ICI insemination especially where the woman has no underlying fertility issues.
Men may also store their own sperm at a sperm bank for future use particularly where they anticipate traveling to a war zone or having to undergo chemotherapy which might damage the testes.
Sperm from a sperm donor may also be used in surrogacy arrangements and for creating embryos for embryo donation. Donor sperm may be supplied by the sperm bank directly to the recipient to enable a woman to perform her own artificial insemination which can be carried out using a needleless syringe or a cervical cap conception device. The cervical cap conception device allows the donor semen to be held in place close to the cervix for between six and eight hours to allow fertilization to take place. Alternatively, donor sperm can be supplied by a sperm bank through a registered medical practitioner who will perform an appropriate method of insemination or IVF treatment using the donor sperm in order for the woman to become pregnant. | 1 | Biochemistry |
Mehrotra, during his early years in research, made notable contributions in analytical chemistry which included studies on tin, gold and hydrated copper
oxide. Through his researches on the chemical theory of indicators, he elucidated the applicability of universal type of indicators, ceramic salts and of hypobromites and widened the understanding of alkoxides and carboxylates of many elements. His work covered the synthesis of several metallic compounds such as polymetaphosphates, alkoxides, beta-diketonates, carboxylates, thiolates and dialky 1 dithiophosphates. | 0 | Organic Chemistry |
POCIS can be deployed in a wide range of aquatic environments including stagnant pools, rivers, springs, estuarine systems, and wastewater streams. However, there has been little research into the use of POCIS in strictly marine environments. Prior to deployment of a POCIS device, it is essential to select a study site that will maximize the effectiveness of the sampler. Selecting an area that is shaded will help prevent light sensitive chemicals from being degrading. The site should also allow the sampler to be submerged in the water without being buried in the sediment. It is ideal to place the sampler in moving water in order to increase sampling rates, however, areas with an extremely turbulent water flow should be avoided as to prevent damage to the POCIS device. Passive samplers are very vulnerable to vandalism and it is therefore important to secure the sampler in areas that are not easily visible and that are away from areas frequently used by people.
POCIS samplers can be deployed for a period of time ranging from weeks to months. The shortest deployment lengths are typically 7 days but average 2–3 months. It is important to have a long enough deployment period to allow for adequate detection of contaminants at ambient environmental concentrations. Often, the two different types of POCIS devices will be deployed together in order to provide the greatest understanding of contamination. It is also important to deploy enough POCIS devices to ensure a large enough sample of contaminant is recovered for chemical analysis. An estimate or the number of samplers needed at a given site can be determined by the following equation.
::::R x t x n x C x P x E > MQL x V
::where
::*C is the predicted environmental concentration of the contaminant
::*t is the deployment time in days
::*R is sampling rate in liters of water extracted by the passive sampler per day(L/day)
::*P is the overall method recovery for the analyte (expressed as a factor of one; ::therefore 0.9 is used for 90 percent recovery),
::*n is the number of passive samplers combined into a single sample,
::*E is the fraction of the total sample extract which is injected into the ::instrument for quantification
::*MQL is the method quantification limit
::*V is the volume of standard injection (commonly 1 μL). | 3 | Analytical Chemistry |
The Hopp–Woods hydrophilicity scale of amino acids is a method of ranking the amino acids in a protein according to their water solubility in order to search for surface locations on proteins, and especially those locations that tend to form strong interactions with other macromolecules such as proteins, DNA, and RNA.
Given the amino acid sequence of any protein, likely interaction sites can be identified by taking the moving average of six amino acid hydrophilicity values along the polypeptide chain, and looking for local peaks in the data plot.
In subsequent papers after their initial publication of the method, Hopp and Woods demonstrated that the data plots, or hydrophilicity profiles, contained much information about protein folding, and that the hydrophobic valleys of the profiles corresponded to internal structures of proteins such as beta-strands and alpha-helices. Furthermore, long hydrophobic valleys were shown to correspond quite closely to the membrane-spanning helices identified by the later-published Kyte and Doolittle hydropathic plotting method. | 1 | Biochemistry |
Model organisms have been used in the study of TCF7L2 function. A conditional knockout mouse line called Tcf7l2 was generated at the Wellcome Trust Sanger Institute. Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion. Additional screens performed: - In-depth immunological phenotyping
Variations of the protein encoding gene are found in rats, zebra fish, drosophila, and budding yeast. Therefore, all of those organisms can be used as model organisms in the study of TCF7L2 function. | 1 | Biochemistry |
Sweat diagnostics is an emerging non-invasive technique used to provide insights to the health of the human body. Common sweat diagnostic tests include testing for cystic fibrosis and illicit drugs. Most testing of human sweat is in reference to the eccrine sweat gland which in contrast to the apocrine sweat gland, has a lower composition of oils.
Although sweat is mostly water, there are many solutes which are found in sweat that have at least some relation to biomarkers found in blood. These include: sodium (Na), chloride (Cl), potassium (K), ammonium (NH), alcohols, lactate, peptides & proteins. Development of devices, sensing techniques and biomarker identification in sweat continues to be an expanding field for medical diagnostics and athletics applications.
The use of smart biosensors for on-skin sweat analysis has been described as internet-enabled Sudorology (iSudorology) by Brasier et al. in 2019. It describes the lab-independent detection of molecular, next-generation digital biomarkers in sweat. | 1 | Biochemistry |
Mitogen-activated protein kinase (MAPK) pathways can induce enzymes such as the COX-2 enzyme. MAPK pathways may also play a role in the regulation of PTGS2. | 1 | Biochemistry |
An instance where hyperconjugation may be overlooked as a possible chemical explanation is in rationalizing the rotational barrier of ethane (CH). It had been accepted as early as the 1930s that the staggered conformations of ethane were more stable than the eclipsed conformation. Wilson had proven that the energy barrier between any pair of eclipsed and staggered conformations is approximately 3 kcal/mol, and the generally accepted rationale for this was the unfavorable steric interactions between hydrogen atoms.
In their 2001 paper, however, Pophristic and Goodman revealed that this explanation may be too simplistic. Goodman focused on three principal physical factors: hyperconjugative interactions, exchange repulsion defined by the Pauli exclusion principle, and electrostatic interactions (Coulomb interactions). By comparing a traditional ethane molecule and a hypothetical ethane molecule with all exchange repulsions removed, potential curves were prepared by plotting torsional angle versus energy for each molecule. The analysis of the curves determined that the staggered conformation had no connection to the amount of electrostatic repulsions within the molecule. These results demonstrate that Coulombic forces do not explain the favored staggered conformations, despite the fact that central bond stretching decreases electrostatic interactions.
Goodman also conducted studies to determine the contribution of vicinal (between two methyl groups) vs. geminal (between the atoms in a single methyl group) interactions to hyperconjugation. In separate experiments, the geminal and vicinal interactions were removed, and the most stable conformer for each interaction was deduced.
From these experiments, it can be concluded that hyperconjugative effects delocalize charge and stabilize the molecule. Further, it is the vicinal hyperconjugative effects that keep the molecule in the staggered conformation. Thanks to this work, the following model of the stabilization of the staggered conformation of ethane is now more accepted:
Hyperconjugation can also explain several other phenomena whose explanations may also not be as intuitive as that for the rotational barrier of ethane.
The matter of the rotational barrier of ethane is not settled within the scientific community. An analysis within quantitative molecular orbital theory shows that 2-orbital-4-electron (steric) repulsions are dominant over hyperconjugation. A valence bond theory study also emphasizes the importance of steric effects. | 7 | Physical Chemistry |
Arc is critical as a ubiquitous signaling factor in early embryonic development and is required for growth and patterning during gastrulation. The first knockouts (KOs) for Arc were therefore incompatible with life. Subsequent efforts produced homozygous knockout mice by targeting the entire Arc gene rather than portions of the coding region, eliminating dominant negative effects. These animals proved viable and exhibit no gross malformations in neuronal architecture, but express higher levels of the GluR1 subunit and increased miniature excitatory postsynaptic currents (mEPSCs) in addition to displaying deficiencies in long-term memory. | 1 | Biochemistry |
Benson and Buss originated the BGIT in a 1958 article. Within this manuscript, Benson and Buss proposed four approximations:
# A limiting law for additivity rules.
# Zero-order approximation. Additivity of atomic properties.
# First-order approximation. Additivity of bond properties.
# Second-order approximation. Additivity of group properties.
These approximations account for the atomic, bond, and group contributions to heat capacity (C), enthalpy (ΔH°), and entropy (ΔS°). The most important of these approximations to the group-increment theory is the second-order approximation, because this approximation "leads to the direct method of writing the properties of a compound as the sum of the properties of its group".
The second-order approximation accounts for two molecular atoms or structural elements that are within relative proximity to one another (approximately 3–5 ångstroms as proposed in the article). By using a series of disproportionation reactions of symmetrical and asymmetrical framework, Benson and Buss concluded that neighboring atoms within the disproportionation reaction under study are not affected by the change.
; Symmetrical
; Asymmetrical
In the symmetrical reaction the cleavage between the CH in both reactants leads to one product formation. that the neighboring carbons are not changed as the rearrangement occurs. In the asymmetrical reaction the hydroxyl–methyl bond is cleaved and rearranged on the ethyl moiety of the methoxyethane. The methoxy and hydroxyl rearrangement display clear evidence that the neighboring groups are not affected in the disproportionation reaction.
The "disproportionation" reactions that Benson and Buss refer to are termed loosely as "radical disproportionation" reactions. From this they termed a "group" as a polyvalent atom connected together with its ligands. However, they noted that under all approximations ringed systems and unsaturated centers do not follow additivity rules due to their preservation under disproportionation reactions. A ring must be broken at more than one site to actually undergo a disproportionation reaction. This holds true with double and triple bonds, as they must break multiple times to break their structure. They concluded that these atoms must be considered as distinct entities. Hence we see C and C groups, which take into account these groups as being individual entities. Furthermore, this leaves error for ring strain, as we will see in its limitations.
From this Benson and Buss concluded that the ΔH of any saturated hydrocarbon can be precisely calculated due to the only two groups being a methylene [C−(C)(H)] and the terminating methyl group [C−(C)(H)]. Benson later began to compile actual functional groups from the second-order approximation. Ansylyn and Dougherty explained in simple terms how the group increments, or Benson increments, are derived from experimental calculations. By calculating the ΔΔH between extended saturated alkyl chains (which is just the difference between two ΔH values), as shown in the table, one can approximate the value of the C−(C)(H) group by averaging the ΔΔH values. Once this is determined, all one needs to do is take the total value of ΔH, subtract the ΔH caused by the C−(C)(H) group(s), and then divide that number by two (due to two C−(C)(H) groups), obtaining the value of the C−(C)(H) group. From the knowledge of these two groups, Benson moved forward obtain and list functional groups derived from countless numbers of experimentation from many sources, some of which are displayed below. | 7 | Physical Chemistry |
Cells in all organisms regulate gene expression by turnover of gene transcripts (single stranded RNA): The amount of an expressed gene in a cell can be measured by the number of copies of an RNA transcript of that gene present in a sample. In order to robustly detect and quantify gene expression from small amounts of RNA, amplification of the gene transcript is necessary. The polymerase chain reaction (PCR) is a common method for amplifying DNA; for RNA-based PCR the RNA sample is first reverse-transcribed to complementary DNA (cDNA) with reverse transcriptase.
In order to amplify small amounts of DNA, the same methodology is used as in conventional PCR using a DNA template, at least one pair of specific primers, deoxyribonucleotide triphosphates, a suitable buffer solution and a thermo-stable DNA polymerase. A substance marked with a fluorophore is added to this mixture in a thermal cycler that contains sensors for measuring the fluorescence of the fluorophore after it has been excited at the required wavelength allowing the generation rate to be measured for one or more specific products.
This allows the rate of generation of the amplified product to be measured at each PCR cycle. The data thus generated can be analysed by computer software to calculate relative gene expression (or mRNA copy number) in several samples. Quantitative PCR can also be applied to the detection and quantification of DNA in samples to determine the presence and abundance of a particular DNA sequence in these samples. This measurement is made after each amplification cycle, and this is the reason why this method is called real time PCR (that is, immediate or simultaneous PCR).
Quantitative PCR and DNA microarray are modern methodologies for studying gene expression. Older methods were used to measure mRNA abundance: differential display, RNase protection assay and northern blot. Northern blotting is often used to estimate the expression level of a gene by visualizing the abundance of its mRNA transcript in a sample. In this method, purified RNA is separated by agarose gel electrophoresis, transferred to a solid matrix (such as a nylon membrane), and probed with a specific DNA or RNA probe that is complementary to the gene of interest. Although this technique is still used to assess gene expression, it requires relatively large amounts of RNA and provides only qualitative or semi quantitative information of mRNA levels. Estimation errors arising from variations in the quantification method can be the result of DNA integrity, enzyme efficiency and many other factors. For this reason a number of standardization systems (often called normalization methods) have been developed. Some have been developed for quantifying total gene expression, but the most common are aimed at quantifying the specific gene being studied in relation to another gene called a normalizing gene, which is selected for its almost constant level of expression. These genes are often selected from housekeeping genes as their functions related to basic cellular survival normally imply constitutive gene expression. This enables researchers to report a ratio for the expression of the genes of interest divided by the expression of the selected normalizer, thereby allowing comparison of the former without actually knowing its absolute level of expression.
The most commonly used normalizing genes are those that code for the following molecules: tubulin, glyceraldehyde-3-phosphate dehydrogenase, albumin, cyclophilin, and ribosomal RNAs. | 1 | Biochemistry |
The dynamic Wilhelmy method is a method for calculating average advancing and receding contact angles on solids of uniform geometry. Both sides of the solid must have the same properties. Wetting force on the solid is measured as the solid is immersed in or withdrawn from a liquid of known surface tension. Also in that case it is possible to measure the equilibrium contact angle by applying a very controlled vibration. That methodology, called VIECA, can be implemented in a quite simple way on every Wilhelmy balance. | 7 | Physical Chemistry |
Gold mining began in Gedebey in 2009. In 2016, Azer Gold CJSC began gold mining in the Chovdar deposit. In 2017, 6,390.8 kg of gold was mined (which exceeded the 2016 production by 3.4 times. Gold production in January–May 2018 amounted to 2,081.7 kg, which exceeds last years data by 19.5%. In the first quarter of 2018, the companys exports amounted to $30 million. In 2017, 59,617 ounces of gold produces by Anglo Asian Mining PLC (the main gold producer in Azerbaijan) from Gadir Ugur and Gosha deposits. | 8 | Metallurgy |
There are several implications of an excess of reducing equivalents: regulation of cellular signaling pathways by decreasing cell growth responses, modification of transcriptional activity, perturbs disulfide bond formation within proteins, increase of mitochondrial malfunction, decrease in cellular metabolism, and cytotoxicity. The over expression of antioxidant enzymatic systems promote the excess production of reducing equivalents resulting in the depletion of ROS and prompting RS in cells. Nuclear factor erythroid 2–related factor 2 (Nrf2) is an important transcription factor that regulates a multitude of genes that code for antioxidant response and after uncontrolled amplification of this signaling pathway RS increases. Although different organelles may each have a different redox status, through probing for factors such as glutathione and hydrogen peroxide (HO), it was determined that reductive stress is present in the endoplasmic reticulum (ER) of senescent cells. Reductive stress is significant in the aging process of a cell and when ER oxidation status is elevated, cellular aging is slowed. In particular, when reductive stress is increased, it may result in many downstream effects such as increased apoptosis, decreased cell survival, and mitochondrial dysfunction—all of which need to be properly regulated to ensure that the needs of the cell are met. Data shows, in an isolated mitochondria, when there is a high ratio of NADH/NAD+, an example of RS, ROS increases significantly in the mitochondrial matrix which results in H2O2 spillover from the mitochondria. Reductive stress has even been suggested to lead to higher probability of cardiomyopathy in humans. This has also been mysteriously linked to the abundant presence of heat shock protein 27 (Hsp27), suggesting that high levels of Hsp27 induce can induce cardiomyopathy. Reductive stress is present in many diseases with abnormalities such as the increase of reducing equivalents, resulting in issues such as hypoxia-induced oxidative stress. A more reductive redox environment promotes cancer metastasis and cancer cells use reductive stress to promote growth and resist anti-cancer agents, such as chemotherapy and radiotherapy. | 1 | Biochemistry |
A micelle () or micella () ( or micellae, respectively) is an aggregate (or supramolecular assembly) of surfactant amphipathic lipid molecules dispersed in a liquid, forming a colloidal suspension (also known as associated colloidal system). A typical micelle in water forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single-tail regions in the micelle centre.
This phase is caused by the packing behavior of single-tail lipids in a bilayer. The difficulty in filling the volume of the interior of a bilayer, while accommodating the area per head group forced on the molecule by the hydration of the lipid head group, leads to the formation of the micelle. This type of micelle is known as a normal-phase micelle (or oil-in-water micelle). Inverse micelles have the head groups at the centre with the tails extending out (or water-in-oil micelle).
Micelles are approximately spherical in shape. Other shapes, such as ellipsoids, cylinders, and bilayers, are also possible. The shape and size of a micelle are a function of the molecular geometry of its surfactant molecules and solution conditions such as surfactant concentration, temperature, pH, and ionic strength. The process of forming micelles is known as micellisation and forms part of the phase behaviour of many lipids according to their polymorphism. | 6 | Supramolecular Chemistry |
Transduction is the process by which foreign DNA is introduced into a cell by a virus or viral vector. An example is the viral transfer of DNA from one bacterium to another and hence an example of horizontal gene transfer. Transduction does not require physical contact between the cell donating the DNA and the cell receiving the DNA (which occurs in conjugation), and it is DNase resistant (transformation is susceptible to DNase). Transduction is a common tool used by molecular biologists to stably introduce a foreign gene into a host cell's genome (both bacterial and mammalian cells). | 1 | Biochemistry |
Glass fiber filter has the pore size of 1 μm, it is useful for filtering highly contaminated solutions or difficult-to-filter solution. Also, glass fiber filter has extends filter life, wide range of particulate loads and can prevent sample contamination. In addition, different types of glass fiber filter are suitable for different filtration situation. There are 7 different types of glass fiber filters and the major difference is thickness. | 3 | Analytical Chemistry |
Both the CB1 and CB2 receptors (the bonding site of anandamide) seem to play a role in the identification of positive and negative interpretation of environment and setting. In animal models, anandamide mediates the interpretation of stimulus; specifically, optimism and pessimism in the presence of an ambiguous cue. Anandamide has been shown to impair working memory in rats, while THC (the compound in cannabis that binds to the CB1 and CB2 receptors) also shows a deficit in working memory.
This binding relationship of anandamide and the CB1/CB2 may affect neurotransmission of dopamine, serotonin, GABA, and glutamate. There is currently encouraging, albeit embryonic, evidence for medicinal cannabis in the treatment of a range of psychiatric disorders. Supportive findings are emerging for some key isolates, however, clinicians need to be mindful of a range of prescriptive and occupational safety considerations, especially if initiating higher dose THC formulas.
Anandamide injected directly into the forebrain reward-related brain structure nucleus accumbens enhances the pleasurable responses of rats to a rewarding sucrose taste, and enhances food intake as well. Increasing anandamide seems to increase the intrinsic value of food, not necessarily by stimulation of appetite or hunger.
Anandamide may affect hunger, sleep, pain modulation, working memory, identification of novelty, and interpretation of environment. | 1 | Biochemistry |
Trimethylsulfoxonium iodide is a sulfoxonium salt. It is used to generate dimethyloxosulfonium methylide by reaction with sodium hydride. The latter compound is used as a methylene-transfer reagent, and is used to prepare epoxides.
This compound is commercially available. It may be prepared by the reaction of dimethyl sulfoxide and iodomethane:
: (CH)SO + CHI → (CH)SOI | 0 | Organic Chemistry |
Like many organolithium reagents, lithium bis(trimethylsilyl)amide can form aggregates in solution. The extent of aggregation depends on the solvent. In coordinating solvents, such as ethers and amines, the monomer and dimer are prevalent. In the monomeric and dimeric state, one or two solvent molecules bind to lithium centers. With ammonia as donor base lithium bis(trimethylsilyl)amide forms a trisolvated monomer that is stabilized by intermolecular hydrogen bonds. In noncoordinating solvents, such as aromatics or pentane, the complex oligomers predominate, including the trimer. In the solid state structure is trimeric. | 0 | Organic Chemistry |
Shortly after the teratogenic properties of thalidomide were recognized in the mid-1960s, its anti-cancer potential was explored and two clinical trials were conducted in people with advanced cancer, including some people with multiple myeloma; the trials were inconclusive.
Little further work was done with thalidomide in cancer until the 1990s.
Judah Folkman pioneered studies into the role of angiogenesis (the proliferation and growth of blood vessels) in the development of cancer, and in the early 1970s had shown that solid tumors could not expand without it. In 1993 he surprised the scientific world by hypothesizing the same was true of blood cancers, and the next year he published work showing that a biomarker of angiogenesis was higher in all people with cancer, but especially high in people with blood cancers, and other evidence emerged as well. Meanwhile, a member of his lab, Robert DAmato, who was looking for angiogenesis inhibitors, discovered in 1994 that thalidomide inhibited angiogenesis and was effective in suppressing tumor growth in rabbits. Around that time, the wife of a man who was dying of multiple myeloma and whom standard treatments had failed, called Folkman asking him about his anti-angiogenesis ideas. Folkman persuaded the patients doctor to try thalidomide, and that doctor conducted a clinical trial of thalidomide for people with multiple myeloma in which about a third of the subjects responded to the treatment. The results of that trial were published in the New England Journal of Medicine in 1999.
After further work was done by Celgene and others, in 2006 the US Food and Drug Administration granted accelerated approval for thalidomide in combination with dexamethasone for the treatment of newly diagnosed multiple myeloma patients.
It was also evaluated whether thalidomide can be combined with melphalan and prednisone for patients with multiple myeloma. This combination of drugs probably results in an increase of the overall survival. | 4 | Stereochemistry |
Commonly used protein production systems include those derived from bacteria, yeast, baculovirus/insect, mammalian cells, and more recently filamentous fungi such as Myceliophthora thermophila. When biopharmaceuticals are produced with one of these systems, process-related impurities termed host cell proteins also arrive in the final product in trace amounts. | 1 | Biochemistry |
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