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In particle physics, the quantum yield (denoted ) of a radiation-induced process is the number of times a specific event occurs per photon absorbed by the system. | 7 | Physical Chemistry |
Red HE-3B or Reactive Red 120 has a formula of CHClNOS and a molecular weight of 1338.1 g/mol, containing two monochlorotriazine rings. It is highly soluble in water. The dehydrogenases binding ability of Red HE-3B is greater to NADP+ dependent dehydrogenases than NAD+ dependent dehydrogenases, vice versa for Cibacron Blue F3G-A. It can be used to purify enterotoxins A, B, and C from Staphylococcus aureus using Procion Red HE-3B on sepharose, eluting out with 60 mM and 150 mM phosphate. | 3 | Analytical Chemistry |
Indigotindisulfonate sodium, sold under the brand name Bludigo, is used as a diagnostic dye during surgical procedures. It is indicated for use as a visualization aid in the cystoscopic assessment of the integrity of the ureters in adults following urological and gynecological open, robotic, or endoscopic surgical procedures. It was approved for medical use in the United States in July 2022.
In obstetric surgery, indigo carmine solutions are sometimes employed to detect amniotic fluid leaks. In urologic surgery, intravenous injection of indigo carmine is often used to highlight portions of the urinary tract. The dye is filtered rapidly by the kidneys from the blood, and colors the urine blue. This enables structures of the urinary tract to be seen in the surgical field, and demonstrate if there is a leak. However, the dye can cause a potentially dangerous increase in blood pressure in some cases.
Although not absorbed by the cells, indigo carmine stain, sprayed onto regions of interest, highlights the topography of the mucosal surface with its blue coloring. Generally used at a concentration around 0.2%, indigo carmine stain is useful as a screening method for diagnosing minute lesions, to differentiate between benign and malignant lesions, as well as to facilitate application of magnifying endoscopes to observe and analyze the surface structure of a lesion, delineate boundaries of early stage malignant lesions and estimate the invasion depth of cancer. It has been used to diagnose Barrett’s esophagus, evaluate villous atrophy, diagnose and discriminate polypoid and non-polypoid lesions in the colon, and diagnose gastric adenoma and cancer. | 3 | Analytical Chemistry |
Planetary scientists often classify volatiles with exceptionally low melting points, such as hydrogen and helium, as gases, whereas those volatiles with melting points above about 100 K (–173 °C, –280 °F) are referred to as ices. The terms "gas" and "ice" in this context can apply to compounds that may be solids, liquids or gases. Thus, Jupiter and Saturn are gas giants, and Uranus and Neptune are ice giants, even though the vast majority of the "gas" and "ice" in their interiors is a hot, highly dense fluid that gets denser as the center of the planet is approached. Inside of Jupiter's orbit, cometary activity is driven by the sublimation of water ice. Supervolatiles such as CO and CO have generated cometary activity as far out as . | 9 | Geochemistry |
To annotate the vast amounts of available NGS data, currently a large number of SNPs annotation tools are available. Some of them are specific to specific SNPs while others are more general. Some of the available SNPs annotation tools are as follows SNPeff, Ensembl Variant Effect Predictor (VEP), ANNOVAR, FATHMM, PhD-SNP, PolyPhen-2, SuSPect, F-SNP, AnnTools, SeattleSeq, SNPit, SCAN, Snap, SNPs&GO, LS-SNP, Snat, TREAT, TRAMS, Maviant, MutationTaster, SNPdat, Snpranker, NGS – SNP, SVA, VARIANT, SIFT, LIST-S2, PhD-SNP and FAST-SNP. The functions and approaches used in SNPs annotation tools are listed below. | 1 | Biochemistry |
A tree wrap or tree wrapping is a wrap of garden tree saplings, roses, and other delicate plants to protect them from frost damage (e.g. frost cracks or complete death). In the past it was made of straw (straw wrap) . Now there are commercial tree wrap materials, such as crepe paper or burlap tapes. Tree wrapping is also used to prevent saplings from sunscald and drying of the bark. A disadvantage of tape wrapping is dampness under the wrapping during rainy seasons. | 1 | Biochemistry |
With Lewis acid catalysts like ferric chloride or aluminium chloride, acyl chlorides participate in Friedel-Crafts acylations, to give aryl ketones:
Because of the harsh conditions and the reactivity of the intermediates, this otherwise quite useful reaction tends to be messy, as well as environmentally unfriendly. | 0 | Organic Chemistry |
A highly ordered π-conjugation TP-COF, consisting of pyrene and triphenylene functionalities alternately linked in a mesoporous hexagonal skeleton, is highly luminescent, harvests a wide wavelength range of photons, and allows energy transfer and migration. Furthermore, TP-COF is electrically conductive and capable of repetitive on–off current switching at room temperature. | 6 | Supramolecular Chemistry |
Rapid equilibration between enantiomeric conformers and irreversible hydrogenation place the reaction under Curtin–Hammett control. The use of a chiral catalyst results in a higher-energy and a lower-energy transition state for hydrogenation of the two enantiomers. The transformation occurs via the lower-energy transition state to form the product as a single enantiomer.
Consistent with the Curtin–Hammett principle, the ratio of products depends on the absolute energetic barrier of the irreversible step of the reaction, and does not reflect the equilibrium distribution of substrate conformers. The relative free energy profile of one example of the Noyori asymmetric hydrogenation is shown below: | 7 | Physical Chemistry |
Coupling MALS with an in-line concentration detector following a sample separation means like SEC permits the calculation of the molar mass of the eluting sample in addition to its root-mean-square radius. The figure below represents a chromatographic separation of BSA aggregates. The 90° light scattering signal from a MALS detector and the molar mass values for each elution slice are shown. | 7 | Physical Chemistry |
Development of AFA superalloys with a 35 wt.% Ni-base have shown potential for use in operating temperatures upwards to 1,100 °C. | 8 | Metallurgy |
The enzymes are encoded and used by viruses that use reverse transcription as a step in the process of replication. Reverse-transcribing RNA viruses, such as retroviruses, use the enzyme to reverse-transcribe their RNA genomes into DNA, which is then integrated into the host genome and replicated along with it. Reverse-transcribing DNA viruses, such as the hepadnaviruses, can allow RNA to serve as a template in assembling and making DNA strands. HIV infects humans with the use of this enzyme. Without reverse transcriptase, the viral genome would not be able to incorporate into the host cell, resulting in failure to replicate. | 1 | Biochemistry |
Sensor-based sorting, is an umbrella term for all applications in which particles are detected using a sensor technique and rejected by an amplified mechanical, hydraulic or pneumatic process.
The technique is generally applied in mining, recycling and food processing and used in the particle size range between . Since sensor-based sorting is a single particle separation technology, the throughput is proportional to the average particle size and weight fed onto the machine. | 3 | Analytical Chemistry |
It was established by the decree of Peter the Great to process the local copper deposits. The Polevskoy Plant was named after the local river Polevaya. The plant became the basis for the settlement which later grew into the town of Polevskoy.
The place for a new plant was chosen by Vasily Tatishchev. Georg Wilhelm de Gennin was in charge of the construction. The Plant became active in 1724. The copper was branded with the symbol of the Roman goddess Venus. The Venus symbol (♀), which represents copper as a chemical element, is now displayed in the Polevskoy town coat of arms.
In 1757 the Polevskoy Plant was purchased by the Ural merchant Alexei Turchaninov along with the Seversky Pipe Plant. Along with the Seversky and Sysertsky Plants, the Polevskoy Plant represented the Sysert Mining District. It was extremely profitable. Turchaninov's descendants managed the plant til 1912. For a long time the main ore supplier for the plant was the Gumyoshevsky mine, called "The Copper Mountain" by the local populace. However in the 19th century the Gumyoshevsky mine was exhausted. After it was shut down in 1870, the Polevskoy Copper Smelting Plant was reorganized to the iron plant. In this capacity the plant stayed active until 1923, but then shut down due to the lack of prospects. | 8 | Metallurgy |
In order to isolate noble-metalliferous materials, pyrolysis and/or hydrolysis procedures are used. In pyrolysis, the noble-metalliferous products are released from the other materials by solidifying in a melt to become cinder and then poured off or oxidized. In hydrolysis, the noble-metalliferous products are dissolved either in aqua regia (consisting of hydrochloric acid and nitric acid) or in hydrochloric acid and chlorine gas in solution. Subsequently, certain metals can be precipitated or reduced directly with a salt, gas, organic, and/or nitro hydrate connection. Afterwards, they go through cleaning stages or are recrystallized. The precious metals are separated from the metal salt by calcination. The noble-metalliferous materials are hydrolyzed first and thermally prepared (pyrolysed) thereafter. The processes are better yielding when using catalysts that may sometimes contain precious metals themselves. When using catalysts, the recycling product is removed in each case and driven several times through the cycle. | 8 | Metallurgy |
For over 30 years, several research groups actively pursued the total synthesis of dodecahedrane. A review article published in 1978 described the different strategies that existed up to then. The first attempt was initiated in 1964 by R.B. Woodward with the synthesis of the compound triquinacene which was thought to be able to simply dimerize to dodecahedrane. Other groups were also in the race, for example that of Philip Eaton and Paul von Ragué Schleyer.
Leo Paquette's group at Ohio State University was the first to succeed, by a complex 29-step route that mostly builds the dodecahedral skeleton one ring at a time, and finally closes the last hole.
In 1987, more versatile alternative synthesis route was found by the Horst Prinzbach's group. Their approach was based on the isomerization pagodane, obtained from isodrin (isomer of aldrin) as starting material i.a. through [6+6]photocycloaddition. Schleyer had followed a similar approach in his synthesis of adamantane.
Following that idea, joint efforts of the Prinzbach team and the Schleyer group succeeded but obtained only 8% yield for the conversion at best. In the following decade the group greatly optimized that route, so that dodecahedrane could be obtained in multi-gram quantities. The new route also made it easier to obtain derivatives with selected substitutions and unsaturated carbon-carbon bonds. Two significant developments were the discovery of σ-bishomoaromaticity and the formation of C fullerene from highly brominated dodecahedrane species. | 0 | Organic Chemistry |
A topologically associating domain (TAD) is a self-interacting genomic region, meaning that DNA sequences within a TAD physically interact with each other more frequently than with sequences outside the TAD. The median size of a TAD in mouse cells is 880 kb, and they have similar sizes in non-mammalian species. Boundaries at both side of these domains are conserved between different mammalian cell types and even across species and are highly enriched with CCCTC-binding factor (CTCF) and cohesin. In addition, some types of genes (such as transfer RNA genes and housekeeping genes) appear near TAD boundaries more often than would be expected by chance.
The functions of TADs are not fully understood and are still a matter of debate. Most of the studies indicate TADs regulate gene expression by limiting the enhancer-promoter interaction to each TAD; however, a recent study uncouples TAD organization and gene expression. Disruption of TAD boundaries are found to be associated with wide range of diseases such as cancer, variety of limb malformations such as synpolydactyly, Cooks syndrome, and F-syndrome, and number of brain disorders like Hypoplastic corpus callosum and Adult-onset demyelinating leukodystrophy.
The mechanisms underlying TAD formation are also complex and not yet fully elucidated, though a number of protein complexes and DNA elements are associated with TAD boundaries. However, the handcuff model and the loop extrusion model describe the TAD formation by the aid of CTCF and cohesin proteins. Furthermore, it has been proposed that the stiffness of TAD boundaries itself could cause the domain insulation and TAD formation. | 1 | Biochemistry |
The following is a partial list of "housekeeping genes." For a more complete and updated list, see [http://www.housekeeping.unicamp.br HRT Atlas database] compiled by Bidossessi W. Hounkpe et al. The database was constructed by mining more than 12000 human and mouse RNA-seq datasets. | 1 | Biochemistry |
In human biology, footedness is the natural preference of one's left or right foot for various purposes. It is the foot equivalent of handedness. While purposes vary, such as applying the greatest force in a certain foot to complete the action of kick as opposed to stomping, footedness is most commonly associated with the preference of a particular foot in the leading position while engaging in foot- or kicking-related sports, such as association football and kickboxing. A person may thus be left-footed, right-footed or ambipedal (able to use both feet equally well). | 4 | Stereochemistry |
His research interests cover/have covered the following topics:
* enantioselective synthesis of mono- and polyfluorinated compounds and synthesis via perfluorinated reagents (perfluorinated oxaziridines as powerful yet selective oxidizing agents)
* fluorinated contrast agents for magnetic resonance imaging
* intermolecular forces and their use in crystal engineering; supramolecular chemistry, Borromean rings, and self-assembly processes in the design and preparation of functional materials
* halogen bond and iodine chemistry; chalcogen bond.
* green chemistry | 0 | Organic Chemistry |
A related family of reactions are the transmetalations, wherein two organometallic compounds exchange their metals. Many examples of such reactions involve lithium exchange with tin:
:CHLi + MeSnAr → CHSnMe + LiAr (where Ar is aryl and Me is methyl)
The tin–lithium exchange reactions have one major advantage over the halogen–lithium exchanges for the preparation of organolithium reagents, in that the product tin compounds (CHSnMe in the example above) are much less reactive towards lithium reagents than are the halide products of the corresponding halogen–lithium exchanges (CHBr or CHCl). Other metals and metalloids which undergo such exchange reactions are organic compounds of mercury, selenium, and tellurium. | 0 | Organic Chemistry |
Reductions with hydrosilanes are methods used for hydrogenation and hydrogenolysis of organic compounds. The approach is a subset of ionic hydrogenation. In this particular method, the substrate is treated with a hydrosilane and auxiliary reagent, often a strong acid, resulting in formal transfer of hydride from silicon to carbon. This style of reduction with hydrosilanes enjoys diverse if specialized applications. | 0 | Organic Chemistry |
Some phosphorus oxoacids have two or more P atoms in different oxidation states. One example is
* Isohypophosphoric acid, (or H(OH)(O)P−O−P(O)(OH)), a tetraprotic acid and isomer of hypophosphoric acid, containing P in oxidation state +3 and +5 | 0 | Organic Chemistry |
Most organic solvents have a lower density than water, which means they are lighter than and will form a layer on top of water. Important exceptions are most of the halogenated solvents like dichloromethane or chloroform will sink to the bottom of a container, leaving water as the top layer. This is crucial to remember when partitioning compounds between solvents and water in a separatory funnel during chemical syntheses.
Often, specific gravity is cited in place of density. Specific gravity is defined as the density of the solvent divided by the density of water at the same temperature. As such, specific gravity is a unitless value. It readily communicates whether a water-insoluble solvent will float (SG < 1.0) or sink (SG > 1.0) when mixed with water. | 2 | Environmental Chemistry |
In chemistry and chemical physics, a mesophase or mesomorphic phase is a phase of matter intermediate between solid and liquid. Gelatin is a common example of a partially ordered structure in a mesophase. Further, biological structures such as the lipid bilayers of cell membranes are examples of mesophases. Mesophases with long-range positional order but no orientational order are plastic crystals, whereas those with long-range orientational order but only partial or no positional order are liquid crystals.
Georges Friedel (1922) called attention to the "mesomorphic states of matter" in his scientific assessment of observations of the so-called liquid crystals. Conventionally a crystal is solid, and crystallization converts liquid to solid. The oxymoron of the liquid crystal is resolved through the notion of mesophases. The observations noted an optic axis persisting in materials that had been melted and had begun to flow. The term liquid crystal persists as a colloquialism, but use of the term was criticized in 1993: In The Physics of Liquid Crystals the mesophases are introduced from the beginning:
:...certain organic materials do not show a single transition from solid to liquid, but rather a cascade of transitions involving new phases. The mechanical properties and the symmetry properties of these phases are intermediate between those of a liquid and those of a crystal. For this reason they have often been called liquid crystals. A more proper name is ‘mesomorphic phases’ (mesomorphic: intermediate form)
Further, "The classification of mesophases (first clearly set out by G. Friedel in 1922) is essentially based on symmetry."
Molecules that demonstrate mesophases are called mesogens.
In technology, molecules in which the optic axis is subject to manipulation during a mesophase have become commercial products as they can be used to manufacture display devices, known as liquid-crystal displays (LCDs). The susceptibility of the optical axis, called a director, to an electric or magnetic field produces the potential for an optical switch that obscures light or lets it pass. Methods used include the Freedericksz transition, the twisted nematic field effect and the in-plane switching effect. From early liquid crystal displays the buying public has embraced the low-power optical switch facility of mesophases with director.
Consider a solid consisting of a single molecular species and subjected to melting. Ultimately it is rendered to an isotropic state classically referred to as liquid. Mesophases occur before then when an intermediate state of order is still maintained as in the nematic, smectic, and columnar phases of liquid crystals. Mesophases thus exhibit anisotropy. LCD devices work as an optical switch which is turned off and on by an electric field applied to the mesogen with director. The response of the director to the field is expressed with viscosity parameters, as in the Ericksen-Leslie theory in continuum mechanics developed by Jerald Ericksen and Frank Matthews Leslie. LCD devices work only up to the transition temperature when the mesophase changes to the isotropic liquid phase at the so-called clearing point.
Mesophase phenomena are important in many scientific fields. The publishing arms of professional societies have academic journals as needed. For instance, the American Chemical Society has both Macromolecules and Langmuir, while Royal Society of Chemistry has Soft Matter, and American Physical Society has Physical Review E, and Elsevier has Advances in Colloid and Interface Science. | 7 | Physical Chemistry |
Plotting the Nyquist diagram with a potentiostat and an impedance analyzer, most often included in modern potentiostats, allows the user to determine charge transfer resistance, double-layer capacitance and ohmic resistance. The exchange current density can be easily determined measuring the impedance of a redox reaction for .
Nyquist diagrams are made of several arcs for reactions more complex than redox reactions and with mass-transfer limitations. | 7 | Physical Chemistry |
DNA storage is an important aspect of DNA extraction projects as it ensures the integrity and stability of the extracted DNA for downstream applications.
One common method of DNA storage is ethanol precipitation, which involves adding ethanol and a salt, such as sodium chloride or potassium acetate, to the extracted DNA to precipitate it out of solution. The DNA is then pelleted by centrifugation and washed with 70% ethanol to remove any remaining contaminants. The DNA pellet is then air-dried and resuspended in a buffer, such as Tris-EDTA (TE) buffer, for storage.
Another method is freezing the DNA in a buffer such as TE buffer, or in a cryoprotectant such as glycerol or DMSO, at -20 or -80 degrees Celsius. This method preserves the integrity of the DNA and slows down the activity of any enzymes that may degrade it.
It's important to note that the choice of storage buffer and conditions will depend on the downstream application for which the DNA is intended. For example, if the DNA is to be used for PCR, it may be stored in TE buffer at 4 degrees Celsius, while if it is to be used for long-term storage or shipping, it may be stored in ethanol at -20 degrees Celsius. The extracted DNA should be regularly checked for its quality and integrity, such as by running a gel electrophoresis or spectrophotometry. The storage conditions should be also noted and controlled, such as the temperature and humidity.
It's also important to consider the long-term stability of the DNA and the potential for degradation over time. The extracted DNA should be stored for as short a time as possible, and the conditions for storage should be chosen to minimize the risk of degradation.
In general, the extracted DNA should be stored under the best possible conditions to ensure its stability and integrity for downstream applications. | 1 | Biochemistry |
Trace metal stable isotope biogeochemistry is the study of the distribution and relative abundances of trace metal isotopes in order to better understand the biological, geological, and chemical processes occurring in an environment. Trace metals are elements such as iron, magnesium, copper, and zinc that occur at low levels in the environment. Trace metals are critically important in biology and are involved in many processes that allow organisms to grow and generate energy. In addition, trace metals are constituents of numerous rocks and minerals, thus serving as an important component of the geosphere. Both stable and radioactive isotopes of trace metals exist, but this article focuses on those that are stable. Isotopic variations of trace metals in samples are used as isotopic fingerprints to elucidate the processes occurring in an environment and answer questions relating to biology, geochemistry, and medicine. | 9 | Geochemistry |
Differential dynamic microscopy (DDM) is an optical technique that allows performing light scattering experiments by means of a simple optical microscope. DDM is suitable for typical soft materials such as for instance liquids or gels made of colloids, polymers and liquid crystals but also for biological materials like bacteria and cells. | 7 | Physical Chemistry |
The two major species of deer found in North America are the white-tailed deer (Odocoileus virginianus) and the mule deer (Odocoileus hemionus). The most important sense in these animals is olfaction (the sense of smell)—so much so that they have an accessory olfaction system.
The vomeronasal organ, located at the base of the nasal cavity, is the sensory organ for this system. Besides locating food and water, deer rely on their two separate olfactory systems to detect the presence of predators, as well as to supply them with information about the identity, sex, dominance status and reproductive status of other deer.
The preorbital gland of O. virginianus is about in length, while that of O. hemionus is roughly in length. In black-tailed deer (O. h. columbianus), a subspecies of O. hemionus, the preorbital gland measures about . In all of these animals, the preorbital glands are surrounded by muscle which is under voluntary control, at least to some extent.
It is not entirely clear whether the preorbital gland secretions of North American deer are significant for chemical communication. Most of the time the glands remain closed, but deer are capable of opening them to emit an odor in certain circumstances. For example, a rutting male may dilate its preorbital glands in order to signal aggression to another nearby male. Female deer often open their glands while caring for their young. | 1 | Biochemistry |
Both the vancomycin aglycone and the complete vancomycin molecule have been targets successfully reached by total synthesis. The target was first achieved by David Evans in October 1998, KC Nicolaou in December 1998, Dale Boger in 1999, and has recently been more selectively synthesized again by Dale Boger in 2020. | 0 | Organic Chemistry |
Heat is primarily generated in muscle tissue, including the heart, and in the liver, while it is lost through the skin (90%) and lungs (10%). Heat production may be increased two- to four-fold through muscle contractions (i.e. exercise and shivering). The rate of heat loss is determined, as with any object, by convection, conduction, and radiation. The rates of these can be affected by body mass index, body surface area to volume ratios, clothing and other environmental conditions.
Many changes to physiology occur as body temperatures decrease. These occur in the cardiovascular system leading to the Osborn J wave and other dysrhythmias, decreased central nervous system electrical activity, cold diuresis, and non-cardiogenic pulmonary edema.
Research has shown that glomerular filtration rates (GFR) decrease as a result of hypothermia. In essence, hypothermia increases preglomerular vasoconstriction, thus decreasing both renal blood flow (RBF) and GFR. | 1 | Biochemistry |
In his autobiography, What Mad Pursuit, Crick wrote about his choice of the word dogma and some of the problems it caused him:
Similarly, Horace Freeland Judson records in The Eighth Day of Creation: | 1 | Biochemistry |
Naturally occurring sea foam is not inherently toxic; however, it can be exposed to high concentrations of contaminants in the surface microlayer derived from the breakdown of algal blooms, fossil fuel production and transport, and stormwater runoff. These contaminants contribute to the formation of noxious sea foam through adsorption onto bubbles. Bubbles may burst and release toxins into the atmosphere in the form of sea spray or aerosol, or they may persist in foams. Toxins released through aerosols and breaking bubbles can be inhaled by humans. The microorganisms that occupy sea foams as habitat have increased susceptibility for contaminant exposure. Consequently, these toxic substances can be integrated into the trophic food web. | 9 | Geochemistry |
Inosine chemical erasing (ICE) refer to a process in which acrylonitrile is reacted with inosine to form N1-cyanoethylinosine (ce1I). This serves to stall reverse transcriptase and lead to truncated cDNA molecules. This was combined with deep-sequencing in a developed method called ICE-seq. Computational methods for automated analysis of the data are available, the main premise being the comparison of treated and untreated samples to identify truncated transcripts and thus infer an inosine modification by read count, with a step to reduce false positives by comparison to online database dbSNP. | 1 | Biochemistry |
To identify the putative functions and annotations of the genes, MG-RAST follows a multi-step process. Initially, it builds clusters of proteins at a 90% identity level using the UCLUST implementation in QIIME. The longest sequence within each cluster is then selected for further analysis.
For the similarity analysis, MG-RAST employs sBLAT, a parallelized version of the BLAT algorithm using OpenMP. The search is conducted against a protein database derived from the M5nr, which integrates nonredundant sequences from various databases such as GenBank, SEED, IMG, UniProt, KEGG, and eggNOGs.
In the case of reads associated with rRNA sequences, a clustering step is performed at a 97% identity level. The longest sequence from each cluster is chosen as the representative and is used for a BLAT search against the M5rna database. This database integrates sequences from SILVA, Greengenes, and RDP, providing a comprehensive reference for the analysis of ribosomal RNA sequences. | 1 | Biochemistry |
Oxalosuccinic acid is a substrate of the citric acid cycle. It is acted upon by isocitrate dehydrogenase. Salts and esters of oxalosuccinic acid are known as oxalosuccinates.
Oxalosuccinic acid/oxalosuccinate is an unstable 6-carbon intermediate in the tricarboxylic acid cycle. It's a keto acid, formed during the oxidative decarboxylation of isocitrate to alpha-ketoglutarate, which is catalyzed by the enzyme isocitrate dehydrogenase. Isocitrate is first oxidized by coenzyme NAD+ to form oxalosuccinic acid/oxalosuccinate. Oxalosuccinic acid is both an alpha-keto and a beta-keto acid (an unstable compound) and it is the beta-ketoic property that allows the loss of carbon dioxide in the enzymatic reaction in conversion to the five-carbon molecule 2-oxoglutarate. | 1 | Biochemistry |
Non-competitive inhibition models a system where the inhibitor and the substrate may both be bound to the enzyme at any given time. When both the substrate and the inhibitor are bound, the enzyme-substrate-inhibitor complex cannot form product and can only be converted back to the enzyme-substrate complex or the enzyme-inhibitor complex. Non-competitive inhibition is distinguished from general mixed inhibition in that the inhibitor has an equal affinity for the enzyme and the enzyme-substrate complex.
For example, in the enzyme-catalyzed reactions of glycolysis, accumulation phosphoenol is catalyzed by pyruvate kinase into pyruvate. Alanine is an amino acid which is synthesized from pyruvate also inhibits the enzyme pyruvate kinase during glycolysis. Alanine is a non-competitive inhibitor, therefore it binds away from the active site to the substrate in order for it to still be the final product.
Another example of non-competitive inhibition is given by glucose-6-phosphate inhibiting hexokinase in the brain. Carbons 2 and 4 on glucose-6-phosphate contain hydroxyl groups that attach along with the phosphate at carbon 6 to the enzyme-inhibitor complex. The substrate and enzyme are different in their group combinations that an inhibitor attaches to. The ability of glucose-6-phosphate to bind at different places at the same time makes it a non-competitive inhibitor.
The most common mechanism of non-competitive inhibition involves reversible binding of the inhibitor to an allosteric site, but it is possible for the inhibitor to operate via other means including direct binding to the active site. It differs from competitive inhibition in that the binding of the inhibitor does not prevent binding of substrate, and vice versa, but simply prevents product formation for a limited time.
This type of inhibition reduces the maximum rate of a chemical reaction without changing the apparent binding affinity of the catalyst for the substrate (K – see Michaelis-Menten kinetics). When a non-competitive inhibitor is added the Vmax is changed, while the Km remains unchanged. According to the Lineweaver-Burk plot the Vmax is reduced during the addition of a non-competitive inhibitor, which is shown in the plot by a change in both the slope and y-intercept when a non-competitive inhibitor is added.
The primary difference between competitive and non-competitive is that competitive inhibition affects the substrate's ability to bind by binding an inhibitor in place of a substrate, which lowers the affinity of the enzyme for the substrate. In non-competitive inhibition, the inhibitor binds to an allosteric site and prevents the enzyme-substrate complex from performing a chemical reaction. This does not affect the Km (affinity) of the enzyme (for the substrate). Non-competitive inhibition differs from uncompetitive inhibition in that it still allows the substrate to bind to the enzyme-inhibitor complex and form an enzyme-substrate-inhibitor complex, this is not true in uncompetitive inhibition, it prevents the substrate from binding to the enzyme inhibitor through conformational change upon allosteric binding. | 1 | Biochemistry |
This method very sharply separates molecules, and is so sharp that it can even separate different molecular isotopes from one another. | 3 | Analytical Chemistry |
Anthropogenic (man-made) sources of arsenic, like the natural sources, are mainly arsenic oxides and the associated anions. Man-made sources of arsenic, include wastes from mineral processing, swine and poultry farms. For example, many ores, especially sulfide minerals, are contaminated with arsenic, which is released in roasting (burning in air). In such processing, arsenide is converted to arsenic trioxide, which is volatile at high temperatures and is released into the atmosphere. Poultry and swine farms make heavy use of the organoarsenic compound roxarsone as an antibiotic in feed. Some wood is treated with copper arsenates as a preservative. The mechanisms by which these sources affect "downstream" living organisms remains uncertain but are probably diverse. One commonly cited pathway involves methylation.
The monomethylated acid, methanearsonic acid (CHAsO(OH)), is a precursor to fungicides (tradename Neoasozin) in the cultivation of rice and cotton. Derivatives of phenylarsonic acid (CHAsO(OH)) are used as feed additives for livestock, including 4-hydroxy-3-nitrobenzenearsonic acid (3-NHPAA or Roxarsone), ureidophenylarsonic acid, and p-arsanilic acid. These applications are controversial as they introduce soluble forms of arsenic into the environment. | 1 | Biochemistry |
Non-carbon-fixing proteins similar to RuBisCO, termed RuBisCO-like proteins (RLPs), are also found in the wild in organisms as common as Bacillus subtilis. This bacterium has a rbcL-like protein with a 2,3-diketo-5-methylthiopentyl-1-phosphate enolase function, part of the methionine salvage pathway. Later identifications found functionally divergent examples dispersed all over bacteria and archaea, as well as transitionary enzymes performing both RLP-type enolase and RuBisCO functions. It is now believed that the current RuBisCO evolved from a dimeric RLP ancestor, acquiring its carboxylase function first before further oligomerizing and then recruiting the small subunit to form the familiar modern enzyme. The small subunit probably first evolved in anaerobic and thermophilic organisms, where it enabled RuBisCO to catalyze its reaction at higher temperatures. In addition to its effect on stabilizing catalysis, it enabled the evolution of higher specificities for over O by modulating the effect that substitutions within RuBisCO have on enzymatic function. Substitutions that do not have an effect without the small subunit suddenly become beneficial when it is bound. Furthermore, the small subunit enabled the accumulation of substitutions that are only tolerated in its presence. Accumulation of such substitutions leads to a strict dependence on the small subunit, which is observed in extant Rubiscos that bind a small subunit. | 5 | Photochemistry |
Biolistics introduces DNA randomly into the target cells. Thus the DNA may be transformed into whatever genomes are present in the cell, be they nuclear, mitochondrial, plasmid or any others, in any combination, though proper construct design may mitigate this. The delivery and integration of multiple templates of the DNA construct is a distinct possibility, resulting in potential variable expression levels and copy numbers of the inserted gene. This is due to the ability of the constructs to give and take genetic material from other constructs, causing some to carry no transgene and others to carry multiple copies; the number of copies inserted depends on both how many copies of the transgene an inserted construct has, and how many were inserted. Also, because eukaryotic constructs rely on illegitimate recombination—a process by which the transgene is integrated into the genome without similar genetic sequences—and not homologous recombination, they cannot be targeted to specific locations within the genome, unless the transgene is co-delivered with genome editing reagents. | 1 | Biochemistry |
Typically, single chain cyclized/knotted polymers are synthesized by deactivation enhanced ATRP of multivinyl monomers via kinetically controlled strategy. There are several main reactions during this polymerization process: initiation, activation, deactivation, chain propagation, intramolecular cyclization and intermolecular crosslinking. The polymerization process is explained in Figure 2.
In a similar way to normal ATRP, the polymerization is started by initiation to produce a free radical, followed by chain propagation and reversible activation/deactivation equilibrium. Unlike the polymerization of single vinyl monomers, for the polymerization of multivinyl monomers, the chain propagation occurs between the active centres and one of the vinyl groups from the free monomers. Therefore, multiple unreacted pendent vinyl groups are introduced into the linear primary polymer chains, resulting in a high local/spatial vinyl concentration. As the chain grows, the propagating centre reacts with their own pendent vinyl groups to form intramolecular cyclized rings (i.e. intramolecular cyclization). The unique alternating chain propagation/intramolecular cyclization process eventually leads to the single chain cyclized/knotted polymer architecture. | 7 | Physical Chemistry |
One study that was done by Royal College of Surgeons (RCS) in rat model shows that a recessive mutation in a receptor tyrosine kinase gene, mertk results in a premature stop codon and impaired phagocytosis function by RPE cells. This mutation causes the accumulation of outer segment debris in the subretinal space, which causes photoreceptor cell death. The model organism with this disease received a subretinal injection of AAV serotype 2 carrying a mouse Mertk cDNA under the control of either the CMV or RPE65 promoters. This treatment was found to prolong photoreceptor cell survival for several months and also the number of photoreceptor was 2.5 fold higher in AAV-Mertk- treated eyes compared with controls 9 weeks after injection, also they found decreased amount of debris in the subretinal space.
The protein RPE65 is used in the retinoid cycle where the all-trans-retinol within the rod outer segment is isomerized to its 11-cis form and oxidized to 11-cis retinal before it goes back to the photoreceptor and joins with opsin molecule to form functional rhodopsin. In animal knockout model (RPE65-/-), gene transfer experiment shows that early intraocular delivery of human RPE65 vector on embryonic day 14 shows efficient transduction of retinal pigment epithelium in the RPE65-/- knockout mice and rescues visual functions. This shows successful gene therapy can be attributed to early intraocular deliver to the diseased animal. | 1 | Biochemistry |
The Organismic Interactions Department, headed by Regine Kahmann, is focused on the biology of phytopathogenic fungi and in particular the mechanisms that underlie morphological differentiation and communication of these fungi with their plant hosts. Furthermore, the department is focused on the mechanisms that enable fungi to colonize plants successfully and on the processes accounting for variations in host preference and fungal lifestyles. There are three research groups:
* Molecular phytopathology (Regine Kahmann)
* Establishment of compatibility in biotrophic interactions (Gunther Döhlemann)
* Functional genomics and molecular biology of symbiotic fungi (Alga Zuccaro) | 9 | Geochemistry |
The term anti-periplanar was first coined by Klyne and Prelog in their work entitled "Description of steric relationships across single bonds", published in 1960. ‘Anti’ refers to the two functional groups lying on opposite sides of the plane of the bond. ‘Peri’ comes from the Greek word for ‘near’ and so periplanar means “approximately planar”. In their article “Periplanar or Coplanar?” Kane and Hersh point out that many organic textbooks use anti-periplanar to mean completely anti-planar, or anti-coplanar, which is technically incorrect. | 0 | Organic Chemistry |
Many biological and forensic cases involving genetic analysis require sequencing of DNA from minute amounts of sample, such as DNA from uncultured single cells or trace amounts of tissue collected from crime scenes. Conventional Polymerase Chain Reaction (PCR)-based DNA amplification methods require sequence-specific oligonucleotide primers and heat-stable (usually Taq) polymerase, and can be used to generate significant amounts of DNA from minute amounts of DNA. However, this is not sufficient for modern techniques which use sequencing-based DNA analysis. Therefore, a more efficient non-sequence-specific method to amplify minute amounts of DNA is necessary, especially in single-cell genomic studies. | 1 | Biochemistry |
Diazotrophs are widespread within domain Bacteria including cyanobacteria (e.g. the highly significant Trichodesmium and Cyanothece), green sulfur bacteria, purple sulfur bacteria, Azotobacteraceae, rhizobia and Frankia. Several obligately anaerobic bacteria fix nitrogen including many (but not all) Clostridium spp. Some archaea such as Methanosarcina acetivorans also fix nitrogen, and several other methanogenic taxa, are significant contributors to nitrogen fixation in oxygen-deficient soils.
Cyanobacteria, commonly known as blue-green algae, inhabit nearly all illuminated environments on Earth and play key roles in the carbon and nitrogen cycle of the biosphere. In general, cyanobacteria can use various inorganic and organic sources of combined nitrogen, such as nitrate, nitrite, ammonium, urea, or some amino acids. Several cyanobacteria strains are also capable of diazotrophic growth, an ability that may have been present in their last common ancestor in the Archean eon. Nitrogen fixation not only naturally occurs in soils but also aquatic systems, including both freshwater and marine. Indeed, the amount of nitrogen fixed in the ocean is at least as much as that on land. The colonial marine cyanobacterium Trichodesmium is thought to fix nitrogen on such a scale that it accounts for almost half of the nitrogen fixation in marine systems globally. Marine surface lichens and non-photosynthetic bacteria belonging in Proteobacteria and Planctomycetes fixate significant atmospheric nitrogen. Species of nitrogen fixing cyanobacteria in fresh waters include: Aphanizomenon and Dolichospermum (previously Anabaena). Such species have specialized cells called heterocytes, in which nitrogen fixation occurs via the nitrogenase enzyme. | 1 | Biochemistry |
Removal of the chlorides is essential. In practice this first involves physical cleaning (with a wooden or even metal pick) to remove the bulk of the chlorides and then chemical treatment. One chemical treatment is soaking the object in a 5% sodium sesquicarbonate solution. This serves to neutralize the acid that attacks the metal as well as converting the reactive cuprous chloride to largely inert cuprous oxide. The oxide may coat the artefact with unsightly but harmless black spots or generally darken the metal.
The duration of soaking may be days to weeks or even a year for severely contaminated objects. The sesquicarbonate may remove copper from the artefact as it forms a complex ion with copper. Amateurs report that the patina may be stripped from the artefact but this is when the solution is boiled so that the carbonate rinse removes the chlorides in hours rather than the cool bath of long duration used by professional conservators.
Soaking in sodium carbonate—which does not form a complex ion with copper and is unlikely to affect the patina but is slower than the sesquicarbonate—or benzotriazole aqueous solutions may also be used. The carbonate is similar in effect to the sesquicarbonate. The benzotriazole does not remove the chlorides or neutralize the acid present but acts as a physical barrier to water, oxygen, and chlorides and so can be used as a final step in all cases but as a first or only step in only minor cases.
Use of tap water for initial carbonate rinses is fine as any chloride content in the water is low compared to the content found when the chlorides from the contaminated artefact have dissolved into the water. Later rinses should be with distilled water though the chlorine of a chlorinated town water supply is likely to have evaporated from tap water inside 24 hours and therefore will not further contaminate the object.
Instead of rinses, electrolysis may be used, often with sodium carbonate as the electrolyte and mild or stainless steel as the anode. This converts the cuprous ions to elemental copper. Elemental copper released from the chlorides may be redeposited on the artefact as a pinkish coating. A coin may take only hours, whereas a large artefact, such as a cannon, may take months.
Once treated, the specimen should be held in a dry environment and periodically inspected for recurrence of bronze disease as no long-term treatment has been confirmed. | 8 | Metallurgy |
In 2006 the U.S. National Research Council published a report, Human Biomonitoring for Environmental Chemicals. The report recognized the value of biomonitoring for better understanding exposure to environmental chemicals, and included several findings and recommendations to improve the utility of biomonitoring data for health risk assessment. In summary, the report called for more rigorous health-based criteria for selecting chemicals to include in biomonitoring studies; the development of tools and techniques to improve risk-based interpretation and communication of biomonitoring data; integration of biomonitoring into exposure assessment and epidemiological research; and exploration of bioethical issues around biomonitoring, including informed consent, confidentiality of results, and others.
The issue of exposure to environmental chemicals has received attention as a result of televised reports by Bill Moyers for PBS and Anderson Cooper for CNNs "Planet in Peril" series. The book Our Stolen Future', with a foreword by former Vice President Al Gore, also raised awareness by focusing on endocrine disruption.
Surveys of human exposure to chemicals do not usually integrate the number of chemical compounds detected per person and the concentration of each compound. This leaves untested relevant exposure situations; e.g., whether individuals with low concentrations of some compounds have high concentrations of the other compounds. Analyses of the concentrations of a given compound usually show that most citizens have much lower concentrations than a certain minority. A study based on a representative sample of the population of Catalonia (Spain), which integrated the number of compounds detected per person and the concentration of each compound, found that more than half of the population had concentrations in the top quartile of 1 or more of the 19 persistent toxic substances (PTS) (pesticides, PCBs) analyzed. Significant subgroups of the population accumulated PTS mixtures at high concentrations. For instance, 48% of women 60–74 years had concentrations of 6 or more PTS in the top quartile; half of the entire population had levels of 1 to 5 PTS above 500 ng/g, and less than 4% of citizens had all PTS in the lowest quartile. Thus, PTS concentrations appear low in most of the population only when each individual compound is looked at separately. It is not accurate to state that most of the population has low concentrations of PTS. The assessment of mixture effects must address the fact that most individuals are contaminated by PTS mixtures made of compounds at both low and high concentrations. | 2 | Environmental Chemistry |
The generalized Woodward–Hoffmann rules, first given in 1969, are equivalent to an earlier general approach, the Möbius-Hückel concept of Zimmerman, which was first stated in 1966 and is also known as aromatic transition state theory. As its central tenet, aromatic transition state theory holds that allowed pericyclic reactions proceed via transition states with aromatic character, while forbidden pericyclic reactions would encounter transition states that are antiaromatic in nature. In the Dewar-Zimmerman analysis, one is concerned with the topology of the transition state of the pericyclic reaction. If the transition state involves 4n electrons, the Möbius topology is aromatic and the Hückel topology is antiaromatic, while if the transition state involves 4n + 2 electrons, the Hückel topology is aromatic and the Möbius topology is antiaromatic. The parity of the number of phase inversions (described in detail below) in the transition state determines its topology. A Möbius topology involves an odd number of phase inversions whereas a Hückel topology involves an even number of phase inversions.
In connection with Woodward–Hoffmann terminology, the number of antarafacial components and the number of phase inversions always have the same parity. Consequently, an odd number of antarafacial components gives Möbius topology, while an even number gives Hückel topology. Thus, to restate the results of aromatic transition state theory in the language of Woodward and Hoffmann, a 4n-electron reaction is thermally allowed if and only if it has an odd number of antarafacial components (i.e., Möbius topology); a (4n + 2)-electron reaction is thermally allowed if and only if it has an even number of antarafacial components (i.e., Hückel topology).
Procedure for Dewar-Zimmerman analysis (examples shown on the right): Step 1. Shade in all basis orbitals that are part of the pericyclic system. The shading can be arbitrary. In particular the shading does not need to reflect the phasing of the polyene MOs; each basis orbital simply need to have two oppositely phased lobes in the case of p or sp hybrid orbitals, or a single phase in the case of an s orbital. Step 2. Draw connections between the lobes of basis orbitals that are geometrically well-disposed to interact at the transition state. The connections to be made depend on the transition state topology. (For example, in the figure, different connections are shown in the cases of con- and disrotatory electrocyclization.) Step 3. Count the number of connections that occur between lobes of opposite shading: each of these connections constitutes a phase inversion. If the number of phase inversions is even, the transition state is Hückel, while if the number of phase inversions is odd, the transition state is Möbius. Step 4. Conclude that the pericyclic reaction is allowed if the electron count is 4n + 2 and the transition state is Hückel, or if the electron count is 4n and the transition state is Möbius; otherwise, conclude that the pericyclic reaction is forbidden.
Importantly, any scheme of assigning relative phases to the basis orbitals is acceptable, as inverting the phase of any single orbital adds 0 or ±2 phase inversions to the total, an even number, so that the parity of the number of inversions (number of inversions modulo 2) is unchanged. | 7 | Physical Chemistry |
In electrochemistry, electrosynthesis is the synthesis of chemical compounds in an electrochemical cell. Compared to ordinary redox reactions, electrosynthesis sometimes offers improved selectivity and yields. Electrosynthesis is actively studied as a science and also has industrial applications. Electrooxidation has potential for wastewater treatment as well. | 7 | Physical Chemistry |
An akamptisomer is a type of conformational isomer characterized by a hindered inversion of a bond angle. It was first discovered in 2018 in a series of bridged porphyrin molecules. | 4 | Stereochemistry |
In chemistry, coalescence is a process in which two phase domains of the same composition come together and form a larger phase domain. In other words, the process by which two or more separate masses of miscible substances
seem to "pull" each other together should they make the slightest
contact. | 7 | Physical Chemistry |
1-Octene, 1-hexene, and 1-butene are used comonomers in the manufacture of polyethylenes. The advantages to such copolymers has led to a focus on catalysts that facilitate the incorporation of these comonomers, e.g., constrained geometry complexes.
Comonomers are often employed to improve the plastification of polymeric materials, i.e. the flexibility of the polymer. Unlike traditional plasticizers, comonomers are not leachable. | 7 | Physical Chemistry |
The objectives of the charity are:
# To implement carbon reduction projects
# To challenge the misconceptions surrounding carbon reduction amongst individuals and organizations
# To encourage greater adoption of sustainable solutions | 2 | Environmental Chemistry |
Porphyrin ligands can be innocent (2-) or noninnocent (1-). In the enzymes chloroperoxidase and cytochrome P450, the porphyrin ligand sustains oxidation during the catalytic cycle, notably in the formation of Compound I. In other heme proteins, such as myoglobin, ligand-centered redox does not occur and the porphyrin is innocent. | 0 | Organic Chemistry |
Eriochrome Black T is a complexometric indicator that is used in complexometric titrations, e.g. in the water hardness determination process. It is an azo dye. Eriochrome is a trademark of Huntsman Petrochemical, LLC.
In its deprotonated form, Eriochrome Black T is blue. It turns red when it forms a complex with calcium, magnesium, or other metal ions. | 3 | Analytical Chemistry |
Other molecules besides ATP undergo dephosphorylation as part of other biological systems. Different compounds produce different free energy changes as a result of dephosphorylation.
Psilocybin also relies on dephosphorylation to be metabolized into psilocin and further eliminated. No information on psilocybin's effect on the change in free energy is currently available. | 1 | Biochemistry |
Ammonia oxidation in autotrophic nitrification is a complex process that requires several enzymes as well as oxygen as a reactant. The key enzymes necessary for releasing energy during oxidation of ammonia to nitrite are ammonia monooxygenase (AMO) and hydroxylamine oxidoreductase (HAO). The first is a transmembrane copper protein which catalyzes the oxidation of ammonia to hydroxylamine () taking two electrons directly from the quinone pool. This reaction requires O.
The second step of this process has recently fallen into question. For the past few decades, the common view was that a trimeric multiheme c-type HAO converts hydroxylamine into nitrite in the periplasm with production of four electrons (). The stream of four electrons is channeled through cytochrome c to a membrane-bound cytochrome c. Two of the electrons are routed back to AMO, where they are used for the oxidation of ammonia (quinol pool). The remaining two electrons are used to generate a proton motive force and reduce NAD(P) through reverse electron transport.
Recent results, however, show that HAO does not produce nitrite as a direct product of catalysis. This enzyme instead produces nitric oxide and three electrons. Nitric oxide can then be oxidized by other enzymes (or oxygen) to nitrite. In this paradigm, the electron balance for overall metabolism needs to be reconsidered. | 1 | Biochemistry |
The GADV-protein world hypothesis was first proposed by Kenji Ikehara at Nara Women's University. It is supported by GNC-SNS primitive gene code hypothesis (GNC hypothesis) also formulated by him. In the GNC hypothesis, the origin of the present standard genetic code is considered to be the GNC genetic code that includes the codons GGC, GCC, GAC, GUC, respectively coding glycine, alanine, aspartic acid, and valine; it also follows the SNS primitive genetic code that codes ten amino acids, where N denotes arbitrary four RNA bases and S denotes guanine (G) and cytosine (C).
The GADV hypothesis proposes these mechanisms:
* Analysis on present proteins and simulation using chemical factors of amino acid shows GADV-proteins that contains almost the same amount of the four amino acids can form four basic structures of protein, namely, hydrophobic and hydrophilic structures, α-helices and β-sheets.
* Therefore, GADV-proteins polymerized from randomly chosen amino acids from the four choices, probably becoming globular and water-soluble like some present proteins.
* Proteins generated like this have different primary structures. However, their simple composition leads to the formation of similar spherical and water-soluble proteins that have bulky and hydrophobic valines inside and hydrophilic aspartic acids outside.
* GADV-peptides can polymerize by simple cycles of evaporation and hydration. This gives a rationale for the production of GADV-peptides in tide pools on the early Earth. Moreover, GADV-peptides randomly polymerized as above have the catalytic activity to hydrolyze peptide bonds in bovine serum albumin. Therefore, they can catalyze the formation of peptide bonds as the reverse reaction.
* GADV-proteins can multiply by pseudo-replication in the absence of genes, considering the features above. | 9 | Geochemistry |
The chemistry of Lawessons reagent and related substances has been reviewed by several times. The main use of Lawessons reagent is the thionation of carbonyl compounds. For instance, Lawessons reagent will convert a carbonyl into a thiocarbonyl. Additionally, Lawessons reagent has been used to thionate enones, esters, lactones, amides, lactams, and quinones.
In one study, reaction of maltol with LR results in a selective oxygen replacement in two positions.
A combination of silver perchlorate and Lawesson's reagent is able to act as an oxophilic Lewis acid with the ability to catalyze the Diels–Alder reaction of dienes with α,β-unsaturated aldehydes.
in some cases, alcohols may be converted to thiols by treatment with Lawesson's reagent.
Lawesson's reagent reacts with sulfoxides to form thioethers. | 0 | Organic Chemistry |
As of December 20, 2006, ORegAnno contained 4220 regulatory sequences (excluding deprecated records) for 2190 transcription factor binding sites, 1853 regulatory regions (enhancers, promoters, etc.), 170 regulatory polymorphisms, and 7 regulatory haplotypes for 17 different organisms (predominantly Drosophila melanogaster, Homo sapiens, Mus musculus, Caenorhabditis elegans, and Rattus norvegicus in that order). These records were obtained by manual curation of 828 publications by 45 ORegAnno users from the gene regulation community. The ORegAnno publication queue contained 4215 publications of which 858 were closed, 34 were in progress (open status), and 3321 were awaiting annotation (pending status). ORegAnno is continually updated and therefore current database contents should be obtained from [http://www.oreganno.org www.oreganno.org]. | 1 | Biochemistry |
RNA-Seq was first developed in mid 2000s with the advent of next-generation sequencing technology. The first manuscripts that used RNA-Seq even without using the term includes those of prostate cancer cell lines (dated 2006), Medicago truncatula (2006), maize (2007), and Arabidopsis thaliana (2007), while the term "RNA-Seq" itself was first mentioned in 2008. The number of manuscripts referring to RNA-Seq in the title or abstract (Figure, blue line) is continuously increasing with 6754 manuscripts published in 2018. The intersection of RNA-Seq and medicine (Figure, gold line) has similar celerity. | 1 | Biochemistry |
Human iron homeostasis is regulated at two different levels. Systemic iron levels are balanced by the controlled absorption of dietary iron by enterocytes, the cells that line the interior of the intestines, and the uncontrolled loss of iron from epithelial sloughing, sweat, injuries and blood loss. In addition, systemic iron is continuously recycled. Cellular iron levels are controlled differently by different cell types due to the expression of particular iron regulatory and transport proteins. | 1 | Biochemistry |
The chemical composition of slag can reveal much about the smelting process. XRF is the most commonly used tool in analysing the chemical composition of slag. Through chemical analysis, the composition of the charge, the firing temperature, the gas atmosphere and the reaction kinetics can be determined.
Ancient slag composition is usually a quaternary eutectic system CaO-SiO-FeO-AlO simplified to CaO-SiO-FeO, giving a low and uniform melting point. In some circumstances, the eutectic system was created according to the proportion of silicates to metal oxides in the gangue, together with the type of ore and the furnace lining. In other instances, a flux was required to achieve the correct system.
The melting temperature of slag can be determined by plotting its chemical composition in a ternary plot.
The viscosity of slag can be calculated through its chemical composition with equation:
where is the index of viscosity.
With recent advances in rotational viscometry techniques, viscosities of iron oxide slags are also widely undertaken. Coupled with phase equilibria studies, these analysis provide a better understanding of physico-chemical behaviour of slags at high temperatures.
In the early stages of smelting, the separation between melting metal and slag is not complete. Hence, the main, minor and trace elements of metal in the slag can be indicators of the type of ore used in the smelting process. | 8 | Metallurgy |
In thermodynamics, the phase rule is a general principle governing "pVT" systems, whose thermodynamic states are completely described by the variables pressure (), volume () and temperature (), in thermodynamic equilibrium. If is the number of degrees of freedom, is the number of components and is the number of phases, then
It was derived by American physicist Josiah Willard Gibbs in his landmark paper titled On the Equilibrium of Heterogeneous Substances, published in parts between 1875 and 1878.
The rule assumes the components do not react with each other.
The number of degrees of freedom is the number of independent intensive variables, i.e. the largest number of thermodynamic parameters such as temperature or pressure that can be varied simultaneously and arbitrarily without determining one another. An example of one-component system is a system involving one pure chemical, while two-component systems, such as mixtures of water and ethanol, have two chemically independent components, and so on. Typical phases are solids, liquids and gases. | 7 | Physical Chemistry |
Plumbide is an anion of lead atoms. There are three plumbide anions, written as Pb, Pb and Pb with 3 oxidation states, -1, -2 and -4, respectively.
A plumbide can refer to one of two things: an intermetallic compound that contains lead, or a Zintl phase compound with lead as the anion. | 7 | Physical Chemistry |
In eukaryotic cells the structure of the chromatin complex of DNA is folded in a way that functionally mimics the supercoiled state characteristic of prokaryotic DNA, so although the enhancer DNA may be far from the gene in a linear way, it is spatially close to the promoter and gene. This allows it to interact with the general transcription factors and RNA polymerase II. The same mechanism holds true for silencers in the eukaryotic genome. Silencers are antagonists of enhancers that, when bound to its proper transcription factors called repressors, repress the transcription of the gene. Silencers and enhancers may be in close proximity to each other or may even be in the same region only differentiated by the transcription factor the region binds to.
An enhancer may be located upstream or downstream of the gene it regulates. Furthermore, an enhancer does not need to be located near the transcription initiation site to affect transcription, as some have been found located several hundred thousand base pairs upstream or downstream of the start site. Enhancers do not act on the promoter region itself, but are bound by activator proteins. These activator proteins interact with the mediator complex, which recruits polymerase II and the general transcription factors which then begin transcribing the genes. Enhancers can also be found within introns. An enhancer's orientation may even be reversed without affecting its function; additionally, an enhancer may be excised and inserted elsewhere in the chromosome, and still affect gene transcription. That is one reason that introns polymorphisms may have effects although they are not translated. Enhancers can also be found at the exonic region of an unrelated gene and they may act on genes on another chromosome.
Enhancers are bound by p300-CBP and their location can be predicted by ChIP-seq against this family of coactivators. | 1 | Biochemistry |
Contraindications, conditions that warrant withholding treatment with lovastatin, include pregnancy, breast feeding, and liver disease. Lovastatin is contraindicated during pregnancy (Pregnancy Category X); it may cause birth defects such as skeletal deformities or learning disabilities. Owing to its potential to disrupt infant lipid metabolism, lovastatin should not be taken while breastfeeding. Patients with liver disease should not take lovastatin. | 0 | Organic Chemistry |
The Ernst Schering Prize is awarded annually by the Ernst Schering Foundation for especially outstanding basic research in the fields of medicine, biology or chemistry anywhere in the world. Established in 1991 by the Ernst Schering Research Foundation, and named after the German apothecary and industrialist, Ernst Christian Friedrich Schering, who founded the Schering Corporation, the prize is now worth €50,000. | 1 | Biochemistry |
The allyl cation has two contributing structures with a positive charge on the terminal carbon atoms. In the hybrid structure their charge is +. The full positive charge can also be depicted as delocalized among three carbon atoms.
The diborane molecule is described by contributing structures, each with electron-deficiency on different atoms. This reduces the electron-deficiency on each atom and stabilizes the molecule. Below are the contributing structures of an individual 3c-2e bond in diborane. | 7 | Physical Chemistry |
Phosphodiester bonds make up the backbones of DNA and RNA. In the phosphodiester bonds of nucleic acids, a phosphate is attached to the 5 carbon of one nucleoside and to the 3 carbon of the adjacent nucleoside. Specifically, it is the phosphodiester bonds that link the 3 carbon atom of one sugar molecule and the 5 carbon atom of another (hence the name 3, 5 phosphodiester linkage used with reference to this kind of bond in DNA and RNA chains). The involved saccharide groups are deoxyribose in DNA and ribose in RNA. In order for the phosphodiester bond to form, joining the nucleosides, the tri-phosphate or di-phosphate forms of the nucleotide building blocks are broken apart to give off energy required to drive the enzyme-catalyzed reaction. In DNA replication, for example, formation of the phosphodiester bonds is catalyzed by a DNA polymerase enzyme, using a pair of magnesium cations and other supporting structures. Formation of the bond occurs not only in DNA and RNA replication, but also in the repair and recombination of nucleic acids, and may require the involvement of various polymerases, primers, and/or ligases. During the replication of DNA, for example, the DNA polymerase I leaves behind a hole between the phosphates in the newly formed backbone. DNA ligase is able to form a phosphodiester bond between the nucleotides on each side of the gap.
Phosphodiesters are negatively charged at pH 7. The negative charge attracts histones, metal cations such as magnesium, and polyamines [needs citation]. Repulsion between these negative charges influences the conformation of the polynucleic acids. | 1 | Biochemistry |
The first on-line coupling of gas chromatography to a mass spectrometer was reported in the late 1950s. An interest in coupling the methods had been suggested as early as December 1954.
The development of affordable and miniaturized computers has helped in the simplification of the use of this instrument, as well as allowed great improvements in the amount of time it takes to analyze a sample. In 1964, Electronic Associates, Inc. (EAI), a leading U.S. supplier of analog computers, began development of a computer controlled quadrupole mass spectrometer under the direction of Robert E. Finnigan. By 1966 Finnigan and collaborator Mike Uthes EAI division had sold over 500 quadrupole residual gas-analyzer instruments. In 1967, Finnigan left EAI to form the Finnigan Instrument Corporation along with Roger Sant, T. Z. Chou, Michael Story, Lloyd Friedman, and William Fies. In early 1968, they delivered the first prototype quadrupole GC/MS instruments to Stanford and Purdue University. When Finnigan Instrument Corporation was acquired by Thermo Instrument Systems (later Thermo Fisher Scientific) in 1990, it was considered "the worlds leading manufacturer of mass spectrometers". | 3 | Analytical Chemistry |
In parallel with this work, the Cell was tested for the recovery of fine coal at the Newlands coal mine, also owned by MIM Holdings Limited. This fines stream was cyclone overflow, which contained 15–50% ash and was previously discarded. The particle size of this stream was less than 25 μm. Pilot plant testing showed that it was possible to achieve greater than 90% recovery of coal, with less than 10% ash in the product.
Subsequently, a full-scale plant was commissioned at Newlands in the 1988–89 financial year, with six rectangular Cells (1.5 m × 3.5 m) installed in a two-stage arrangement. The cells in the first stage had seven downcomers, while those in the second had six.
These cells were in continuous operation at Newlands for 15 years until a new washing plant was built to replace the old one in 2006.
Two additional Cells were installed at MIM Holdings' Collinsville Coal operations in 1990. These had 10 downcomers each. | 8 | Metallurgy |
This first strategy involves locally depositing self-assembled monolayers on the surface only where the nanostructure will later be located. This strategy is advantageous because it involves high throughput methods that generally involve fewer steps than the other two strategies. The major techniques that use this strategy are:
* Micro-contact printing
:Micro-contact printing or soft lithography is analogous to printing ink with a rubber stamp. The SAM molecules are inked onto a pre-shaped elastomeric stamp with a solvent and transferred to the substrate surface by stamping. The SAM solution is applied to the entire stamp but only areas that make contact with the surface allow transfer of the SAMs. The transfer of the SAMs is a complex diffusion process that depends on the type of molecule, concentration, duration of contact, and pressure applied. Typical stamps use PDMS because its elastomeric properties, E = 1.8 MPa, allow it to fit the contour of micro surfaces and its low surface energy, γ = 21.6 dyn/cm². This is a parallel process and can thus place nanoscale objects over a large area in a short time.
* Dip-pen nanolithography
:Dip-pen nanolithography is a process that uses an atomic force microscope to transfer molecules on the tip to a substrate. Initially the tip is dipped into a reservoir with an ink. The ink on the tip evaporates and leaves the desired molecules attached to the tip. When the tip is brought into contact with the surface a water meniscus forms between the tip and the surface resulting in the diffusion of molecules from the tip to the surface. These tips can have radii in the tens of nanometers, and thus SAM molecules can be very precisely deposited onto a specific location of the surface. This process was discovered by Chad Mirkin and co-workers at Northwestern University. | 6 | Supramolecular Chemistry |
Stevens' research has contributed to understanding how changes in the levels of nitrogen compounds in the soil, deposited from the atmosphere, have had significant effects on the composition of the UK flora. This has shown that the number of different species of plants present is reduced as soils receive more inorganic nitrogen compounds from the atmosphere. Stevens has been involved with a long-term project at Tadmore Moor that started in 1986 following the effects of nitrogen fertiliser on this wetland. No fertiliser was added after 1990 but she could still find effects in 2005.
Stevens is part of the Nutrient Network, an international collaboration investigating how grasslands are affected by global climate change, specifically how anthropogenic increases in nitrogen and phosphorus levels affect plant productivity and diversity and the interaction of the plants with grazing animals. This research involves the partners setting up the same experiment in their location so that global comparisons can readily be made. It started in 2005 and had grown to 130 sites by 2021.
She is a trustee of the Ecological Continuity Trust that maintains long-term ecological field experiments and their data in the UK. | 9 | Geochemistry |
Bifunctional purine biosynthesis protein PURH is a protein that in humans is encoded by the ATIC gene.
ATIC encodes an enzyme which generates inosine monophosphate from aminoimidazole carboxamide ribonucleotide.
It has two functions:
* - 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase
* - IMP cyclohydrolase | 1 | Biochemistry |
In humans and many other animals, acid–base homeostasis is maintained by multiple mechanisms involved in three lines of defense:
# Chemical: The first lines of defense are immediate, consisting of the various chemical buffers which minimize pH changes that would otherwise occur in their absence. These buffers include the bicarbonate buffer system, the phosphate buffer system, and the protein buffer system.
# Respiratory component: The second line of defense is rapid consisting of the control the carbonic acid (HCO) concentration in the ECF by changing the rate and depth of breathing by hyperventilation or hypoventilation. This blows off or retains carbon dioxide (and thus carbonic acid) in the blood plasma as required.
# Metabolic component: The third line of defense is slow, best measured by the base excess, and mostly depends on the renal system which can add or remove bicarbonate ions () to or from the ECF. Bicarbonate ions are derived from metabolic carbon dioxide which is enzymatically converted to carbonic acid in the renal tubular cells. There, carbonic acid spontaneously dissociates into hydrogen ions and bicarbonate ions. When the pH in the ECF falls, hydrogen ions are excreted into urine, while bicarbonate ions are secreted into blood plasma, causing the plasma pH to rise. The converse happens if the pH in the ECF tends to rise: bicarbonate ions are then excreted into the urine and hydrogen ions into the blood plasma.
The second and third lines of defense operate by making changes to the buffers, each of which consists of two components: a weak acid and its conjugate base. It is the ratio concentration of the weak acid to its conjugate base that determines the pH of the solution. Thus, by manipulating firstly the concentration of the weak acid, and secondly that of its conjugate base, the pH of the extracellular fluid (ECF) can be adjusted very accurately to the correct value. The bicarbonate buffer, consisting of a mixture of carbonic acid (HCO) and a bicarbonate () salt in solution, is the most abundant buffer in the extracellular fluid, and it is also the buffer whose acid-to-base ratio can be changed very easily and rapidly. | 7 | Physical Chemistry |
Photothermal spectroscopy is a group of high sensitivity spectroscopy techniques used to measure optical absorption and thermal characteristics of a sample. The basis of photothermal spectroscopy is the change in thermal state of the sample resulting from the absorption of radiation. Light absorbed and not lost by emission results in heating. The heat raises temperature thereby influencing the thermodynamic properties of the sample or of a suitable material adjacent to it. Measurement of the temperature, pressure, or density changes that occur due to optical absorption are ultimately the basis for the photothermal spectroscopic measurements.
As with photoacoustic spectroscopy, photothermal spectroscopy is an indirect method for measuring optical absorption, because it is not based on the direct measure of the light which is involved in the absorption. In another sense, however, photothermal (and photoacoustic) methods measure directly the absorption, rather than e.g. calculate it from the transmission, as is the case of more usual (transmission) spectroscopic techniques. And it is this fact that gives the technique its high sensitivity, because in transmission techniques the absorbance is calculated as the difference between total light impinging on the sample and the transmitted (plus reflected, plus scattered) light, with the usual problems of accuracy when one deals with small differences between large numbers, if the absorption is small. In photothermal spectroscopies, instead, the signal is essentially proportional to the absorption, and is zero when there is zero true absorption, even in the presence of reflection or scattering.
There are several methods and techniques used in photothermal spectroscopy. Each of these has a name indicating the specific physical effect measured.
* Photothermal lens spectroscopy (PTS or TLS) measures the thermal blooming that occurs when a beam of light heats a transparent sample. It is typically applied for measuring minute quantities of substances in homogeneous gas and liquid solutions.
* Photothermal deflection spectroscopy (PDS), also called the mirage effect, measures the bending of light due to optical absorption. This technique is particularly useful for measuring surface absorption and for profiling thermal properties in layered materials.
* Photothermal diffraction, a type of four wave mixing, monitors the effect of transient diffraction gratings "written" into the sample with coherent lasers. It is a form of real-time holography.
* Photothermal emission measures an increase in sample infrared radiance occurring as a consequence of absorption. Sample emission follows Stefan's law of thermal emission. This methods is used to measure the thermal properties of solids and layered materials.
* Photothermal single particle microscopy. This technique allows the detection of single absorbing nanoparticles via the creation of a spherically symmetric thermal lens for imaging and correlation spectroscopy. | 7 | Physical Chemistry |
Oxoalkoxometalates are clusters that contain both oxide and alkoxide ligands. Typically they lack terminal oxo ligands. Examples include the dodecatitanate TiO(OPri) (where OPri stands for an alkoxy group), the iron oxoalkoxometalates and iron and copper Keggin ions. | 7 | Physical Chemistry |
Light enters the eye, passes through the optical media, then the inner neural layers of the retina before finally reaching the photoreceptor cells in the outer layer of the retina. The light may be absorbed by a chromophore bound to an opsin, which photoisomerizes the chromophore, initiating both the visual cycle, which "resets" the chromophore, and the phototransduction cascade, which transmits the visual signal to the brain. The cascade begins with graded polarisation (an analog signal) of the excited photoreceptor cell, as its membrane potential increases from a resting potential of -70 mV, proportional to the light intensity. At rest, the photoreceptor cells are continually releasing glutamate at the synaptic terminal to maintain the potential. The transmitter release rate is lowered (hyperpolarization) as light intensity increases. Each synaptic terminal makes up to 500 contacts with horizontal cells and bipolar cells. These intermediate cells (along with amacrine cells) perform comparisons of photoreceptor signals within a receptive field, but their precise functionalities are not well understood. The signal remains as a graded polarization in all cells until it reaches the RGCs, where it is converted to an action potential and transmitted to the brain. | 1 | Biochemistry |
People generate aerosols for various purposes, including:
* as test aerosols for calibrating instruments, performing research, and testing sampling equipment and air filters;
* to deliver deodorants, paints, and other consumer products in sprays;
* for dispersal and agricultural application
* for medical treatment of respiratory disease; and
* in fuel injection systems and other combustion technology.
Some devices for generating aerosols are:
* Aerosol spray
* Atomizer nozzle or nebulizer
* Electrospray
* Electronic cigarette
* Vibrating orifice aerosol generator (VOAG) | 7 | Physical Chemistry |
The main shortcoming related to the free volume concept is that it is not so well defined at the molecular level. A more precise, molecular-level derivation of the Flory–Fox equation has been developed by Alessio Zaccone and Eugene Terentjev. The derivation is based on a molecular-level model of the temperature-dependent shear modulus G of glassy polymers. The shear modulus of glasses has two main contributions, one which is related to affine displacements of the monomers in response to the macroscopic strain, which is proportional to the local bonding environment and also to the non-covalent van der Waals-type interactions, and a negative contribution that corresponds to random (nonaffine) monomer-level displacements due to the local disorder. Due to thermal expansion, the first (affine) term decreases abruptly near the glass transition temperature T because of the weakening of the non-covalent interactions, while the negative nonaffine term is less affected by temperature. Experimentally, it is observed indeed that G drops sharply by many orders of magnitude at or near T (it does not really drop to zero but to the much lower value of the rubber elasticity plateau). By setting at the point where the G drops abruptly and solving for T, one obtains the following relation:
In this equation, is the maximum volume fraction, or packing fraction, occupied by the monomers at the glass transition if there were no covalent bonds, i.e. in the limit of average number of covalent bonds per monomer .
If the monomers can be approximated as soft spheres, then as in the jamming of soft frictionless spheres.
In the presence of covalent bonds between monomers, as is the case in the polymer, the packing fraction is lowered, hence , where is a parameter that expresses the effect of topological constraints due to covalent bonds on the total packing fraction occupied by the monomers in a given polymer.
Finally, the packing fraction occupied by the monomers in the absence of covalent bonds is related to via thermal expansion, according to , which comes from integrating the thermodynamic relation between thermal expansion coefficient and volume V, , where is the coefficient of thermal expansion of the polymer in the glassy state. Note the relation between packing fraction and total volume given by , where is the total number of monomers, with molecular volume , contained in the total volume of the material, which has been used above. Hence is the integration constant in , and it was found that for the case of polystyrene. Also, is the molecular weight of one monomer in the polymer chain.
Hence the above equation clearly recovers the Flory–Fox equation with its dependence on the number average molecular weight , and provides a molecular-level meaning to the empirical parameters present in the Fox-Flory equation. Furthermore, it predicts that , i.e. that the glass transition temperature is inversely proportional to the thermal expansion coefficient in the glass state. | 7 | Physical Chemistry |
Muon beams are classified into three types based on the energy of the muons being produced: high-energy, surface or "Arizona", and ultra-slow muon beams.
High-energy muon beams are formed by the pions escaping the production target at high energies. They are collected over a certain solid angle by quadrupole magnets and directed onto a decay section consisting of a long superconducting solenoid with a field of several tesla. If the pion momentum is not too high, a large fraction of the pions will have decayed before they reach the end of the solenoid. In the laboratory frame the polarization of a high-energy muon beam is limited to about 80% and its energy is of the order of ~40-50MeV. Although such a high energy beam requires the use of suitable moderators and samples with sufficient thickness, it guarantees a homogeneous implantation of the muons in the sample volume. Such beams are also used to study specimens inside of recipients, e.g. samples inside pressure cells. Such muon beams are available at PSI, TRIUMF, J-PARC and [https://web.archive.org/web/20110624051656/http://riken.nd.rl.ac.uk/ral.html RIKEN-RAL].
The second type of muon beam is often called the surface or Arizona beam (recalling the pioneering work of Pifer et al. from the University of Arizona). In these beams, muons arise from pions decaying at rest inside but near the surface of the production target. Such muons are 100% polarized, ideally monochromatic, and have a very low momentum of 29.8 MeV/c (corresponding to a kinetic energy of 4.1 MeV). They have a range width in matter of the order of 180 mg/cm. The paramount advantage of this type of beam is the ability to use relatively thin samples. Beams of this type are available at PSI (Swiss Muon Source SµS), TRIUMF, J-PARC, ISIS Neutron and Muon Source and RIKEN-RAL.
Positive muon beams of even lower energy (ultra-slow muons with energy down to the eV-keV range) can be obtained by further reducing the energy of an Arizona beam by utilizing the energy-loss characteristics of large band gap solid moderators. This technique was pioneered by researchers at the TRIUMF cyclotron facility in Vancouver, B.C., Canada. It was christened with the acronym μSOL (muon separator on-line) and initially employed LiF as the moderating solid. The same 1986 paper also reported the observation of negative muonium ions (i.e., Mu or μ e e) in vacuum. In 1987, the slow μ production rate was increased 100-fold using thin-film rare-gas solid moderators, producing a usable flux of low-energy positive muons. This production technique was subsequently adopted by PSI for their low-energy positive muon beam facility. The tunable energy range of such muon beams corresponds to implantation depths in solids of less than a nanometer up to several hundred nanometers. Therefore, the study of magnetic properties as a function of the distance from the surface of the sample is possible. At the present time, PSI is the only facility where such a low-energy muon beam is available on a regular basis. Technical developments have been also conducted at RIKEN-RAL, but with a strongly reduced low-energy muon rate. J-PARC is projecting the development of a high-intensity low-energy muon beam. | 7 | Physical Chemistry |
The glycine cleavage system (GCS) is also known as the glycine decarboxylase complex or GDC. The system is a series of enzymes that are triggered in response to high concentrations of the amino acid glycine. The same set of enzymes is sometimes referred to as glycine synthase when it runs in the reverse direction to form glycine. The glycine cleavage system is composed of four proteins: the T-protein, P-protein, L-protein, and H-protein. They do not form a stable complex, so it is more appropriate to call it a "system" instead of a "complex". The H-protein is responsible for interacting with the three other proteins and acts as a shuttle for some of the intermediate products in glycine decarboxylation. In both animals and plants, the glycine cleavage system is loosely attached to the inner membrane of the mitochondria. Mutations in this enzymatic system are linked with glycine encephalopathy. | 1 | Biochemistry |
Enzyme-based cleaners are especially useful for biofilm removal. Bacteria are somewhat difficult to remove with traditional alkaline or acid cleaners. Enzyme cleaners are more effective on biofilms since they work as proteases by breaking down proteins at bacterial attachment sites. They work at maximum efficiency at high pH and at temperatures below 60 °C. Enzyme cleaners are an increasingly attractive alternative to traditional chemical cleaners because of biodegradability and other environmental factors, such as reduced wastewater generation and energy savings from using cold water. However, they are typically more expensive than alkaline or acid cleaners. | 1 | Biochemistry |
Morpholinos can interfere with pre-mRNA processing steps either by preventing splice-directing small nuclear ribonucleoproteins (snRNP) complexes from binding to their targets at the borders of introns on a strand of pre-mRNA, or by blocking the nucleophilic adenine base and preventing it from forming the splice lariat structure, or by interfering with the binding of splice regulatory proteins such as splice silencers and splice enhancers. Preventing the binding of snRNP U1 (at the donor site) or U2/U5 (at the polypyrimidine moiety and acceptor site) can cause modified splicing, commonly excluding exons from the mature mRNA. Targeting some splice targets results in intron inclusions, while activation of cryptic splice sites can lead to partial inclusions or exclusions. Targets of U11/U12 snRNPs can also be blocked. Splice modification can be conveniently assayed by reverse-transcriptase polymerase chain reaction (RT-PCR) and is seen as a band shift after gel electrophoresis of RT-PCR products. | 1 | Biochemistry |
Air pollution research show biological and health effects after exposure to mixtures are more potent than effects from exposures of individual components. | 7 | Physical Chemistry |
The North Australian Pastoral Company (NAPCO) is a large, privately owned, Australian cattle company which operates 13 cattle stations (as well as the Wainui farm and feedlot) covering over 60,000 km, managing about 200,000 cattle, in Queensland and the Northern Territory. It produces beef cattle which are grass fed and grain finished before sale to Australian meat processors who onsell beef to domestic and international customers. | 2 | Environmental Chemistry |
Hollow cathode lamps (HCL) are the most common radiation source in LS AAS. Inside the sealed lamp, filled with argon or neon gas at low pressure, is a cylindrical metal cathode containing the element of interest and an anode. A high voltage is applied across the anode and cathode, resulting in an ionization of the fill gas. The gas ions are accelerated towards the cathode and, upon impact on the cathode, sputter cathode material that is excited in the glow discharge to emit the radiation of the sputtered material, i.e., the element of interest. In the majority of cases single element lamps are used, where the cathode is pressed out of predominantly compounds of the target element. Multi-element lamps are available with combinations of compounds of the target elements pressed in the cathode. Multi element lamps produce slightly less sensitivity than single element lamps and the combinations of elements have to be selected carefully to avoid spectral interferences. Most multi-element lamps combine a handful of elements, e.g.: 2 - 8. Atomic Absorption Spectrometers can feature as few as 1-2 hollow cathode lamp positions or in automated multi-element spectrometers, a 8-12 lamp positions may be typically available. | 3 | Analytical Chemistry |
BLOSUM matrices are also used as a scoring matrix when comparing DNA sequences or protein sequences to judge the quality of the alignment. This form of scoring system is utilized by a wide range of alignment software including BLAST. | 1 | Biochemistry |
* John Christopher Draper (1835–1885)
* Henry Draper (1837–1882)
* Virginia Draper Maury (1839–1885)
* Daniel Draper (1841–1931)
* William Draper (1845–1853)
* Antonia Draper Dixon (1849–1923) | 5 | Photochemistry |
Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation and sea spray. Human activities, such as the burning of fossil fuels in vehicles, wood burning, stubble burning, power plants, road dust, wet cooling towers in cooling systems and various industrial processes, also generate significant amounts of particulates. Coal combustion in developing countries is the primary method for heating homes and supplying energy. Because salt spray over the oceans is the overwhelmingly most common form of particulate in the atmosphere, anthropogenic aerosols—those made by human activities—currently account for about 10 percent of the total mass of aerosols in our atmosphere.
Microplastics are an emerging source of atmospheric pollution, particularly fine plastic fibers that are light enough to be carried by the wind. Microplastics traveling in the air cannot be traced back to their specific original sources, as the wind can blow the infinitesimal particles thousands of miles from where they were originally shed. Microplastics are being found in very remote regions of the Earth, where there are no apparent nearby sources of plastic. A common source of airborne microplastic fibers is plastic textiles. While most atmospheric microplastics tend to come from land, microplastics are also entering the atmosphere through ocean and sea mist. | 2 | Environmental Chemistry |
The reductive processes discussed above can be enhanced in two ways. One is by increasing the amount of usable iron in the subsurface to increase the rate of the reduction by chemical or biological means. The second method is to enhance the reducing ability of the iron by coupling it with other chemical reductants or using biological reduction with it. Using this processes, scientists combined sodium dithionite with iron to treat Chrominum VI and TCE effectively.
Combining bacterial action and biological processes with iron is also known to be effective. The most evident uses of biological processes are with the EZVI technology created by NASA and with the EHC product created by Adventus. Both of these materials have iron within some biological matrix (iron is suspended in vegetable oil in EZVI and in organic carbon in EHC) and use microbial organisms to enhance the reduction zone and to create a more anaerobic environment for the reactions to take place in. | 2 | Environmental Chemistry |
* Norris Award (1968)
* Priestley Medal (1976)
* Golden Plate Award of the American Academy of Achievement (1976)
* National Medal of Science (1994)
* Glenn T. Seaborg Medal (1994)
* Othmer Gold Medal (2003) | 7 | Physical Chemistry |
The principle of the test is simple:
• A defined amount of distilled or deionized water is poured into the floor pan of the test chamber.
• The samples are placed in the chamber above the water level. The door or hood of the chamber is tightly closed and hermetically sealed for safety.
• A fixed volume of sulfur dioxide is introduced into the chamber, usually either 1 L (0.33%) or 2 L (0.66%) Volume of SO.
The test is performed in two sections,
o Test section 1: 8 hours warm-up to 40±3 °C (relative humidity 100%)
o Test section 2: 16 hours cooling to 18 to 28 °C (relative humidity max. 75 %)
The test is usually carried out in cycles of 24 hours each.
Caution: The atmosphere containing sulfur dioxide must not be released into the room air. | 8 | Metallurgy |
The units of the structure-factor amplitude depend on the incident radiation. For X-ray crystallography they are multiples of the unit of scattering by a single electron (2.82 m); for neutron scattering by atomic nuclei the unit of scattering length of m is commonly used.
The above discussion uses the wave vectors and . However, crystallography often uses wave vectors and . Therefore, when comparing equations from different sources, the factor may appear and disappear, and care to maintain consistent quantities is required to get correct numerical results. | 3 | Analytical Chemistry |
Molar concentration or molarity is most commonly expressed in units of moles of solute per litre of solution. For use in broader applications, it is defined as amount of substance of solute per unit volume of solution, or per unit volume available to the species, represented by lowercase :
Here, is the amount of the solute in moles, is the number of constituent particles present in volume (in litres) of the solution, and is the Avogadro constant, since 2019 defined as exactly . The ratio is the number density .
In thermodynamics the use of molar concentration is often not convenient because the volume of most solutions slightly depends on temperature due to thermal expansion. This problem is usually resolved by introducing temperature correction factors, or by using a temperature-independent measure of concentration such as molality.
The reciprocal quantity represents the dilution (volume) which can appear in Ostwald's law of dilution.
; Formality or analytical concentration
If a molecular entity dissociates in solution, the concentration refers to the original chemical formula in solution, the molar concentration is sometimes called formal concentration or formality (F) or analytical concentration (c). For example, if a sodium carbonate solution () has a formal concentration of c() = 1 mol/L, the molar concentrations are c() = 2 mol/L and c() = 1 mol/L because the salt dissociates into these ions. | 3 | Analytical Chemistry |
Subcritical crack propagation in glasses falls into three regions. In region I, the velocity of crack propagation increases with ambient humidity due to stress-enhanced chemical reaction between the glass and water. In region II, crack propagation velocity is diffusion controlled and dependent on the rate at which chemical reactants can be transported to the tip of the crack. In region III, crack propagation is independent of its environment, having reached a critical stress intensity. Chemicals other than water, like ammonia, can induce subcritical crack propagation in silica glass, but they must have an electron donor site and a proton donor site. | 8 | Metallurgy |
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