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Oxaziridines have been found to undergo rearrangement reactions via a radical mechanism when irradiated with UV light or in the presence of a single electron transfer reagent such as Cu. spirocylic oxaziridines undergo ring expansions to the corresponding lactam. The migrating substituent is determined by a stereoelectronic effect where the group trans to the lone pair on the nitrogen will always be the predominant migration product. In light of this effect, it is possible to take advantage of the chiral nitrogen due to high inversion barrier to direct the rearrangement. This phenomenon is demonstrated by observed selectivities in the rearrangements below. In the rearrangement on the left the thermodynamically unfavorable product is observed exclusively, while in the reaction on the right the product derived from the less stable radical intermediate is favored.
Aubé takes advantage of this rearrangement as the key step in his synthesis of (+)-yohimbine, a natural medicine classified by the NIH as possibly effective in the treatment of erectile dysfunction and the sexual problems caused by selective serotonin reuptake inhibitors.
It is also notable that oxaziridines will thermally rearrange to nitrones. Cis-trans selectivity of the resulting nitrone is poor, however, yields are good to excellent. It is thought that some oxaziridines racemize over time through a nitrone intermediate. | 0 | Organic Chemistry |
A in plant cell is a complex amorphous polymer and it is from three aromatic alcohols, namely [https://pubchem.ncbi.nlm.nih.gov/compound/p-Coumaryl-alcohol P-Coumaryl], [https://pubchem.ncbi.nlm.nih.gov/compound/Coniferyl-alcohol Coniferyl], and [https://pubchem.ncbi.nlm.nih.gov/compound/Sinapyl-alcohol Sinapyl] alcohols. Lignin is a highly branched polymer and accounts for 15-30% by weight of , so the structure of lignin will vary significantly according to the type of LCBM and the composition will depend on the degradation process. This biosynthesis process is mainly consists of radical coupling reactions and it generates a particular lignin polymer in each plant species. So due to having a complex structure, various molecular spectroscopic methods have been applied to resolve the aromatic units and different interunit linkages in lignin from distinct plant species. | 7 | Physical Chemistry |
Identity by descent (IBD) mapping generally uses single nucleotide polymorphism (SNP) arrays to survey known polymorphic sites throughout the genome of affected individuals and their parents and/or siblings, both affected and unaffected. While these SNPs probably do not cause the disease, they provide valuable insight into the makeup of the genomes in question. A region of the genome is considered identical by descent if contiguous SNPs share the same genotype. When comparing an affected individual to his/her affected sibling, all identical regions are recorded (ex. Shaded in red in above figure). Given that an affected sibling and an unaffected sibling do not have the same disease phenotype, their DNA must by definition be different (barring the presence of a genetic or environmental modifier). Thus, the IBD mapping results can be further supplemented by removing any regions that are identical in both affected individuals and unaffected siblings. This is then repeated for multiple families, thus generating a small, overlapping fragment, which theoretically contains the disease gene. | 1 | Biochemistry |
The Directorate of Precious Metals & Gemstone Testing is one of fourteen directorates forming the Ministry of Industry, Commerce and Tourism. The directorate itself is composed of two sections that deal with assaying and gemmology and the three main functions of the directorate as a whole are:
1. Serving the trade and public with their gemmological and assaying needs.
2. Overseeing the local jewellery sector to ensure that traders adhere to national and international laws and nomenclature.
3. Protecting consumers and the trade from fraud within the market place.
The two sections of the Directorate deal with all aspects of gemmology and precious metal assaying and have existed for over a decade. The Assay Office was established in 1979 via Amiri Decree No.19 and the Gem & Pearl Testing Laboratory followed in 1990 via Amiri Decree No. 10.
Both sections were amongst the first to be established in the Middle East and since their establishment they have developed a positive reputation within the Middle East and beyond. | 3 | Analytical Chemistry |
Van den Bergh reaction is a chemical reaction used to measure bilirubin levels in blood. More specifically, it determines the amount of conjugated bilirubin in the blood. The reaction produces azobilirubin.
Principle: bilirubin reacts with diazotised sulphanilic acid to produce purple coloured azobilirubin. This reaction is highly useful in understanding the nature of jaundice. This was pioneered by the Dutch physician, Abraham Albert Hijmans van den Bergh (1869–1943) of Utrecht. This test helps to identify the type of jaundice. The serum of the patient is mixed with diazo reagent. If a red colour develops immediately it is called a direct positive. It happens if conjugated bilirubin is present.
In an indirect positive test, the patient's serum is first treated with alcohol and later mixed with diazo reagent. This causes development of a red colour. It is seen if unconjugated bilirubin is present.
If both conjugated and unconjugated bilirubin are present the reaction is termed a biphasic reaction. | 3 | Analytical Chemistry |
Molecular propellers can be rotated by molecular motors that can be driven by chemical, biological, optical and electrical means, or various ratchet-like mechanisms. Nature realizes most biological activities with a large number of highly sophisticated molecular motors, such as myosin, kinesin, and ATP synthase. For example, rotary molecular motors attached to protein-based tails called flagella can propel bacteria. | 6 | Supramolecular Chemistry |
Diebold's first appointment after graduation was as a post-doctoral research associate in the group of Theodore E. Madey in the department of physics at Rutgers University (1990-1993). It was there that she was first introduced to oxide surfaces, an area that she would later come to refer to as "the love of her scientific life". Her first faculty appointment followed, at Tulane University, New Orleans, USA, where she was an assistant professor (1993–1999), associate professor (1999–2001), and professor of physics (2001–2009), and also an adjunct professor of chemistry (1993–2009). During this time period, she also completed her habilitation in experimental physics (TU Vienna, 1998), held the Yahoo! Founder Chair in Science and Engineering (2006–2009), and was the associate department chair (2002–2009).
In 2005, Diebold and her group were forced to temporarily evacuate from New Orleans, which experienced massive flooding and power outages from the impact of Hurricane Katrina. They were hosted by the group of Theodore E. Madey at Rutgers University during this challenging period.
In 2010 she moved to the Institute of Applied Physics at TU Wien where she is currently a professor of surface science and deputy department head, and retains the title of research professor at Tulane University.. Since 2022 she also serves as Vice President of the Austrian Academy of Sciences. | 7 | Physical Chemistry |
The materials used for generation of terahertz radiation by optical rectification can also be used for its detection by using the Pockels effect, where particular crystalline materials become birefringent in the presence of an electric field. The birefringence caused by the electric field of a terahertz pulse leads to a change in the optical polarization of the detection pulse, proportional to the terahertz electric-field strength. With the help of polarizers and photodiodes, this polarization change is measured.
As with the generation, the bandwidth of the detection is dependent on the laser pulse duration, material properties, and crystal thickness. | 7 | Physical Chemistry |
The CBS catalyst or Corey–Bakshi–Shibata catalyst is an asymmetric catalyst derived from proline. It finds many uses in organic reactions such as the CBS reduction, Diels-Alder reactions and (3+2) cycloadditions. Proline, a naturally occurring chiral compound, is readily and cheaply available. It transfers its stereocenter to the catalyst which in turn is able to drive an organic reaction selectively to one of two possible enantiomers. This selectivity is due to steric strain in the transition state that develops for one enantiomer but not for the other. | 0 | Organic Chemistry |
The following references are for critical reviews of published stability constants for various classes of ligands. All these reviews are published by IUPAC and the full text is available, free of charge, in pdf format.
*ethylenediamine (en)
*Nitrilotriacetic acid (NTA)
*aminopolycarboxylic acids (complexones)
*Alpha hydroxy acids and other hydroxycarboxylic acids
*crown ethers
*phosphonic acids
*imidazoles and histamines
*amino acids with polar side-chains
*nucleotides
*acetylacetone
*general
*Chemical speciation of environmentally significant heavy metals with inorganic ligands. Part 1: The Hg–Cl, OH, , , and systems.
*Chemical speciation of environmentally significant metals with inorganic ligands Part 2: The Cu–OH, Cl</sup>, , , and aqueous systems
*Chemical speciation of environmentally significant metals with inorganic ligands Part 3: The Pb–OH, Cl</sup>, , , and systems
*Chemical speciation of environmentally significant metals with inorganic ligands. Part 4: The Cd–OH, Cl, , , and systems | 7 | Physical Chemistry |
5-Bromouracil (5-BrU, 5BrUra, or br5Ura) is a brominated derivative of uracil that acts as an antimetabolite or base analog, substituting for thymine in DNA, and can induce DNA mutation in the same way as 2-aminopurine. It is used mainly as an experimental mutagen, but its deoxyriboside derivative (5-bromo-2-deoxy-uridine) is used to treat neoplasms.
5-BrU exists in three tautomeric forms that have different base pairing properties. The keto form (shown in the infobox) is complementary to adenine, so it can be incorporated into DNA by aligning opposite adenine residues during DNA replication (see below left). Alternatively, the enol (below right) and ion forms are complementary to guanine. This means that 5-BrU can be present in DNA either opposite adenine or guanine.
The three forms frequently interchange so base-pairing properties can become altered at any time. The result of this is that during a subsequent round of replication a different base is aligned opposite the 5-BrU residue. Further rounds of replication fix the change by incorporating a normal nitrogen base into the complementary strand.
Thus 5-BrU induces a point mutation via base substitution. This base pair will change from an A-T to a G-C or from a G-C to an A-T after a number of replication cycles, depending on whether 5-BrU is within the DNA molecule or is an incoming base when it is enolized or ionized. | 1 | Biochemistry |
These three metals generally form in a certain type of granite, via a similar mechanism to intrusive-related gold and copper. They are considered together because the process of forming these deposits is essentially the same. Skarn type mineralisation related to these granites is a very important type of tin, tungsten, and molybdenum deposit. Skarn deposits form by reaction of mineralised fluids from the granite reacting with wall rocks such as limestone. Skarn mineralisation is also important in lead, zinc, copper, gold, and occasionally uranium mineralisation.
Greisen granite is another related tin-molybdenum and topaz mineralisation style. | 9 | Geochemistry |
More than 600 million SNPs have been identified across the human genome in the world's population. A typical genome differs from the reference human genome at 4 to 5 million sites, most of which (more than 99.9%) consist of SNPs and short indels. | 1 | Biochemistry |
Total carbon (TC) is an analytical parameter representing the concentration of carbon in a sample. TC includes carbon in any form, whether organic or inorganic, volatile or fixed, dissolved or suspended. In many application areas, rather than TC, a parameter representing of subset of TC is measured; examples include Total organic carbon (TOC), Particulate inorganic carbon (PIC), and Dissolved organic carbon (DOC). | 3 | Analytical Chemistry |
EMBO Reports is a peer-reviewed scientific journal covering research related to biology at a molecular level. It publishes primary research papers, reviews, and essays and opinion. It also features commentaries on the social impact of advances in the life sciences and the converse influence of society on science. A sister journal to The EMBO Journal, EMBO Reports was established in 2000 and was published on behalf of the European Molecular Biology Organization by Nature Publishing Group since 2003. It is now published by EMBO Press. | 1 | Biochemistry |
Crotonyl-coenzyme A is an intermediate in the fermentation of butyric acid, and in the metabolism of lysine and tryptophan. It is important in the metabolism of fatty acids and amino acids. | 1 | Biochemistry |
Common synthetic polymers that can be attacked include polypropylene and LDPE, where tertiary carbon bonds in their chain structures are the centres of attack. Ultraviolet rays interact with these bonds to form free radicals, which then react further with oxygen in the atmosphere, producing carbonyl groups in the main chain. The exposed surfaces of products may then discolour and crack, and in extreme cases, complete product disintegration can occur.
In fibre products like rope used in outdoor applications, product life will be low because the outer fibres will be attacked first, and will easily be damaged by abrasion for example. Discolouration of the rope may also occur, thus giving an early warning of the problem.
Polymers which possess UV-absorbing groups such as aromatic rings may also be sensitive to UV degradation. Aramid fibres like Kevlar, for example, are highly UV-sensitive and must be protected from the deleterious effects of sunlight. | 5 | Photochemistry |
Diphosphagermylenes are a class of compounds containing a divalent germanium atom bound to two phosphorus atoms. While these compounds resemble diamidocarbenes, such as N-heterocyclic carbenes (NHC), diphosphagermylenes display bonding characteristics distinct from those of diamidocarbenes. In contrast to NHC compounds, in which there is effective N-C p(π)-p(π) overlap between the lone pairs of planar nitrogens and an empty p-orbital of a carbene, systems containing P-Ge p(π)-p(π) overlap are rare. Until 2014, the geometry of phosphorus atoms in all previously reported diphosphatetrylenes are pyramidal, with minimal P-Ge p(π)-p(π) interaction. It has been suggested that the lack of p(π)-p(π) in Ge-P bonds is due to the high energetic barrier associated with achieving a planar configuration at phosphorus, which would allow for efficient p(π)-p(π) overlap between the phosphorus lone pair and the empty P orbital of Ge. The resulting lack of π stabilization contributes to the difficulty associated with isolating diphosphagermylene and the Ge-P double bonds. However, utilization of sterically encumbering phosphorus centers has allowed for the isolation of diphosphagermylenes with a planar phosphorus center with a significant P-Ge p(π)-p(π) interaction. | 0 | Organic Chemistry |
One limitation of EPIC-seq is its reliance on prior knowledge of genes associated with specific cancers. The effectiveness of the EPIC-seq model hinges on the availability of comprehensive gene expression profiles for the targeted cancer types. This dependency may restrict its applicability to cancers with well-characterized gene expression patterns, limiting its utility in cancers with less understood molecular signatures. | 1 | Biochemistry |
Thiol groups contain the functionality R−SH. Thiols are structurally similar to the alcohol group, but these functionalities are very different in their chemical properties. Thiols are more nucleophilic, more acidic, and more readily oxidized. This acidity can differ by 5 pK units.
The difference in electronegativity between sulfur (2.58) and hydrogen (2.20) is small and therefore hydrogen bonding in thiols is not prominent. Aliphatic thiols form monolayers on gold, which are topical in nanotechnology.
Certain aromatic thiols can be accessed through a Herz reaction.
Disulfides R−S−S−R with a covalent sulfur to sulfur bond are important for crosslinking: in biochemistry for the folding and stability of some proteins and in polymer chemistry for the crosslinking of rubber.
Longer sulfur chains are also known, such as in the natural product varacin which contains an unusual pentathiepin ring (5-sulfur chain cyclised onto a benzene ring). | 9 | Geochemistry |
This method of deoxidization involves adding specific metals into the steel. These metals will react with the unwanted oxygen, forming a strong oxide that, compared to pure oxygen, will reduce the steel's strength and qualities by a lesser amount.
The chemical equation for deoxidization is represented by:
where n and m are coefficients, D is the deoxidizing agent, and O is oxygen.
Thus, the chemical equilibrium equation involved is:
where a is the activity, or concentration, of the oxide in the steel,
a is the activity of the deoxidizing agent,
and a is the activity of the oxygen.
An increase in the equilibrium constant K will cause an increase in a, and thus more of the oxide product.
K can be manipulated by the steel temperature via the following equation:
where A and B are parameters specific to different deoxidizers and T is the temperature in K°. Below are the values for certain deoxidizers at a temperature of 1873 K°.
Below is a list of commonly used metallic deoxidizers:
* Ferrosilicon, ferromanganese, calcium silicide - used in steelmaking in production of carbon steels, stainless steels, and other ferrous alloys
* Manganese - used in steelmaking
* Silicon carbide, calcium carbide - used as ladle deoxidizer in steel production
* Aluminum dross - also a ladle deoxidizer, used in secondary steelmaking
* Calcium - used as a deoxidizer, desulfurizer, or decarbonizer for ferrous and non-ferrous alloys
* Titanium - used as a deoxidizer for steels
* Phosphorus, copper(I) phosphide - used in production of oxygen-free copper
* Calcium hexaboride - used in production of oxygen-free copper, yields higher conductivity copper than phosphorus-deoxidized
* Yttrium - used to deoxidize vanadium and other non-ferrous metals
* Zirconium
* Magnesium
* Carbon
* Tungsten | 8 | Metallurgy |
Marcus' theory of outer sphere electron transfer predicts that such a tunneling process will occur most quickly in systems where the electron transfer is thermodynamically favorable (i.e. between strong reductants and oxidants) and where the electron transfer has a low intrinsic barrier.
The intrinsic barrier of electron transfer derives from the Franck–Condon principle, stating that electronic transition takes place more quickly given greater overlap between the initial and final electronic states. Interpreted loosely, this principle suggests that the barrier of an electronic transition is related to the degree to which the system seeks to reorganize. For an electronic transition with a system, the barrier is related to the "overlap" between the initial and final wave functions of the excited electron–i.e. the degree to which the electron needs to "move" in the transition.
In an intermolecular electron transfer, a similar role is played by the degree to which the nuclei seek to move in response to the change in their new electronic environment. Immediately after electron transfer, the nuclear arrangement of the molecule, previously an equilibrium, now represents a vibrationally excited state and must relax to its new equilibrium geometry. Rigid systems, whose geometry is not greatly dependent on oxidation state, therefore experience less vibrational excitation during electron transfer, and have a lower intrinsic barrier. Photocatalysts such as [Ru(bipy)], are held in a rigid arrangement by flat, bidentate ligands arranged in an octahedral geometry around the metal center. Therefore, the complex does not undergo much reorganization during electron transfer. Since electron transfer of these complexes is fast, it is likely to take place within the duration of the catalyst's active state, i.e. during the lifetime of the triplet excited state. | 5 | Photochemistry |
In order to provide access to relevant data to users ChemSeer provides new features that are not available in traditional search engines or digital libraries.
# Chemical Entity Search: A tool capable of identifying Chemical formulae and chemical names, and extracting and disambiguating them from general terms within documents. Those disambiguated terms are used for performing searches.
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In addition to these tools, ChemSeer will integrate the advances made by its sister project CiteSeer to provide:
* Full text search
* Author, affiliation, title and venue search
* Citation and acknowledgement search
* Citation linking and statistics | 2 | Environmental Chemistry |
The total quantity of ATP in the human body is about 0.1 mol/L. The majority of ATP is recycled from ADP by the aforementioned processes. Thus, at any given time, the total amount of ATP + ADP remains fairly constant.
The energy used by human cells in an adult requires the hydrolysis of 100 to 150 mol/L of ATP daily, which means a human will typically use their body weight worth of ATP over the course of the day. Each equivalent of ATP is recycled 1000–1500 times during a single day (), at approximately 9×10 molecules/s. | 1 | Biochemistry |
Monocyclic cycloalkenes are cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, and so on. Bicyclic alkenes include norbornene and norbornadiene.
Two more examples are shown below, methylenecyclohexane on the left and 1-methylcyclohexene on the right:
An exocyclic group is always shown outside the ring structure, take for instance the exocyclic double bond of the former molecule. Isotoluenes are a prominent class of compounds with exocyclic double bonds.
The placement of double bonds in many alicyclic compounds can be predicted with Bredt's rule. | 0 | Organic Chemistry |
Sand casting is one of the most popular and simplest types of casting, and has been used for centuries. Sand casting allows for smaller batches than permanent mold casting and at a very reasonable cost. Not only does this method allow manufacturers to create products at a low cost, but there are other benefits to sand casting, such as very small-size operations. The process allows for castings small enough fit in the palm of one's hand to those large enough for a train car bed (one casting can create the entire bed for one rail car). Sand casting also allows most metals to be cast depending on the type of sand used for the molds.
Sand casting requires a lead time of days, or even weeks sometimes, for production at high output rates (1–20 pieces/hr-mold) and is unsurpassed for large-part production. Green (moist) sand, which is black in color, has almost no part weight limit, whereas dry sand has a practical part mass limit of . Minimum part weight ranges from . The sand is bonded using clays, chemical binders, or polymerized oils (such as motor oil). Sand can be recycled many times in most operations and requires little maintenance. | 8 | Metallurgy |
In 2023, researchers in the United States developed a method to determine BET surface areas using a thermogravimetric analyzer (TGA). This method uses a TGA to heat a porous sample loaded with an adsorbate, the produced plot of sample mass vs. temperature is then mapped into a standard isotherm to which BET theory is applied as normal. Common fluids, e.g. water or toluene, can be used as adsorbates for the TGA method allowing the specific interactions of different adsorbates to be determined, as these frequently differ from the commonly used nitrogen. | 7 | Physical Chemistry |
Conservation of substance implies that the volume of wine in the barrel holding mostly water has to be equal to the volume of water in the barrel holding mostly wine.
The mixtures can be visualised as separated into their water and wine components:
To help in grasping this, the wine and water may be represented by, say, 100 red and 100 white marbles, respectively. If 25, say, red marbles are mixed in with the white marbles, and 25 marbles of any color are returned to the red container, then there will again be 100 marbles in each container. If there are now x white marbles in the red container, then there must be x red marbles in the white container. The mixtures will therefore be of equal purity. An example is shown below. | 7 | Physical Chemistry |
Cryosurgery (with cryo from the Ancient Greek ) is the use of extreme cold in surgery to destroy abnormal or diseased tissue; thus, it is the surgical application of cryoablation.
Cryosurgery has been historically used to treat a number of diseases and disorders, especially a variety of benign and malignant skin conditions. | 1 | Biochemistry |
After studying at the École nationale supérieure des industries chimiques de Nancy from 1958 to 1961, he obtained a doctorate under the supervision of Professor Serge David in 1966 and continued for two years at Harvard University in Massachusetts (United States) as a post-doctoral researcher with Professor Roger W. Jeanloz. He then entered the University of Orléans in 1969 as a professor, where he was Director of the Institute of Organic and Analytical Chemistry from 1978 to 1987. He then became Professor of Chemistry in 1986 at the Université Pierre-et-Marie-Curie, where he then headed the Laboratory of Selective Processes in Organic and Bioorganic Chemistry in the Department of Chemistry at the École normale supérieure. He then became Professor Emeritus at Sorbonne University in 2006 and joined the Paris Institute of Molecular Chemistry. | 0 | Organic Chemistry |
Shikimic acid is a precursor for:
* indole, indole derivatives and aromatic amino acid tryptophan and tryptophan derivatives such as the psychedelic compound dimethyltryptamine
* many alkaloids and other aromatic metabolites | 1 | Biochemistry |
Berthelot independently enunciated a generalization (commonly known as Berthelot's Third Principle, or Principle of Maximum Work), which may be briefly stated as: every pure chemical reaction is accompanied by evolution of heat. Whilst this principle is undoubtedly applicable to the great majority of chemical actions under ordinary conditions, it is subject to numerous exceptions, and cannot therefore be taken (as its authors originally intended) as a secure basis for theoretical reasoning on the connection between thermal effect and chemical affinity. The existence of reactions which are reversible on slight alteration of conditions at once invalidates the principle, for if the action proceeding in one direction evolves heat, it must absorb heat when proceeding in the reverse direction. As the principle was abandoned even by its authors, it is now only of historical importance, although for many years it exerted considerable influence on thermochemical research.
Thus, to summarize, in 1875 by the French chemist Marcellin Berthelot which stated that chemical reactions will tend to yield the maximum amount of chemical energy in the form of work as the reaction progresses.
In 1876, however, through the works of Willard Gibbs and others to follow, the work principle was found to be a particular case of a more general statement:
The principle of work was a precursor to the development of the thermodynamic concept of free energy. | 7 | Physical Chemistry |
Until around 1975, when HEp-2 cells were introduced, animal tissue was used as the standard substrate for immunofluorescence. HEp-2 cells are currently one of the most common substrates for ANA detection by immunofluorescence.
Originally started a laryngeal carcinoma strain, the cell line was contaminated and displaced by HeLa cells, and has now been identified as actually HeLa cells.
They are superior to the previously used animal tissues because of their large size and the high rate of mitosis (cell division) in the cell line. This allows the detection of antibodies to mitosis-specific antigens, such as centromere antibodies. They also allow identification of anti-Ro antibodies, because acetone is used for fixation of the cells (other fixatives can wash the antigen away).
There are many nuclear staining patterns seen on HEp-2 cells: homogeneous, speckled, nucleolar, nuclear membranous, centromeric, nuclear dot and pleomorphic. The homogeneous pattern is seen when the condensed chromosomes and interphase chromatin stain. This pattern is associated with anti-dsDNA antibodies, antibodies to nucleosomal components, and anti-histone antibodies. There are two speckled patterns: fine and coarse. The fine speckled pattern has fine nuclear staining with unstained metaphase chromatin, which is associated with anti-Ro and anti-La antibodies. The coarse staining pattern has coarse granular nuclear staining, caused by anti-U1-RNP and anti-Sm antibodies. The nucleolar staining pattern is associated with many antibodies including anti-Scl-70, anti-PM-Scl, anti-fibrillarin and anti-Th/To. Nuclear membrane staining appears as a fluorescent ring around the cell nucleus and are produced by anti-gp210 and anti-p62 antibodies. The centromere pattern shows multiple nuclear dots in interphase and mitotic cells, corresponding to the number of chromosomes in the cell. Nuclear dot patterns show between 13 and 25 nuclear dots in interphase cells and are produced by anti-sp100 antibodies. Pleomorphic pattern is caused by antibodies to the proliferating cell nuclear antigen. Indirect immunofluorescence has been shown to be slightly superior compared to ELISA in detection of ANA from HEp-2 cells. | 1 | Biochemistry |
Microfluidic diffusional sizing (MDS) is a method to measure the size of particles based on the degree to which they diffuse within a microfluidic laminar flow. It allows size measurements to be taken from extremely small quantities of material (nano-grams) and is particularly useful when sizing molecules which may vary in size depending on their environment - e.g. protein molecules which may unfold or become denatured in unfavourable conditions. | 1 | Biochemistry |
Many schemes attempting to quantify relative nucleophilic strength have been devised. The following empirical data have been obtained by measuring reaction rates for many reactions involving many nucleophiles and electrophiles. Nucleophiles displaying the so-called alpha effect are usually omitted in this type of treatment. | 7 | Physical Chemistry |
Some drugs that contain a catechol group react with phosphomolybdic acid (HPMoO) to give the heteropoly-molybdenum blue colour. Micro quantities of the drugs can be determined. | 7 | Physical Chemistry |
A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, flower, and fruit collectively form the shoot system. In most leaves, the primary photosynthetic tissue is the palisade mesophyll and is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of Eucalyptus, palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Most leaves are flattened and have distinct upper (adaxial) and lower (abaxial) surfaces that differ in color, hairiness, the number of stomata (pores that intake and output gases), the amount and structure of epicuticular wax and other features. Leaves are mostly green in color due to the presence of a compound called chlorophyll which is essential for photosynthesis as it absorbs light energy from the sun. A leaf with lighter-colored or white patches or edges is called a variegated leaf.
Leaves can have many different shapes, sizes, textures and colors. The broad, flat leaves with complex venation of flowering plants are known as megaphylls and the species that bear them, the majority, as broad-leaved or megaphyllous plants, which also include acrogymnosperms and ferns. In the lycopods, with different evolutionary origins, the leaves are simple (with only a single vein) and are known as microphylls. Some leaves, such as bulb scales, are not above ground. In many aquatic species, the leaves are submerged in water. Succulent plants often have thick juicy leaves, but some leaves are without major photosynthetic function and may be dead at maturity, as in some cataphylls and spines. Furthermore, several kinds of leaf-like structures found in vascular plants are not totally homologous with them. Examples include flattened plant stems called phylloclades and cladodes, and flattened leaf stems called phyllodes which differ from leaves both in their structure and origin. Some structures of non-vascular plants look and function much like leaves. Examples include the phyllids of mosses and liverworts. | 5 | Photochemistry |
In chemistry, a foldamer is a discrete chain molecule (oligomer) that folds into a conformationally ordered state in solution. They are artificial molecules that mimic the ability of proteins, nucleic acids, and polysaccharides to fold into well-defined conformations, such as α-helices and β-sheets. The structure of a foldamer is stabilized by noncovalent interactions between nonadjacent monomers. Foldamers are studied with the main goal of designing large molecules with predictable structures. The study of foldamers is related to the themes of molecular self-assembly, molecular recognition, and host–guest chemistry. | 6 | Supramolecular Chemistry |
Flux, or metabolic flux is the rate of turnover of molecules through a metabolic pathway. Flux is regulated by the enzymes involved in a pathway. Within cells, regulation of flux is vital for all metabolic pathways to regulate the pathway's activity under different conditions. Flux is therefore of great interest in metabolic network modelling, where it is analysed via flux balance analysis and metabolic control analysis.
In this manner, flux is the movement of matter through metabolic networks that are connected by metabolites and cofactors, and is therefore a way of describing the activity of the metabolic network as a whole using a single characteristic. | 1 | Biochemistry |
Martin Schoell is a German geochemist. His research focuses on using stable isotopes to characterize the geochemistry of petroleum. Schoell is known for his work regarding CO, sedimentary rocks, methane, natural gas, carbon isotopes, and acetate fermentation and how these factors enable identification of the origins of greenhouse gasses. Schoell was the founder, CEO and president of Gas Consult International, Inc., a private natural gas consulting firm, from 2001 to 2015. Schoell was awarded the Alfred Treibs Award by the Geochemical Society in 2008. | 9 | Geochemistry |
Reflection high-energy electron diffraction (RHEED) is a technique used to characterize the surface of crystalline materials. RHEED systems gather information only from the surface layer of the sample, which distinguishes RHEED from other materials characterization methods that also rely on diffraction of high-energy electrons. Transmission electron microscopy, another common electron diffraction method samples mainly the bulk of the sample due to the geometry of the system, although in special cases it can provide surface information. Low-energy electron diffraction (LEED) is also surface sensitive, but LEED achieves surface sensitivity through the use of low energy electrons. | 3 | Analytical Chemistry |
Many small replicons that have circular genomes such as circular ssDNA viruses and circular plasmids replicate via rolling circle replication (RCR), which is a unidirectional, strand displacement form of DNA replication similar to RHR. In RCR, successive rounds of replication, which proceeds in a loop around the genome, are initiated and terminated by site-specific single-strand nicks made by a replicon-encoded endonuclease, variously called the nickase, relaxase, mobilization protein (mob), transesterase, or replication protein (Rep). The replication initiator protein of parvoviruses is genetically related to these other endonucleases.
RCR initiator proteins contain three motifs considered to be important for replication. Two of these are retained within parvovirus initiator proteins: an HUHUUU cluster, which is presumed to bind to a ion required for nicking, and a YxxxK motif that contains the active-site tyrosine residue that attacks the phosphodiester bond of target DNA. In contrast to RCR initiator proteins, which can join together DNA strands, RHR initiator proteins have only vestigial traces of being able to perform ligation.
RCR begins when the initiator protein nicks a DNA strand at a specific sequence in the replication origin region. This is done through a transesterification reaction that forms a 5′-phosphate bond that connects the DNA to the active-site tyrosine and frees the 3′-end hydroxyl (3′-OH) adjacent to the nick site. The 3′-end is then used as a primer for the host DNA polymerase to begin replication while the initiator protein remains attached to the 5′-end of the "original" strand. After one loop of replication around the circular genome, the initiator protein returns to the nick site, i.e. the original initiator complex, while still attached to the parent strand and attacks the regenerated duplex nick site, or a nearby second site in some cases, by means of a topoisomerase-like nicking-joining reaction.
During the aforementioned reaction, the initiator protein cleaves a new nick site and is transferred across the analogous phosphodiester bond. It thereby becomes attached to the new 5′-end while ligating the 5′-end of the first strand to which it was originally attached to the 3′-end of the same strand. This second mechanism varies depending on the replicon. Some replicons such as the virus ΦX174 contain a second active tyrosine residue in the initiator protein. Others use the analogous active-site tyrosine in a second initiator protein that is present as part of a multimeric nickase complex.
This second nicking reaction may occur after one loop or successive loops may occur in which a concatemer containing multiple copies of the genome is created. The result of this nick is that displaced genomes become detached from the replicative molecule. These copies of the genome are ligated and may either be encapsidated into progeny capsids, provided they are monomeric, or converted to a covalently-closed double-stranded form by a host DNA polymerase for further replication. While RHR generally involves replication of both sense strands in a continuous process, RCR has complementary strand synthesis and genomic strand synthesis occur separately.
The strategies used in RHR to engage the nick site are also present in RCR. Most RCR origins are in the form of duplex DNA that has to be melted before nicking. RCR initiators accomplish this by binding to specific DNA-binding sequences in the origin next to the initiation site. The latter site is then melted in a process that consumes ATP and which is assisted by the ability of the separated strands to reconfigure into stem-loop structures. In these structures, the nick site is presented on an exposed loop. Like RHR initiator proteins, many RCR initiator proteins contain helicase activity, which allows them to melt the DNA prior to nicking and serve as the 3′-to-5′ helicase in the replication fork. | 1 | Biochemistry |
Australian rangelands cover approximately 75% of the nations land mass. Characteristically arid and semi arid the rangelands offer wide variations in climate, land and soil. The pastoral industry and particularly pastoral practices equate to 60% of rangeland usage. Subsequently, Australias 25.5 million beef cattle generate a gross average of $7.4 million per year. The Northern Rangelands are the centre for beef productivity in Australia, producing 70% of national beef in the year 2005 - 2006. The grazing of cattle is the primary use of Australias Northern Rangelands, and as such, it has enabled them to become a central organ for Australian agricultural enterprises. The production of beef in these rangelands draws upon a traditional low input-low output system of land management. Australias Northern rangelands have engaged in recent innovations to increase beef productivity whilst reducing greenhouse gas emissions. These strategies include; improving herd genetics, utilising feed bases, and promoting both feedlot finishing and property infrastructure. Species of cows such as the Red Angus, Tuli, Belmont Reds, Senapol and Brahman bulls are common species utilised in the Northern Rangeland industry for sustained productivity and carcass yields given Australia's arid and semi arid climate.
NAPCO has adopted these strategies and complemented them by utilising solar energy systems, perennial pastures and minimum tillage to increase productivity and limit carbon emissions. Further, the company has significantly contributed to developing a genetic improvement program which has introduced a tropically adapted cattle breed which has improved fertility and growth. NAPCO's composite cattle breeds, the Alexandria and Kynuna composites, are suited to arid and semi arid climates which are the product of the environmental conditions in the northern rangelands. The composite cattle proves to be more durable compared to the Shorthorn cow variations, due to their increased drought and disease resistance and heat tolerance. The composites are a more profitable long term species for NAPCO that has ensured beef productivity has been maintained whilst minimising environmental degradation. | 2 | Environmental Chemistry |
In order to levitate the particle in air, the downward force of gravity must be countered by the forces stemming from photon momentum transfer. Typically photon radiation pressure of a focused laser beam of enough intensity counters the downward force of gravity while also preventing lateral (side to side) and vertical instabilities to allow for a stable optical trap capable of holding small particles in suspension.
Micrometer sized (from several to 50 micrometers in diameter) transparent dielectric spheres such as fused silica spheres, oil or water droplets, are used in this type of experiment. The laser radiation can be fixed in wavelength such as that of an argon ion laser or that of a tunable dye laser. Laser power required is of the order of 1 Watt focused to a spot size of several tens of micrometers. Phenomena related to morphology-dependent resonances in a spherical optical cavity have been studied by several research groups.
For a shiny object, such as a metallic micro-sphere, stable optical levitation has not been achieved. Optical levitation of a macroscopic object is also theoretically possible, and can be enhanced with nano-structuring.
Materials that have been successfully levitated include Black liquor, aluminum oxide, tungsten, and nickel. | 1 | Biochemistry |
The class Gammaproteobacteria forms one of the largest groups of bacteria. It is currently distinguished from other bacteria solely by 16s rRNA-based phylogenetic trees. No molecular characteristics unique to the class or its different subgroups are known. A detailed CSI-based study was conducted to better understand the phylogeny of this class. Firstly, a phylogenetic tree based on concatenated sequences of a number of universally-distributed proteins was created. The branching order of the different orders of the class Gammaproteobacteria (from most recent to the earliest diverging) was: Enterobacteriales >Pasteurellales >Vibrionales, Aeromonadales >Alteromonadales >Oceanospirillales, Pseudomonadales >Chromatiales, Legionellales, Methylococcales, Xanthomonadales, Cardiobacteriales, Thiotrichales. Additionally, 4 CSIs were discovered that were unique to most species of the class Gammaproteobacteria. A 2 aa deletion in AICAR transformylase was uniquely shared by all gammaproteobacteria except for Francisella tularensis. A 4 aa deletion in RNA polymerase b-subunit and a 1 aa deletion in ribosomal protein L16 were found uniquely in various species belonging to the orders Enterobacteriales, Pasteurellales, Vibrionales, Aeromonadales and Alteromonadales, but were not found in other gammaproteobacteria. Lastly, a 2 aa deletion in leucyl-tRNA synthetase was commonly present in the above orders of the class Gammaproteobacteria and in some members of the order Oceanospirillales. Another CSI-based study has also identified 4 CSIs that are exclusive to the order Xanthomonadales. Taken together, these two facts show that Xanthomonadales is a monophyletic group that is ancestral to other Gammaproteobacteria, which further shows that Xanthomonadales is an independent subdivision, and constitutes one of the deepest-branching lineages within the Gammaproteobacteria clade. | 1 | Biochemistry |
Kikuchi lines, first observed by Seishi Kikuchi in 1928, are linear features created by electrons scattered both inelastically and elastically. As the electron beam interacts with matter, the electrons are diffracted via elastic scattering, and also scattered inelastically losing part of their energy. These occur simultaneously, and cannot be separated – according to the Copenhagen interpretation of quantum mechanics, only the probabilities of electrons at detectors can be measured. These electrons form Kikuchi lines which provide information on the orientation.
Kikuchi lines come in pairs forming Kikuchi bands, and are indexed in terms of the crystallographic planes they are connected to, with the angular width of the band equal to the magnitude of the corresponding diffraction vector . The position of Kikuchi bands is fixed with respect to each other and the orientation of the sample, but not against the diffraction spots or the direction of the incident electron beam. As the crystal is tilted, the bands move on the diffraction pattern. Since the position of Kikuchi bands is quite sensitive to crystal orientation, they can be used to fine-tune a zone-axis orientation or determine crystal orientation. They can also be used for navigation when changing the orientation between zone axes connected by some band, an example of such a map produced by combining many local sets of experimental Kikuchi patterns is in Figure 8; Kikuchi maps are available for many materials. | 7 | Physical Chemistry |
*Orexins (-A and -B) are involved in a number of cognitive processes, including appetite, arousal, and reward, among many others.
*Neurohypophysial hormones:
**Arginine-vasopressin
**Oxytocin regulates social cognition (e.g., trust and pair-bonding) and modulates maternal behavior.
*Endogenous opioids:
**Dynorphins
**Endorphins
**Endomorphins
**Enkephalins
* Neurotrophic factors are biomolecules – nearly all of which are peptides or small proteins – that support the growth, survival, and differentiation of both developing and mature neurons. Examples of notable neurotrophic factors include:
** Insulin-like growth factor-1 (IGF-1)
** Glial cell line-derived neurotrophic factor (GDNF)
** Vascular endothelial growth factor (VEGF)
** Brain-derived neurotrophic factor (BDNF)
** Nerve growth factor
** Neurotrophin-3
** Neurotrophin-4
** Ephrins
** Neuregulins | 1 | Biochemistry |
The Bromley equation was developed in 1973 by Leroy A. Bromley with the objective of calculating activity coefficients for aqueous electrolyte solutions whose concentrations are above the range of validity of the Debye–Hückel equation. This equation, together with Specific ion interaction theory (SIT) and Pitzer equations is important for the understanding of the behaviour of ions dissolved in natural waters such as rivers, lakes and sea-water. | 7 | Physical Chemistry |
Charge referencing is needed when a sample suffers a charge induced shift of experimental binding energies to obtain meaningful binding energies from both wide-scan, high sensitivity (low energy resolution) survey spectra (0-1100 eV), and also narrow-scan, chemical state (high energy resolution) spectra. Charge induced shifting is normally due to a modest excess of low voltage (-1 to -20 eV) electrons attached to the surface, or a modest shortage of electrons (+1 to +15 eV) within the top 1-12 nm of the sample caused by the loss of photo-emitted electrons. If, by chance, the charging of the surface is excessively positive, then the spectrum might appear as a series of rolling hills, not sharp peaks as shown in the example spectrum.
Charge referencing is performed by adding a Charge Correction Factor to each of the experimentally measured peaks. Since various hydrocarbon species appear on all air-exposed surfaces, the binding energy of the hydrocarbon C (1s) XPS peak is used to charge correct all energies obtained from non-conductive samples or conductors that have been deliberately insulated from the sample mount. The peak is normally found between 284.5 eV and 285.5 eV. The 284.8 eV binding energy is routinely used as the reference binding energy for charge referencing insulators, so that the charge correction factor is the difference between 284.8 eV and the experimentally measured C (1s) peak position.
Conductive materials and most native oxides of conductors should never need charge referencing. Conductive materials should never be charge referenced unless the topmost layer of the sample has a thick non-conductive film. The charging effect, if needed, can also be compensated by providing suitable low energy charges to the surface by the use of low-voltage (1-20 eV) electron beam from an electron flood gun, UV lights, low-voltage argon ion beam with low-voltage electron beam (1-10 eV), aperture masks, mesh screen with low-voltage electron beams, etc. | 7 | Physical Chemistry |
Biolistic transformation involves the integration of a functional fragment of DNA—known as a DNA construct—into target cells. A gene construct is a DNA cassette containing all required regulatory elements for proper expression within the target organism. While gene constructs may vary in their design depending on the desired outcome of the transformation procedure, all constructs typically contain a combination a promoter sequence, a terminator sequence, the gene of interest, and a reporter gene.
;Promoter:Promoters control the location and magnitude of gene expression and function as “the steering wheel and gas pedal” of a gene. Promoters precede the gene of interest in the DNA construct and can be changed through laboratory design to fine-tune transgene expression. The 35S promoter from Cauliflower mosaic virus is an example of a commonly used promoter that results in robust constitutive gene expression within plants.
;Terminator:Terminator sequences are required for proper gene expression and are placed after the coding region of the gene of interest within the DNA construct. A common terminator for biolistic transformation is the NOS terminator derived from Agrobacterium tumefaciens. Due to the high frequency of use of this terminator in genetically engineered plants, strategies have been developed to detect its presence within the food supply to monitor for unauthorized GE crops.
;Reporter gene: A gene encoding a selectable marker is a common element within DNA constructs and is used to select for properly transformed cells. The selectable marker chosen will depend on the species being transformed, but it will typically be a gene granting cells a detoxification capacity for certain herbicides or antibiotics such as kanamycin, hygromycin B, or glyphosate.
;Additional elements: Optional components of a DNA construct include elements such as cre-lox sequences that allow for controlled removal of the construct from the target genome. Such elements are chosen by the construct developer to perform specialized functions alongside the main gene of interest. | 1 | Biochemistry |
In 1992, Canadian authorities determined that eating fish contaminated with malachite green posed a significant health risk. Malachite green was classified a Class II Health Hazard. Due to its low manufacturing cost, malachite green is still used in certain countries with less restrictive laws for non aquaculture purposes. In 2005, analysts in Hong Kong found traces of malachite green in eels and fish imported from China. In 2006, the United States Food and Drug Administration (FDA) detected malachite green in seafood from China, among others, where the substance is also banned for use in aquaculture. In June 2007, the FDA blocked the importation of several varieties of seafood due to continued malachite green contamination.
Malachite green has been banned in the United States since 1983 in food-related applications. The substance is also banned in the United Kingdom. It is prohibited from the use in food in Macao.
Animals metabolize malachite green to its leuco form. Being lipophillic (the leuco form has a log P of 5.70), the metabolite is retained in catfish muscle longer (HL = 10 days) than is the parent molecule (HL = 2.8 days). | 3 | Analytical Chemistry |
Most prominent example of the application of sensor-based ore sorting is the rejection of barren waste before transporting and comminution. Waste rejection is also known under the term pre-concentration. A discrimination has been introduced by Robben. Rule of thumb is that at least 25% of liberated barren waste must be present in the fraction to be treated by sensor-based ore sorting to make waste rejection financially feasible.
Reduction of waste before it enters comminution and grinding processes does not only reduce the costs in those processes, but also releases the capacity that can be filled with higher grade material and thus implies higher productivity of the system. A prejudice against the application of a waste rejection process is, that the valuable content lost in this process is a penalty higher than the savings that can be achieved. But it is reported in the literature that the overall recovery even increases through bringing higher grade material as feed into the mill. In addition, the higher productivity is an additional source of income. If noxious waste such as acid consuming calcite is removed, the downstream recovery increases and the downstream costs decrease disproportionally as reported for example by Bergmann. The coarse waste rejected can be an additional source of income if there is a local market for aggregates. | 3 | Analytical Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2021 impact factor of 3.623. | 9 | Geochemistry |
Experimental Exchangeability was devised by Yampolsky and Stoltzfus. It is the measure of the mean effect of exchanging one amino acid into a different amino acid.
It is based on analysis of experimental studies where 9671 amino acids replacements from different proteins, were compared for effect on protein activity. | 1 | Biochemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2021 impact factor of 5.921. | 9 | Geochemistry |
Artificial nucleic acid analogues have been designed and synthesized. They include peptide nucleic acid, morpholino- and locked nucleic acid, glycol nucleic acid, and threose nucleic acid. Each of these is distinguished from naturally occurring DNA or RNA by changes to the backbone of the molecules. | 1 | Biochemistry |
A melanoblast is a precursor cell of a melanocyte. These cells migrate from the trunk neural crest cells (in terms of axial level from neck to posterior end) dorsolaterally between the ectoderm and dorsal surface of the somites. | 1 | Biochemistry |
M. Nosonovsky and B. Bhushan studied the effect of unitary (non-hierarchical) structures of micro and nano roughness, and hierarchical structures (micro roughness covered with nano roughness). They found that hierarchical structure was not only necessary for a high contact angle but essential for the stability of the water-solid and water-air interfaces (the composite interface). Due to an external perturbation, a standing capillary wave can form at the liquid–air interface. If the amplitude of the capillary wave is greater than the height of the asperity, the liquid can touch the valley between the asperities; and if the angle under which the liquid comes in contact with the solid is greater than h, it is energetically profitable for the liquid to fill the valley. The effect of capillary waves is more pronounced for small asperities with heights comparable to the wave amplitude. An example of this is seen in the case of unitary roughness, where the amplitude of asperity is very low. This is why the likelihood of instability of a unitary interface will be very high. However, in a recent study, Eyal Bittoun and Abraham Marmur found that multiscale roughness is not necessarily essential for superhydrophobicity but beneficial for mechanical stability of the surface. | 6 | Supramolecular Chemistry |
Tairus (, a portmanteau of Тайско (Thai) and Русский (Russian)) is a synthetic gemstone manufacturer. It was formed in 1989 as part of Mikhail Gorbachev's perestroika initiative to establish a joint venture between the Russian Academy of Sciences and Tairus Created Gems Co Ltd. of Bangkok, Thailand. Today Tairus is a major supplier of hydrothermally grown gemstones to the jewellery industry. Later, Tairus became a privately held enterprise, operating out of its Bangkok distribution hub under the trade name Tairus, owned by Tairus Created Gems Co Ltd. of Bangkok, Thailand.
In the beginning, the team was led by the scientist and developer of the hydrothermal process, the late Alexander Lebedev, whose name was kept secret by the Soviet regime for many years, and Walter Barshai, who was appointed to be the Chairman of the Board of the Joint Venture Tairus. Their objective was to grow and to supply emeralds, rubies, sapphires, alexandrite and other gems to the jewelry industry. The driving force was late Academician Nikolai Dobretsov, former President of the Siberian Branch of the Russian Academy of Sciences. Tairus has achieved many scientific breakthroughs. For example, the development of the hydrothermally grown corundum, aquamarine and the development of a revolutionary process of horizontal crystallization for growing corundum (ruby), chrysoberyl and alexandrite.
After many years of development, scientists at Tairus had succeeded to commercially grow emeralds in a laboratory environment that resemble in color and have gemological properties that “overlap natural emeralds from various localities, especially those of low alkali-bearing stones from Colombia” ([https://docs.wixstatic.com/ugd/31202c_ba81f0c232274bd6b1183aff1242b3ff.pdf The Journal of Gemmology, 2006, Vol. 30, Nos 1/2, 59-74]). | 3 | Analytical Chemistry |
The term co-receptor is prominent in literature regarding signal transduction, the process by which external stimuli regulate internal cellular functioning. The key to optimal cellular functioning is maintained by possessing specific machinery that can carry out tasks efficiently and effectively. Specifically, the process through which intermolecular reactions forward and amplify extracellular signals across the cell surface has developed to occur by two mechanisms.
First, cell surface receptors can directly transduce signals by possessing both serine and threonine or simply serine in the cytoplasmic domain. They can also transmit signals through adaptor molecules through their cytoplasmic domain which bind to signalling motifs. Secondly, certain surface receptors lacking a cytoplasmic domain can transduce signals through ligand binding. Once the surface receptor binds the ligand it forms a complex with a corresponding surface receptor to regulate signalling. These categories of cell surface receptors are prominently referred to as co-receptors. Co-receptors are also referred to as accessory receptors, especially in the fields of biomedical research and immunology.
Co-receptors are proteins that maintain a three-dimensional structure. The large extracellular domains make up approximately 76–100% of the receptor. The motifs that make up the large extracellular domains participate in ligand binding and complex formation.
The motifs can include glycosaminoglycans, EGF repeats, cysteine residues or ZP-1 domains. The variety of motifs leads to co-receptors being able to interact with two to nine different ligands, which themselves can also interact with a number of different co-receptors.
Most co-receptors lack a cytoplasmic domain and tend to be GPI-anchored, though a few receptors have been identified which contain short cytoplasmic domains that lack intrinsic kinase activity. | 1 | Biochemistry |
Hu Hongwen (; 16 March 1925 – 19 May 2016) was a Chinese organic chemist, educator and an academician of the Chinese Academy of Sciences (CAS). He was known as the Chief editor of Chinese higher education textbook Organic Chemistry.
Hu died on 19 May 2016 at the age of 91 in Nanjing. | 0 | Organic Chemistry |
A neuron's ability to generate and propagate an action potential changes during development. How much the membrane potential of a neuron changes as the result of a current impulse is a function of the membrane input resistance. As a cell grows, more channels are added to the membrane, causing a decrease in input resistance. A mature neuron also undergoes shorter changes in membrane potential in response to synaptic currents. Neurons from a ferret lateral geniculate nucleus have a longer time constant and larger voltage deflection at P0 than they do at P30. One consequence of the decreasing action potential duration is that the fidelity of the signal can be preserved in response to high frequency stimulation. Immature neurons are more prone to synaptic depression than potentiation after high frequency stimulation.
In the early development of many organisms, the action potential is actually initially carried by calcium current rather than sodium current. The opening and closing kinetics of calcium channels during development are slower than those of the voltage-gated sodium channels that will carry the action potential in the mature neurons. The longer opening times for the calcium channels can lead to action potentials that are considerably slower than those of mature neurons. Xenopus neurons initially have action potentials that take 60–90 ms. During development, this time decreases to 1 ms. There are two reasons for this drastic decrease. First, the inward current becomes primarily carried by sodium channels. Second, the delayed rectifier, a potassium channel current, increases to 3.5 times its initial strength.
In order for the transition from a calcium-dependent action potential to a sodium-dependent action potential to proceed new channels must be added to the membrane. If Xenopus neurons are grown in an environment with RNA synthesis or protein synthesis inhibitors that transition is prevented. Even the electrical activity of the cell itself may play a role in channel expression. If action potentials in Xenopus myocytes are blocked, the typical increase in sodium and potassium current density is prevented or delayed.
This maturation of electrical properties is seen across species. Xenopus sodium and potassium currents increase drastically after a neuron goes through its final phase of mitosis. The sodium current density of rat cortical neurons increases by 600% within the first two postnatal weeks. | 7 | Physical Chemistry |
Thermoplastic polymers like polyolefins can be remelted and reformed into new items. This approach is referred to as mechanical recycling and is usually the simplest and most economical form of recovery. Post-consumer plastic will usually already bare a degree of degradation. Another round of melt-processing will exacerbate this, with the result being that mechanically recycled plastic will usually have poorer mechanical properties than virgin plastic. Degradation can be enhanced by high concentrations of hydroperoxides, cross-contamination between different types of plastic and by additives present within the plastic. Technologies developed to enhance the biodegradation of plastic can also conflict with its recycling, with oxo-biodegradable additives, consisting of metallic salts of iron, magnesium, nickel, and cobalt, increasing the rate of thermal degradation. Depending on the polymer in question, an amount of virgin material may be added to maintain the quality of the product. | 7 | Physical Chemistry |
There is a hypoxic zone covers the coasts of Oregon and Washington that reached peak size in 2006 at an area of over 1,158 square miles. Strong surface winds between April and September cause frequent upwelling that results in an increase of algae blooms, rendering the hypoxia a seasonal occurrence. The upwelling has contributed to lower temperatures within the zone. The dead zone has resulted in sea organisms such as crabs and fish relocating and an interference of commercial fishing. Organisms that cannot relocate have been found to suffocate, leaving them unable to be used by fishermen. In 2009, one scientist described "thousands and thousands" of suffocated, crabs, worms, and sea stars along the seafloor of the hypoxic zone. In 2021, 1.9 million dollars were put into monitoring and continuing to study the hypoxic conditions in the area that the dead zone occurs in. | 9 | Geochemistry |
Virodhamine (O-arachidonoyl ethanolamine; O-AEA) is an endocannabinoid and a nonclassic eicosanoid, derived from arachidonic acid. O-Arachidonoyl ethanolamine is arachidonic acid and ethanolamine joined by an ester linkage, the opposite of the amide linkage found in anandamide. Based on this opposite orientation, the molecule was named virodhamine from the Sanskrit word virodha, which means opposition. It acts as an antagonist of the CB receptor and agonist of the CB receptor. Concentrations of virodhamine in the human hippocampus are similar to those of anandamide, but they are 2- to 9-fold higher in peripheral tissues that express CB. Virodhamine lowers body temperature in mice, demonstrating cannabinoid activity in vivo. | 1 | Biochemistry |
DCC (acronym for N,N-dicyclohexylcarbodiimide) was one of the first carbodiimides developed as a reagent. It is widely used for amide and ester formation, especially for solid-phase synthesis of peptides. DCC has achieved popularity mainly because of its high-yielding amide coupling reactions and the fact that it is quite inexpensive.
However, DCC does have some serious drawbacks, and its use is often avoided for several reasons:
#The byproduct N,N-dicyclohexylurea is mostly removed by filtration, but trace impurities can be difficult to remove. It is incompatible with traditional solid-phase peptide synthesis.
#DCC is a potent allergen, and repeated contact with skin increases the probability of sensitization to the compound. Clinical reports of individuals who cannot enter rooms where peptide coupling agents are used have been reported. | 0 | Organic Chemistry |
Mycoremediation (from ancient Greek (), meaning "fungus", and the suffix , in Latin meaning restoring balance) is a form of bioremediation in which fungi-based remediation methods are used to decontaminate the environment. Fungi have been proven to be a cheap, effective and environmentally sound way for removing a wide array of contaminants from damaged environments or wastewater. These contaminants include heavy metals, organic pollutants, textile dyes, leather tanning chemicals and wastewater, petroleum fuels, polycyclic aromatic hydrocarbons, pharmaceuticals and personal care products, pesticides and herbicides in land, fresh water, and marine environments.
The byproducts of the remediation can be valuable materials themselves, such as enzymes (like laccase), edible or medicinal mushrooms, making the remediation process even more profitable. Some fungi are useful in the biodegradation of contaminants in extremely cold or radioactive environments where traditional remediation methods prove too costly or are unusable. | 2 | Environmental Chemistry |
The Crabtree effect, named after the English biochemist Herbert Grace Crabtree, describes the phenomenon whereby the yeast, Saccharomyces cerevisiae, produces ethanol (alcohol) in aerobic conditions at high external glucose concentrations rather than producing biomass via the tricarboxylic acid (TCA) cycle, the usual process occurring aerobically in most yeasts e.g. Kluyveromyces spp. This phenomenon is observed in most species of the Saccharomyces, Schizosaccharomyces, Debaryomyces, Brettanomyces, Torulopsis, Nematospora, and Nadsonia genera. Increasing concentrations of glucose accelerates glycolysis (the breakdown of glucose) which results in the production of appreciable amounts of ATP through substrate-level phosphorylation. This reduces the need of oxidative phosphorylation done by the TCA cycle via the electron transport chain and therefore decreases oxygen consumption. The phenomenon is believed to have evolved as a competition mechanism (due to the antiseptic nature of ethanol) around the time when the first fruits on Earth fell from the trees. The Crabtree effect works by repressing respiration by the fermentation pathway, dependent on the substrate.
Ethanol formation in Crabtree-positive yeasts under strictly aerobic conditions was firstly thought to be caused by the inability of these organisms to increase the rate of respiration above a certain value. This critical value, above which alcoholic fermentation occurs, is dependent on the strain and the culture conditions. More recent evidences demonstrated that the occurrence of alcoholic fermentation might not be primarily due to a limited respiratory capacity, but could be caused by a limit in the cellular Gibbs energy dissipation rate.
For S. cerevisiae in aerobic conditions, glucose concentrations below 150 mg/L did not result in ethanol production. Above this value, ethanol was formed with rates increasing up to a glucose concentration of 1000 mg/L. Thus, above 150 mg/L glucose the organism exhibited a Crabtree effect.
It was the study of tumor cells that led to the discovery of the Crabtree effect. Tumor cells have a similar metabolism, the Warburg effect, in which they favor glycolysis over the oxidative phosphorylation pathway. | 1 | Biochemistry |
Ischemic cell death, or oncosis, is a form of accidental cell death. The process is characterized by an ATP depletion within the cell leading to impairment of ionic pumps, cell swelling, clearing of the cytosol, dilation of the endoplasmic reticulum and golgi apparatus, mitochondrial condensation, chromatin clumping, and cytoplasmic bleb formation. Oncosis refers to a series of cellular reactions following injury that precedes cell death. The process of oncosis is divided into three stages. First, the cell becomes committed to oncosis as a result of damage incurred to the plasma membrane through toxicity or ischemia, resulting in the leak of ions and water due to ATP depletion. The ionic imbalance that occurs subsequently causes the cell to swell without a concurrent change in membrane permeability to reverse the swelling. In stage two, the reversibility threshold for the cell is passed and the cell becomes committed to cell death. During this stage the membrane becomes abnormally permeable to trypan blue and propidium iodide, indicating membrane compromise. The final stage is cell death and removal of the cell via phagocytosis mediated by an inflammatory response. | 1 | Biochemistry |
CKLF-like MARVEL transmembrane domain-containing protein 2 (i.e. CMTM2), previously termed chemokine-like factor superfamily 2 ( i.e. CKLFSF2), is a member of the CKLF-like MARVEL transmembrane domain-containing family (CMTM) of proteins. In humans, it is encoded by the CMTM2 gene located in band 22 on the long (i.e. "q") arm of chromosome 16. CMTM2 protein is expressed in the bone marrow and various circulating blood cells. It is also highly expressed in testicular tissues: The CMTM2 gene and CMTM2 protein, it is suggested, may play an important role in testicular development.
Studies find that the levels of CMTM2 protein in hepatocellular carcinoma tissues of patients are lower higher than their levels in normal liver tissues. CMTM2 protein levels were also lower in the hepatocellular carcinoma tissues that had a more aggressive pathology and therefore a possible poorer prognosis. Finally, the forced overexpression of CMTM2 protein in cultured hepatocellular tumor cells inhibited their invasiveness and migration. These findings suggest that CMTM2 protein suppresses the development and/or progression of hepatocellular carcinoma and therefore that the CMTM2 gene acts as a tumor suppressor in this cancer. Patients with higher CMTM2 levels in their linitis plastica stomach cancer (i.e. a type of gastric cancer also termed diffuse-type gastric cancer or diffuse type adenocarcinoma of the stomach) tissues had better prognoses than patients with lower CMTM2 levels in their linitis plastica tissues. And, the CMTM2 gene has been found to be more highly expressed in the salivary gland adenoid cystic carcinoma tissues of patients who did not develop tumor recurrences or perineural invasion of their carcinomas compared to the expression of this gene in patients whose adenoid cystic carcinoma tissues went on to develop these complications. These findings suggest that the CMTM2 gene may act as a tumor suppressor not only in hepatocellular carcinoma but also in linitis plastica and salivary gland adenoid cystic carcinoma. Further studies are needed to confirm these findings and determine if CMTM2 protein can serve as a marker for the severity of these three cancers and/or as a therapeutic target for treating them. | 1 | Biochemistry |
Thiomers are capable of forming disulfide bonds with cysteine substructures of the mucus gel layer covering mucosal membranes. Because of this property they exhibit up to 100-fold higher mucoadhesive properties in comparison to the corresponding unthiolated polymers. Because of their mucoadhesive properties, thiolated polymers are an effective tool in the treatment of diseases such as dry eye, dry mouth, and dry vagina syndrome where dry mucosal surfaces are involved. | 7 | Physical Chemistry |
Viability PCR, also named v-PCR or vPCR, is an evolution of PCR. Through the use of a simple pre-treatment of the sample by the means of specific intercalating photo-reactive reagents it's possible to neutralize the DNA of dead cells. As a result, only DNA from live cells will be detected by PCR. This approach expands a lot the analytical scope of PCR procedures. The capability to detect only living cells become very important, because in key applications is more important to know the amount of live cells, than the total cell level. Examples of this are: food and water quality control, infectious diseases diagnostic, veterinary applications, ecological dynamics...
The first referenced work about this analytical approach was in 2003, Norwegian researchers suggest the use of Ethidium Monoazide, an azide form of Ethidium Bromide, which was used in other analytical fields as Flow Cytometry as a candidate for viability PCR. However, the main important advances were done by Nocker and colleagues, which demonstrated in successive works the potential of this technology and also suggested Propidium monoazide as a better reagent for vPCR.
This field still is in development, from 2003 up to 2015, the scientific evidences about the applicability of vPCR are stacking, nowadays main efforts are focused in procedure optimization. Since a simple reagent mix with the sample, photo-activation and subsequent PCR not always shows expected results, each procedure needs some optimization. Up to now the main improvements has been :
- Improving the efficiency of photo activation: early procedures were based on high power halogen lamps which overheated the samples and don't ensured constant light dose, these home made solutions have been replaced by led based instruments.[http://www.geniul.com/en/products/instruments/phast-blue-for-nucleic-acids-photo-labeling][https://www.qiagen.com/us/shop/sample-technologies/dna/dna-preparation/blu-v-system/]
- The use of long PCR amplicons as targets.
- The increase of temperature during dark incubation.
Through combining different optimizations strategies and controlling the analytical bias, nowadays the vPCR becomes a powerful analytical tool. | 1 | Biochemistry |
A widespread experimental investigation of DSW material systems and evolution of related practical devices has been largely limited by the stringent anisotropy conditions necessary for successful DSW propagation, particularly the high degree of birefringence of at least one of the constituent materials and the limited number of naturally available materials fulfilling this requirement. However, this is about to change in light of novel artificially engineered metamaterials and revolutionary material synthesis techniques.
The extreme sensitivity of DSW to anisotropy, and thereby to stress, along with their low-loss (long-range) character render them particularly attractive for enabling high sensitivity tactile and ultrasonic sensing for next-generation high-speed transduction and read-out technologies. Moreover, the unique directionality of DSW can be used for the steering of optical signals. | 7 | Physical Chemistry |
Ideal grain growth is a special case of normal grain growth where boundary motion is driven only by local curvature of the grain boundary. It results in the reduction of the total amount of grain boundary surface area i.e. total energy of the system. Additional contributions to the driving force by e.g. elastic strains or temperature gradients are neglected. If it holds that the rate of growth is proportional to the driving force and that the driving force is proportional to the total amount of grain boundary energy, then it can be shown that the time t required to reach a given grain size is approximated by the equation
where d is the initial grain size, d is the final grain size and k is a temperature dependent constant given by an exponential law:
where k is a constant, T is the absolute temperature and Q is the activation energy for boundary mobility. Theoretically, the activation energy for boundary mobility should equal that for self-diffusion but this is often found not to be the case.
In general these equations are found to hold for ultra-high purity materials but rapidly fail when even tiny concentrations of solute are introduced. | 8 | Metallurgy |
Eslicarbazepine acetate is contraindicated in people with second- or third-degree atrioventricular block, a type of heart block, and in people who are hypersensitive to eslicarbazepine, oxcarbazepine or carbamazepine. | 4 | Stereochemistry |
The insulator element that is found in the gypsy retrotransposon of Drosophila is one of several sequences that have been studied in detail. The gypsy insulator can be found in the 5 untranslated region (UTR) of the retrotransposon element. Gypsy' affects the expression of adjacent genes pending insertion into a new genomic location, causing mutant phenotypes that are both tissue specific and present at certain developmental stages. The insulator likely has an inhibitory effect on enhancers that control the spatial and temporal expression of the affected gene. | 1 | Biochemistry |
Some chloroplasts contain a structure called the chloroplast peripheral reticulum. It is often found in the chloroplasts of plants, though it has also been found in some angiosperms, and even some gymnosperms. The chloroplast peripheral reticulum consists of a maze of membranous tubes and vesicles continuous with the inner chloroplast membrane that extends into the internal stromal fluid of the chloroplast. Its purpose is thought to be to increase the chloroplast's surface area for cross-membrane transport between its stroma and the cell cytoplasm. The small vesicles sometimes observed may serve as transport vesicles to shuttle stuff between the thylakoids and intermembrane space. | 5 | Photochemistry |
The CIPW Norm was developed in the early 1900s and named after its creators, the petrologists Charles Cross, Joseph Iddings, Louis Pirsson, and the geochemist Henry Washington. The CIPW normative mineralogy calculation is based on the typical minerals that may be precipitated from an anhydrous melt at low pressure, and simplifies the typical igneous geochemistry seen in nature with the following four constraints:
* The magma crystallizes under anhydrous conditions so that no hydrous minerals (hornblende, biotite) are formed.
* The ferromagnesian minerals are assumed to be free of AlO.
* The Fe/Mg ratio for all ferromagnesian minerals is assumed to be the same.
* Several minerals are assumed to be incompatible, thus nepheline and/or olivine never appear with quartz in the norm.
This is an artificial set of constraints, and therefore the results of the CIPW norm do not reflect the true course of igneous differentiation in nature.
The primary benefit of calculating a CIPW norm is determining what the ideal mineralogy of an aphanitic or porphyritic igneous rock is. Secondly, the degree of silica saturation of the melt that formed the rock can be assessed in the absence of diagnostic feldspathoid species.
The silica saturation of a rock varies not only with silica content but the proportion of the various alkalis and metal species within the melt. The silica saturation eutectic plane is thus different for various families of rocks and cannot be easily estimated, hence the requirement to calculate whether the rock is silica saturated or not.
This is achieved by assigning cations of the major elements within the rock to silica anions in modal proportion, to form solid solution minerals in the idealised mineral assemblage starting with phosphorus for apatite, chlorine and sodium for halite, sulfur and FeO into pyrite, FeO and CrO is allocated for chromite, FeO and equal molar amount of TiO for ilmenite, CaO and CO for calcite, to complete the most common non-silicate minerals.
From the remaining chemical constituents, AlO and KO are allocated with silica for orthoclase; sodium, aluminium and potassium for albite, and so on until either there is no silica left (in which case feldspathoids are calculated) or excess, in which case the rock contains normative quartz. | 9 | Geochemistry |
In the process of smelting, inorganic chlorides, fluorides (see fluorite), limestone and other materials are designated as "fluxes" when added to the contents of a smelting furnace or a cupola for the purpose of purging the metal of chemical impurities such as phosphorus, and of rendering slag more liquid at the smelting temperature. Slag is a liquid mixture of ash, flux, and other impurities. This reduction of slag viscosity with temperature, increasing the flow of slag in smelting, is the origin of the word flux in metallurgy.
The flux most commonly used in iron and steel furnaces is limestone, which is charged in the proper proportions with the iron and fuel. | 8 | Metallurgy |
Lewis acids easily add to the nitrogen atom of pyridine, forming pyridinium salts. The reaction with alkyl halides leads to alkylation of the nitrogen atom. This creates a positive charge in the ring that increases the reactivity of pyridine to both oxidation and reduction. The Zincke reaction is used for the selective introduction of radicals in pyridinium compounds (it has no relation to the chemical element zinc). | 0 | Organic Chemistry |
Recent advances in the identification of the tethers between the mitochondrial and ER membranes suggest that the scaffolding function of the molecular elements involved is secondary to other, non-structural functions. In yeast, ERMES, a multiprotein complex of interacting ER- and mitochondrial-resident membrane proteins, is required for lipid transfer at the MAM and exemplifies this principle. One of its components, for example, is also a constituent of the protein complex required for insertion of transmembrane beta-barrel proteins into the lipid bilayer. However, a homologue of the ERMES complex has not yet been identified in mammalian cells. Other proteins implicated in scaffolding likewise have functions independent of structural tethering at the MAM; for example, ER-resident and mitochondrial-resident mitofusins form heterocomplexes that regulate the number of inter-organelle contact sites, although mitofusins were first identified for their role in fission and fusion events between individual mitochondria. Glucose-related protein 75 (grp75) is another dual-function protein. In addition to the matrix pool of grp75, a portion serves as a chaperone that physically links the mitochondrial and ER Ca channels VDAC and IP3R for efficient Ca transmission at the MAM. Another potential tether is Sigma-1R, a non-opioid receptor whose stabilization of ER-resident IP3R may preserve communication at the MAM during the metabolic stress response. | 1 | Biochemistry |
Sensitive electronic equipment are vulnerable to interference and unauthorized surveillance. These products also require protection from high voltages. Radio frequency (RF) shielding can address these issues by reducing the transmission of electric or magnetic fields from one space to another.
Copper is an excellent material for RF shielding because it absorbs radio and magnetic waves. Other useful properties for RF shielding is that copper has a high electrical conductivity, is ductile, malleable, and solders easily.
RF shielding enclosures filter a range of frequencies for specific conditions. Properly designed and constructed copper enclosures satisfy most RF shielding needs, from computer and electrical switching rooms to hospital CAT-scan and MRI facilities. Special attention needs to be addressed regarding potential shield penetrations, such as doors, vents, and cables.
A shield can be effective against one type of electromagnetic field but not against another. For example, a copper foil or screen RF shield will be minimally effective against power frequency magnetic fields. A power frequency magnetic shield could offer little reduction of radio frequency fields. The same is true for different RF frequencies. A simple large-mesh screen shield can work well for lower frequencies, but can be ineffective for microwaves.
Sheet copper for RF shielding can be formed into essentially any shape and size. Electrical connection to a grounding system provides an effective RF enclosure. | 8 | Metallurgy |
Like other siderophores, petrobactin is secreted by an animal pathogenic bacterium. B. anthracis uses petrobactin to acquire iron from its host. Interestingly, while the 3,4-catecholate ends of petrobactin do not improve iron(III) affinity relative to hydroxamate ends, they speed up iron removal from human diferric transferrin. Petrobactin in its ferric and iron-free forms is bound selectively by YclQ (an isogenic disruption mutant in the transporter encoded by the yclNOPQ operon in Bacillus subtilis), as is petrobactin's precursor protocatechuic acid and the ferric petrobactin photoproduct. The yclNOPQ operon is required for the utlization of petrobactin and yclNOPQ orthologs likely contribute to the pathogenicity of Bacilli. | 1 | Biochemistry |
Mass spectrometry (MS) is an analytical technique that measures the mass-to-charge ratio (m/z) of charged particles (ions). Although there are many different kinds of mass spectrometers, all of them make use of electric or magnetic fields to manipulate the motion of ions produced from an analyte of interest and determine their m/z. The basic components of a mass spectrometer are the ion source, the mass analyzer, the detector, and the data and vacuum systems. The ion source is where the components of a sample introduced in a MS system are ionized by means of electron beams, photon beams (UV lights), laser beams or corona discharge. In the case of electrospray ionization, the ion source moves ions that exist in liquid solution into the gas phase. The ion source converts and fragments the neutral sample molecules into gas-phase ions that are sent to the mass analyzer. While the mass analyzer applies the electric and magnetic fields to sort the ions by their masses, the detector measures and amplifies the ion current to calculate the abundances of each mass-resolved ion. In order to generate a mass spectrum that a human eye can easily recognize, the data system records, processes, stores, and displays data in a computer.
The mass spectrum can be used to determine the mass of the analytes, their elemental and isotopic composition, or to elucidate the chemical structure of the sample. MS is an experiment that must take place in gas phase and under vacuum (1.33 * 10 to 1.33 * 10 pascal). Therefore, the development of devices facilitating the transition from samples at higher pressure and in condensed phase (solid or liquid) into a vacuum system has been essential to develop MS as a potent tool for identification and quantification of organic compounds like peptides. MS is now in very common use in analytical laboratories that study physical, chemical, or biological properties of a great variety of compounds. Among the many different kinds of mass analyzers, the ones that find application in LC–MS systems are the quadrupole, time-of-flight (TOF), ion traps, and hybrid quadrupole-TOF (QTOF) analyzers. | 3 | Analytical Chemistry |
* Anandamide
* 2-Arachidonoylglycerol
* 2-Arachidonyl glyceryl ether
* Oleamide
* Oleoylethanolamide
* Virodhamine
* Docosatetraenoylethanolamide
* Stearoylethanolamide
* N-Arachidonylglycine
* Arachidonoyl serotonin
* N-Arachidonoyl dopamine
* N-Acylethanolamine | 1 | Biochemistry |
This table gives the number of space group types in small dimensions, including the numbers of various classes of space group. The numbers of enantiomorphic pairs are given in parentheses. | 4 | Stereochemistry |
Trimethylsilyldiazomethane is the organosilicon compound with the formula (CH)SiCHN. It is classified as a diazo compound. Trimethylsilyldiazomethane is a commercially available reagent used in organic chemistry as a methylating agent and as a source of CH group. Its behavior is akin to the less convenient reagent diazomethane. | 0 | Organic Chemistry |
Native gels, also known as non-denaturing gels, analyze proteins that are still in their folded state. Thus, the electrophoretic mobility depends not only on the charge-to-mass ratio, but also on the physical shape and size of the protein. | 1 | Biochemistry |
Ferhan Çeçen was born on June 15, 1961, in Istanbul, Turkey. She graduated from the Deutsche Schule Istanbul in 1980 and speaks fluent English and German in addition to her native Turkish. Çeçen completed a B.S. in chemical engineering at Boğaziçi University in 1984.
In 1986, she completed a M.S. in environmental engineering at the Istanbul Technical University (ITU). Her Masters thesis was titled Metal Complexation and its Implications on related Technologies'. Her graduate advisor was .
Çeçen earned a Ph.D. in environmental engineering at ITU in 1990. Her dissertation was titled Nitrogen Removal from High-strength Wastewaters by Upflow Submerged Nitrification and Denitrification Filters. Her doctoral advisor was . | 2 | Environmental Chemistry |
Nicotinamide cofactor analogues (mNADs) are compounds that mimic the natural nicotinamide adenine dinucleotide cofactors in structure, to explore a mechanism or be used in biocatalysis or other applications.
These nicotinamide cofactor mimics generally retain the nicotinamide moiety with varying substituents. | 1 | Biochemistry |
Common sphere packings taken on by atomic systems are listed below with their corresponding packing fraction.
* Hexagonal close-packed (HCP): 0.74
* Face-centered cubic (FCC): 0.74 (also called cubic close-packed, CCP)
* Body-centered cubic (BCC): 0.68
* Simple cubic: 0.52
* Diamond cubic: 0.34
The majority of metals take on either the HCP, FCC, or BCC structure. | 3 | Analytical Chemistry |
In general, if an excitatory synapse is strong enough, an action potential in the presynaptic neuron will trigger an action potential in the postsynaptic cell. In many cases the excitatory postsynaptic potential (EPSP) will not reach the threshold for eliciting an action potential. When action potentials from multiple presynaptic neurons fire simultaneously, or if a single presynaptic neuron fires at a high enough frequency, the EPSPs can overlap and summate. If enough EPSPs overlap, the summated EPSP can reach the threshold for initiating an action potential. This process is known as summation, and can serve as a high pass filter for neurons.
On the other hand, a presynaptic neuron releasing an inhibitory neurotransmitter, such as GABA, can cause an inhibitory postsynaptic potential (IPSP) in the postsynaptic neuron, bringing the membrane potential farther away from the threshold, decreasing its excitability and making it more difficult for the neuron to initiate an action potential. If an IPSP overlaps with an EPSP, the IPSP can in many cases prevent the neuron from firing an action potential. In this way, the output of a neuron may depend on the input of many different neurons, each of which may have a different degree of influence, depending on the strength and type of synapse with that neuron. John Carew Eccles performed some of the important early experiments on synaptic integration, for which he received the Nobel Prize for Physiology or Medicine in 1963. | 1 | Biochemistry |
When the hydrogen atoms in an alkyl radical are displaced with deuterium, disproportionation proceeds at a slightly slower rate whereas the rate of recombination remains the same. Thus disproportionation is weakly affected by the kinetic isotope effect with k/k = 1.20 ± 0.15 for ethylene. Hydrogens and deuterons are not involved in recombination reactions. However, deuteron abstraction during disproportionation occurs more slowly than hydrogen abstraction due to the increased mass and reduced vibrational energy of deuterium, although the experimentally observed k/k is close to one. | 0 | Organic Chemistry |
For this synthesis (Scheme 3) the morpholine enamine of ethyl isopropyl ketone was reacted with acryloyl chloride in a combined nucleophilic conjugate addition and nucleophilic acyl substitution to give after hydrolysis diketone 25. Reaction with hydrazine in triethylamine and ethanol afforded hydrazone 26. After an unusual hydrazone iodination that also involved iodination alpha to a carbonyl group and elimination of HI, fully conjugated vinyl iodide 28 was produced in an unexpected dehydrogenation. The ketone was converted into cyanohydrin 29 with trimethylsilyl cyanide, potassium cyanide and a crown ether.
As shown in Scheme 4, the bottom part of the taxol B ring synthesis involved the reaction of ring C aldehyde group of 21. The ketone group was deprotected by action of tetra-n-butylammonium fluoride, and the double bond was epoxidized with meta-chloroperoxybenzoic acid to epoxide 32. This epoxide was then hydrogenated with hydrogen over palladium on carbon to give diol 33, which was protected in the next step as the cyclic carbonate ester (34).
L-Selectride reduction of enone 34 gave ketone 35. The ketone was converted into vinyl triflate 36 using phenyl triflimide and potassium hexamethyldisilazide in tetrahydrofuran at −78 °C. This vinyl triflate was one of the functional groups required for the Heck reaction. For the generation of the other reactive group the acetal group was removed to give aldehyde 37 which was subsequently converted to the terminal alkene 38 in a Wittig reaction involving methylenetriphenylphosphorane. The intramolecular Heck reaction involved tetrakis(triphenylphosphine)palladium(0) and potassium carbonate in acetonitrile at reflux to give diene 39 and to complete the formation of the B ring. | 0 | Organic Chemistry |
The Goldsmiths' Professorship of Materials Science is a professorship in the University of Cambridge, associated with the Department of Materials Science and Metallurgy.
The professorship was established by grace of 20 November 1931 as the Goldsmiths Professorship of Metallurgy to replace the Goldsmiths Readership in Metallurgy. A further gift of £12,500 was received from the Goldsmiths Company in 1933. It was retitled the Goldsmiths Professorship of Materials Science by grace 4 of 19 June 1991. | 8 | Metallurgy |
In organic chemistry, the term acetylenic designates
*A doubly unsaturated position (sp-hybridized) on a molecular framework, for instance in an alkyne such as acetylene;
*An ethynyl fragment, HCC–, or substituted homologue. | 0 | Organic Chemistry |
Herbert's wife Cathleen Synge Morawetz was a prolific mathematician at NYU. His sister Sonja Morawetz Sinclair revealed in 2017 she was a WW2 codebreaker after seven decades of secrecy by Bletchley Park Signals Intelligence. He helped organize the defection of Mikhail Barishnikov from the USSR 1974. His brother, Oskar Morawetz was a Canadian composer Oskar Morawetz. His brother John Morawetz was a Canadian businessman. | 7 | Physical Chemistry |
Traditional active cancellation techniques for tremor reduction use electrical, hydraulic, or pneumatic systems to actuate an object in the direction opposite to the disturbance. However, these systems are limited due to the large infrastructure required to produce large amplitudes of power at human tremor frequencies. SMAs have proven to be an effective method of actuation in hand-held applications, and have enabled a new class active tremor cancellation devices. One recent example of such device is the Liftware spoon, developed by Verily Life Sciences subsidiary Lift Labs. | 8 | Metallurgy |
Phytomining was first proposed in 1983 by Rufus Chaney, a USDA agronomist. He and Alan Baker, a University of Melbourne professor, first tested it in 1996. They, as well as Jay Scott Angle and Yin-Ming Li, filed a patent on the process in 1995 which expired in 2015. | 2 | Environmental Chemistry |
Duplex sequencing is a new method and its efficiency was studied in limited applications such as detecting point mutations using targeted capture sequencing. More studies need to be performed to expand the application and feasibility of duplex sequencing to more complex samples with larger numbers of mutations, indels, and copy number variations. | 1 | Biochemistry |
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