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High pressure carbon monoxide forms the high energy polycarbonyl covalent solid, however it is not expected to be present inside the Earth. | 9 | Geochemistry |
In organic chemistry, Markovnikovs rule or Markownikoffs rule describes the outcome of some addition reactions. The rule was formulated by Russian chemist Vladimir Markovnikov in 1870. | 7 | Physical Chemistry |
Lithium is a teratogen, causing birth defects in a small number of newborn babies. Case reports and several retrospective studies have demonstrated possible increases in the rate of a congenital heart defect known as Ebsteins anomaly, if taken during a womans pregnancy. As a consequence, fetal echocardiography is routinely performed in pregnant women taking lithium to exclude the possibility of cardiac anomalies. Lamotrigine seems to be a possible alternative to lithium in pregnant women for the treatment of acute bipolar depression or for the management of bipolar patients with normal mood. Gabapentin and clonazepam are also indicated as antipanic medications during the childbearing years and during pregnancy. Valproic acid and carbamazepine also tend to be associated with teratogenicity.
While it appears to be safe to use while breastfeeding a number of guidelines list it as a contraindication including the British National Formulary. | 1 | Biochemistry |
NCoR (nuclear receptor co-repressor) directly binds to the D and E domains of nuclear receptors and represses their transcriptional activity. Class I histone deacetylases are recruited by NCoR through SIN3, and NCoR directly binds to class II histone deacetylases. | 1 | Biochemistry |
The Arctic ocean covers an area of 14,056,000 square kilometers, and supports a diverse and important socioeconomic food web of organisms, despite its average water temperature being 32 degrees Fahrenheit. Over the last three decades, the Arctic Ocean has experienced drastic changes due to climate change. One of the changes is in the acidity levels of the ocean, which have been consistently increasing at twice the rate of the Pacific and Atlantic oceans. Arctic Ocean acidification is a result of feedback from climate system mechanisms, and is having negative impacts on Arctic Ocean ecosystems and the organisms that live within them. | 9 | Geochemistry |
Carbon-based life originates from carboxylation that couples atmospheric carbon dioxide to a sugar. The process is usually catalysed by the enzyme RuBisCO. Ribulose-1,5-bisphosphate carboxylase/oxygenase, the enzyme that catalyzes this carboxylation, is possibly the single most abundant protein on Earth.
Many carboxylases, including Acetyl-CoA carboxylase, Methylcrotonyl-CoA carboxylase, Propionyl-CoA carboxylase, and Pyruvate carboxylase require biotin as a cofactor. These enzymes are involved in various biogenic pathways. In the EC scheme, such carboxylases are classed under EC 6.3.4, "Other Carbon—Nitrogen Ligases".
Another example is the posttranslational modification of glutamate residues, to γ-carboxyglutamate, in proteins. It occurs primarily in proteins involved in the blood clotting cascade, specifically factors II, VII, IX, and X, protein C, and protein S, and also in some bone proteins. This modification is required for these proteins to function. Carboxylation occurs in the liver and is performed by γ-glutamyl carboxylase (GGCX). GGCX requires vitamin K as a cofactor and performs the reaction in a processive manner. γ-carboxyglutamate binds calcium, which is essential for its activity. For example, in prothrombin, calcium binding allows the protein to associate with the plasma membrane in platelets, bringing it into close proximity with the proteins that cleave prothrombin to active thrombin after injury. | 0 | Organic Chemistry |
There are two approaches to methylation analysis: typing and profiling technologies. Typing technologies are targeted towards a small number of loci across many samples, and involve the use of techniques such as PCR, restriction enzymes, and mass spectrometry. Profiling technologies such as MeDIP are targeted towards a genome- or methylome-wide level assessment of methylation; this includes restriction landmark genomic scanning (RLGS), and bisulfite conversion-based methods, which rely on the treatment of DNA with bisulfite to convert unmethylated cytosine residues to uracil. | 1 | Biochemistry |
1961: Eugène Schuëller Prize (ENSCP)
1971: prize of the Organic Chemistry Division of the French Chemical Society
1986: La Caze Prize of the French Academy of sciences and Berthelot Medal of the French Academy of sciences
1988: CNRS silver medal
1993: Corresponding member of the French Academy of sciences.
1994: Achille-Le-Bel Grand Prize of the Chemical Society of France.
2000: Officier of the Ordre National du Mérite
2012: Officier of the Ordre national de la Légion d'Honneur
2018: Commandeur in the Ordre des Palmes Académiques | 0 | Organic Chemistry |
In the late 1990s, the World Trade Organization authorized the United States and Canada to impose retaliatory tariffs of US$116.8 million per year on the European Union after it found the EU beef hormone ban to be in violation of the WTO Agreement on the Application of Sanitary and Phytosanitary Measures (SPS Agreement). In September 2009, the trade representatives from the US and EU signed a memorandum of understanding, which established a new duty-free import quota in the European Union for grain-fed, high-quality beef as part of a compromise solution. | 4 | Stereochemistry |
Deprotonation at the α-carbon of an oxazolidinone imide with a strong base such as lithium diisopropylamide selectively furnishes the (Z)-enolate, which can undergo stereoselective alkylation.
Activated electrophiles, such as allylic or benzylic halides, are very good substrates. | 4 | Stereochemistry |
Kidney impairment decreases the rate of elimination of levetiracetam from the body. Individuals with reduced kidney function may require dose adjustments. Kidney function can be estimated from the rate of creatinine clearance.
Dose adjustment of levetiracetam is not necessary in liver impairment. | 4 | Stereochemistry |
The Wyckoff positions are named after Ralph Walter Graystone Wyckoff, an American X-ray crystallographer who authored several books in the field. His 1922 book, The Analytical Expression of the Results of the Theory of Space Groups, contained tables with the positional coordinates, both general and special, permitted by the symmetry elements. This book was the forerunner of International Tables for X-ray Crystallography, which first appeared in 1935. | 3 | Analytical Chemistry |
In chemistry there is a practice known as synthesis. This process is used to form complex chemical compounds from simpler ones. These complex compounds are desirable for their ranging abilities and properties. In order to produce the complex compounds, the simpler ones must “cooperate” in a specific way. This can be very difficult and requires patience, because of the time required to make the bonds so their uses and properties can be tested. There was a need for optimization of this process in order to speed up the development and testing of new compounds. Catellani and her team in 1997 found such a method to optimize this process. Catellani discovered a chain reaction process that simplified and increased yield for desirable complex compounds. One bond the Catellani Reaction is heavily used to create is Carbon-Carbon bonds. These bonds are desirable for their stability and strength. These qualities make the bonds very useful in the makeup of more complex compounds.
Since its discovery, the Catellani Reaction has opened the door to other discoveries or improvements in chemistry. Specifically in the world of pharmaceuticals, the Catellani Reaction has been a useful tool for synthesizing drugs in a more efficient way to aid in their development. Lenoxipen is an example of one of the complex compounds now much easier to achieve with the discovery of Catellani Reactions. This compound belongs to a group of compounds known as Lignans that are useful for relieving pain and may provide benefits to cancer patients. These examples of the uses for Catellani Reactions show the vast and indirect benefits to its discovery. To chemists, the Catellani Reaction is a tool that acts to optimize the process for making new compounds. These new compounds are pivotal for advancing what is possible through chemistry. As new scientists study and try to build upon the Catellani Reaction, it is important to remember who provided the first understanding as it would open up a new world of opportunity. | 0 | Organic Chemistry |
* Used from ~1837 to reduce local action which degraded operation of Voltaic piles. See History of the battery#Invention.
* To chemically reduce metallic ions in solution. See Jones reductor.
*To reduce ketones and aldehydes to alkanes via the Clemmensen reduction in acidic conditions. | 7 | Physical Chemistry |
P680, or photosystem II primary donor, is the reaction-center chlorophyll a molecular dimer associated with photosystem II in plants, algae, and cyanobacteria, and central to oxygenic photosynthesis. | 5 | Photochemistry |
In quantum mechanical processes, the total number of particles may not be preserved. The concept is therefore generalized to the particle number operator, that is, the observable that counts the number of constituent particles. In quantum field theory, the particle number operator (see Fock state) is conjugate to the phase of the classical wave (see coherent state). | 7 | Physical Chemistry |
Alloy broadening is a spectral-line broadening mechanism caused by random distribution of the atoms in an alloy.
The alloy broadening is one of the line broadening mechanisms. The random distribution of atoms in an alloy causes a different material composition at different positions. In semiconductors and insulators the different material composition leads to different band gap energies. This gives different exciton recombination energies. Therefore, depending on the position where an exciton recombines the emitted light has a different energy. The alloy broadening is an inhomogeneous line broadening, meaning that its shape is Gaussian. | 7 | Physical Chemistry |
Nanofluidic diodes are utilized for rectification of ionic transport. A diode in electronic circuits limits the flow of electric current to one direction. A nanofluidic diode has the same function to restrict the ionic flow in one direction. A nanofluidic diode is a channel with its radius dimension of several nanometers. The inner surface of the channel is coated with surface charges. Current rectification can occur when the surface charges at the wall are of the same sign. It is also observed that, when a half of the channel is coated with opposite sign or electrically neutral, the rectification will be enhanced.
When the wall of the channel is coated with positive charges, the negative charged ions in the electrolyte will be attracted and accumulated within the channel. In this case, the flow of positive charges passing through the channel is not favorable, resulting in a decrease in ionic current. Therefore, the ionic current becomes asymmetric if the biasing voltage is reversed. | 7 | Physical Chemistry |
Reaction of carbon monoxide (CO), hydrogen sulfide (HS) and methanethiol CHSH in the presence of nickel sulfide and iron sulfide generates the methyl thioester of acetic acid [CH-CO-SCH] and presumably thioacetic acid (CH-CO-SH) as the simplest activated acetic acid analogues of acetyl-CoA. These activated acetic acid derivatives serve as starting materials for subsequent exergonic synthetic steps. They also serve for energy coupling with endergonic reactions, notably the formation of (phospho)anhydride compounds. However, Huber and Wächtershäuser reported low 0.5% acetate yields based on the input of CHSH (methanethiol) (8 mM) in the presence of 350 mM CO. This is about 500 times and 3700 times the highest CHSH and CO concentrations respectively measured to date in a natural hydrothermal vent fluid.
Reaction of nickel hydroxide with hydrogen cyanide (HCN) (in the presence or absence of ferrous hydroxide, hydrogen sulfide or methyl mercaptan) generates nickel cyanide, which reacts with carbon monoxide (CO) to generate pairs of α-hydroxy and α-amino acids: e.g. glycolate/glycine, lactate/alanine, glycerate/serine; as well as pyruvic acid in significant quantities. Pyruvic acid is also formed at high pressure and high temperature from CO, HO, FeS in the presence of nonyl mercaptan. Reaction of pyruvic acid or other α-keto acids with ammonia in the presence of ferrous hydroxide or in the presence of ferrous sulfide and hydrogen sulfide generates alanine or other α-amino acids. Reaction of α-amino acids in aqueous solution with COS or with CO and HS generates a peptide cycle wherein dipeptides, tripeptides etc. are formed and subsequently degraded via N-terminal hydantoin moieties and N-terminal urea moieties and subsequent cleavage of the N-terminal amino acid unit.
Proposed reaction mechanism for reduction of CO on FeS: Ying et al. (2007) have shown that direct transformation of mackinawite (FeS) to pyrite (FeS) on reaction with HS till 300 °C is not possible without the presence of critical amount of oxidant. In the absence of any oxidant, FeS reacts with HS up to 300 °C to give pyrrhotite. Farid et al. have experimentally shown that mackinawite (FeS) has ability to reduce CO to CO at temperature higher than 300 °C. They reported that the surface of FeS is oxidized, which on reaction with HS gives pyrite (FeS). It is expected that CO reacts with HO in the Drobner experiment to give H. | 1 | Biochemistry |
In budding yeast, SIR proteins are found at the silent mating type loci, telomeres, and at the rDNA locus. At the silent mating type loci and at the telomeres, SIR proteins participate in transcriptional silencing of genes within their domain of localization. At the rDNA locus, SIR proteins are thought to primarily be important for repressing recombination between rDNA repeats rather than for suppressing transcription. | 1 | Biochemistry |
p-Dimethylaminocinnamaldehyde (DMACA) is an aromatic hydrocarbon. It is used in an acidic solution to detect indoles. | 3 | Analytical Chemistry |
The Sherritt process is a hydrometallurgical process named for Sherritt Gordon Mines Ltd. (now Sherritt International) of Sherridon and Lynn Lake Manitoba Canada, based on the older Forward process developed by Dr. Frank Forward for the recovery of copper and nickel from those same mines. Nickel sulfide concentrates can be treated by either roasting or flash smelting to produce matte from which nickel and cobalt can be recovered hydrometallurgically, or they may be treated by an ammonia solution pressure leach. The residue is removed. A feed of matte and sulfide concentrate containing approximately 0.4% cobalt and 30% sulfur is pressure leached at elevated temperature and pressure in an ammoniacal solution to produce a solution of nickel, copper and cobalt. By boiling away the ammonia; copper is precipitated as a sulfide and sent to a smelter. Hydrogen sulfide is added to the autoclave to remove nickel sulfide and copper sulfide which is fed back to the leaching process. Air is then passed through the solution in the autoclave for oxyhydrolysis. The solution is then reduced with hydrogen, again at high temperature and pressure, to precipitate nickel powder (>99%). The remaining solution (containing approximately equal proportions of nickel and cobalt sulfides), is then adjusted (to a lower temperature and pressure) to precipitate the mixed sulfides and the fluid is concentrated and crystallized into ammonium sulfate ((NH)SO). The mixed sulfides are pressure leached with air and sulfuric acid. Ammonia is then added to remove potassium and iron as jarosite (KFe (OH)(SO)). More ammonia and air is added for oxidation. The solution is removed from the autoclave and sulfuric acid added to remove nickel as nickel(II) sulfate-ammonium sulfate hexahydrate ([NiSO]•[(NH)SO]•6HO) which is then sent to have its nickel recovered. The solution is then further reduced with more sulfuric acid and cobalt metal powder is added to aid in the nucleation of precipitants (seeding). Addition of hydrogen gas to saturation precipitates cobalt powder with a purity of approximately 99.6%. | 8 | Metallurgy |
Numerous destructive and non-destructive evaluation (NDE) methods exist for characterizing coatings. The most common destructive method is microscopy of a mounted cross-section of the coating and its substrate. The most common non-destructive techniques include ultrasonic thickness measurement, X-ray fluorescence (XRF), X-Ray diffraction (XRD) and micro hardness indentation. X-ray photoelectron spectroscopy (XPS) is also a classical characterization method to investigate the chemical composition of the nanometer thick surface layer of a material. Scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDX, or SEM-EDS) allows to visualize the surface texture and to probe its elementary chemical composition. Other characterization methods include transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning tunneling microscope (STM), and Rutherford backscattering spectrometry (RBS). Various methods of Chromatography are also used, as well as thermogravimetric analysis. | 8 | Metallurgy |
Owing to inductive effects, the basicity of an amine might be expected to increase with the number of alkyl groups on the amine. Correlations are complicated owing to the effects of solvation which are opposite the trends for inductive effects. Solvation effects also dominate the basicity of aromatic amines (anilines). For anilines, the lone pair of electrons on nitrogen delocalizes into the ring, resulting in decreased basicity. Substituents on the aromatic ring, and their positions relative to the amino group, also affect basicity as seen in the table. | 0 | Organic Chemistry |
PELP1 is located on chromosome 17p13.2 and PELP1 is expressed in a wide variety of tissues; its highest expression levels are found in the brain, testes, ovaries, and uterus. Currently, there are two known isoforms (long 3.8 Kb and short 3.4 Kb) and short isoform is widely expressed in cancer cells. | 1 | Biochemistry |
Relatively little is known about isotopic fractionation of zinc by biological processes, but several studies have elucidated that Zn isotopes fractionate during surface adsorption, intracellular uptake processes and speciation. Many organisms, including certain species of fish, plants and marine phytoplankton, have both high- and low-affinity Zn transport systems, which appear to fractionate Zn isotopes differently. A study by John et al. observed apparent isotope effects associated with Zn uptake by the marine diatom Thalassiosira oceanica of -0.2‰ for high-affinity uptake (at low Zn concentrations) and -0.8‰ for low-affinity uptake (at high Zn concentrations). Additionally, in this study, unwashed cells were enriched in Zn, indicating preferential adsorption of Zn to the extracellular surfaces of T. oceanica. Results from John et al. demonstrating apparent discrimination against the heavy isotope (Zn) during uptake conflict with results by Gélabert et al. in which marine phytoplankton and freshwater periphytic organisms preferentially uptook Zn from solution. The latter authors explained these results as due to a preferential partitioning of Zn into a tetrahedrally coordinated structure (i.e., with carboxylate, amine or silanol groups on or inside the cell) over an octahedral coordination with six water molecules in the aqueous phase, consistent with quantum mechanical predictions. Kafantaris and Borrok grew model organisms B. subtilis, P. mendocina and E. coli, as well as a natural bacterial consortium collected from soil, on high and low concentrations of Zn. In the high [Zn] condition, the average fractionation of Zn isotopes imparted by cellular surface adsorption was +0.46‰ (i.e., Zn was preferentially adsorbed), while fractionation upon intracellular incorporation varied from -0.2 to +0.5‰ depending on the bacterial species and growth phase. Empirical models of the low [Zn] condition estimated larger Zn isotope fractionation factors for surface adsorption ranging from +2 to +3‰. Overall, Zn isotope ratios in microbes appear to be driven by a number of complex factors including surface interactions, bacterial metal metabolism and metal speciation, but by understanding the relative contributions of these factors to Zn isotope signals, one can use Zn isotopes to investigate metal-binding pathways operating in natural communities of microbes. | 9 | Geochemistry |
In 1845, the English physicist James Joule wrote a paper On the mechanical equivalent of heat for the British Association meeting in Cambridge. In this paper, he reported his best-known experiment, in which the mechanical power released through the action of a "weight falling through a height" was used to turn a paddle-wheel in an insulated barrel of water.
In this experiment, the motion of the paddle wheel, through agitation and friction, heated the body of water, so as to increase its temperature. Both the temperature change of the water and the height of the fall of the weight were recorded. Using these values, Joule was able to determine the mechanical equivalent of heat. Joule estimated a mechanical equivalent of heat to be 819 ft•lbf/Btu (4.41 J/cal). The modern day definitions of heat, work, temperature, and energy all have connection to this experiment. In this arrangement of apparatus, it never happens that the process runs in reverse, with the water driving the paddles so as to raise the weight, not even slightly. Mechanical work was done by the apparatus of falling weight, pulley, and paddles, which lay in the surroundings of the water. Their motion scarcely affected the volume of the water. A quantity of mechanical work, measured as force × distance in the surroundings, that does not change the volume of the water, is said to be isochoric. Such work reaches the system only as friction, through microscopic modes, and is irreversible. It does not count as thermodynamic work. The energy supplied by the fall of the weight passed into the water as heat. | 7 | Physical Chemistry |
Homology directed repair (HDR) is a technique repairs breaks or lesions in DNA molecules. The most common technique to add inserts to desired sequences is the use of homologous recombination. This technique has a specific requirement where the insert can only be added after it has been introduced to the nucleus of the cell, which can be added to the genome mostly during the G2 and S phases in the cell cycle. | 1 | Biochemistry |
A Coulomb crystal (also Ion Coulomb crystal) is a collection of trapped ions confined in a crystal-like structure at low temperature. The structures represent an equilibrium between the repulsive Coulomb interaction between ions and the electric and magnetic fields used to confine the ions. Depending on the confinement techniques and parameters, as well as the number of ions in the trap, these can be 1-, 2- or 3-dimensional, with typical spacing between ions of ~10μm, which is significantly larger than typical solid-state crystal structures. Outside of ion traps, Coulomb crystals also occur naturally in celestial objects such as neutron stars. | 7 | Physical Chemistry |
Le Bail analysis is commonly a part of Rietveld analysis software, such as GSAS/EXPGUI. It is also used in ARITVE, BGMN, EXPO, EXTRACT, FullProf, GENEFP, Jana2006, Overlap, Powder Cell, Rietan, TOPAS and Highscore. | 3 | Analytical Chemistry |
Like inorganic carbon, there are two main forms of organic carbon found in the ocean (dissolved and particulate). Dissolved organic carbon (DOC) is defined operationally as any organic molecule that can pass through a 0.2 µm filter. DOC can be converted into particulate organic carbon through heterotrophy and it can also be converted back to dissolved inorganic carbon (DIC) through respiration.
Those organic carbon molecules being captured on a filter are defined as particulate organic carbon (POC). POC is composed of organisms (dead or alive), their fecal matter, and detritus. POC can be converted to DOC through disaggregation of molecules and by exudation by phytoplankton, for example. POC is generally converted to DIC through heterotrophy and respiration. | 9 | Geochemistry |
* Kumar, Praveen; Mittal, Amit; Firoz, Mohammad (2020). "Carbon credit issuance: accounting based financial performance". SCMS Journal of Indian Management. 17(2): 111–119. | 2 | Environmental Chemistry |
With single or prolonged exposure by inhalation the lungs may become sensitized to beryllium. Berylliosis has a slow onset and progression. Some people who are sensitized to beryllium may not have symptoms. Continued exposure causes the development of small inflammatory nodules, called granulomas. Of note, the authors of a 2006 study suggested that beryllium inhalation was not the only form of exposure and perhaps skin exposure was also a cause, as they found that a reduction in beryllium inhalation did not result in a reduction in chronic beryllium disease or beryllium sensitization.
Granuloma formation is seen in other diseases such as tuberculosis and sarcoidosis. Sarcoidosis, like berylliosis, also produces granulomas without a necrotic core, and so distinction between the two processes can be difficult.
Ultimately, this process leads to restrictive lung disease (a decrease in diffusion capacity).
The earliest symptoms are typically cough and shortness of breath. Other symptoms include chest pain, joint aches, weight loss, and fever.
Rarely, one can get granulomas in other organs including the liver.
The onset of symptoms can range from weeks up to tens of years from the initial exposure. In some individuals, a single exposure to beryllium can cause berylliosis. | 1 | Biochemistry |
is a Japanese chemist and Nobel Prize Laureate (2010), who first published the Suzuki reaction, the organic reaction of an aryl- or vinyl-boronic acid with an aryl- or vinyl-halide catalyzed by a palladium(0) complex, in 1979. | 0 | Organic Chemistry |
Gas-diffusion electrocrystallization (GDEx) is an electrochemical process consisting on the reactive precipitation of metal ions in solution (or dispersion) with intermediaries produced by the electrochemical reduction of gases (such as oxygen), at gas diffusion electrodes. It can serve for the recovery of metals or metalloids into solid precipitates or for the synthesis of libraries of nanoparticles. | 7 | Physical Chemistry |
Marcus published his theory in 1956. For many years there was an intensive search for the inverted region which would be a proof of the theory. But all experiments with series of reactions of more and more negative ΔG revealed only an increase of the reaction rate up to the diffusion limit, i.e. to a value indicating that every encounter lead to electron transfer, and that limit held also for very negative ΔG values (Rehm-Weller behaviour). It took about 30 years until the inverted region was unequivocally substantiated by Miller, Calcaterra and Closs for an intramolecular electron transfer in a molecule where donor and acceptor are kept at a constant distance by means of a stiff spacer (Fig.4).
A posteriori one may presume that in the systems where the reaction partners may diffuse freely the optimum distance for the electron jump may be sought, i.e. the distance for which ΔG = 0 and ΔG = - λ. For λ is dependent on R, λ increases for larger R and the opening of the parabola smaller. It is formally always possible to close the parabola in Fig. 2 to such an extent, that the f-parabola intersects the i-parabola in the apex. Then always ΔG = 0 and the rate k reaches the maximum diffusional value for all very negative ΔG. There are, however, other concepts for the phenomenon, e.g. the participation of excited states or that the decrease of the rate constants would be so far in the inverted region that it escapes measurement.
R. A. Marcus and his coworkers have further developed the theory outlined here in several aspects. They have included inter alia statistical aspects and quantum effects, they have applied the theory to chemiluminescence and electrode reactions. R. A. Marcus received the Nobel Prize in Chemistry in 1992, and his Nobel Lecture gives an extensive view of his work. | 7 | Physical Chemistry |
The dynamic sessile drop is similar to the static sessile drop but requires the drop to be modified. A common type of dynamic sessile drop study determines the largest contact angle possible without increasing its solid–liquid interfacial area by adding volume dynamically. This maximum angle is the advancing angle. Volume is removed to produce the smallest possible angle, the receding angle. The difference between the advancing and receding angle is the contact angle hysteresis. | 7 | Physical Chemistry |
Cold vapour atomic fluorescence spectroscopy (CVAFS) is a subset of the analytical technique known as atomic fluorescence spectroscopy (AFS). | 7 | Physical Chemistry |
The protein is a member of the tripartite motif family. This motif includes three zinc-binding domains:
* RING
* B-box type 1 zinc finger
* B-box type 2 zinc finger
and a coiled-coil region.
Three alternatively spliced transcript variants for this gene have been described, however, the full-length nature of one variant has not been determined. | 1 | Biochemistry |
ChIP-exo is a chromatin immunoprecipitation based method for mapping the locations at which a protein of interest (transcription factor) binds to the genome. It is a modification of the ChIP-seq protocol, improving the resolution of binding sites from hundreds of base pairs to almost one base pair. It employs the use of exonucleases to degrade strands of the protein-bound DNA in the 5-3 direction to within a small number of nucleotides of the protein binding site. The nucleotides of the exonuclease-treated ends are determined using some combination of DNA sequencing, microarrays, and PCR. These sequences are then mapped to the genome to identify the locations on the genome at which the protein binds.
__TOC__ | 1 | Biochemistry |
Other experts have proposed building reservoirs to prevent the movement of algae downstream. However, that can lead to the growth of algae within the reservoir, which become sediment traps with a resultant buildup of nutrients. Some researchers found that intensive blooms in reservoirs were the primary source of toxic algae observed downstream, but the movement of algae has so far been less studied, although it is considered a likely cause of algae transport. | 3 | Analytical Chemistry |
Organic peroxides are classified (i) by the presence or absence of a hydroxyl (-OH) terminus and (ii) by the presence of alkyl vs acyl substituents.
One gap in the classes of organic peroxides is diphenyl peroxide. Quantum chemical calculations predict that it undergoes a nearly barrierless reaction akin to the benzidine rearrangement. | 0 | Organic Chemistry |
In reversed-phase (e.g. aqueous mobile phase) elution, the aqueous phase is used as the mobile phase with a less polar stationary phase. In countercurrent chromatography the same solvent system may be used in either normal or reversed phase mode simply by switching the direction of mobile phase flow through the column. | 3 | Analytical Chemistry |
Bennett explores which specific expression for ΔF is the most efficient, in the sense of yielding the smallest standard error for a given simulation time. He shows that the optimal choice is to take
# , which is essentially the Fermi–Dirac distribution (satisfying indeed the detailed balance condition).
# . This value, of course, is not known (it is exactly what one is trying to compute), but it can be approximately chosen in a self-consistent manner.
Some assumptions needed for the efficiency are the following:
# The densities of the two super states (in their common configuration space) should have a large overlap. Otherwise, a chain of super states between A and B may be needed, such that the overlap of each two consecutive super states is adequate.
# The sample size should be large. In particular, as successive states are correlated, the simulation time should be much larger than the correlation time.
# The cost of simulating both ensembles should be approximately equal - and then, in fact, the system is sampled roughly equally in both super states. Otherwise, the optimal expression for C is modified, and the sampling should devote equal times (rather than equal number of time steps) to the two ensembles. | 7 | Physical Chemistry |
Newly synthesized DNA, otherwise known as Okazaki fragments, are bound by DNA ligase, which forms a new strand of DNA. There are two strands that are created when DNA is synthesized. The leading strand is continuously synthesized and is elongated during this process to expose the template that is used for the lagging strand (Okazaki fragments). During the process of DNA replication, DNA and RNA primers are removed from the lagging strand of DNA to allow Okazaki fragments to bind to. Since this process is so common, Okazaki maturation will take place around a million times during one completion of DNA replication. For Okazaki maturation to occur, RNA primers must create segments on the fragments to be ligated. This is used as a building block for the synthesis of DNA in the lagging strand. On the template strand, polymerase will synthesize in the opposite direction from the replication fork. Once the template becomes discontinuous, it will create an Okazaki fragment. Defects in the maturation of Okazaki fragments can potentially cause strands in the DNA to break and cause different forms of chromosome abnormality. These mutations in the chromosomes can affect the appearance, the number of sets, or the number of individual chromosomes. Since chromosomes are fixed for each specific species, it can also change the DNA and cause defects in the genepool of that species. | 1 | Biochemistry |
Acid rain was first systematically studied in Europe, in the 1960s, and in the United States and Canada, the following decade. | 2 | Environmental Chemistry |
Brazil's National Health Surveillance Agency banned the use of tanning beds for cosmetic purposes in 2009, making that country the first to enact a ban. It followed a 2002 ban on minors using the beds. | 5 | Photochemistry |
Spinodal phase decomposition has been used to generate architected materials by interpreting one phase as solid, and the other phase as void. These spinodal architected materials present interesting mechanical properties, such as high energy absorption, insensitivity to imperfections, superior mechanical resilience, and high stiffness-to-weight ratio. Furthermore, by controlling the phase separation, i.e., controlling the proportion of materials, and/or imposing preferential directions in the decompositions, one can control the density, and preferential directions effectively tuning the strength, weight, and anisotropy of the resulting architected material. Another interesting property of spinodal materials is the capability to seamlessly transition between different classes, orientations, and densities, thereby enabling the manufacturing of effectively multi-material structures. | 7 | Physical Chemistry |
In organic chemistry, aldol reactions are acid- or base-catalyzed reactions of aldehydes or ketones.
Aldol addition or aldolization refers to the addition of an enolate or enolation as a nucleophile to a carbonyl moiety as an electrophile. This produces a β-hydroxyaldehyde or β-hydroxyketone. In an aldol condensation, water is subsequently eliminated and an α,β-unsaturated carbonyl is formed. The aldol cleavage or Retro-aldol reaction is the reverse reaction into the starting compounds.
The name aldehyde -alcohol reaction derives from the reaction product in the case of a reaction among aldehydes, a β-hydroxy aldehyde.
Aldol reactions are important reactions for carbon-carbon bond formation and a fundamental reaction principle in organic chemistry. | 0 | Organic Chemistry |
Fulmer was a pioneer of Contract R&D in the UK. During its forty five years it provided technical solutions and research results as well as testing and consultancy for hundreds of companies and national and international agencies across the whole field of materials technology and related areas of physics and chemistry. Many papers were published in learned journals and books and many patents were granted to Fulmer authors.
Fulmer sponsored the further education of its technicians and helped many young graduates in metallurgy, physics and other sciences on the road to successful careers. In the 1970s and 80s Fulmer undertook curriculum development projects in Berkshire and Buckinghamshire primary and secondary schools. It thus introduced many young people to engineering, to problem solving methods and to working in teams.[49] A senior staff member joined the Berkshire education advisory service from Fulmer to continue and extend work of this kind.
Among the companies and organizations that owe their origins to Fulmer are:
* Applied Microengineering Limited. In-situ aligned wafer bonding machines and services
* Archer Technicoat Limited. Chemical vapour deposition and infiltration; manufacture and supply of related equipment
* Building Investigation and Testing Services Limited
* Chemlab Technology (Singapore) Pte Ltd. Set up in 1982 as a joint venture between Fulmer and Chemlab International (Singapore) Pte Ltd.
* Hansford Sensors Limited. Manufacture and supply of vibration measurement equipment
* IPH Fulmer Rope Tension Meters
* JRD Fluorochemicals Limited
* M4 Technologies Ltd – a Nottingham University spin-out. Research, consultancy and technology transfer services in the fields of materials and surface engineering, metallurgy, manufacturing and project management.
* Phoenix Scientific Industries Limited. Gas atomization for the production of metal powders; manufacture and supply of related equipment
* Questans Limited. Software development and consultancy specializing in thesaurus management and R&D management. Traded until December 2007
* Quo-tec Limited. Consultancy on the management of innovation. Sold in 2003 to CSIR (South Africa).
* the Technical Service Centre of The Pakistan Standards and Quality Control Authority (PSQCA).
* USL Ultrasonic Sciences. A major supplier to industry of automated and semi-automated ultrasonic testing systems and instruments, worldwide. | 8 | Metallurgy |
TCE has also been used as a dry cleaning solvent, although mostly replaced by tetrachloroethylene (also known as perchloroethylene), except for spot cleaning where it is still used under the trade name Picrin.
Perhaps the greatest use of TCE is as a degreaser for metal parts. It has been widely used in degreasing and cleaning since the 1920s because of its low cost, low flammability, low toxicity and high effectivity as a solvent. The demand for TCE as a degreaser began to decline in the 1950s in favor of the less toxic 1,1,1-trichloroethane. However, 1,1,1-trichloroethane production has been phased out in most of the world under the terms of the Montreal Protocol due to its effect of ozone depletion. As a result, trichloroethylene has experienced some resurgence in use as a degreaser.
Trichloroethylene is used to remove grease and lanolin from wool before weaving.
TCE has also been used in the United States to clean kerosene-fueled rocket engines (TCE was not used to clean hydrogen-fueled engines such as the Space Shuttle Main Engine). During static firing, the RP-1 fuel would leave hydrocarbon deposits and vapors in the engine. These deposits had to be flushed from the engine to avoid the possibility of explosion during engine handling and future firing. TCE was used to flush the engines fuel system immediately before and after each test firing. The flushing procedure involved pumping TCE through the engines fuel system and letting the solvent overflow for a period ranging from several seconds to 30–35 minutes, depending upon the engine. For some engines, the engine's gas generator and liquid oxygen (LOX) dome were also flushed with TCE before test firing. The F-1 rocket engine had its LOX dome, gas generator, and thrust chamber fuel jacket flushed with TCE during launch preparations. | 2 | Environmental Chemistry |
The Biomolecular Object Network Databank is a bioinformatics databank containing information on small molecule structures and interactions. The databank integrates a number of existing databases to provide a comprehensive overview of the information currently available for a given molecule. | 1 | Biochemistry |
Metallurgists throughout medieval Europe were generally free to move within different regions. For instance, German metallurgists in search of rich precious metal ores took the lead in mining and influenced the course of metal production, not only in East and South Germany but also in almost all of Central Europe and the Eastern Alps.
As mining gradually became a task for specialized craftsmen, miners moved in large groups and formed settlements close to mines, each with their own customs. They were always welcomed by regional authorities, as the latter were interested in increasing revenue through the profitable exploitation of the mineral-rich subsurface. These authorities claimed a portion of the output, and smiths and miners were provided with land for cottages, mills, forges, farming, and pasture, while also being allowed to utilize streams and lumber. (Nef 1987, 706–715).
Advancing into the high and late Middle Ages, a notable shift occurred where smelting sites gained geographical independence from mines, leading to the separation of metalworking from ore smelting. The urban expansion that unfolded from the 10th century onwards, coupled with the pivotal influence of towns, afforded metallurgists an optimal setting to cultivate and refine their technological advancements. This era witnessed the systematic formation of metallurgical guilds, with their workshops often converging on the outskirts of these urban centers. (McLees 1996).
In medieval societies, liberal and mechanical arts were considered to be totally different disciplines. Metallurgists, like all craftsmen and artisans, almost always lacked the formal education that would inform a methodical intellectual background. Instead, they were the pioneers of causal thinking based on empirical observation and experimentation (Zilsel 2000). | 8 | Metallurgy |
T.V. (Babu) RajanBabu is an organic chemist who holds the position of Distinguished Professor of Chemistry in the College of Arts and Sciences at the Ohio State University. His laboratory traditionally focuses on developing transition metal-catalyzed reactions. RajanBabu is known for helping develop the Nugent-RajanBabu reagent (Bis(cyclopentadienyl)titanium(III) chloride), a chemical reagent used in synthetic organic chemistry as a single electron reductant. | 0 | Organic Chemistry |
Litmus is a water-soluble mixture of different dyes extracted from lichens. It is often absorbed onto filter paper to produce one of the oldest forms of pH indicator, used to test materials for acidity. In an acidic medium, blue litmus paper turns red, while in a basic or alkaline medium, red litmus paper turns blue. In short, it is a dye and indicator which is used to place substances on a pH scale. | 3 | Analytical Chemistry |
The softening point is the temperature at which a material softens beyond some arbitrary softness. It can be determined, for example, by the Vicat method (ASTM-D1525 or ISO 306), Heat Deflection Test (ASTM-D648) or a ring and ball method (ISO 4625 or ASTM E28-67/E28-99 or ASTM D36 or ASTM D6493 - 11 or JIS K 6863). A ring and ball apparatus can also be used for the determination of softening point of bituminous materials. | 7 | Physical Chemistry |
The versatile chemistry of elemental sulfur is largely due to catenation. In the native state, sulfur exists as S molecules. On heating these rings open and link together giving rise to increasingly long chains, as evidenced by the progressive increase in viscosity as the chains lengthen. Also, sulfur polycations, sulfur polyanions (polysulfides) and lower sulfur oxides are all known. Furthermore, selenium and tellurium show variants of these structural motifs. | 0 | Organic Chemistry |
Fulgurites (), commonly called "fossilized lightning", are natural tubes, clumps, or masses of sintered, vitrified, or fused soil, sand, rock, organic debris and other sediments that sometimes form when lightning discharges into ground. When composed of silica, fulgurites are classified as a variety of the mineraloid lechatelierite.
When ordinary positive polarity cloud-ground lightning charges into a grounding less than 100 volts (100 V) of potential difference may be bridged. Such current may propagate into silica-rich quartzose sand, mixed soil, clay, or other sediments, rapidly vaporizing and melting resistant materials within such a common dissipation regime. This results in the formation of generally hollow and/or vesicular, branching assemblages of glassy tubes, crusts, and clumped masses. Fulgurites have no fixed composition because their chemical composition is determined
Fulgurites are structurally similar to Lichtenberg figures, which are the branching patterns produced on surfaces of insulators during dielectric breakdown by high-voltage discharges, such as lightning. | 9 | Geochemistry |
Hiyama is best known for developing:
*The Nozaki-Hiyama-Kishi reaction (NHK reaction) is a nickel/chromium mediated cross-coupling reaction between an allyl, vinyl or aryl halide and an aldehyde to form an alcohol upon aqueous workup.
It was originally discovered in 1977, where Hiyama and Nozaki reported a chemospecific synthesis of homoallyl alcohols from an aldehyde and allyl halide using chromium(II) chloride.
In 1983, Hiyama and Nozaki published another paper extending the scope of the reaction to include aryl and vinyl halides.
In 1986, Nozaki and Kishi independently discovered that the reaction depended on the nickel impurities in the chromium(II) chloride salt. Since then, nickel(II) chloride has been used as a co-catalyst.
The NHK reaction demonstrates high chemoselectivity towards aldehydes, as it tolerates a range of functional groups, and has been used on the process scale.
*The Hiyama coupling is a palladium-catalyzed cross-coupling reaction between aryl, alkenyl or alkyl halides and an organosilicon compound to form a C-C bond.
:* : Aryl, Alkenyl or Alkynyl
:* : Aryl, Alkenyl, Alkynyl or Alkyl
:* : Cl, F or Alkyl
:* : Cl, Br, I or OTf
Hiyama developed this reaction in 1988. He says he developed this method in order to overcome the shortcomings of Grignard reagents. While Grignard reagents are powerful, Hiyama says, they can be hard to use in total synthesis as they are not as tolerant of other functional groups. | 0 | Organic Chemistry |
Chain shuttling polymerization is a dual-catalyst method for producing block copolymers with alternating or variable tacticity. The desired effect of this method is to generate hybrid polymers that bear the properties of both polymer chains, such as a high melting point accompanied by high elasticity. It is a relatively new method, the first instance of its use being reported by Arriola et al. in May 2006. | 7 | Physical Chemistry |
In the laboratory, acyl chlorides are generally prepared by treating carboxylic acids with thionyl chloride (). The reaction is catalyzed by dimethylformamide and other additives.
Thionyl chloride is a well-suited reagent as the by-products (HCl, ) are gases and residual thionyl chloride can be easily removed as a result of its low boiling point (76 °C). | 0 | Organic Chemistry |
A lamella (: lamellae) in biology refers to a thin layer, membrane or plate of tissue. This is a very broad definition, and can refer to many different structures. Any thin layer of organic tissue can be called a lamella and there is a wide array of functions an individual layer can serve. For example, an intercellular lipid lamella is formed when lamellar disks fuse to form a lamellar sheet. It is believed that these disks are formed from vesicles, giving the lamellar sheet a lipid bilayer that plays a role in water diffusion.
Another instance of cellular lamellae can be seen in chloroplasts. Thylakoid membranes are actually a system of lamellar membranes working together, and are differentiated into different lamellar domains. This lamellar system allows plants to convert light energy into chemical energy. Chloroplasts are characterized by a system of membranes embedded in a hydrophobic proteinaceous matrix, or stroma. The basic unit of the membrane system is a flattened single vesicle called the thylakoid; thylakoids stack into grana. All the thylakoids of a granum are connected with each other, and the grana are connected by intergranal lamellae.
It is placed between the two primary cell walls of two plant cells and made up of intracellular matrix. The lamella comprises a mixture of polygalacturons (D-galacturonic acid) and neutral carbohydrates. It is soluble in the pectinase enzyme.
Lamella, in cell biology, is also used to describe the leading edge of a motile cell, of which the lamellipodia is the most forward portion.
The lipid bilayer core of biological membranes is also called lamellar phase. Thus, each bilayer of multilamellar liposomes and wall of a unilamellar liposome is also referred to as a lamella. | 5 | Photochemistry |
Ridged mirrors are not yet commercialized, although certain achievements can be mentioned. The reflectivity of a ridged atomic mirror can be orders of magnitude better than that of a flat surface. The use of a ridged mirror as an atomic hologram has been demonstrated.
In Shimizus and Fujitas work, atom holography is achieved via electrodes implanted into SiN film over an atomic mirror, or maybe as the atomic mirror itself.
Ridged mirrors can also reflect visible light; however, for light waves, the performance is not better than that of a flat surface. An ellipsoidal ridged mirror is proposed as the focusing element for an atomic optical system with submicrometre resolution (atomic nanoscope). | 7 | Physical Chemistry |
Photo-reduction, i.e., photochemical reduction. A colorant molecule with an unsaturated double bond (typical to alkenes) or triple bond (typical to alkynes) acting as a chromophore undergoes reduction in the presence of hydrogen and photons of sufficient energy, forming a saturated chromophoric system. Saturation reduces the length of the chromophoric system, resulting in the fading of the colorant. | 5 | Photochemistry |
Inositol hexaphosphate (IP6) is the most abundant inositol phosphate isomer found. IP6 is solely involved in various biological activities such as neurotransmission, immune response, regulation of kinase and phosphatase proteins as well as activation of calcium channels. IP6 is also involved in ATP regeneration seen in plants as well as insulin exocytosis in pancreatic β cells.
Inositol hexaphosphate also facilitates the formation of the six-helix bundle and assembly of the immature HIV-1 Gag lattice. IP6 makes ionic contacts with two rings of lysine residues at the centre of the Gag hexamer. Proteolytic cleavage then unmasks an alternative binding site, where IP6 interaction promotes the assembly of the mature capsid lattice. These studies identify IP6 as a naturally occurring small molecule that promotes both assembly and maturation of HIV-1. | 1 | Biochemistry |
This concept was suggested by the 19th-century chemist Emil Fischer. He proposed that the active site and substrate are two stable structures that fit perfectly without any further modification, just like a key fits into a lock. If one substrate perfectly binds to its active site, the interactions between them will be strongest, resulting in high catalytic efficiency.
As time went by, limitations of this model started to appear. For example, the competitive enzyme inhibitor methylglucoside can bind tightly to the active site of 4-alpha-glucanotransferase and perfectly fits into it. However, 4-alpha-glucanotransferase is not active on methylglucoside and no glycosyl transfer occurs. The Lock and Key hypothesis cannot explain this, as it would predict a high efficiency of methylglucoside glycosyl transfer due to its tight binding. Apart from competitive inhibition, this theory cannot explain the mechanism of action of non-competitive inhibitors either, as they do not bind to the active site but nevertheless influence catalytic activity. | 1 | Biochemistry |
Magneto-optic generalized ellipsometry (MOGE) is an advanced infrared spectroscopic ellipsometry technique for studying free charge carrier properties in conducting samples. By applying an external magnetic field it is possible to determine independently the density, the optical mobility parameter and the effective mass parameter of free charge carriers. Without the magnetic field only two out of the three free charge carrier parameters can be extracted independently. | 7 | Physical Chemistry |
Until Yukito Tanabe and Satoru Sugano published their paper "On the absorption spectra of complex ions", in 1954, little was known about the excited electronic states of complex metal ions. They used Hans Bethes crystal field theory and Giulio Racahs linear combinations of Slater integrals, now called Racah parameters, to explain the absorption spectra of octahedral complex ions in a more quantitative way than had been achieved previously. Many spectroscopic experiments later, they estimated the values for two of Racah's parameters, B and C, for each d-electron configuration based on the trends in the absorption spectra of isoelectronic first-row transition metals. The plots of the energies calculated for the electronic states of each electron configuration are now known as Tanabe–Sugano diagrams.
Number must be fit for each octahedral coordination complex because the C/B can deviate strongly from the theoretical value of 4.0. This ratio changes the relative energies of the levels in the Tanabe–Sugano diagrams, and thus the diagrams may vary slightly between sources depending on what C/B ratio was selected when plotting. | 7 | Physical Chemistry |
Although selenium is an essential trace element, it is toxic if taken in excess. Exceeding the Tolerable Upper Intake Level of 400 micrograms per day can lead to selenosis. This 400 microgram (µg) Tolerable Upper Intake Level is based primarily on a 1986 study of five Chinese patients who exhibited overt signs of selenosis and a follow-up study on the same five people in 1992. The 1992 study actually found the maximum safe dietary Se intake to be approximately 800 micrograms per day (15 micrograms per kilogram body weight), but suggested 400 micrograms per day to not only avoid toxicity, but also to avoid creating an imbalance of nutrients in the diet and to account for data from other countries. In China, people who ingested corn grown in extremely selenium-rich stony coal (carbonaceous shale) have suffered from selenium toxicity. This coal was shown to have selenium content as high as 9.1%, the highest concentration in coal ever recorded in literature.
Symptoms of selenosis include a garlic odor on the breath, gastrointestinal disorders, hair loss, sloughing of nails, fatigue, irritability, and neurological damage. Extreme cases of selenosis can result in cirrhosis of the liver, pulmonary edema, and death. Elemental selenium and most metallic selenides have relatively low toxicities because of their low bioavailability. By contrast, selenates and selenites are very toxic, having an oxidant mode of action similar to that of arsenic trioxide. The chronic toxic dose of selenite for humans is about 2400 to 3000 micrograms of selenium per day for a long time. Hydrogen selenide is an extremely toxic, corrosive gas. Selenium also occurs in organic compounds, such as dimethyl selenide, selenomethionine, selenocysteine and methylselenocysteine, all of which have high bioavailability and are toxic in large doses.
Selenium poisoning of water systems may result whenever new agricultural runoff courses through normally dry, undeveloped lands. This process leaches natural soluble selenium compounds (such as selenates) into the water, which may then be concentrated in new "wetlands" as the water evaporates. High selenium levels produced in this fashion have been found to have caused certain congenital disorders in wetland birds.
In fish and other wildlife, low levels of selenium cause deficiency while high levels cause toxicity. For example, in salmon, the optimal concentration of selenium in the fish tissue (whole body) is about 1 microgram selenium per gram of tissue (dry weight). At levels much below that concentration, young salmon die from selenium deficiency; much above that level they die from toxic excess. | 1 | Biochemistry |
Photoproteins are a type of enzyme produced by bioluminescent organisms. They add to the function of the luciferins whose usual light-producing reaction is catalyzed by the enzyme luciferase. | 1 | Biochemistry |
Biuret is a chemical compound with the chemical formula . It is a white solid that is soluble in hot water. A variety of organic derivatives are known. The term "biuret" also describes a family of organic compounds with the chemical formula , where are hydrogen, organyl or other groups. Also known as carbamylurea, it results from the condensation of two equivalents of urea. It is a common undesirable impurity in urea-based fertilizers, as biuret is toxic to plants. | 0 | Organic Chemistry |
Octasulfur is not typically produced as per se. It is the main (99%) component of elemental sulfur, which is recovered from volcanic sources and is a major product of the Claus process, associated with petroleum refineries. | 1 | Biochemistry |
The compound hydrolyzes to hydrazoic acid:
The compound adds to ketones and aldehydes to give the siloxy azides and subsequently tetrazoles:
It ring-opens epoxides to give azido alcohols.
It has been used in the Oseltamivir total synthesis. | 0 | Organic Chemistry |
Some materials, such as certain silicate minerals, absorb little or no solar radiation, but may still participate in light-driven reactions by mechanisms other than direct transfer of energy to reactants. | 5 | Photochemistry |
In Complex III (cytochrome bc complex or CoQH-cytochrome c reductase; ), the Q-cycle contributes to the proton gradient by an asymmetric absorption/release of protons. Two electrons are removed from QH at the Q site and sequentially transferred to two molecules of cytochrome c, a water-soluble electron carrier located within the intermembrane space. The two other electrons sequentially pass across the protein to the Q site where the quinone part of ubiquinone is reduced to quinol. A proton gradient is formed by one quinol () oxidations at the Q site to form one quinone () at the Q site. (In total, four protons are translocated: two protons reduce quinone to quinol and two protons are released from two ubiquinol molecules.)
When electron transfer is reduced (by a high membrane potential or respiratory inhibitors such as antimycin A), Complex III may leak electrons to molecular oxygen, resulting in superoxide formation.
This complex is inhibited by dimercaprol (British Antilewisite, BAL), naphthoquinone and antimycin. | 1 | Biochemistry |
The key concepts of physical chemistry are the ways in which pure physics is applied to chemical problems.
One of the key concepts in classical chemistry is that all chemical compounds can be described as groups of atoms bonded together and chemical reactions can be described as the making and breaking of those bonds. Predicting the properties of chemical compounds from a description of atoms and how they bond is one of the major goals of physical chemistry. To describe the atoms and bonds precisely, it is necessary to know both where the nuclei of the atoms are, and how electrons are distributed around them. | 7 | Physical Chemistry |
Fulmer grew steadily so that by 1960 there were about 100 staff. Individual research investigators were often recruited to work on specific projects as contracts were obtained. Each recruit was also expected to develop proposals for work in his or her areas of expertise, whether or not these fitted into Fulmers existing pattern of work. This system resulted in a progressive evolution and wide diversification of Fulmers skills base. This was a strength in that faced with a materials problem Fulmer could usually help the client with new perspectives. | 8 | Metallurgy |
More than 371 drugs approved by the FDA between the years of 1951 and 2020 contain either a phenol or a phenolic ether (a phenol with an alkyl), with nearly every class of small molecule drugs being represented, and natural products making up a large portion of this list. | 0 | Organic Chemistry |
* 1900 – Max Planck suggests that light may be emitted in discrete frequencies, giving his law of black-body radiation
* 1905 – Albert Einstein, in the first of his miracle year papers, argues that the reality of quanta would explain the photoelectric effect
* 1905 – Einstein mathematically analyzes Brownian motion as a result of random molecular motion in his paper On the movement of small particles suspended in a stationary liquid demanded by the molecular-kinetic theory of heat
* 1906 – Nernst presents a formulation of the third law of thermodynamics
* 1907 – Einstein uses quantum theory to estimate the heat capacity of an Einstein solid
* 1909 – Constantin Carathéodory develops an axiomatic system of thermodynamics
* 1910 – Einstein and Marian Smoluchowski find the Einstein–Smoluchowski formula for the attenuation coefficient due to density fluctuations in a gas
* 1911 – Paul Ehrenfest and Tatjana Ehrenfest–Afanassjewa publish their classical review on the statistical mechanics of Boltzmann, Begriffliche Grundlagen der statistischen Auffassung in der Mechanik
* 1912 – Peter Debye gives an improved heat capacity estimate by allowing low-frequency phonons
* 1916 – Sydney Chapman and David Enskog systematically develop the kinetic theory of gases
* 1916 – Einstein considers the thermodynamics of atomic spectral lines and predicts stimulated emission
* 1919 – James Jeans discovers that the dynamical constants of motion determine the distribution function for a system of particles
* 1920 – Meghnad Saha states his ionization equation
* 1923 – Debye and Erich Hückel publish a statistical treatment of the dissociation of electrolytes
* 1924 – Satyendra Nath Bose introduces Bose–Einstein statistics, in a paper translated by Einstein
* 1926 – Enrico Fermi and Paul Dirac introduce Fermi–Dirac statistics
* 1927 – John von Neumann introduces the density matrix representation, establishing quantum statistical mechanics
* 1928 – John B. Johnson discovers Johnson noise in a resistor
* 1928 – Harry Nyquist derives the fluctuation-dissipation theorem, a relationship to explain Johnson noise in a resistor
* 1931 – Lars Onsager publishes his groundbreaking paper deriving the Onsager reciprocal relations
* 1935 – Ralph H. Fowler invents the title the zeroth law of thermodynamics to summarise postulates made by earlier physicists that thermal equilibrium between systems is a transitive relation
* 1938 – Anatoly Vlasov proposes the Vlasov equation for a correct dynamical description of ensembles of particles with collective long range interaction
* 1939 – Nikolay Krylov and Nikolay Bogolyubov give the first consistent microscopic derivation of the Fokker–Planck equation in the single scheme of classical and quantum mechanics
* 1942 – Joseph L. Doob states his theorem on Gauss–Markov processes
* 1944 – Lars Onsager gives an analytic solution to the 2-dimensional Ising model, including its phase transition | 7 | Physical Chemistry |
Dinoflagellate luciferase is a multi-domain eukaryote protein, consisting of an N-terminal domain, and three catalytic domains, each of which preceded by a helical bundle domain. The structure of the dinoflagellate luciferase catalytic domain has been solved. The core part of the domain is a 10 stranded beta barrel that is structurally similar to lipocalins and FABP.
The N-terminal domain is conserved between dinoflagellate luciferase and luciferin binding proteins (LBPs). It has been suggested that this region may mediate an interaction between LBP and luciferase or their association with the vacuolar membrane.
The helical bundle domain has a three helix bundle structure that holds four important histidines that are thought to play a role in the pH regulation of the enzyme. There is a large pocket in the β-barrel of the dinoflagellate luciferase at pH 8 to accommodate the tetrapyrrole substrate but there is no opening to allow the substrate to enter. Therefore, a significant conformational change must occur to provide access and space for a ligand in the active site and the source for this change is through the four N-terminal histidine residues. At pH 8, it can be seen that the unprotonated histidine residues are involved in a network of hydrogen bonds at the interface of the helices in the bundle that block substrate access to the active site and disruption of this interaction by protonation (at pH 6.3) or by replacement of the histidine residues by alanine causes a large molecular motion of the bundle, separating the helices by 11Å and opening the catalytic site. Logically, the histidine residues cannot be replaced by alanine in nature but this experimental replacement further confirms that the larger histidine residues block the active site. Additionally, three Gly-Gly sequences, one in the N-terminal helix and two in the helix-loop-helix motif, could serve as hinges about which the chains rotate in order to further open the pathway to the catalytic site and enlarge the active site.
A dinoflagellate luciferase is capable of emitting light due to its interaction with its substrate (luciferin) and the luciferin-binding protein (LBP) in the scintillon organelle found in dinoflagellates. The luciferase acts in accordance with luciferin and LBP in order to emit light but each component functions at a different pH. Luciferase and its domains are not active at pH 8 but they are extremely active at the optimum pH of 6.3 whereas LBP binds luciferin at pH 8 and releases it at pH 6.3. Consequently, luciferin is only released to react with an active luciferase when the scintillon is acidified to pH 6.3. Therefore, in order to lower the pH, voltage-gated channels in the scintillon membrane are opened to allow the entry of protons from a vacuole possessing an action potential produced from a mechanical stimulation. Hence, it can be seen that the action potential in the vacuolar membrane leads to acidification and this in turn allows the luciferin to be released to react with luciferase in the scintillon, producing a flash of blue light. | 1 | Biochemistry |
Most of the well-recognized phototrophs are autotrophic, also known as photoautotrophs, and can fix carbon. They can be contrasted with chemotrophs that obtain their energy by the oxidation of electron donors in their environments. Photoautotrophs are capable of synthesizing their own food from inorganic substances using light as an energy source. Green plants and photosynthetic bacteria are photoautotrophs. Photoautotrophic organisms are sometimes referred to as holophytic.
Oxygenic photosynthetic organisms use chlorophyll for light-energy capture and oxidize water, "splitting" it into molecular oxygen. | 5 | Photochemistry |
The combination drug dextromethorphan/quinidine (AVP-923), traditionally used to treat pseudobulbar affect, is under investigation for the treatment of a variety of other neurological and neuropsychiatric conditions including agitation associated with Alzheimer's disease, among others. In 2013, a randomized clinical trial found that dextromethorphan may reduce the overall discomfort and duration of withdrawal symptoms associated with opioid use disorder. When combined with clonidine, dextromethorphan reduced the overall time needed for withdrawal symptoms to peak by 24 hours while reducing severity of symptoms compared to clonidine alone. | 4 | Stereochemistry |
Lithium carbonate () is the most commonly used form of lithium, although lithium citrate () and other salts, including lithium sulfate, lithium chloride, and lithium orotate are also used. Nanoparticles and microemulsions have also been invented as drug delivery mechanisms. As of 2020, there is a lack of evidence that alternate formulations or salts of lithium would reduce the need for monitoring serum lithium levels or to lower systemic toxicity.
As of 2017 lithium was marketed under many brand names worldwide, including Cade, Calith, Camcolit, Carbolim, Carbolit, Carbolith, Carbolithium, Carbolitium, Carbonato de Litio, Carboron, Ceglution, Contemnol, D-Gluconsäure, Lithiumsalz, Efadermin (Lithium and Zinc Sulfate), Efalith (Lithium and Zinc Sulfate), Elcab, Eskalit, Eskalith, Frimania, Hypnorex, Kalitium, Karlit, Lalithium, Li-Liquid, Licarb, Licarbium, Lidin, Ligilin, Lilipin, Lilitin, Limas, Limed, Liskonum, Litarex, Lithane, Litheum, Lithicarb, Lithii carbonas, Lithii citras, Lithioderm, Lithiofor, Lithionit, Lithium, Lithium aceticum, Lithium asparagicum, Lithium Carbonate, Lithium Carbonicum, Lithium Citrate, Lithium DL-asparaginat-1-Wasser, Lithium gluconicum, Lithium-D-gluconat, Lithiumcarbonaat, Lithiumcarbonat, Lithiumcitrat, Lithiun, Lithobid, Lithocent, Lithotabs, Lithuril, Litiam, Liticarb, Litijum, Litio, Litiomal, Lito, Litocarb, Litocip, Maniprex, Milithin, Neurolepsin, Plenur, Priadel, Prianil, Prolix, Psicolit, Quilonium, Quilonorm, Quilonum, Téralithe, and Theralite. | 1 | Biochemistry |
Mary Jean Garson (born 6 November 1953) is an organic chemist and academic in Australia. She currently works for the University of Queensland. | 0 | Organic Chemistry |
In nanogap cells the high electric field can distribute uniformly across the entire gap (see section "Electric field distribution"). This is different from ion transport in the macrosystem: now newly generated OH ions can immediately migrate from cathode to anode. In the case where the two electrodes are close enough, the mass transport rate can be even larger than the electron-transfer rate. This results in OH ions clustering for electron-transfer at the anode, rather than accumulating at the cathode. In this way the entire reaction can keep going and not self-limit.
Notice that for pure water electrolysis in nanogap cells, the net OH ion accumulation near the anode not only increases the local reactant concentration but also decreases the overpotential requirement (as in the Frumkin effect). According to Butler–Volmer equation, such ion accumulation increases the electrolysis current, i.e. the water splitting throughput and efficiency.
Thus even pure water can be efficiently electrolyzed, when the electrode gap is small enough. | 7 | Physical Chemistry |
Silicon carbide (SiC), also known as carborundum (), is a hard chemical compound containing silicon and carbon. A semiconductor, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder and crystal since 1893 for use as an abrasive. Grains of silicon carbide can be bonded together by sintering to form very hard ceramics that are widely used in applications requiring high endurance, such as car brakes, car clutches and ceramic plates in bulletproof vests. Large single crystals of silicon carbide can be grown by the Lely method and they can be cut into gems known as synthetic moissanite.
Electronic applications of silicon carbide such as light-emitting diodes (LEDs) and detectors in early radios were first demonstrated around 1907. SiC is used in semiconductor electronics devices that operate at high temperatures or high voltages, or both. | 8 | Metallurgy |
Another approach to evaluation of ion suppression is to make a comparison between:
* Detector response of calibration standard (either aqueous or in another suitable solvent) - This gives the best case scenario for detector response, i.e. under conditions of zero ion suppression
* Pre-prepared sample matrix spiked with an identical concentration of analyte - This demonstrates the effect of ion suppression
* Detector response of sample matrix spiked with an identical concentration of analyte and subjected to the usual sample preparation procedure - This can demonstrate the difference between any signal loss due to under-recovery during the sample preparation process and true ion suppression | 3 | Analytical Chemistry |
In the field of statistics, the Neyman–Pearson lemma states that the most powerful way to distinguish between the two distributions and based on an observation (drawn from one of them) is through the log of the ratio of their likelihoods: . The KL divergence is the expected value of this statistic if is actually drawn from . Kullback motivated the statistic as an expected log likelihood ratio. | 7 | Physical Chemistry |
There are historical reports of acute hypervitaminosis from Arctic explorers consuming bearded seal or polar bear liver, both very rich sources of stored retinol, and there are also case reports of acute hypervitaminosis from consuming fish liver, but otherwise there is no risk from consuming too much via commonly consumed foods. Only consumption of retinol-containing dietary supplements can result in acute or chronic toxicity. Acute toxicity occurs after a single or short-term doses of greater than 150,000 μg. Symptoms include blurred vision, nausea, vomiting, dizziness and headache within 8 to 24 hours. For infants ages 0–6 months given an oral dose to prevent development of vitamin A deficiency, bulging skull fontanel was evident after 24 hours, usually resolved by 72 hours. Chronic toxicity may occur with long-term consumption of vitamin A at doses of 25,000–33,000 IU/day for several months. Excessive consumption of alcohol can lead to chronic toxicity at lower intakes. Symptoms may include nervous system effects, liver abnormalities, fatigue, muscle weakness, bone and skin changes and others. The adverse effects of both acute and chronic toxicity are reversed after consumption is stopped.
In 2001, for the purpose of determining ULs for adults, the US Institute of Medicine considered three primary adverse effects and settled on two: teratogenicity, i.e., causing birth defects, and liver abnormalities. Reduced bone mineral density was considered, but dismissed because the human evidence was contradictory. During pregnancy, especially during the first trimester, consumption of retinol in amounts exceeding 4,500 μg/day increased the risk of birth defects, but not below that amount, thus setting a "No-Observed Adverse-Effect Level" (NOAEL). Given the quality of the clinical trial evidence, the NOAEL was divided by an uncertainty factor of 1.5 to set the UL for women of reproductive age at 3,000 μg/day of preformed vitamin A. For all other adults, liver abnormalities were detected at intakes above 14,000 μg/day. Given the weak quality of the clinical evidence, an uncertainty factor of 5 was used, and with rounding, the UL was set at 3,000 μg/day. Despite a US UL set at 3,000 μg, it is possible to buy over-the-counter dietary supplement products which are 7,500 μg (25,000 IU), with a label caution statement "Not intended for long term use unless under medical supervision."
For children, ULs were extrapolated from the adult value, adjusted for relative body weight. For infants, several case studies reported adverse effects that include bulging fontanels, increased intracranial pressure, loss of appetite, hyperirritability and skin peeling after chronic ingestion of the order of 6,000 or more μg/day. Given the small database, an uncertainty factor of 10 divided into the "Lowest-Observed-Adverse-Effect Level" (LOAEL) led to a UL of 600 μg/day. | 1 | Biochemistry |
Acetals, ketals, and aminals are reduced in the presence of hydrosilanes and acid. Site-selective reduction of acetals and ketals whose oxygens are inequivalent have been reported—the example below is used in a synthesis of Tamiflu.
Other functional groups that have been reduced with hydrosilanes include amides, and α,β-unsaturated esters enamines, imines, and azides. | 0 | Organic Chemistry |
Tensioned screen cloth is typically 4 feet by the width or the length of the screening machine depending on whether the deck is side or end tensioned. Screen cloth for tensioned decks can be made with hooks and are attached with clamp rails bolted on both sides of the screen box. When the clamp rail bolts are tightened, the cloth is tensioned or even stretched in the case of some types of self-cleaning screen media. To ensure that the center of the cloth does not tap repeatedly on the deck due to the vibrating shaker and that the cloth stays tensioned, support bars are positioned at different heights on the deck to create a crown curve from hook to hook on the cloth. Tensioned screen cloth is available in various materials: stainless steel, high carbon steel and oil tempered steel wires, as well as moulded rubber or polyurethane and hybrid screens (a self-cleaning screen cloth made of rubber or polyurethane and metal wires).
Commonly, vibratory-type screening equipment employs rigid, circular sieve frames to which woven wire mesh is attached. Conventional methods of producing tensioned meshed screens has given way in recent years to bonding, whereby the mesh is no longer tensioned and trapped between a sieve frame body and clamping ring; instead, developments in modern adhesive technologies has allowed the industry to adopt high strength structural adhesives to bond tensioned mesh directly to frames. | 8 | Metallurgy |
This chemical similarity can be exploited in cancer, where a protein may mutate into an "always on" (constitutively active) state. A mutation may occur to replace a tyrosine (which needs to be phosphorylated in order to activate the protein) with an aspartic acid (which would not need to be phosphorylated). In a laboratory setting, the use of recombinant proteins to artificially introduce phosphomimetics is a common tool for studying phosphorylation and protein activation. For example, the IRF3 protein must be phosphorylated for its normal activity (transcription of its target genes, like IFNβ), but when serine amino acid residues were mutated to aspartic acid, the activity increased 90-fold. Phosphomimetics are commonly used in a gain of function experiment with respect to phosphorylation. For example, aspartate mutants were successfully used to probe the biological function of the phosphorylation of a threonine residue of a ribosomal protein both in vivo and in vitro to investigate a gain-of-function mutation on a kinase that is related to Parkinson's disease. Phosphomimetics were also used to investigate the therapeutic potential of proteins or peptides. For example, phosphomimetic mutants (using glutamate to mimic serine phosphorylation) have been used to demonstrate that the phosphorylated glycoprotein may have stronger anti-melanoma effects that the wildtype protein. This approach is in particularly useful as up to three serine residues can be phosphoylated on the said protein, and hence phosphomimetic mutants are useful to probe the function of the individual phosphorylation. | 1 | Biochemistry |
Research has demonstrated that overexpression of CRBP-I increases the ability of RBP-ROH complex to phosphorylate STRA6 and, later, JAK2 and STAT5. Suppressing CRBP-I, on the other hand, led to decreased ability of RBP-ROH complex to phosphorylate STRA6 and signaling components. Similarly, reducing the expression of LRAT also decreased the ability of RBP-ROH complex to phosphorylate JAK2 and STAT5. Therefore, both CRBP-I and LRAT are necessary for the STRA6 signaling cascade upon the binding and transport of retinol. JAK2 is also conversely responsible for the activation of STRA6, after which apo-CRBP-I is recruited to the intercellular CBL of STRA6 and vitamin A might be transferred by the receptor to CRBP-I. Thus, both STRA6 signaling and STRA6 transport of vitamin A are dependent upon each other. Uptake of retinol is required for STRA6 signaling and JAK2 activation of STRA6 is necessary for retinol uptake. | 1 | Biochemistry |
Intrachromosomal homologous recombination in Arabidopsis thaliana plants was found to occur in all organs examined from the seed stage to the flowering stage of somatic plant development. Recombination frequencies were typically in the range of 10 to 10 events per genome. A. thaliana mutants selected for hypersensitivity to X-irradiation also proved to be simultaneously hypersensitive to the DNA damaging agents mitomycin C and/or methyl methanesulfonate. The mutants were also deficient in somatic homologous recombination. These findings suggest that repair of some types of DNA damage requires a recombinational process that was defective in the mutants studied. In nature, plants are continuously exposed to UV-B (280-320 nm) radiation, a component of sunlight that damages the DNA of somatic cells. Cyclobutane pyrimidine dimers (CPD) are a type of damage induced by UV-B. In A. thaliana, homologous recombination appears to be directly involved in repairing CPD damage. | 1 | Biochemistry |
With the development of the first two laws of thermodynamics in the 1850s and 60s, heats of reaction and the work associated with these processes were given a more accurate mathematical basis. In 1876, Willard Gibbs unified all of this in his 300-page "On the Equilibrium of Heterogeneous Substances". Suppose, for example, we have a general thermodynamic system, called the "primary" system and that we mechanically connect it to a "reversible work source". A reversible work source is a system which, when it does work, or has work done to it, does not change its entropy. It is therefore not a heat engine and does not suffer dissipation due to friction or heat exchanges. A simple example would be a frictionless spring, or a weight on a pulley in a gravitational field. Suppose further, that we thermally connect the primary system to a third system, a "reversible heat source". A reversible heat source may be thought of as a heat source in which all transformations are reversible. For such a source, the heat energy δQ added will be equal to the temperature of the source (T) times the increase in its entropy. (If it were an irreversible heat source, the entropy increase would be larger than δQ/T)
Define:
We may now make the following statements
Eliminating , , and gives the following equation:
When the primary system is reversible, the equality will hold and the amount of work delivered will be a maximum. Note that this will hold for any reversible system which has the same values of dU and dS . | 7 | Physical Chemistry |
Thioesters are common intermediates in many biosynthetic reactions, including the formation and degradation of fatty acids and mevalonate, precursor to steroids. Examples include malonyl-CoA, acetoacetyl-CoA, propionyl-CoA, cinnamoyl-CoA, and acyl carrier protein (ACP) thioesters. Acetogenesis proceeds via the formation of acetyl-CoA. The biosynthesis of lignin, which comprises a large fraction of the Earth's land biomass, proceeds via a thioester derivative of caffeic acid. These thioesters arise analogously to those prepared synthetically, the difference being that the dehydration agent is ATP. In addition, thioesters play an important role in the tagging of proteins with ubiquitin, which tags the protein for degradation.
Oxidation of the sulfur atom in thioesters (thiolactones) is postulated in the bioactivation of the antithrombotic prodrugs ticlopidine, clopidogrel, and prasugrel. | 0 | Organic Chemistry |
Clinical chemistry (also known as chemical pathology, clinical biochemistry or medical biochemistry) is a division in medical laboratory sciences focusing on qualitative tests of important compounds, referred to as analytes or markers, in bodily fluids and tissues using analytical techniques and specialized instruments. This interdisciplinary field includes knowledge from medicine, biology, chemistry, biomedical engineering, informatics, and an applied form of biochemistry (not to be confused with medicinal chemistry, which involves basic research for drug development).
The discipline originated in the late 19th century with the use of simple chemical reaction tests for various components of blood and urine. In the many decades since, clinical chemists use automated analyzer in many clinical laboratories, which does experimental techniques ranging from pipetting specimens and specimen labelling to advanced measurement techniques such as spectrometry, chromatography, photometry, potentiometry, etc. These instruments provide different results that help identify uncommon analytes, changes in light and electronic voltage properties of naturally-occurring analytes such as enzymes, ions, electrolytes, and their concentrations, all of which are important for diagnosing diseases.
Blood and urine are the most common test specimens clinical chemists or medical laboratory scientists collect for clinical routine tests, with a main focus on serum and plasma in blood. There are now many blood tests and clinical urine tests with extensive diagnostic capabilities. Some clinical tests require clinical chemists to process the specimen before testing. Clinical chemists and medical laboratory scientists serve as the interface between the laboratory side and the clinical practice, providing suggestions to physicians on which test panel to order and interpret any irregularities in test results that reflect on the patients health status and organ system functionality. This allows healthcare providers to make more accurate evaluation of a patients health and to diagnose disease, predicting the progression of a disease (prognosis), screening, and monitoring the treatment's efficiency in a timely manner. The type of test required dictates what type of sample is used. | 1 | Biochemistry |
The first analysis, assuming a Faraday efficiency of 100%, yielded an average apparent excess heat of 21% of input power. The term "apparent excess heat" was coined by the investigators to indicate that the actual Faraday efficiency was ignored in the analysis. | 7 | Physical Chemistry |
The effectiveness of methods such as chemotherapy to treat cancer tends to plateau after some initial time as the cells undergo molecular changes that render them insensitive to the effect of anticancer drugs. Hence, it is imperative to detect the presence of cancerous cells early. An important biomarker, microRNA (miRNA), is crucial in this detection via its expression patterns. Zhang et al. have demonstrated an INHIBIT-OR gate cascade for the purpose, Yue and co. used an AND gate to construct a system with two miRNA inputs and a quantum dot photoluminescence output, and Peng et al. also constructed an AND gate-based dual-input system for the simultaneous detection of miRNAs from tumor cells.
Akkaya et al. illustrated the application of a logic gate for photodynamic therapy in their work. A bodipy dye attached to a crown-ether and two pyridyl groups separated by spacers works according to an AND logic gate. The molecule works as a photodynamic agent upon irradiation at 660 nm under conditions of relatively high sodium and proton ion concentrations by converting triplet oxygen to cytotoxic singlet oxygen. This prototypical example would take advantage of the higher sodium levels and lower pH in tumor tissue compared to the levels in normal cells. When these two cancer-related cellular parameters are satisfied, a change is observed in the absorbance spectrum. This technique could be useful for the treatment of malignant tumors as it is non-invasive and specific. | 6 | Supramolecular Chemistry |
Unlike small interfering RNA (siRNA) therapeutics that turn over within a cell and consequently only silence genes transiently, DNA constructs are continually transcribed, replenishing the cellular ‘dose’ of short-hairpin RNA (shRNA), thereby enabling long-term silencing of targeted genes. The ddRNAi mechanism, therefore, offers the potential for ongoing clinical benefit with reduced medical intervention. | 1 | Biochemistry |
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