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Upon deprotonation, the corrinoid ring is capable of binding cobalt. In vitamin B, the resulting complex also features a benzimidazole-derived ligand, and the sixth site on the octahedron serves as the catalytic center.
The corrin ring resembles the porphyrin ring. Both feature four pyrrole-like subunits organized into rings. Corrins have a central 15-membered ring whereas porphryins have an interior 16-membered ring. All four nitrogen centers are linked by conjugation structure, with alternating double and single bonds. In contrast to porphyrins, corrins lack one of the carbon groups that link the pyrrole-like units into a fully conjugated structure. With a conjugated system that extends only 3/4 of the way around the ring, and does not include any of the outer edge carbons, corrins have a number of non-conjugated sp carbons, making them more flexible than porphyrins and not as flat. A third closely related biological structure, the chlorin ring system found in chlorophyll, is intermediate between porphyrin and corrin, having 20 carbons like the porphyrins and a conjugated structure extending all the way around the central atom, but with only 6 of the 8 edge carbons participating.
Corroles (octadehydrocorrins) are fully aromatic derivatives of corrins. | 1 | Applied and Interdisciplinary Chemistry |
Compounds that are prepared by reaction of other compounds are known as "synthetic". They may be either compounds that are already found in plants/animals or those artificial compounds that do not occur naturally.
Most polymers (a category that includes all plastics and rubbers) are organic synthetic or semi-synthetic compounds. | 0 | Theoretical and Fundamental Chemistry |
Amorphous materials have an internal structure consisting of interconnected structural blocks that can be similar to the basic structural units found in the corresponding crystalline phase of the same compound. Unlike in crystalline materials, however, no long-range order exists. Amorphous materials therefore cannot be defined by a finite unit cell. Statistical methods, such as the atomic density function and radial distribution function, are more useful in describing the structure of amorphous solids.
Although amorphous materials lack long range order, they exhibit localized order on small length scales. Localized order in amorphous materials can be categorized as short or medium range order. By convention, short range order extends only to the nearest neighbor shell, typically only 1-2 atomic spacings. Medium range order is then defined as the structural organization extending beyond the short range order, usually by 1-2 nm. | 0 | Theoretical and Fundamental Chemistry |
Covalent inhibitors can be used to assess target engagement which can sometimes be used pre-clinically and clinically to assess the relationship between dose of drug and efficacy or toxicity. This approach was used for covalent Btk inhibitors pre-clinically and clinically to understand the relationship between dose administered and efficacy in animal models of arthritis and target occupancy in a clinical study of healthy volunteers. | 1 | Applied and Interdisciplinary Chemistry |
Radioactive isotopes are used in medicine for both treatment and diagnostic scans. The most common isotope used in diagnostic scans is Tc-99m (Technetium-99m), being used in approximately 85% of all nuclear medicine diagnostic scans worldwide. It is used for diagnoses involving a large range of body parts and diseases such as cancers and neurological problems. Another well-known radioactive isotope used in medicine is I-131 (Iodine-131), which is used as a radioactive label for some radiopharmaceutical therapies or the treatment of some types of thyroid cancer. | 1 | Applied and Interdisciplinary Chemistry |
The discovery of the perfect liquid was a turning point in physics. Experiments at RHIC have revealed a wealth of information about this remarkable substance, which we now know to be a QGP. Nuclear matter at "room temperature" is known to behave like a superfluid. When heated the nuclear fluid evaporates and turns into a dilute gas of nucleons and, upon further heating, a gas of baryons and mesons (hadrons). At the critical temperature, T, the hadrons melt and the gas turns back into a liquid. RHIC experiments have shown that this is the most perfect liquid ever observed in any laboratory experiment at any scale. The new phase of matter, consisting of dissolved hadrons, exhibits less resistance to flow than any other known substance. The experiments at RHIC have, already in 2005, shown that the Universe at its beginning was uniformly filled with this type of material—a super-liquid—which once the Universe cooled below T evaporated into a gas of hadrons. Detailed measurements show that this liquid is a quark–gluon plasma where quarks, antiquarks and gluons flow independently.
In short, a quark–gluon plasma flows like a splat of liquid, and because it is not "transparent" with respect to quarks, it can attenuate jets emitted by collisions. Furthermore, once formed, a ball of quark–gluon plasma, like any hot object, transfers heat internally by radiation. However, unlike in everyday objects, there is enough energy available so that gluons (particles mediating the strong force) collide and produce an excess of the heavy (i.e., high-energy) strange quarks. Whereas, if the QGP did not exist and there was a pure collision, the same energy would be converted into a non-equilibrium mixture containing even heavier quarks such as charm quarks or bottom quarks.
The equation of state is an important input into the flow equations. The speed of sound (speed of QGP-density oscillations) is currently under investigation in lattice computations. The mean free path of quarks and gluons has been computed using perturbation theory as well as string theory. Lattice computations have been slower here, although the first computations of transport coefficients have been concluded. These indicate that the mean free time of quarks and gluons in the QGP may be comparable to the average interparticle spacing: hence the QGP is a liquid as far as its flow properties go. This is very much an active field of research, and these conclusions may evolve rapidly. The incorporation of dissipative phenomena into hydrodynamics is another active research area. | 0 | Theoretical and Fundamental Chemistry |
An S-shaped trap is also known as an S-bend. It was invented by Alexander Cumming in 1775 but became known as the U-bend following the introduction of the U-shaped trap by Thomas Crapper in 1880. The new U-bend could not jam, so, unlike the S-bend, it did not need an overflow.
Once invented, despite being simple and reasonably reliable, widespread use was slow coming. In Britain, the requirement to use traps was introduced only after the Great Stink in London, in the summer of 1858, when the objectionable smell of the River Thames, which was effectively an open sewer, affected the nearby Houses of Parliament. That motivated the legislators to authorise the construction of a modern sewerage system in the city, of which the S-bend was an essential component. , only about two-thirds of the world population have access to traps, in spite of the evidence that good sewage systems significantly improve economic productivity in places that employ them. | 1 | Applied and Interdisciplinary Chemistry |
An intense effort has been made towards the total synthesis of (+)-discodermolide in order to meet the growing interest of studying its clinical profile. More than a dozen of syntheses have been published by different research groups. After decade of work, discodermolide syntheses have become more convergent and more practical. All of the total syntheses approaches started with the construction of three major fragments of roughly equivalent complexity, each of which contains the methyl-hydroxyl-methyl triad of contiguous centers that matches the stereogenicity of discodermolide target. Here are three examples of the retrosynthetic analyses of (+)-discodermolide: | 0 | Theoretical and Fundamental Chemistry |
Captive populations are subject to problems such as inbreeding depression, loss of genetic diversity and adaptations to captivity. It is important to manage captive populations in a way that minimizes these issues so that the individuals to be introduced will resemble the original founders as closely as possible, which will increase the chances of successful reintroductions. During the initial growth phase, the population size is rapidly expanded until a target population size is reached. The target population size is the number of individuals that are required to maintain appropriate levels of genetic diversity, which is generally considered to be 90% of the current genetic diversity after 100 years. The number of individuals required to meet this goal varies based on potential growth rate, effective size, current genetic diversity, and generation time. Once the target population size is reached, the focus shifts to maintaining the population and avoiding genetic issues within the captive population. | 1 | Applied and Interdisciplinary Chemistry |
For Reynolds number greater than 4000, the flow is turbulent; the resistance to flow follows the Darcy–Weisbach equation: it is proportional to the square of the mean flow velocity. Over a domain of many orders of magnitude of (), the friction factor varies less than one order of magnitude (). Within the turbulent flow regime, the nature of the flow can be further divided into a regime where the pipe wall is effectively smooth, and one where its roughness height is salient. | 1 | Applied and Interdisciplinary Chemistry |
United States Environmental Protection Agency (EPA) standards, published in 40 CFR Parts 280 and 281, mandate double-walled piping for many below-ground transport systems in wastewater treatment plants and at sanitary or hazardous-waste landfills or remediation sites. These and other regulations affect below-grade transport of hazardous materials in fuel storage systems, tank farms, drainage or runoff from process plants, and some food-processing and related applications. Double-walled containment systems are also used for certain classes of toxic or corrosive chemicals, mostly gases, used in semiconductor fabrication. Double-walled pipes may also be used where a waste water pipe traverses a drinking water catchment area. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogel encapsulation of the QDs opens up a new range of applications, such as:
* Biosensors
:Enzymes and other bio-active molecules serve as biorecognition units while QDs serve as signalling units. By adding enzymes to the QD hydrogel network both units can be combined to form a biosensor. The enzymatic reaction that detects a particular molecule causes the fluoresce of QDs to be quenched. In this way, the location of molecules of interest can be observed.
* Cell Influence and Imaging
: Adding iron oxide nanoparticles to the QD micelles allows them to be fluorescent and magnetic. These micelles can be moved in a magnetic field to create concentration gradients that will influence a cell's processes.
* Gold Hyperthermia
:When excited by high energy radiation, such as with a laser, gold nanoparticles emit a thermal field. This phenomenon can be used as a form of hyperthermia therapy to destroy malignant cancers without damaging surrounding tissues. When combined with QDs in a hydrogel this could facilitate real-time monitoring of the tumor treatment. | 0 | Theoretical and Fundamental Chemistry |
Everolimus is the second novel Rapamycin analog. Compared with the parent compound rapamycin, everolimus is more selective for the mTORC1 protein complex, with little impact on the mTORC2 complex. mTORC1 inhibition by everolimus has been shown to normalize tumor blood vessels, to increase tumor-infiltrating lymphocytes, and to improve adoptive cell transfer therapy.
From March 30, 2009, to May 5, 2011, the U.S. FDA approved everolimus for the treatment of advanced renal cell carcinoma after failure of treatment with sunitinib or sorafenib, subependymal giant cell astrocytoma (SEGA) associated with tuberous sclerosis (TS), and progressive neuroendocrine tumors of pancreatic origin (PNET). In July and August 2012, two new indications were approved, for advanced hormone receptor-positive, HER2-negative breast cancer in combination with exemestane, and pediatric and adult patients with SEGA. In 2009 and 2011, it was also approved throughout the European Union for advanced breast cancer, pancreatic neuroendocrine tumours, advanced renal cell carcinoma, and SEGA in patients with tuberous sclerosis. | 1 | Applied and Interdisciplinary Chemistry |
A field effect is the polarization of a molecule through space. The effect is a result of an electric field produced by charge localization in a molecule. This field, which is substituent and conformation dependent, can influence structure and reactivity by manipulating the location of electron density in bonds and/or the overall molecule. The polarization of a molecule through its bonds is a separate phenomenon known as induction. Field effects are relatively weak, and diminish rapidly with distance, but have still been found to alter molecular properties such as acidity. | 0 | Theoretical and Fundamental Chemistry |
In 1991, Ye joined the National Institute for Materials Science. She was made Director of Photocatalytic Materials Center in 2006 and Director of Environmental Remediation Materials in 2011.
Ye has dedicated her career to the realization of artificial photosynthesis. She is particularly interested in the development of materials that harvest the most sunlight. Ye has studied the reaction mechanisms, and, in an effort to overcome harsh reaction kinetics, has worked on the careful construction of interfaces. In particular, Ye has developed nano-structured surfaces that enhance reactivities, and, using localized surface plasmon resonance, broaden the spectral range of her photocatalytic materials.
Ye was elected Fellow of the Royal Society of Chemistry in 2016. In 2022, she was included by the American Chemical Society Energy Letters in their list of the world's leading women scientists in energy research. | 0 | Theoretical and Fundamental Chemistry |
The use of pesticides inherently entails the risk of resistance developing. Various techniques and procedures of pesticide application can slow the development of resistance, as can some natural features of the target population and surrounding environment. | 1 | Applied and Interdisciplinary Chemistry |
Methanosaeta harundinacea 6Ac, a methanogenic archaeon, produces carboxylated acyl homoserine lactone compounds that facilitate the transition from growth as short cells to growth as filaments. | 1 | Applied and Interdisciplinary Chemistry |
Since refinement depends on finding the best fit between a calculated and experimental pattern, it is important to have a numerical figure of merit quantifying the quality of the fit. Below are the figures of merit generally used to characterize the quality of a refinement. They provide insight to how well the model fits the observed data.
Profile residual (reliability factor):
Weighted profile residual:
Bragg residual:
Expected profile residual:
Goodness of fit:
It is worth mentioning that all but one () figure of merit include a contribution from the background. There are some concerns about the reliability of these figures, as well there is no threshold or accepted value which dictates what represents a good fit. The most popular and conventional figure of merit used is the goodness of fit which should approach unity given a perfect fit, though this is rarely the case. In practice, the best way to assess quality is a visual analysis of the fit by plotting the difference between the observed and calculated data plotted on the same scale. | 0 | Theoretical and Fundamental Chemistry |
Detonation sprayed coatings are primarily mechanically bonded. This means that the surface of the component being sprayed, must be properly prepared so as to maximise the bond strength between the sprayed coating and the substrate. To successfully prepare the surface it must be cleaned of all greases, oils, dirt and other contaminants and sufficiently roughened to provide enough of a surface irregularity for the coating to cling to. Chemical processes are generally the most suitable methods used to clean the substrate surface. After which care must be taken not to touch and/or dirty the surface prior to spraying. The three methods used to roughen up the substrate surface are abrasive blasting, machining and bond coating. Cleaning occurs only after the roughening of the surface except for when a bond coating is used; the surface must be cleaned before and possibly after this process too. Application of the detonation spray coating should be performed as soon as possible after a substrates surface has been prepared. | 1 | Applied and Interdisciplinary Chemistry |
Structural genomics takes advantage of completed genome sequences in several ways in order to determine protein structures. The gene sequence of the target protein can also be compared to a known sequence and structural information can then be inferred from the known protein's structure. Structural genomics can be used to predict novel protein folds based on other structural data. Structural genomics can also take modeling-based approach that relies on homology between the unknown protein and a solved protein structure. | 1 | Applied and Interdisciplinary Chemistry |
Daniela Blanco is a Venezuelan-born chemical engineer and co-founder and CEO of Sunthetics. Sunthetics is a sustainable materials startup company that is seeking to move the chemical industry away from its reliance on fossil fuels, such as gas and oil. Sunthetics focuses on electrochemical processes and utilizes its own proprietary Artificial Intelligence software to increase the efficiency of reactions that are powered using electricity. These chemical reactions are driven by "complex pulses of electrical current" using renewable energy as opposed to the traditional method requiring heat, which is dependent on the use of fossil fuels. In 2020, Blanco was named a Top Innovator under 35 in Latin America by MIT Technology Review. | 1 | Applied and Interdisciplinary Chemistry |
Natural products chemist Udo Gräfe collected a sample of P. rudis HKI 0254 from a dead log in Siberia from which hexacyclinol was isolated. His group's 2002 paper showed that the compound behaved as an antiproliferative drug against cancer cell lines and proposed a structure (2) for the compound.
An initial total synthesis was published by James J. La Clair in 2006, purporting a synthesis of Gräfe's proposed structure based on H nuclear magnetic resonance (NMR) spectra.
Natural products chemist Scott D. Rychnovsky simulated the C nuclear magnetic resonance spectrum of the structure proposed by Gräfe and found that it did not correspond to the spectrum of the structure allegedly synthesized by La Clair. Rychnovsky proposed a different structure (1) based on panepophenanthrin, another molecule isolated from a different strain of P. rudis. The scientific community then began criticizing La Clairs work, claiming that his work was sloppy or that he fabricated data. La Clairs publication of his purported synthesis was retracted in 2012, citing a lack of validation of its claims.
In 2006, a group led by John Porco, Jr. synthesized Rychnovskys proposed structure. They showed that the H- and C-NMR spectra matched that of the compound isolated by Gräfe, confirming Rychnovskys structure. La Clair claimed that since the two structures were isomers, it is possible that they would have similar H-NMR spectra. However, a later paper by Saielli and Bagno claims that there would be significant differences in the H- and C-NMR spectra of compounds (1) and (2).
The controversy was covered extensively by a number of science blogs.
In response to the controversy, Nobel Prize-winning synthetic chemist E.J. Corey remarked, "Occasionally, blatantly wrong science is published, and to the credit of synthetic chemistry, the corrections usually come quickly and cleanly." | 0 | Theoretical and Fundamental Chemistry |
Extractive distillation is similar to azeotropic distillation, except in this case the entrainer is less volatile than any of the azeotrope's constituents. For example, the azeotrope of 20% acetone with 80% chloroform can be broken by adding water and distilling the result. The water forms a separate layer in which the acetone preferentially dissolves. The result is that the distillate is richer in chloroform than the original azeotrope. | 1 | Applied and Interdisciplinary Chemistry |
The product of the process, sodium hypochlorite, provides 0.7% to 1% chlorine. Anything below the concentration of 1% chlorine is considered a non-hazardous chemical although still a very effective disinfectant. The sodium hypochlorite produced is in the range of pH 6-7.5, relatively neutral in regards to acidity or baseness. At that pH range, the sodium hypochlorite is relatively stable. | 0 | Theoretical and Fundamental Chemistry |
The Greek physician Pedanius Dioscorides, of Anazarbus in Asia Minor, wrote a five-volume treatise concerning medical matters, entitled Περὶ ὕλης ἰατρικῆς in Greek or De materia medica in Latin. This famous commentary covered about 600 plants along with therapeutically useful animal and mineral products. It documented the effects of drugs made from these substances on patients. De materia medica was the first extensive pharmacopeia, including about a thousand natural product drugs (mostly plant-based), 4,740 medicinal usages for drugs, and 360 medical properties (such as antiseptic, anti-inflammatory, stimulant). The book was heavily translated, and portrayed some of the emblematic actions of physicians and herbalists. One such page is Physician Preparing an Elixir.
Dioscorides' plant descriptions use an elementary classification, though he cannot be said to have used botanical taxonomy. Book one describes the uses for aromatic oils, salves and ointments, trees and shrubs, and fleshy fruits, even if not aromatic. Book two included uses for animals, parts of animals, animal products, cereals, leguminous, malvaceous, cruciferous, and other garden herbs. Book three detailed the properties of roots, juices, herbs and seeds used for food or medicine. Book four continued to describe the uses for roots and herbs, specifically narcotic and poisonous medicinal plants. Book five dealt with the medicinal uses for wine and metallic ores. It is a precursor to all modern pharmacopeias, and is considered one of the most influential herbal books in history. It remained in use until about 1600 AD. | 1 | Applied and Interdisciplinary Chemistry |
The complex is the simplest PPC appearing in nature and therefore a suitable test object for the development of methods that can be transferred to more complex systems like photosystem I. Engel and co-workers observed that the FMO complex exhibits remarkably long quantum coherence, but after about a decade of debate, it was shown that this quantum coherence has no significance to the functioning of the complex. Furthermore, it was shown that the reported long lived oscillations observed in the spectra are solely due to groundstate vibrational dynamics and do not reflect any energy transfer dynamics. | 0 | Theoretical and Fundamental Chemistry |
The term "representative layer" refers to a hypothetical plane parallel layer that has properties relevant to absorption spectroscopy that are representative of a sample as a whole. For particulate samples, a layer is representative if each type of particle in the sample makes up the same fraction of volume and surface area in the layer as in the sample. The void fraction in the layer is also the same as in the sample. Implicit in the representative layer theory is that absorption occurs at the molecular level, but that scatter is from a whole particle. | 0 | Theoretical and Fundamental Chemistry |
As of August 2023, proposed legislation banning polystyrene has passed at least one legislative chamber in two states and one territory. In Connecticut, SB 118 passed the state Senate in April 2022, but died when the session ended. In Illinois, the state House passed HB2376 on March 21, 2023.
The territory of the Northern Mariana Islands passed HB21-89 in its House of Representatives in 2020.
In September 2021, Florida introduced a proposed phaseout of polystyrene foam food packaging. Commissioner of Agriculture Nikki Fried, whose Florida Department of Agriculture and Consumer Services oversees food safety in Florida, proposed a rule to phase out polystyrene in 40,000 grocery stores, food markets, convenience stores, and gas stations that the agency regulates in Florida. The Florida Legislature will consider the proposed rule in 2022. | 0 | Theoretical and Fundamental Chemistry |
The functional significance of respirasomes is not entirely clear but more recent research is beginning to shed some light on their purpose. It has been hypothesized that the organization of respiratory enzymes into supercomplexes reduces oxidative damage and increases metabolism efficiency. Schäfer et al. (2006) demonstrated that supercomplexes comprising Complex IV had higher activities in Complex I and III, indicating that the presence of Complex IV modifies the conformation of the other complexes to enhance catalytic activity. Evidence has also been accumulated to show that the presence of respirasomes is necessary for the stability and function of Complex I. In 2013, Lapuente-Brun et al. demonstrated that supercomplex assembly is "dynamic and organizes electron flux to optimize the use of available substrates." | 1 | Applied and Interdisciplinary Chemistry |
Trifluoroacetic acid is a corrosive strong acid but it does not pose the hazards associated with hydrofluoric acid because the carbon-fluorine bond is not labile. TFA is harmful when inhaled, causes severe skin burns and is toxic for aquatic organisms even at low concentrations.
TFA's reaction with bases and metals, especially light metals, is strongly exothermic. The reaction with lithium aluminium hydride (LAH) results in an explosion.
TFA is a metabolic breakdown product of the volatile anaesthetic agent halothane. It is thought to be responsible for halothane induced hepatitis. | 0 | Theoretical and Fundamental Chemistry |
The main light harvesting complex in Green bacteria is known as the chlorosome. The chlorosome is equipped with rod-like BChl c aggregates with protein embedded lipids surrounding it. Chlorosomes are found outside of the membrane which covers the reaction centre. Green sulphur bacteria and some Chloroflexia use ellipsoidal complexes known as the chlorosome to capture light. Their form of bacteriochlorophyll is green. | 0 | Theoretical and Fundamental Chemistry |
Red phosphorus may be formed by heating white phosphorus to in the absence of air or by exposing white phosphorus to sunlight. Red phosphorus exists as an amorphous network. Upon further heating, the amorphous red phosphorus crystallizes. Bulk red phosphorus does not ignite in air at temperatures below , whereas pieces of white phosphorus ignite at about .
Under standard conditions it is more stable than white phosphorus, but less stable than the thermodynamically stable black phosphorus. The standard enthalpy of formation of red phosphorus is −17.6 kJ/mol. Red phosphorus is kinetically most stable.
It was first presented by Anton von Schrötter before the Vienna Academy of Sciences on December 9, 1847, although others had doubtlessly had this substance in their hands before, such as Berzelius. | 0 | Theoretical and Fundamental Chemistry |
DNA is precipitated by first ensuring that the correct concentration of positive ions is present in solution (too much will result in a lot of salt co-precipitating with DNA, too little will result in incomplete DNA recovery) and then adding two to three volumes of at least 95% ethanol. Many protocols advise storing DNA at low temperature at this point, but there are also observations that it may not improve DNA recovery, and may even lower precipitation efficiency while using over-night incubation time. Therefore, good efficiency can be achieved at room temperature, but when possible degradation is taken into account, it is probably better to incubate DNA on wet ice. Optimal incubation time depends on the length and concentration of DNA. Smaller fragments and lower concentrations will require longer times to achieve acceptable recovery. For very small lengths and low concentrations over-night incubation is recommended. In such cases use of carriers like tRNA, glycogen or linear polyacrylamide can greatly improve recovery.
During incubation DNA and some salts will precipitate from solution, in the next step this precipitate is collected by centrifugation in a microcentrifuge tube at high speeds (~12,000g). Time and speed of centrifugation has the biggest effect on DNA recovery rates. Again smaller fragments and higher dilutions require longer and faster centrifugation. Centrifugation can be done either at room temperature or in 4 °C or 0 °C.
During centrifugation precipitated DNA has to move through ethanol solution to the bottom of the tube, lower temperatures increase viscosity of the solution and larger volumes make the distance longer, so both those factors lower efficiency of this process requiring longer centrifugation for the same effect.
After centrifugation the supernatant solution is removed, leaving a pellet of crude DNA. Whether the pellet is visible depends on the amount of DNA and on its purity (dirtier pellets are easier to see) or the use of co-precipitants.
In the next step, 70% ethanol is added to the pellet, and it is gently mixed to break the pellet loose and wash it. This removes some of the salts present in the leftover supernatant and bound to DNA pellet making the final DNA cleaner. This suspension is centrifuged again to once again pellet DNA and the supernatant solution is removed. This step is repeated once.
Finally, the pellet is air-dried and the DNA is resuspended in water or other desired buffer. It is important not to over-dry the pellet as it may lead to denaturation of DNA and make it harder to resuspend.
Isopropanol can also be used instead of ethanol; the precipitation efficiency of the isopropanol is higher making one volume enough for precipitation. However, isopropanol is less volatile than ethanol and needs more time to air-dry in the final step. The pellet might also adhere less tightly to the tube when using isopropanol. | 1 | Applied and Interdisciplinary Chemistry |
Beta particle-emitting substances sometimes exhibit a weak radiation with continuous spectrum that is due to bremsstrahlung (see the "outer bremsstrahlung" below). In this context, bremsstrahlung is a type of "secondary radiation", in that it is produced as a result of stopping (or slowing) the primary radiation (beta particles). It is very similar to X-rays produced by bombarding metal targets with electrons in X-ray generators (as above) except that it is produced by high-speed electrons from beta radiation. | 0 | Theoretical and Fundamental Chemistry |
Owing their large radii, transition metals generally form clusters that are larger than main group elements. One consequence of their increased size, these clusters often contain atoms at their centers. A prominent example is [FeC(CO)]. In such cases, the rules of electron counting assume that the interstitial atom contributes all valence electrons to cluster bonding. In this way, [FeC(CO)] is equivalent to [Fe(CO)] or [Fe(CO)]. | 0 | Theoretical and Fundamental Chemistry |
Microarrays can be fabricated using a variety of technologies, including printing with fine-pointed pins onto glass slides, photolithography using pre-made masks, photolithography using dynamic micromirror devices, ink-jet printing, or electrochemistry on microelectrode arrays.
In spotted microarrays, the probes are oligonucleotides, cDNA or small fragments of PCR products that correspond to mRNAs. The probes are synthesized prior to deposition on the array surface and are then "spotted" onto glass. A common approach utilizes an array of fine pins or needles controlled by a robotic arm that is dipped into wells containing DNA probes and then depositing each probe at designated locations on the array surface. The resulting "grid" of probes represents the nucleic acid profiles of the prepared probes and is ready to receive complementary cDNA or cRNA "targets" derived from experimental or clinical samples.
This technique is used by research scientists around the world to produce "in-house" printed microarrays in their own labs. These arrays may be easily customized for each experiment, because researchers can choose the probes and printing locations on the arrays, synthesize the probes in their own lab (or collaborating facility), and spot the arrays. They can then generate their own labeled samples for hybridization, hybridize the samples to the array, and finally scan the arrays with their own equipment. This provides a relatively low-cost microarray that may be customized for each study, and avoids the costs of purchasing often more expensive commercial arrays that may represent vast numbers of genes that are not of interest to the investigator.
Publications exist which indicate in-house spotted microarrays may not provide the same level of sensitivity compared to commercial oligonucleotide arrays, possibly owing to the small batch sizes and reduced printing efficiencies when compared to industrial manufactures of oligo arrays.
In oligonucleotide microarrays, the probes are short sequences designed to match parts of the sequence of known or predicted open reading frames. Although oligonucleotide probes are often used in "spotted" microarrays, the term "oligonucleotide array" most often refers to a specific technique of manufacturing. Oligonucleotide arrays are produced by printing short oligonucleotide sequences designed to represent a single gene or family of gene splice-variants by synthesizing this sequence directly onto the array surface instead of depositing intact sequences. Sequences may be longer (60-mer probes such as the Agilent design) or shorter (25-mer probes produced by Affymetrix) depending on the desired purpose; longer probes are more specific to individual target genes, shorter probes may be spotted in higher density across the array and are cheaper to manufacture.
One technique used to produce oligonucleotide arrays include photolithographic synthesis (Affymetrix) on a silica substrate where light and light-sensitive masking agents are used to "build" a sequence one nucleotide at a time across the entire array. Each applicable probe is selectively "unmasked" prior to bathing the array in a solution of a single nucleotide, then a masking reaction takes place and the next set of probes are unmasked in preparation for a different nucleotide exposure. After many repetitions, the sequences of every probe become fully constructed. More recently, Maskless Array Synthesis from NimbleGen Systems has combined flexibility with large numbers of probes. | 1 | Applied and Interdisciplinary Chemistry |
In 2015, Viel started to teach an online course MCB63X - Principles of Biochemistry with Rachelle Gaudet on edX. | 1 | Applied and Interdisciplinary Chemistry |
Lysergic acid is a chiral compound with two stereocenters. The isomer with inverted configuration at carbon atom 8 close to the carboxyl group is called isolysergic acid. Inversion at carbon 5 close to the nitrogen atom leads to -lysergic acid and -isolysergic acid, respectively. | 0 | Theoretical and Fundamental Chemistry |
In 2011, the Magnetic Space Groups data compiled from H.T. Stokes & B.J. Campbells and D. Litvins's works general positions/symmetry operations and Wyckoff positions for different settings, along with systematic absence rules have also been incorporated into the server and a new shell has been dedicated to the related tools ([http://www.cryst.ehu.es/cgi-bin/cryst/programs/magget_gen.pl MGENPOS], [http://www.cryst.ehu.es/cgi-bin/cryst/programs/magget_wp.pl MWYCKPOS], [http://www.cryst.ehu.es/cryst/magnext.html MAGNEXT]). | 0 | Theoretical and Fundamental Chemistry |
The per base accuracy achieved in house by Ion Torrent on the [http://www.lifetechnologies.com/iontorrent Ion Torrent] Ion semiconductor sequencer as of February 2011 was 99.6% based on 50 base reads, with 100 Mb per run. The read-length as of February 2011 was 100 base pairs. The accuracy for homopolymer repeats of 5 repeats in length was 98%. Later releases show a read length of 400 base pairs These figures have not yet been independently verified outside of the company. | 1 | Applied and Interdisciplinary 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 | Theoretical and Fundamental Chemistry |
Despite the different stoichiometry in these mixtures which varies the concentration of the reagent, they all follow the same idea of adding HgO to distilled water and concentrated sulfuric acid. The Denigés' reagent is ultimately mercury(II) sulfate in an aqueous solution.
*5 grams of mercury(II) oxide (HgO) is dissolved in 40 mL of distilled water. The mixture is slowly stirred, while 20 mL of concentrated sulfuric acid is added. After adding another 40 mL of distilled water, the solution is stirred until the HgO is completely dissolved.
* The Denigés' reagent can also be prepared by dissolving 5 grams of HgO in 20 mL of concentrated sulfuric acid and 100 mL of distilled water.
*The Denigés' reagent can be modified by using nitric acid in place of sulfuric acid | 0 | Theoretical and Fundamental Chemistry |
Culcheth Laboratories was a British metallurgical and nuclear research institute that researched the structural design of nuclear reactors and reactor pressure vessels in Culcheth, Cheshire, then in south Lancashire and now in the borough of Warrington. | 1 | Applied and Interdisciplinary Chemistry |
The two particular features of PTMS that have determined its applications so far are 1) spectroscopic mapping may be performed at a spatial resolution well below the diffraction limit of IR radiation, ultimately at a scale of 20-30 nm. In principle, this opens the way to sub-wavelength IR microscopy (see scanning probe microscopy) where the image contrast is to be determined by the thermal response of individual sample regions to particular spectral wavelengths and 2) in general, no special preparation technique is required when solid samples are to be studied. For most standard FTIR methods, this is not the case. | 0 | Theoretical and Fundamental Chemistry |
A nine- or ten-membered ring containing a double bond between two triple bonds is termed the warhead of the enediyne. In this state, the warhead is inactive. Enediynes are triggered into a chemically active state via Bergman or Myers-Saito cyclization. The triggering mechanism can be attributed to an intramolecular nucleophilic attack initiated by one of the variable regions of the molecule. Triggering can also occur via attack by an external nucleophile.
Bergman cyclization restructures the enediyne ring into two smaller rings. One electron from each of the enediyne triple bonds is pushed to the adjacent single bonds, generating two new double bonds. Meanwhile, another pair of electrons (one from each alkyne) is used form a new covalent bond. The resulting formation is a 1,4-benzenoid diradical fused to a ring composed of the leftover atoms from the original enediyne.
Some enediynes have an epoxide group attached to their ring, making Bergman cyclization unfavorable due to steric hindrance. For Bergman cyclization to occur, the epoxide must be removed.
Myers-Saito cyclization is another triggering mechanism by which an enediyne warhead becomes a diradical. This mechanism requires the alkene of the enediyne to be part of a diene with a double bond in a variable group. A nucleophile will attack the double bond in the variable region, causing a chain reaction of electron pushing. Ultimately, one of the triple bonds of the enediyne is converted to a cumulene. The cumulene and the remaining alkyne donate one electron each to form a new covalent bond.
The diradicals generated by Bergman and Myers-Saito cyclization are highly reactive. | 0 | Theoretical and Fundamental Chemistry |
In addition to cooling, passive daytime radiative cooling surfaces can be modified to be self-adaptive for temperature-dependent switching from cooling to heating or, in other words, for full-scale thermal regulation. This can be achieved through switching the thermal emittance of the surface from a high to low value. Applications are limited to testing and commercially available self-switching PDRCs are in research and development. | 0 | Theoretical and Fundamental Chemistry |
Neutron scattering allows scientists to count scattered neutrons, measure their energies and the angles at which they scatter, and map their final positions. This information can reveal the molecular and magnetic structure and behavior of materials, such as high-temperature superconductors, polymers, metals, and biological samples. In addition to studies focused on fundamental physics, neutron scattering research has applications in structural biology and biotechnology, magnetism and superconductivity, chemical and engineering materials, nanotechnology, complex fluids, and others. | 0 | Theoretical and Fundamental Chemistry |
Salts of hexol were first described by Jørgensen, although it was Werner who recognized its structure. The cation is prepared by heating a solution containing the cis-diaquotetramminecobalt(III) cation [Co(NH)(HO)] with a dilute base:
:4 [Co(NH)(HO)] + 2 HO → {[Co(NH)(OH)]Co} + 4 NH + 4 HO | 0 | Theoretical and Fundamental Chemistry |
In chemistry a diagonal relationship is said to exist between certain pairs of diagonally adjacent elements in the second and third periods (first 20 elements) of the periodic table. These pairs (lithium (Li) and magnesium (Mg), beryllium (Be) and aluminium (Al), boron (B) and silicon (Si), etc.) exhibit similar properties; for example, boron and silicon are both semiconductors, forming halides that are hydrolysed in water and have acidic oxides.
The organization of elements on the periodic table into horizontal rows and vertical columns makes certain relationships more apparent (periodic law). Moving rightward and descending the periodic table have opposite effects on atomic radii of isolated atoms. Moving rightward across the period decreases the atomic radii of atoms, while moving down the group will increase the atomic radii.
Similarly, on moving rightward a period, the elements become progressively more covalent, less basic and more electronegative, whereas on moving down a group the elements become more ionic, more basic and less electronegative. Thus, on both descending a period and crossing a group by one element, the changes "cancel" each other out, and elements with similar properties which have similar chemistry are often found – the atomic radius, electronegativity, properties of compounds (and so forth) of the diagonal members are similar.
It is found that the chemistry of a period 2 element often has similarities to the chemistry of the period 3 element one column to the right of it in the periodic table. Thus, the chemistry of Li has similarities to that of Mg, the chemistry of Be has similarities to that of Al, and the chemistry of B has similarities to that of Si. These are called diagonal relationships. (They are not as noticeable after B and Si.)
The reasons for the existence of diagonal relationships are not fully understood, but charge density is a factor. For example, Li is a small cation with a +1 charge and Mg is somewhat larger with a +2 charge, so the ionic potential of each of the two ions is roughly the same. It was revealed by an examination that the charge density of lithium is much closer to that of magnesium than to those of the other alkali metals.
Using the Li–Mg pair (under room temperature and pressure):
# When combined with oxygen under standard conditions, Li and Mg form only normal oxides whereas Na forms peroxide and metals below Na, in addition, form superoxides.
# Li is the only group 1 element which forms a stable nitride, LiN. Mg, as well as other group 2 elements, also form nitrides.
# Lithium carbonate, phosphate and fluoride are sparingly soluble in water. The corresponding group 2 salts are insoluble. (Think lattice and solvation energies).
# Both Li and Mg form covalent organometallic compounds. LiMe and MgMe (cf. Grignard reagents) are both valuable synthetic reagents. The other group 1 and group 2 analogues are ionic and extremely reactive (and hence difficult to manipulate).
# Chlorides of both Li and Mg are deliquescent (absorb moisture from surroundings) and soluble in alcohol and pyridine. Lithium chloride, like magnesium chloride (MgCl·6HO) separates out from hydrated crystal LiCl·2HO.
#Lithium carbonate and magnesium carbonate are both unstable and can produce corresponding oxides and carbon dioxide when they are heated.
Further diagonal similarities have also been suggested for carbon-phosphorus and nitrogen-sulfur, along with extending the Li-Mg and Be-Al relationships down into the transition elements (such as scandium). | 0 | Theoretical and Fundamental Chemistry |
The stereochemistry involved in the reactions of five-membered rings can be predicted by an envelope transition state model. Nucleophiles favor addition from the "inside" of the envelope, or from the top of the figure on the right. The "inside" addition produces a results in a staggered conformation, rather than the eclipsed conformation that results from the "outside" addition. | 0 | Theoretical and Fundamental Chemistry |
Pincer complexes have been shown to catalyse Suzuki-Miyaura coupling reactions, a versatile carbon-carbon bond forming reaction.
Typical Suzuki coupling employ Pd(0) catalysts with monodentate tertiary phosphine ligands (e.g. Pd(PPh)). It is a very selective method to couple aryl substituents together, but requires elevated temperatures.
Using PCP pincer-palladium catalysts, aryl-aryl couplings can be achieved with turnover numbers (TONs) upwards of 900,000 and high yields. Additionally, other groups have found that very low catalyst loadings can be achieved with asymmetric palladium pincer complexes. Catalyst loadings of 0.0001 mol % have been found to have TONs upwards of 190,000 and upper limit TONs can reach 1,100,000. | 0 | Theoretical and Fundamental Chemistry |
The Anti-apoptotic Ras signaling cascade is an intracellular signal transduction cascade
that involves the Ras protein and inhibits apoptosis. It is the target of the cancer drug gefitinib.
It may refer to the PI3K/AKT pathway.
It may refer to the MAPK/ERK pathway which involves ras and can affect apoptosis.
The anti-apoptotic STAT pathway does not involve Ras. | 1 | Applied and Interdisciplinary Chemistry |
Aquasomes are self-assembling nanoparticle drug carrier systems composed of three layers: a ceramic core, an oligomer coat, and a biochemically active molecule. Aquasomes are utilized for targeted drug delivery to achieve specific therapeutic effects, and are biocompatible, biodegradable, and stable. Due to their structure, aquasomes are capable of delivering several types of substrates, and can be used for applications such as delivery of antigen, insulin, and hemoglobin.
Aquasomes were first explored by Kossovsky et al. in 1996 in experiments proposing their use in antigen delivery, drug delivery, and hemoglobin delivery in vitro and in animal models. The aim of creating these aquasomes was to address the molecular denaturation of polypeptide pharmaceuticals by forming a molecular carrier using the novel surface modification process. Kossovsky et al. suggested that this system would be able to combat physical and chemical degradative agents affecting bioactive molecules while preserving the molecular structure of the drug.
Since this initial exploration, the researched applications of aquasomes and the scientific knowledge of their composition have increased. Upon synthesis of each layer of the aquasome, aquasomes self-assemble into triple-layered particles. The tri-layer structure enables aquasomes to deliver and release poorly soluble drugs in a controlled manner. Delivery of these poorly soluble drugs within aquasomes increases their solubility, bioavailability, and stability. These drugs are adsorbed on the surface of the aquasome, forming its third layer, which confers bioactive properties to the aquasome. | 0 | Theoretical and Fundamental Chemistry |
DESI mass spectrometry is an ambient ionization technique developed by Professor Zoltan Takáts, et al., in Professor Graham Cooks' group from Purdue University. It combines the ESI and desorption ionization techniques, by directing an electrically charged mist to the sample surface that is a few millimeters away. The technique has been successfully applied to lipidomics as imaging tool to map the lipid distributions within tissue specimens. One of the advantages of DESI MS is that no matrix is required for tissue preparation, allowing multiple consecutive measurements on the same tissue specimen. DESI MS can also be used for imaging of lipids from tissue sections. | 1 | Applied and Interdisciplinary Chemistry |
Water has as much propensity to form hydrogen bonds as any group in a polypeptide. During a folding and association process, peptide and amino acid groups exchange hydrogen bonds with water. Thus, hydrogen bonding does not have a strong stabilizing effect on protein adsorption in an aqueous medium. | 1 | Applied and Interdisciplinary Chemistry |
An optical spectrum analyzer uses reflective or refractive techniques to separate out the wavelengths of light. An electro-optical detector is used to measure the intensity of the light, which is then normally displayed on a screen in a similar manner to a radio- or audio-frequency spectrum analyzer.
The input to an optical spectrum analyzer may be simply via an aperture in the instrument's case, an optical fiber or an optical connector to which a fiber-optic cable can be attached.
Different techniques exist for separating out the wavelengths. One method is to use a monochromator, for example a Czerny–Turner design, with an optical detector placed at the output slit. As the grating in the monochromator moves, bands of different frequencies (colors) are seen by the detector, and the resulting signal can then be plotted on a display. More precise measurements (down to MHz in the optical spectrum) can be made with a scanning Fabry–Pérot interferometer along with analog or digital control electronics, which sweep the resonant frequency of an optically resonant cavity using a voltage ramp to piezoelectric motor that varies the distance between two highly reflective mirrors. A sensitive photodiode embedded in the cavity provides an intensity signal, which is plotted against the ramp voltage to produce a visual representation of the optical power spectrum.
The frequency response of optical spectrum analyzers tends to be relatively limited, e.g. (near-infrared), depending on the intended purpose, although (somewhat) wider-bandwidth general purpose instruments are available. | 0 | Theoretical and Fundamental Chemistry |
Brownian motors are nanoscale or molecular machines that use chemical reactions to generate directed motion in space. The theory behind Brownian motors relies on the phenomenon of Brownian motion, random motion of particles suspended in a fluid (a liquid or a gas) resulting from their collision with the fast-moving molecules in the fluid.
On the nanoscale (1-100 nm), viscosity dominates inertia, and the extremely high degree of thermal noise in the environment makes conventional directed motion all but impossible, because the forces impelling these motors in the desired direction are minuscule when compared to the random forces exerted by the environment. Brownian motors operate specifically to utilise this high level of random noise to achieve directed motion, and as such are only viable on the nanoscale.
The concept of Brownian motors is a recent one, having only been coined in 1995 by Peter Hänggi, but the existence of such motors in nature may have existed for a very long time and help to explain crucial cellular processes that require movement at the nanoscale, such as protein synthesis and muscular contraction. If this is the case, Brownian motors may have implications for the foundations of life itself.
In more recent times, humans have attempted to apply this knowledge of natural Brownian motors to solve human problems. The applications of Brownian motors are most obvious in nanorobotics due to its inherent reliance on directed motion. | 0 | Theoretical and Fundamental Chemistry |
The spectral intensity of a blackbody, was first determined by Max Planck. It is given by Plancks law per unit wavelength as:This formula mathematically follows from calculation of spectral distribution of energy in quantized electromagnetic field which is in complete thermal equilibrium with the radiating object. Plancks law shows that radiative energy increases with temperature, and explains why the peak of an emission spectrum shifts to shorter wavelengths at higher temperatures. It can also be found that energy emitted at shorter wavelengths increases more rapidly with temperature relative to longer wavelengths.
The equation is derived as an infinite sum over all possible frequencies in a semi-sphere region. The energy, , of each photon is multiplied by the number of states available at that frequency, and the probability that each of those states will be occupied. | 0 | Theoretical and Fundamental Chemistry |
To name conformations of pyranose, first the conformer is determined. The common conformers are similar to those found in cyclohexane, and these form the basis of the name. Common conformations are chair (C), boat (B), skew (S), half-chair (H) or envelope (E). The ring atoms are then numbered; the anomeric, or hemiacetal, carbon is always 1. Oxygen atoms in the structure are, in general, referred to by the carbon atom they are attached to in the acyclic form, and designated O. Then:
*Position the ring so that, if looking at the top face, the atoms are numbered clockwise.
*In the chair and skew conformations, the reference plane should be selected. In the chair conformation, the reference plane is chosen such that the lowest-numbered atom (usually C-1) is exoplanar. In the skew conformation, the plane contains three adjacent atoms and one other with the atom with the lowest possible number exoplanar.
*Atoms above the plane are written before the conformer label, as a superscript
*Atoms below the plane are written following the conformer label, as a subscript | 0 | Theoretical and Fundamental Chemistry |
On Friday, April 5 an emergency regime was introduced in the Russian city of Khabarovsk after a local resident accidentally discovered that radiation levels had jumped sharply in one of the industrial areas of the city. According to volunteers of the dosimetric control group, the dosimeter at the NP site showed up to 800 microsieverts, which is 1600 times the safe value.
Employees of the Ministry of Emergency Situations fenced of the area of 30 by 30 meters, where they found a capsule with cesium from a defectoscope. The find was placed in a protective container and taken away for disposal. This was first reported by the Novaya Gazeta. [https://tsn.ua/svit/nadzvichayna-situaciya-u-habarovsku-radiaciyniy-fon-u-1600-raziv-perevischiv-normu-2551414.html Source] | 0 | Theoretical and Fundamental Chemistry |
Cavitation has been applied to egg pasteurization. A hole-filled rotor produces cavitation bubbles, heating the liquid from within. Equipment surfaces stay cooler than the passing liquid, so eggs do not harden as they did on the hot surfaces of older equipment. The intensity of cavitation can be adjusted, making it possible to tune the process for minimum protein damage. | 1 | Applied and Interdisciplinary Chemistry |
In some cases, an achiral Lewis acid may provide good stereoselectivity. Kimura et al. demonstrated the regio- and diastereoselective coupling of 1,3-dienes with aldehydes using a nickel catalyst. | 0 | Theoretical and Fundamental Chemistry |
The Euler pump and turbine equations are the most fundamental equations in the field of turbomachinery. These equations govern the power, efficiencies and other factors that contribute to the design of turbomachines. With the help of these equations the head developed by a pump and the head utilised by a turbine can be easily determined. As the name suggests these equations were formulated by Leonhard Euler in the eighteenth century. These equations can be derived from the moment of momentum equation when applied for a pump or a turbine. | 1 | Applied and Interdisciplinary Chemistry |
In astrophysics, Zeeman–Doppler imaging is a tomographic technique dedicated to the cartography of stellar magnetic fields, as well as surface brightness and temperature distributions.
This method makes use of the ability of magnetic fields to polarize the light emitted (or absorbed) in spectral lines formed in the stellar atmosphere (the Zeeman effect). The periodic modulation of Zeeman signatures during the stellar rotation is employed to make an iterative reconstruction of the vectorial magnetic field at stellar surface.
The method was first proposed by Marsh and Horne in 1988, as a way to interpret the emission line variations of cataclysmic variable stars. This techniques is based on the principle of maximum entropy image reconstruction; it yields the simplest magnetic field geometry (as a spherical harmonics expansion) among the various solutions compatible with the data.
This technique is the first to enable the reconstruction of the vectorial magnetic geometry of stars similar to the Sun. It is now offering the opportunity to undertake systematic studies of stellar magnetism and is also yielding information on the geometry of large arches that magnetic fields are able to develop above stellar surfaces. To collect the observations related to Zeeman-Doppler Imaging, astronomers use stellar spectropolarimeters like ESPaDOnS at CFHT on Mauna Kea (Hawaii), HARPSpol at the ESO's 3.6m telescope (La Silla Observatory, Chile), as well as NARVAL at Bernard Lyot Telescope (Pic du Midi de Bigorre, France).
The technique is very reliable, as the reconstruction of the magnetic field maps with different algorithms yield almost identical results, even with poorly sampled data sets. It has however been shown, from both numerical simulations and observations, that the magnetic field strength and complexity is underestimated if no linear polarization spectra is available from observations. Since linear polarization signatures are weaker compared circular polarization their detections are not as reliable, particularly for cool stars. With more modern spectropolarimeters such as the recently installed SPIRou at CFHT and CRIRES+, currently in the process of installation, at the Very Large Telescope (Chile) the sensitivity to linear polarization will increase, allowing for more detailed studies of cool stars in the future. | 0 | Theoretical and Fundamental Chemistry |
Source: [http://www.divbiolchem.org/awards/recipients/ ACS - Division of Biological Chemistry]
*1986 – Gregorio Weber
*1987 – Thomas C. Bruice
*1988 – Robert H. Abeles
*1989 – Stephen J. Benkovic
*1990 – Harold A. Scheraga
*1991 – William W. Parson
*1992 – Frank H. Westheimer
*1993 – Jeremy R. Knowles
*1994 – Judith P. Klinman
*1995 – W. Wallace Cleland
*1996 – William P. Jencks
*1997 – James A. Spudich
*1998 – David S. Eisenberg
*1999 – Christopher T. Walsh
*2000 – Perry A. Frey
*2001 – Rowena G. Matthews
*2002 – C. Dale Poulter
*2003 – John A. Gerlt
*2004 – JoAnne Stubbe
*2005 – David E. Cane
*2006 – Vern L. Schramm
*2007 – Michael Marletta
*2008 – Hung-Wen (Ben) Liu
*2009 – Frank Raushel
*2010 – Ronald T. Raines
*2011 – Richard Armstrong
*2012 – Carol Fierke
*2013 – David W. Christianson
*2014 – John Lipscomb
*2015 – John S. Blanchard
*2016 – Tadhg Begley
*2017 – Wilfred A. van der Donk
*2018 – Michael H. Gelb
* award suspended - 2018 | 1 | Applied and Interdisciplinary Chemistry |
Pseudoproteases are catalytically-deficient pseudoenzyme variants of proteases that are represented across the kingdoms of life. | 1 | Applied and Interdisciplinary Chemistry |
As the name suggests, eslicarbazepine acetate is the acetate ester prodrug of eslicarbazepine. Eslicarbazepine itself is the pharmacologically more active of the two stereoisomers of licarbazepine. More specifically, it is (S)-(+)-licarbazepine.
;Related drugs and active metabolites for comparison: | 0 | Theoretical and Fundamental Chemistry |
There are five main types of experimental data that are used for the determination of solution equilibrium constants. Potentiometric data obtained with a glass electrode are the most widely used with aqueous solutions. The others are Spectrophotometric, Fluorescence (luminescence) measurements and NMR chemical shift measurements; simultaneous measurement of K and ΔH for 1:1 adducts in biological systems is routinely carried out using Isothermal Titration Calorimetry.
The experimental data will comprise a set of data points. At the ith data point, the analytical concentrations of the reactants, T, T etc. will be experimentally known quantities and there will be one or more measured quantities, y', that depend in some way on the analytical concentrations and equilibrium constants. A general computational procedure has three main components.
# Definition of a chemical model of the equilibria. The model consists of a list of reagents, A, B, etc. and the complexes formed from them, with stoichiometries AB... Known or estimated values of the equilibrium constants for the formation of all complexes must be supplied.
# Calculation of the concentrations of all the chemical species in each solution. The free concentrations are calculated by solving the equations of mass-balance, and the concentrations of the complexes are calculated using the equilibrium constant definitions. A quantity corresponding to the observed quantity can then be calculated using physical principles such as the Nernst potential or Beer-Lambert law which relate the calculated quantity to the concentrations of the species.
# Refinement of the equilibrium constants. Usually a Non-linear least squares procedure is used. A weighted sum of squares, U, is minimized. The weights, w and quantities y may be vectors. Values of the equilibrium constants are refined in an iterative procedure. | 0 | Theoretical and Fundamental Chemistry |
2,2,6,6-Tetramethylpiperidine, abbreviated TMP, HTMP, or TMPH, is an organic compound of the amine class. In appearance, it is a colorless liquid and has a "fishy", amine-like odor. This amine is used in chemistry as a hindered base (hindered amine). Although TMP finds limited use per se, its derivatives are a mainstay of hindered amine light stabilizers.
TMP is the starting material for an even stronger base, lithium tetramethylpiperidide and the radical species TEMPO. Another non-nucleophilic base is N,N-diisopropylethylamine. Its aqueous pK (conjugate acid dissociation constant, a measure of basicity) is 11.07 at 25 °C, while its pK (acid dissociation constant, a measure of acidity) is approximately 37. | 0 | Theoretical and Fundamental Chemistry |
Davy threw himself energetically into the work of the laboratory and formed a long romantic friendship with Mrs Anna Beddoes, the novelist Maria Edgeworth's sister, who acted as his guide on walks and other fine sights of the locality. The critic Maurice Hindle was the first to reveal that Davy and Anna had written poems for each other. Wahida Amin has transcribed and discussed a number of poems written between 1803 and 1808 to "Anna" and one to her infant child. | 1 | Applied and Interdisciplinary Chemistry |
It is manufactured by the reaction of methane and sulfuryl chloride in a radical reaction:
Another method of manufacture entails chlorination of methanesulfonic acid with thionyl chloride or phosgene: | 0 | Theoretical and Fundamental Chemistry |
mTECs are not only capable to present TRAs as efficient APCs. They are also potent in production of these TRAs via unique process called promiscuous gene expression (PGE) and might serve as their reservoir. | 1 | Applied and Interdisciplinary Chemistry |
Following the discovery of induced fission by Otto Hahn and Fritz Strassmann in 1938, Soviet physicists Georgy Flyorov and Konstantin Petrzhak began conducting experiments to explore the effects of incident neutron energy on uranium nuclei. Their equipment recorded fission fragments even when no neutrons were present to induce the decay, and the effect persisted even after the equipment was moved 60 meters underground into the tunnels of the Moscow Metro's Dinamo station in an effort to insulate it from the effects of cosmic rays. The discovery of induced fission itself had come as a surprise, and no other mechanism was known that could account for the observed decays. Such an effect could only be explained by spontaneous fission of the uranium nuclei without external influence. | 0 | Theoretical and Fundamental Chemistry |
During 1799, Beddoes and Davy published Contributions to physical and medical knowledge, principally from the west of England and Essays on heat, light, and the combinations of light, with a new theory of respiration. On the generation of oxygen gas, and the causes of the colors of organic beings. Their experimental work was poor, and the publications were harshly criticised. In after years Davy regretted he had ever published these immature hypotheses, which he subsequently designated "the dreams of misemployed genius which the light of experiment and observation has never conducted to truth." These criticisms, however, led Davy to refine and improve his experimental techniques, spending his later time at the institution increasingly in experimentation.
In December 1799 Davy visited London for the first time and extended his circle of friends. Davy features in the diary of William Godwin, with their first meeting recorded for 4 December 1799.
In 1800, Davy informed Giddy that he had been "repeating the galvanic experiments with success" in the intervals of the experiments on the gases, which "almost incessantly occupied him from January to April." In 1800, Davy published his Researches, Chemical and Philosophical, chiefly concerning Nitrous Oxide and its Respiration, and received a more positive response. | 1 | Applied and Interdisciplinary Chemistry |
In 1990, he was elected Corresponding Member of the Soviet Academy of Sciences and in 2003 a Full Member (Academician) of the Russian Academy of Sciences.
Oganessian has honorary degrees from Goethe University Frankfurt (2002), University of Messina (2009), and Yerevan State University (2022). In 2019, he was elected as an Honorary Fellow of St Catharine's College, Cambridge. | 1 | Applied and Interdisciplinary Chemistry |
The above equation is the one that is used in most applications. However, a full treatment must include the effects of Thomas precession, yielding the equation (in CGS units) (The CGS units are used so that E has the same units as B):
where is the relativistic Lorentz factor (not to be confused with the gyromagnetic ratio above). Notably, for the electron g is very close to 2 (2.002...), so if one sets g = 2, one arrives at | 0 | Theoretical and Fundamental Chemistry |
Mass spectrometry is a way to quantify RNA modifications. More often than not, modifications cause an increase in mass for a given nucleoside. This gives a characteristic readout for the nucleoside and the modified counterpart. Moreover, mass spectrometry allows the investigation of modification dynamics by labelling RNA molecules with stable (non-radioactive) heavy isotopes in vivo. Due to the defined mass increase of heavy isotope labeled nucleosides they can be distinguished from their respective unlabelled isotopomeres by mass spectrometry. This method, called NAIL-MS (nucleic acid isotope labelling coupled mass spectrometry), enables a variety of approaches to investigate RNA modification dynamics. | 1 | Applied and Interdisciplinary Chemistry |
Mitogen-activated protein kinase (MAPK) networks can be found in eukaryotic cells. MAPK pathways in plants are known to regulate cell growth, cell development, cell death, and cell responses to environmental stimuli. Only a few of the MAPK mechanism components are known and have been studied. The components such as Arabidopsis MAPKKKs YODA, ANP2/ANP3, and MP3K6/MP3K7 functions in the development of the cell. MEKK1 and ANP1 function in the response to environmental stress. Unfortunately, only eight out of the twenty mitogen-activated protein kinases have been studied. The most commonly studied MAPKs are MPK3, MPK4, and MPK6, which are activated by a diversity of stimuli including abiotic stresses, pathogens, and oxidative stressors. MPK4 negatively regulates biotic stress signaling, while MPK3 and MPK6 function as positive mediators of defense responses. The plant has these positive and negative mediators allowing for normal plant growth and development, which has been proven true by the severely dwarfed phenotype of mpk4 and the embryo lethal phenotype of mpk3 and mpk6 mutants. | 1 | Applied and Interdisciplinary Chemistry |
Orange carotenoid protein (OCP) is a water-soluble protein which plays a role in photoprotection in diverse cyanobacteria. It is the only photoactive protein known to use a carotenoid as the photoresponsive chromophore. The protein consists of two domains, with a single keto-carotenoid molecule non-covalently bound between the two domains. It is a very efficient quencher of excitation energy absorbed by the primary light-harvesting antenna complexes of cyanobacteria, the phycobilisomes. The quenching is induced by blue-green light. It is also capable of preventing oxidative damage by directly scavenging singlet oxygen (O). | 0 | Theoretical and Fundamental Chemistry |
Black oxide or blackening is a conversion coating for ferrous materials, stainless steel, copper and copper based alloys, zinc, powdered metals, and silver solder. It is used to add mild corrosion resistance, for appearance, and to minimize light reflection. To achieve maximal corrosion resistance the black oxide must be impregnated with oil or wax. One of its advantages over other coatings is its minimal buildup. | 0 | Theoretical and Fundamental Chemistry |
Dissolved and particulate material in water can cause it to be appear more green, tan, brown, or red. For instance, dissolved organic compounds called tannins can result in dark brown colors, or algae floating in the water (particles) can impart a green color. Color variations can be measured with reference to a standard color scale. Two examples of standard color scales for natural water bodies are the Forel-Ule scale and the Platinum-Cobalt scale. For example, slight discoloration is measured against the Platinum-Cobalt scale in Hazen units (HU).
The color of a water sample can be reported as:
* Apparent color is the color of a body of water being reflected from the surface of the water, and consists of color from both dissolved and suspended components. Apparent color may also be changed by variations in sky color or the reflection of nearby vegetation.
* True color is measured after a sample of water has been collected and purified (either by centrifuging or filtration). Pure water tends to look cyan in color and a sample can be compared to pure water with a predetermined color standard or comparing the results of a spectrophotometer.
Testing for color can be a quick and easy test which often reflects the amount of organic material in the water, although certain inorganic components like iron or manganese can also impart color.
Water color can reveal physical, chemical and bacteriological conditions. In drinking water, green can indicate copper leaching from copper plumbing and can also represent algae growth. Blue can also indicate copper, or might be caused by syphoning of industrial cleaners in the tank of commodes, commonly known as backflowing. Reds can be signs of rust from iron pipes or airborne bacteria from lakes, etc. Black water can indicate growth of sulfur-reducing bacteria inside a hot water tank set to too low a temperature. This usually has a strong sulfur or rotten egg (HS) odor and is easily corrected by draining the water heater and increasing the temperature to or higher. The odor will always be in the hot water pipes if sulfate reducing bacteria are the cause and never in the cold water plumbing. Learning the water impurity indication color spectrum can make identifying and solving cosmetic, bacteriological and chemical problems easier. | 0 | Theoretical and Fundamental Chemistry |
For a receptor with n binding sites that independently bind to the ligand, each binding site will have an average occupancy of [L]/(K + [L]). Hence, by considering all n binding sites, there will
ligands bound to each receptor on average, from which the Scatchard equation follows. | 1 | Applied and Interdisciplinary Chemistry |
The preferred method to remove all cellular components from a heart is perfusion decellularization. This technique involves perfusing the heart with detergents such as SDS and Triton X-100 dissolved in distilled water.
The remaining ECM is composed of structural elements such as collagen, laminin, elastin and fibronectin. The ECM scaffold promotes proper cellular proliferation and differentiation, vascular development, as well as providing mechanical support for cellular growth. Because minimal DNA material remains after the decellularization process, the engineered organ is biocompatible with the transplant recipient, regardless of species. Unlike traditional transplant options, recellularized hearts are less immunogenic and have a decreased risk of rejection.
Once the decellularized heart has been sterilized to remove any pathogens, the recellularization process can occur. Multipotent cardiovascular progenitors are then added to the decellularized heart and with additional exogenous growth factors, are stimulated to differentiate into cardiomyocytes, smooth muscle cells and endothelial cells. | 1 | Applied and Interdisciplinary Chemistry |
In elemental analysis by ICP-MS, ICP-AES, GFAA, and Flame AA, dilute nitric acid (0.5–5.0%) is used as a matrix compound for determining metal traces in solutions. Ultrapure trace metal grade acid is required for such determination, because small amounts of metal ions could affect the result of the analysis.
It is also typically used in the digestion process of turbid water samples, sludge samples, solid samples as well as other types of unique samples which require elemental analysis via ICP-MS, ICP-OES, ICP-AES, GFAA and flame atomic absorption spectroscopy. Typically these digestions use a 50% solution of the purchased mixed with Type 1 DI Water.
In electrochemistry, nitric acid is used as a chemical doping agent for organic semiconductors, and in purification processes for raw carbon nanotubes. | 0 | Theoretical and Fundamental Chemistry |
In magnetic resonance imaging or NMR of macromolecular samples, such as protein solutions, at least two types of water molecules, free (bulk) and bound (hydration), are present. Bulk water molecules have many mechanical degrees of freedom, and motion of such molecules thus exhibits statistically averaged behavior. Because of this uniformity, most free water protons have resonance frequencies very near the average Larmor frequency of all such protons. On a properly acquired NMR spectrum this is seen as a narrow Lorentzian line (at 4.8 ppm, 20 C). Bulk water molecules are also relatively far from magnetic field perturbing macromolecules, such that free water protons experience a more homogeneous magnetic field, which results in slower transverse magnetization dephasing and a longer T. Conversely, hydration water molecules are mechanically constrained by extensive interactions with the local macromolecules and hence magnetic field inhomogeneities are not averaged out, which leads to broader resonance lines. This results in faster dephasing of the magnetization that produces the NMR signal and much shorter T values ( values are so short, the NMR signal from the protons of bound water is not typically observed in MRI.
However, using an off-resonance saturation pulse to irradiate protons in the bound (hydration) population can have a detectable effect on the NMR signal of the mobile (free) proton pool. When a population of spins is saturated, such that the magnitude of the macroscopic magnetization vector approaches zero, there is no remaining spin polarization with which to produce an NMR signal. Longitudinal relaxation refers to the return of longitudinal spin polarization, which occurs at a rate described by T1. While the number of hydration water molecules may be insufficient to produce an observable signal, exchange of water molecules between the hydration and bulk population allows characterization of the hydration population, and measurement of the rate at which molecules are exchanging between bulk and bound sites. Such experiments are often termed saturation transfer or chemical exchange saturation transfer (CEST), because the signal of the bulk water is observed to decrease when the hydration population is saturated. Considering these techniques from the opposite perspective, that magnetization (i.e. spin polarization) is being transferred from the bulk water to the spin-saturated hydration population, allows one to conceptually unify chemical exchange methods with other techniques that transfer magnetization between nuclei populations. Since the extent of signal decay depends on the exchange rate between free and hydration water, MT can be used to provide an alternative contrast method in addition to T,T, and proton density differences.
MT is believed to be a nonspecific indicator of the structural integrity of the tissue being imaged.
An extension of MT, the magnetization transfer ratio (MTR) has been used in neuroradiology to highlight abnormalities in brain structures. (The MTR is (M-M)/M.)
A systematic modulation of the precise frequency offset for the saturation pulse can be plotted against the free-water signal to form a "Z-spectrum". This technique is often referred to as "Z-spectroscopy". | 0 | Theoretical and Fundamental Chemistry |
In classical Lewis structures, molecular oxygen, O, is depicted as having a double bond between the two oxygen atoms. However, the molecular orbitals of O are actually more complex than Lewis structures seem to suggest. The highest occupied molecular orbital (HOMO) of O is a pair of degenerate antibonding π orbitals, π* and π*, which are both singly occupied by spin unpaired electrons. These electrons are the cause of O being a triplet diradical in the ground state (indicated as O).
While many stable molecules’ HOMOs consist of bonding molecular orbitals and therefore require a moderate energy jump from bonding to antibonding to reach their first excited state, the antibonding nature of molecular oxygen’s HOMO allows for a lower energy gap between its ground state and first excited state. This makes excitation of O a less energetically restrictive process. In the first excited state of O, a 22 kcal/mol energy increase from the ground state, both electrons in the antibonding orbitals occupy a degenerate π* orbital, and oxygen is now in a singlet state (indicated as O). O is very reactive with a lifetime between 10-100µs. | 0 | Theoretical and Fundamental Chemistry |
Hordein is a prolamin glycoprotein, present in barley and some other cereals, together with gliadin and other glycoproteins (such as glutelins) coming under the general name of gluten. Hordeins are found in the endosperm where one of their functions is to act as a storage unit.
In comparison to other proteins, hordeins are less soluble when compared to proteins such as albumin and globulins.
In relation to amino acids, hordeins have a substantial amount of proline and glutamine but lack charged amino acids such as lysine.
Some people are sensitive to hordein due to disorders such as celiac disease or gluten intolerance.
Along with gliadin (the prolamin gluten found in wheat), hordein is present in many foods and also may be found in beer. Hordein is usually the main problem for coeliacs wishing to drink beer.
Coeliacs are able to find specialist breads that are low in hordein, gliadin and other problematic glycoproteins, just as they can find gluten free beer which either uses ingredients that do not contain gluten, or otherwise has the amounts of gliadin or hordein present controlled to stated limits. | 1 | Applied and Interdisciplinary Chemistry |
A solar cell or photovoltaic cell (PV cell) is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect. It is a form of photoelectric cell, a device whose electrical characteristics (such as current, voltage, or resistance) vary when it is exposed to light. Individual solar cell devices are often the electrical building blocks of photovoltaic modules, known colloquially as "solar panels". The common single-junction silicon solar cell can produce a maximum open-circuit voltage of approximately 0.5 to 0.6 volts.
Photovoltaic cells may operate under sunlight or artificial light. In addition to producing energy, they can be used as a photodetector (for example infrared detectors), detecting light or other electromagnetic radiation near the visible range, or measuring light intensity.
The operation of a PV cell requires three basic attributes:
* The absorption of light, generating excitons (bound electron-hole pairs), unbound electron-hole pairs (via excitons), or plasmons.
* The separation of charge carriers of opposite types.
* The separate extraction of those carriers to an external circuit.
In contrast, a solar thermal collector supplies heat by absorbing sunlight, for the purpose of either direct heating or indirect electrical power generation from heat. A "photoelectrolytic cell" (photoelectrochemical cell), on the other hand, refers either to a type of photovoltaic cell (like that developed by Edmond Becquerel and modern dye-sensitized solar cells), or to a device that splits water directly into hydrogen and oxygen using only solar illumination.
Photovoltaic cells and solar collectors are the two means of producing solar power. | 0 | Theoretical and Fundamental Chemistry |
The optical activity (absorption and scattering of light) and hydrodynamic properties (translational diffusion, sedimentation coefficients, and rotational correlation times) of formamide denatured nucleic acids are similar to those of heat-denatured nucleic acids. Therefore, depending on the desired effect, chemically denaturing DNA can provide a gentler procedure for denaturing nucleic acids than denaturation induced by heat. Studies comparing different denaturation methods such as heating, beads mill of different bead sizes, probe sonication, and chemical denaturation show that chemical denaturation can provide quicker denaturation compared to the other physical denaturation methods described. Particularly in cases where rapid renaturation is desired, chemical denaturation agents can provide an ideal alternative to heating. For example, DNA strands denatured with alkaline agents such as NaOH renature as soon as phosphate buffer is added. | 1 | Applied and Interdisciplinary Chemistry |
Opioid food peptides include:
* Casomorphin (from milk)
* Gluten exorphin (from gluten)
* Gliadorphin/gluteomorphin (from gluten)
* Rubiscolin (from spinach)
* Soymorphin-5 (from soy)
* Oryzatensin (from rice) | 1 | Applied and Interdisciplinary Chemistry |
Source:
* 2024: Kelly Nguyen
* 2023: Stephen Wallace
* 2022: Tanmay A. M. Bharat
* 2021: Giulia Zanetti
* 2020: Stephan Uphoff
* 2019: Melina Schuh
* 2018: Matthew Johnson
* 2017: Markus Ralser
* 2016: David Grainger
* 2015: Helen Walden
* 2014: M. Madan Babu
* 2012: Akhilesh Reddy
* 2011: Sarah Teichmann
* 2007: Frank Sargent
* 2006: Simon J. Boulton
* 2004: James H. Naismith
* 2000: Dario Alessi
* 1999: Nigel Scrutton
* 1998: David Barford
* 1997: Stephen P. Jackson
* 1996: Sheena Radford
* 1995: Jonathon Pines
* 1993: Nicholas Tonks
* 1991: Michael A. J. Ferguson
* 1988: Hugh Pelham
* 1987: C. Peter Downes
* 1986: Greg Winter
* 1985: Alec Jeffreys
* 1981: Terence H. Rabbitts
* 1980: Richard A. Flavell
* 1979: Ronald Laskey
* 1977: Philip Cohen
* 1976: George Brownlee
* 1972: John M. Ashworth
* 1970: Dai Rees
* 1969: George Radda
* 1966: Mark Henry Richmond
* 1964: Jamshed R. Tata
* 1963: Hans Kornberg | 1 | Applied and Interdisciplinary Chemistry |
To deal with decreased ATP production through the electron transport chain, fish must activate anaerobic means of energy production (see anaerobic metabolism) while suppressing metabolic demands. The ability to decrease energy demand by metabolic suppression is essential to ensure hypoxic survival due to the limited efficiency of anaerobic ATP production. | 0 | Theoretical and Fundamental Chemistry |
MLSS is separated from the treated or purified water by settling in a settling tank in the activated sludge process. The excess sludge has to be removed from the system. | 0 | Theoretical and Fundamental Chemistry |
R-22 is often used as an alternative to the highly ozone-depleting CFC-11 and CFC-12, because of its relatively low ozone depletion potential of 0.055, among the lowest for chlorine-containing haloalkanes. However, even this lower ozone depletion potential is no longer considered acceptable.
As an additional environmental concern, R-22 is a powerful greenhouse gas with a GWP equal to 1810 (which indicates 1810 times as powerful as carbon dioxide). Hydrofluorocarbons (HFCs) are often substituted for R-22 because of their lower ozone depletion potential, but these refrigerants often have a higher GWP. R-410A, for example, is often substituted, but has a GWP of 2088. Another substitute is R-404A with a GWP of 3900. Other substitute refrigerants are available with low GWP. Ammonia (R-717), with a GWP of <1, remains a popular substitute on fishing vessels and large industrial applications. Ammonia's toxicity in high concentrations limit its application in small-scale refrigeration applications.
Propane (R-290) is another example, and has a GWP of 3. Propane was the de facto refrigerant in systems smaller than industrial scale before the introduction of CFCs. The reputation of propane refrigerators as a fire hazard kept delivered ice and the ice box the overwhelming consumer choice despite its inconvenience and higher cost until safe CFC systems overcame the negative perceptions of refrigerators. Illegal to use as a refrigerant in the US for decades, propane is now permitted for use in limited mass suitable for small refrigerators. It is not lawful to use in air conditioners or larger refrigerators because of its flammability and potential for explosion. | 1 | Applied and Interdisciplinary Chemistry |
Most amino acids are synthesized from α-ketoacids, and later transaminated from another amino acid, usually glutamate. The enzyme involved in this reaction is an aminotransferase.
: α-ketoacid + glutamate ⇄ amino acid + α-ketoglutarate
Glutamate itself is formed by amination of α-ketoglutarate:
: α-ketoglutarate + ⇄ glutamate
The α-ketoglutarate family of amino acid synthesis (synthesis of glutamate, glutamine, proline and arginine) begins with α-ketoglutarate, an intermediate in the Citric Acid Cycle. The concentration of α-ketoglutarate is dependent on the activity and metabolism within the cell along with the regulation of enzymatic activity. In E. coli citrate synthase, the enzyme involved in the condensation reaction initiating the Citric Acid Cycle is strongly inhibited by α-ketoglutarate feedback inhibition and can be inhibited by DPNH as well high concentrations of ATP. This is one of the initial regulations of the α-ketoglutarate family of amino acid synthesis.
The regulation of the synthesis of glutamate from α-ketoglutarate is subject to regulatory control of the Citric Acid Cycle as well as mass action dependent on the concentrations of reactants involved due to the reversible nature of the transamination and glutamate dehydrogenase reactions.
The conversion of glutamate to glutamine is regulated by glutamine synthetase (GS) and is a key step in nitrogen metabolism. This enzyme is regulated by at least four different mechanisms: 1. Repression and depression due to nitrogen levels; 2. Activation and inactivation due to enzymatic forms (taut and relaxed); 3. Cumulative feedback inhibition through end product metabolites; and 4. Alterations of the enzyme due to adenylation and deadenylation. In rich nitrogenous media or growth conditions containing high quantities of ammonia there is a low level of GS, whereas in limiting quantities of ammonia the specific activity of the enzyme is 20-fold higher. The confirmation of the enzyme plays a role in regulation depending on if GS is in the taut or relaxed form. The taut form of GS is fully active but, the removal of manganese converts the enzyme to the relaxed state. The specific conformational state occurs based on the binding of specific divalent cations and is also related to adenylation. The feedback inhibition of GS is due to a cumulative feedback due to several metabolites including L-tryptophan, L-histidine, AMP, CTP, glucosamine-6-phosphate and carbamyl phosphate, alanine, and glycine. An excess of any one product does not individually inhibit the enzyme but a combination or accumulation of all the end products have a strong inhibitory effect on the synthesis of glutamine. Glutamine synthase activity is also inhibited via adenylation. The adenylation activity is catalyzed by the bifunctional adenylyltransferase/adenylyl removal (AT/AR) enzyme. Glutamine and a regulatory protein called PII act together to stimulate adenylation.
The regulation of proline biosynthesis can depend on the initial controlling step through negative feedback inhibition. In E. coli, proline allosterically inhibits Glutamate 5-kinase which catalyzes the reaction from L-glutamate to an unstable intermediate L-γ-Glutamyl phosphate.
Arginine synthesis also utilizes negative feedback as well as repression through a repressor encoded by the gene argR. The gene product of argR, ArgR an aporepressor, and arginine as a corepressor affect the operon of arginine biosynthesis. The degree of repression is determined by the concentrations of the repressor protein and corepressor level. | 1 | Applied and Interdisciplinary Chemistry |
Selenium may be measured in blood, plasma, serum or urine to monitor excessive environmental or occupational exposure, confirm a diagnosis of poisoning in hospitalized victims or to assist in a forensic investigation in a case of fatal overdosage. Some analytical techniques are capable of distinguishing organic from inorganic forms of the element. Both organic and inorganic forms of selenium are largely converted to monosaccharide conjugates (selenosugars) in the body prior to being eliminated in the urine. Cancer patients receiving daily oral doses of selenothionine may achieve very high plasma and urine selenium concentrations. | 1 | Applied and Interdisciplinary Chemistry |
Acyl azides are carboxylic acid derivatives with the general formula RCON. These compounds, which are a subclass of organic azides, are generally colorless. | 0 | Theoretical and Fundamental Chemistry |
Grb2 has been shown to interact with:
* ADAM15,
* Abl gene,
* Arachidonate 5-lipoxygenase,
* B-cell linker,
* BCAR1,
* BCR gene,
* Beta-2 adrenergic receptor,
* C-Met,
* CBLB,
* CD117,
* CD22,
* CD28,
* CDKN1B,
* CRK,
* Cbl gene,
* Colony stimulating factor 1 receptor,
* DCTN1,
* DNM1,
* Dock180,
* Dystroglycan,
* EPH receptor A2,
* ETV6,
* Epidermal growth factor receptor,
* Erythropoietin receptor,
* FRS2,
* Fas ligand,
* GAB1,
* GAB2,
* Glycoprotein 130,
* Granulocyte colony-stimulating factor receptor,
* HER2/neu,
* HNRNPC,
* Huntingtin,
* INPP5D,
* IRS1,
* ITK,
* Janus kinase 1,
* Janus kinase 2,
* KHDRBS1,
* Linker of activated T cells,
* Lymphocyte cytosolic protein 2,
* MAP2,
* MAP3K1
* MAP4K1,
* MED28,
* MST1R,
* MUC1,
* Mitogen-activated protein kinase 9,
* NCKIPSD,
* NEU3,
* PDGFRB,
* PIK3R1,
* PLCG1,
* PRKAR1A,
* PTK2,
* PTPN11,
* PTPN12,
* PTPN1,
* PTPN6,
* PTPRA,
* RAPGEF1,
* RET proto-oncogene,
* SH2B1,
* SH3KBP1,
* SHC1,
* SOS1,
* Src,
* Syk,
* TNK2,
* TrkA,
* VAV1,
* VAV2,
* VAV3, and
* Wiskott-Aldrich syndrome protein. | 1 | Applied and Interdisciplinary Chemistry |
The spiciness can be calculated in several programming languages with the Gibbs SeaWater (GSW) toolbox. It is used to derive thermodynamic seawater properties and is adopted by the Intergovernmental Oceanographic Commission (IOC), International Association for the Physical Sciences of the Oceans (IAPSO) and the Scientific Committee on Oceanic Research (SCOR). They use the definition of spiciness (gsw_spiciness0(), gsw_spiciness1(), gsw_spiciness2() at respectively 0, 1000 and 2000 dbar) provided by. These isobars are chosen because they correspond to commonly used potential density surfaces. Areas with constant density but different spiciness have a net water flow of heat and salinity due to diffusion. | 0 | Theoretical and Fundamental Chemistry |
Stein Bjornar Jacobsen (born 1950) is a Norwegian-American geochemist who works within cosmochemistry.
Hailing from Drammen, he finished a cand.mag. degree at the University of Oslo before studying geology in California with a Rotary grant. Jacobsen became a professor of geochemistry at Harvard University.
He was an inducted into the Norwegian Academy of Science and Letters in 1994. In 2009 he was inducted into the American Academy of Arts and Sciences, mainly for using "the distribution of long-lived and extinct radioisotopes to date the formation of the earth's core and to define the effects of core separation on the early history of the core-mantle-crust system". | 0 | Theoretical and Fundamental Chemistry |
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