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Deuterium can be used to reinforce specific oxidation-vulnerable C-H bonds within essential or conditionally essential nutrients, such as certain amino acids, or polyunsaturated fatty acids (PUFA), making them more resistant to oxidative damage. Deuterated polyunsaturated fatty acids, such as linoleic acid, slow down the chain reaction of lipid peroxidation that damage living cells. Deuterated ethyl ester of linoleic acid (RT001), developed by Retrotope, is in a compassionate use trial in infantile neuroaxonal dystrophy and has successfully completed a Phase I/II trial in Friedreich's ataxia. | 0 | Theoretical and Fundamental Chemistry |
Before the Industrial Revolution, the ocean was a source of CO to the atmosphere balancing the impact of rock weathering and terrestrial particulate organic carbon; now it has become a sink for the excess atmospheric CO. Carbon dioxide is absorbed from the atmosphere at the ocean's surface at an exchange rate which varies locally but on average, the oceans have a net absorption of CO 2.2 Pg C per year. Because the solubility of carbon dioxide increases when temperature decreases, cold areas can contain more CO and still be in equilibrium with the atmosphere; In contrast, rising sea surface temperatures decrease the capacity of the oceans to take in carbon dioxide. The North Atlantic and Nordic oceans have the highest carbon uptake per unit area in the world, and in the North Atlantic deep convection transports approximately 197 Tg per year of non-refractory carbon to depth.
A 2020 study found significantly higher net flux of carbon into the oceans compared to previous studies. The new study used satellite data to account for small temperature differences between the surface of the ocean and the depth of a few meters where the measurements are made. | 0 | Theoretical and Fundamental Chemistry |
A stannide can refer to an intermetallic compound containing tin combined with one or more other metals; an anion consisting solely of tin atoms or a compound containing such an anion, or, in the field of organometallic chemistry an ionic compound containing an organotin anion (e.g.see an alternative name for such a compound is stannanide.) | 0 | Theoretical and Fundamental Chemistry |
Cold solutions (−10 to −20 °C) are stable for days. Decomposition is accelerated by light and heavy metals. | 0 | Theoretical and Fundamental Chemistry |
The Isa Process was originally developed for the CRL copper electrorefinery in Townsville. It was subsequently licensed to the Copper Range Company for its White Pine copper refinery.
The next licence issued was for an electrowinning application at the Broken Hill Associated Smelters (“BHAS”) lead smelter at Port Pirie, in South Australia. BHAS commissioned in 1985 a solvent extraction and electrowinning (“SX–EW”) to recover copper from copper–lead matte produced as a by-product of the lead smelting operations. The process used involves leaching the copper from the material using an acidic chloride–sulfate solution, followed by solvent extraction to concentrate the leached copper and electrowinning.
Electrowinning copper differs from electrorefining in that electrorefining uses a copper anode that is dissolved and redeposited on the cathode, while in electrowinning the copper is already in solution and is extracted from the solution by passing a current through the solution using an inert lead-alloy anode, and a cathode.
The chloride in the leach solution at Port Pirie proved to be a problem for the stainless steel cathodes of the Isa Process. A small amount of the chloride ions in the leach solution passed through the solvent into the electrolyte, leading to a reported chloride concentration of 80 milligrams per liter (“mg/L”) in the electrolyte. The presence of the chloride in the electrolyte caused pitting corrosion of the stainless steel cathode plates. After trying other types of stainless steel, BHAS switched to using titanium cathode plates.
Other electrowinning operations followed, including Gibraltar Mines’ McLeese Lake operation and Magma Copper’s San Manuel copper mine in 1986, the Mexicana de Cananea operation in Mexico in 1989, and the Gunpowder Copper Limited operation at Gunpowder in north-west Queensland 1990. These operations did not suffer the chloride corrosion problems experienced by BHAS. | 1 | Applied and Interdisciplinary Chemistry |
The most popular biofoam in the use of biomedical devices is PLA as well. PLA's properties are also desirable in biomedical applications, especially in combination with other polymers. Specifically, its biocompatibility and biodegradability make it favorable in tissue engineering through the use of FDM-3D printing. PLA does well in these printing environments as its glass transition temperature as well as shape memory is small. In recent studies, PLA has been specifically combined with hydroxyapatite (HA) in order to make the modulus of the sample more favorable for its application in repairing bone failure. Specifically in tissue engineering, HA has also been shown to generate osteogenesis by triggering osteoblasts and pre-osteoblastic cells. HA is a strong material, which makes it ideal to add to PLA, due to the fact that PLA has weak toughness with a 10% elongation before failure. FFF-based 3D printing was used as well as compression tests demonstrated in Figure 5. The results showed that there was a self-healing capability of the sample, which could be used in certain biomedical practices. | 0 | Theoretical and Fundamental Chemistry |
Animals that eat PCB-contaminated food, even for short periods of time, suffer liver damage and may die. In 1968 in Japan, 400,000 birds died after eating poultry feed that was contaminated with PCBs. Animals that ingest smaller amounts of PCBs in food over several weeks or months develop various health effects, including anemia; acne-like skin conditions (chloracne); liver, stomach, and thyroid gland injuries (including hepatocarcinoma), and thymocyte apoptosis. Other effects of PCBs in animals include changes in the immune system, behavioral alterations, and impaired reproduction. PCBs that have dioxin-like activity are known to cause a variety of teratogenic effects in animals. Exposure to PCBs causes hearing loss and symptoms similar to hypothyroidism in rats. | 1 | Applied and Interdisciplinary Chemistry |
Certain isotopes of trace metals are preferentially oxidized or reduced; thus, transitions between redox species of the metal ions (e.g., Fe → Fe) are fractionating, resulting in different isotopic compositions between the different redox pools in the environment. Additionally, at high temperatures, metals ions can evaporate (and subsequently condense upon cooling), and the relative differences in isotope masses of a given heavy metal leads to fractionation during these evaporation and condensation processes. Diffusion of isotopes through a solution or material can also result in fractionations, as the lighter mass isotopes are able to diffuse at a faster rate. Additionally, isotopes can have slight variations in their solubility and other chemical and physical properties, which can also drive fractionation. | 0 | Theoretical and Fundamental Chemistry |
Consider a thin fluid film that spans a stationary closed contour boundary. Let be the normal component of the velocity field and be the contravariant components of the tangential velocity projection. Let be the covariant surface derivative, be the covariant curvature tensor, be the mixed curvature tensor and be its trace, that is mean curvature. Furthermore, let the internal energy density per unit mass function be so that the total potential energy is given by
This choice of :
where is the surface energy density results in Laplace's classical model for surface tension:
where A is the total area of the soap film.
The governing system reads
where the -derivative is the central operator, originally
due to Jacques Hadamard, in The Calculus of Moving Surfaces. Note that, in compressible models, the combination is commonly identified with pressure . The governing system above was originally formulated in reference 1.
For the Laplace choice of surface tension the system becomes:
Note that on flat () stationary () manifolds, the
system becomes
which is precisely classical Euler's equations of fluid dynamics. | 1 | Applied and Interdisciplinary Chemistry |
Other uses of DNA in chemistry are in DNA-templated synthesis, Enantioselective catalysis, DNA nanowires and DNA computing. | 0 | Theoretical and Fundamental Chemistry |
There are two different configurations that form polarization gradients: lin⊥lin and σσ. Both configurations provide cooling, however, the type of polarization gradient and the physical mechanism for cooling are different between the two. | 0 | Theoretical and Fundamental Chemistry |
Supercritical adsorption also referred to as the adsorption of supercritical fluids, is the adsorption at above-critical temperatures. There are different tacit understandings of supercritical fluids. For example, “a fluid is considered to be ‘supercritical’ when its temperature and pressure exceed the temperature and pressure at the critical point”. In the studies of supercritical extraction, however, “supercritical fluid” is applied for a narrow temperature region of 1-1.2 or to +10 K, which is called the supercritical region. ( is the critical temperature) | 0 | Theoretical and Fundamental Chemistry |
The Nazi German government used benzene administered via injection as one of their many methods for killing. | 1 | Applied and Interdisciplinary Chemistry |
A major advantage of DamID over ChIP seq is that profiling of protein binding sites can be assayed in a particular cell type in vivo without requiring the physical separation of a subpopulation of cells. This allows for investigation into developmental or physiological processes in animal models. | 1 | Applied and Interdisciplinary Chemistry |
To calculate the pressure drop in a given reactor, the following equation may be deduced
This arrangement of the Ergun equation makes clear its close relationship to the simpler Kozeny-Carman equation which describes laminar flow of fluids across packed beds via the first term on the right hand side. On the continuum level, the second order velocity term demonstrates that the Ergun equation also includes the pressure drop due to inertia, as described by the Darcy–Forchheimer equation. Specifically, the Ergun equation gives the following permeability and inertial permeability from the Darcy-Forchheimer law:
and
The extension of the Ergun equation to fluidized beds, where the solid particles flow with the fluid, is discussed by Akgiray and Saatçı (2001). | 1 | Applied and Interdisciplinary Chemistry |
A simpler version of the filament stretching rheometer, the falling plate rheometer sandwiches liquid between two solid surfaces. The top plate is fixed, and bottom plate falls under the influence of gravity, drawing out a string of the liquid. | 1 | Applied and Interdisciplinary Chemistry |
Ultrasensitivity can be achieved through several mechanisms:
#Multistep mechanisms (examples: cooperativity) and multisite phosphorylation
#Buffering mechanisms (examples: decoy phosphorylation sites) or stoichiometric inhibitors
#Changes in localisation (such as translocation across the nuclear envelope)
#Saturation mechanisms (also known as zero-order ultrasensitivity)
#Positive feedback
#Allovalency
#Non-Zero-Order Ultrasensitivity in Membrane Proteins
#Dissipative Allostery | 1 | Applied and Interdisciplinary Chemistry |
Tungsten is one of the oldest metal ions to be incorporated in biological systems, preceding the Great Oxygenation Event. Before the abundance of oxygen in Earth's atmosphere, oceans teemed with sulfur and tungsten, while molybdenum, a metal that is highly similar chemically, was inaccessible in solid form. The abundance of tungsten and lack of free molybdenum likely explains why early marine organisms incorporated the former instead of the latter. However, as cyanobacteria began to fill the atmosphere with oxygen, molybdenum became available (molybdenum becomes soluble when exposed to oxygen) and molybdenum began to replace tungsten in the majority of metabolic processes, which is seen today, as tungsten is only present in the biological complexes of prokaryotes (methanogens, gram-positive bacteria, gram-negative aerobes and anaerobes), and is only obligated in hyperthermophilic archaea such as P. furiosus.
Although research into the specific enzyme complexes in which tungsten is incorporated is relatively recent (1970s), natural tungstoenzymes are abundantly found in a large number of prokaryotic microorganisms. These include formate dehydrogenase, formyl methanufuran dehydrogenase, acetylene hydratase, and a class of phylogenetically related oxidoreductases that catalyze the reversible oxidation of aldehydes. The first crystal structure of a tungsten- or pterin-containing enzyme, that of aldehyde ferredoxin oxidoreductase from P. furiosus, has revealed a catalytic site with one W atom coordinated to two pterin molecules which are themselves bridged by a magnesium ion. | 0 | Theoretical and Fundamental Chemistry |
Quinones methides are commonly invoked in biochemistry, but are rarely observed as long-lived intermediates. | 0 | Theoretical and Fundamental Chemistry |
Associative substitution describes a pathway by which compounds interchange ligands. The terminology is typically applied to organometallic and coordination complexes, but resembles the Sn2 mechanism in organic chemistry. The opposite pathway is dissociative substitution, being analogous to the Sn1 pathway. Intermediate pathways exist between the pure associative and pure dissociative pathways, these are called interchange mechanisms.
Associative pathways are characterized by binding of the attacking nucleophile to give a discrete, detectable intermediate followed by loss of another ligand. Complexes that undergo associative substitution are either coordinatively unsaturated or contain a ligand that can change its bonding to the metal, e.g. change in hapticity or bending of a nitrogen oxide ligand (NO). In homogeneous catalysis, the associative pathway is desirable because the binding event, and hence the selectivity of the reaction, depends not only on the nature of the metal catalyst but also on the substrate.
Examples of associative mechanisms are commonly found in the chemistry of 16e square planar metal complexes, e.g. Vaska's complex and tetrachloroplatinate. These compounds (MX) bind the incoming (substituting) ligand Y to form pentacoordinate intermediates MXY that in a subsequent step dissociates one of their ligands. Dissociation of Y results in no detectable net reaction, but dissociation of X results in net substitution, giving the 16e complex MXY. The first step is typically rate determining. Thus, the entropy of activation is negative, which indicates an increase in order in the system. These reactions follow second order kinetics: the rate of the appearance of product depends on the concentration of MX and Y. The rate law is governed by the Eigen–Wilkins Mechanism. | 0 | Theoretical and Fundamental Chemistry |
Empress Maria Theresia of Austria reformed the measures and weights of the Habsburg monarchy in 1761. The weight of an apothecaries' pound of 12 ounces was increased to a value that was later (after the kilogramme was defined) found to be 420.009 g; this was called the . It was defined as of the unusually heavy Habsburg civil pound (defined as of the civil pound of Cologne) and corresponded to a record ounce weight of 35 g.
Before the reform, in the north of the empire, the Nuremberg standard had been in effect, and in Italy, the local standards had been even lighter. It is not surprising that an increase of 17% and more met with some inertia. The 1770 edition of the pharmacopoeia still used the Nuremberg standard , indicating that even in the Austrian capital Vienna it took some time for the reform to become effective. In 1774, the used the new standard, and in 1783 all old apothecaries' weight pieces that were still in use were directed to be destroyed.
Venice was not part of these reforms and kept its standard of approximately 25 g per ounce.
When Austria started producing scales and weight pieces to the new standard with an excellent quality/price ratio, these were occasionally used by German apothecaries as well. | 1 | Applied and Interdisciplinary Chemistry |
Beginning with the equation of motion for a frictionless fluid (the Euler equations) and taking the curl, one arrives at the equation of motion for the curl of the fluid velocity, that is to say, the vorticity.
In a fluid that is not all of the same density, a source term appears in the vorticity equation whenever surfaces of constant density (isopycnic surfaces) and surfaces
of constant pressure (isobaric surfaces) are not aligned. The material derivative of the local vorticity is given by:
(where is the velocity and is the vorticity, is the pressure, and is the density). The baroclinic contribution is the vector:
This vector, sometimes called the solenoidal vector, is of interest both in compressible fluids and in incompressible (but inhomogeneous) fluids. Internal gravity waves as well as unstable Rayleigh–Taylor modes can be analyzed from the perspective of the baroclinic vector. It is also of interest in the creation of vorticity by the passage of shocks through inhomogeneous media, such as in the Richtmyer–Meshkov instability.
Experienced divers are familiar with the very slow waves that can be excited at a thermocline or a halocline, which are known as internal waves. Similar waves can be generated between a layer of water and a layer of oil. When the interface between these two surfaces is not horizontal and the system is close to hydrostatic equilibrium, the gradient of the pressure is vertical but the gradient of the density is not. Therefore the baroclinic vector is nonzero, and the sense of the baroclinic vector is to create vorticity to make the interface level out. In the process, the interface overshoots, and the result is an oscillation which is an internal gravity wave. Unlike surface gravity waves, internal gravity waves do not require a sharp interface. For example, in bodies of water, a gradual gradient in temperature or salinity is sufficient to support internal gravity waves driven by the baroclinic vector. | 1 | Applied and Interdisciplinary Chemistry |
Air stripping is the transferring of volatile components of a liquid into an air stream. It is an environmental engineering technology used for the purification of groundwaters and wastewaters containing volatile compounds.
Volatile compounds have relatively high vapor pressure and low aqueous solubility characterized by the compounds Henrys law coefficient, which is the ratio of the concentration in air that is in equilibrium with its concentration in water. Pollutants with relatively high Henrys Law coefficients can be economically stripped from water. These include BTEX compounds (benzene, toluene, ethylbenzene, and xylene found in gasoline), and solvents including trichloroethylene and tetrachloroethylene. Ammonia can also be stripped from wastewaters and liquid digestates (often requiring pH adjustment prior to stripping). Since Henrys law coefficient increases with temperature, stripping is easier at warmer temperatures. | 1 | Applied and Interdisciplinary Chemistry |
Pro-inflammatory cytokine IL-12 is produced in heterodimer form by B cells and antigen-presenting cells. Binding of IL-12 to IL-12R, which is composed of two different subunits (IL12Rβ1 and IL12Rβ2), leads to the interaction of IL12Rβ1 and IL12Rβ2 with JAK2 and TYK2, which is followed by phosphorylation of STAT4 tyrosine 693. The pathway then induces IFNγ production and Th1 differentiation. STAT4 is critical in promotion of antiviral response of natural killer (NK) cell by targeting of promotor regions of Runx1 and Runx3. | 1 | Applied and Interdisciplinary Chemistry |
Carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur are the six most important chemical elements whose covalent combinations make up most biological molecules on Earth. All of these elements are nonmetals.
In a human body, the four elements—C, H, O, and N—compose about 96% of the weight, and major minerals (macrominerals) and minor minerals (also called trace elements) compose the remainder.
Sulfur is contained in the amino acids cysteine and methionine.
Phosphorus is contained in phospholipids, a class of lipids that are a major component of all cell membranes, as they can form lipid bilayers, which keep ions, proteins, and other molecules where they are needed for cell function, and prevent them from diffusing into areas where they should not be. Phosphate groups are also an essential component of the backbone of nucleic acids (general name for DNA & RNA) and are required to form ATP – the main molecule used as energy powering the cell in all living creatures.
Carbonaceous asteroids are rich in CHON elements.
These asteroids are the most common type, and frequently collide with Earth as meteorites. Such collisions were especially common early in Earths history, and these impactors may have been crucial in the formation of the planets oceans.
The simplest compounds to contain all of the CHON elements are isomers fulminic acid (HCNO), isofulminic acid (HONC), cyanic acid (HOCN) and isocyanic acid (HNCO), having one of each atom. | 1 | Applied and Interdisciplinary Chemistry |
Rosocyanine and rubrocurcumin are two red colored materials, which are formed by the reaction between curcumin and borates. | 0 | Theoretical and Fundamental Chemistry |
In industry, cavitation is often used to homogenize, or mix and break down, suspended particles in a colloidal liquid compound such as paint mixtures or milk. Many industrial mixing machines are based upon this design principle. It is usually achieved through impeller design or by forcing the mixture through an annular opening that has a narrow entrance orifice with a much larger exit orifice. In the latter case, the drastic decrease in pressure as the liquid accelerates into a larger volume induces cavitation. This method can be controlled with hydraulic devices that control inlet orifice size, allowing for dynamic adjustment during the process, or modification for different substances. The surface of this type of mixing valve, against which surface the cavitation bubbles are driven causing their implosion, undergoes tremendous mechanical and thermal localized stress; they are therefore often constructed of extremely strong and hard materials such as stainless steel, Stellite, or even polycrystalline diamond (PCD).
Cavitating water purification devices have also been designed, in which the extreme conditions of cavitation can break down pollutants and organic molecules. Spectral analysis of light emitted in sonochemical reactions reveal chemical and plasma-based mechanisms of energy transfer. The light emitted from cavitation bubbles is termed sonoluminescence.
Use of this technology has been tried successfully in alkali refining of vegetable oils.
Hydrophobic chemicals are attracted underwater by cavitation as the pressure difference between the bubbles and the liquid water forces them to join. This effect may assist in protein folding. | 1 | Applied and Interdisciplinary Chemistry |
On June 28, 2007, a team at the J. Craig Venter Institute published an article in Science Express, saying that they had successfully transplanted the natural DNA from a Mycoplasma mycoides bacterium into a Mycoplasma capricolum cell, creating a bacterium which behaved like a M. mycoides.
On Oct 6, 2007, Craig Venter announced in an interview with UKs The Guardian newspaper that the same team had synthesized a modified version of the single chromosome of Mycoplasma genitalium artificially. The chromosome was modified to eliminate all genes which tests in live bacteria had shown to be unnecessary. The next planned step in this minimal genome project is to transplant the synthesized minimal genome into a bacterial cell with its old DNA removed; the resulting bacterium will be called Mycoplasma laboratorium. The next day the Canadian bioethics group, ETC Group issued a statement through their representative, Pat Mooney, saying Venters "creation" was "a chassis on which you could build almost anything". The synthesized genome had not yet been transplanted into a working cell.
On May 21, 2010, Science reported that the Venter group had successfully synthesized the genome of the bacterium Mycoplasma mycoides from a computer record, and transplanted the synthesized genome into the existing cell of a Mycoplasma capricolum bacterium that had its DNA removed. The "synthetic" bacterium was viable, i.e. capable of replicating billions of times. The team had originally planned to use the M. genitalium bacterium they had previously been working with, but switched to M. mycoides because the latter bacterium grows much faster, which translated into quicker experiments. Venter describes it as "the first species.... to have its parents be a computer". The transformed bacterium is dubbed "Synthia" by ETC. A Venter spokesperson has declined to confirm any breakthrough at the time of this writing. | 1 | Applied and Interdisciplinary Chemistry |
The plastid is the site of diverse and complex lipid synthesis in plants. The carbon used to form the majority of the lipid is from acetyl-CoA, which is the decarboxylation product of pyruvate. Pyruvate may enter the plastid from the cytosol by passive diffusion through the membrane after production in glycolysis. Pyruvate is also made in the plastid from phosphoenolpyruvate, a metabolite made in the cytosol from pyruvate or PGA. Acetate in the cytosol is unavailable for lipid biosynthesis in the plastid. The typical length of fatty acids produced in the plastid are 16 or 18 carbons, with 0-3 cis double bonds.
The biosynthesis of fatty acids from acetyl-CoA primarily requires two enzymes. Acetyl-CoA carboxylase creates malonyl-CoA, used in both the first step and the extension steps of synthesis. Fatty acid synthase (FAS) is a large complex of enzymes and cofactors including acyl carrier protein (ACP) which holds the acyl chain as it is synthesized. The initiation of synthesis begins with the condensation of malonyl-ACP with acetyl-CoA to produce ketobutyryl-ACP. 2 reductions involving the use of NADPH and one dehydration creates butyryl-ACP. Extension of the fatty acid comes from repeated cycles of malonyl-ACP condensation, reduction, and dehydration.
Other lipids are derived from the methyl-erythritol phosphate (MEP) pathway and consist of gibberelins, sterols, abscisic acid, phytol, and innumerable secondary metabolites. | 0 | Theoretical and Fundamental Chemistry |
* Siddiqui B.S., Afshan F., Rasheed M., Kardar N., Begum S., Faizi S. (2002) Medicinal Plants - A Source of Potential Chemicals of Diverse Structures and Biological Activity. In: Şener B. (eds) Biodiversity. Springer, Boston, MA. | 0 | Theoretical and Fundamental Chemistry |
A common reaction of metal carboxylates is their displacement by more basic ligands. Acetate is a common leaving group. They are especially prone to protonolysis, which is widely used to introduce ligands, displacing the carboxylic acid. In this way octachlorodimolybdate is produced from dimolybdenum tetraacetate:
Acetates of electrophilic metals are proposed to function as bases in concerted metalation deprotonation reactions.
Pyrolysis of metal carboxylates affords acid anhydrides and the metal oxide. This reaction explains the formation of basic zinc acetate from anhydrous zinc diacetate.
In some cases, monodentate carboxylates undergo O-alkylation to give esters. Strong alkylating agents are required. | 0 | Theoretical and Fundamental Chemistry |
Earths core is believed to be mostly an alloy of iron and nickel. The density indicates that it also contains a significant amount of lighter elements. Elements such as hydrogen would be stable in the Earths core, however the conditions at the formation of the core would not be suitable for its inclusion. Carbon is a very likely constituent of the core. Preferential partitioning of the carbon isotopeC into the metallic core, during its formation, may explain why there seems to be more C on the surface and mantle of the Earth compared to other solar system bodies (−5‰ compared to -20‰). The difference can also help to predict the value of the carbon proportion of the core.
The outer core has a density around 11 cm, and a mass of 1.3×10kg. It contains roughly 10 kg of carbon.
Carbon dissolved in liquid iron affect the solution of other elements. Dissolved carbon changes lead from a siderophile to a lithophile. It has the opposite effect on tungsten and molybdenum, causing more tungsten or molybdenum to dissolve in the metallic phase. The measured amounts of these elements in the rocks compared to the Solar System can be explained by a 0.6% carbon composition of the core.
The inner core is about 1221 km in radius. It has a density of 13 g cm, and a total mass of 9×10 kg and a surface area of 18,000,000 square kilometers. Experiments with mixtures under pressure and temperature attempt to reproduce the known properties of the inner and outer core. Carbides are among the first to precipitate from a molten metal mix, and so the inner core may be mostly iron carbides, FeC or FeC. At atmospheric pressure (100 kPa) the iron-FeC eutectic point is at 4.1% carbon. This percentage decreases as pressure increases to around 50 GPa. Above that pressure the percentage of carbon at the eutectic increases. The pressure on the inner core ranges from 330 GPa to 360 GPa at the centre of the Earth. The temperature at the inner core surface is about 6000 K. The material of the inner core must be stable at the pressure and temperature found there, and more dense than that of the outer core liquid. Extrapolations show that either FeC or FeC match the requirements. FeC is 8.4% carbon, and FeC is 6.7% carbon. The inner core is growing by about 1 mm per year, or adding about 18 cubic kilometres per year. This is about 18×10kg of carbon added to the inner core every year. It contains about 8×10 kg of carbon. | 0 | Theoretical and Fundamental Chemistry |
In medicinal chemistry, the incorporation of alkyl chains into some chemical compounds increases their lipophilicity. This strategy has been used to increase the antimicrobial activity of flavanones and chalcones. | 0 | Theoretical and Fundamental Chemistry |
Other alternatives include "laserweeding" – the use of novel agricultural robots for weed control using lasers. | 1 | Applied and Interdisciplinary Chemistry |
In the Old World, the first metals smelted were tin and lead. The earliest known cast lead beads were found in the Çatalhöyük site in Anatolia (Turkey), and dated from about 6500 BC, but the metal may have been known earlier.
Since the discovery happened several millennia before the invention of writing, there is no written record of how it was made. However, tin and lead can be smelted by placing the ores in a wood fire, leaving the possibility that the discovery may have occurred by accident. Recent scholarship however has called this find into question.
Lead is a common metal, but its discovery had relatively little impact in the ancient world. It is too soft to use for structural elements or weapons, though its high density relative to other metals makes it ideal for sling projectiles. However, since it was easy to cast and shape, workers in the classical world of Ancient Greece and Ancient Rome used it extensively to pipe and store water. They also used it as a mortar in stone buildings.
Tin was much less common than lead, is only marginally harder, and had even less impact by itself. | 1 | Applied and Interdisciplinary Chemistry |
Disease gene identification techniques often follow the same overall procedure. DNA is first collected from several patients who are believed to have the same genetic disease. Then, their DNA samples are analyzed and screened to determine probable regions where the mutation could potentially reside. These techniques are mentioned below. These probable regions are then lined-up with one another and the overlapping region should contain the mutant gene. If enough of the genome sequence is known, that region is searched for candidate genes. Coding regions of these genes are then sequenced until a mutation is discovered or another patient is discovered, in which case the analysis can be repeated, potentially narrowing down the region of interest.
The differences between most disease gene identification procedures are in the second step (where DNA samples are analyzed and screened to determine regions in which the mutation could reside). | 1 | Applied and Interdisciplinary Chemistry |
α,β-Unsaturated carbonyl compounds can be subclassified according to the nature of the carbonyl and alkene groups. | 0 | Theoretical and Fundamental Chemistry |
In those cases where operational complexities negate the use of a cored mains frequency approach, the standard RF or MF induction heater can be used. This type of unit uses turns of copper tube wound into an electromagnetic coil. There are no cores required, the coil needs to simply surround or be inserted into the part to be heated this makes automating the process straightforward. A further advantage is the ability to not only shrink fit parts but also remove them.
The RF and MF heaters used for induction shrink fitting vary in power from a few kilowatts to many megawatts and depending on the component geometry/diameter/cross section can vary in frequency from 1 kHz to 200 kHz, although the majority of applications use the range between 1 kHz and 100 kHz.
In general terms, it is best to use the lowest practical frequency and a low power density when undertaking shrink fitting as this will generally provide more evenly distributed heat. The exception to this rule is when using heat to remove parts from shafts. In these cases it is often best to shock the component with a rapid heat, this also has the advantage of shortening the time cycle and preventing heat build up in the shaft which can lead to problems with both parts expanding.
In order to select the correct power it is necessary to first calculate the thermal energy required to raise the material to the required temperature in the time allotted. This can be done using the heat content of the material which is normal expressed in kW hours per tonne, the weight of metal to be processed and the time cycle. Once this has been established other factors such as radiated losses from the component, coil losses and other system losses need to be factored in. Traditionally this process involved lengthy and complex calculations in conjunction with a mixture of practical experience and empirical formula. Modern techniques use finite element analysis and other computer-aided manufacturing techniques, however as with all such methods a thorough working knowledge of the induction heating process is still required. When deciding on the correct approach it is often necessary to consider the overall size and thermal conductivity of the work-piece and its expansion characteristics in order to ensure that enough soak time is allowed to create an even heat throughout the component. | 1 | Applied and Interdisciplinary Chemistry |
When the RNA transcript reaches 7 nucleotides long, transcription enters the elongation phase, the beginning of which is characterised by the collapsing of the DNA bubble and the ejection of TFIIB. This is thought to be because the nascent RNA clashes with the B linker helix when it is 6 bases long and upon further elongation to 12-13 bases it will clash with the B-reader and B-ribbon leading to dissociation. The DNA duplex also clashes with the B linker above the rudder (caused by rewinding of the DNA into a double helix). | 1 | Applied and Interdisciplinary Chemistry |
A Chi site or Chi sequence is a short stretch of DNA in the genome of a bacterium near which homologous recombination is more likely to occur than on average across the genome. Chi sites serve as stimulators of DNA double-strand break repair in bacteria, which can arise from radiation or chemical treatments, or result from replication fork breakage during DNA replication. The sequence of the Chi site is unique to each group of closely related organisms; in E. coli and other enteric bacteria, such as Salmonella, the core sequence is 5-GCTGGTGG-3 plus important nucleotides about 4 to 7 nucleotides to the 3 side of the core sequence. The existence of Chi sites was originally discovered in the genome of bacteriophage lambda, a virus that infects E. coli, but is now known to occur about 1000 times in the E. coli' genome.
The Chi sequence serves as a signal to the RecBCD helicase-nuclease that triggers a major change in the activities of this enzyme. Upon encountering the Chi sequence as it unwinds DNA, RecBCD cuts the DNA a few nucleotides to the 3’ side of Chi, within the important sequences noted above; depending on the reaction conditions, this cut is either a simple nick on the 3'-ended strand or the change of nuclease activity from cutting the 3’-ended strand to cutting the 5’-ended strand. In either case the resulting 3’ single-stranded DNA (ssDNA) is bound by multiple molecules of RecA protein that facilitate "strand invasion," in which one strand of a homologous double-stranded DNA is displaced by the RecA-associated ssDNA. Strand invasion forms a joint DNA molecule called a D-loop. Resolution of the D-loop is thought to occur by replication primed by the 3’ end generated at Chi (in the D-loop). Alternatively, the D-loop may be converted into a Holliday junction by cutting of the D-loop and a second exchange of DNA strands; the Holliday junction can be converted into linear duplex DNA by cutting of the Holliday junction and ligation of the resultant nicks. Either type of resolution can generate recombinant DNA molecules if the two interacting DNAs are genetically different, as well as repair the initially broken DNA.
Chi sites are sometimes referred to as "recombination hot spots". The name "Chi" is an abbreviation of In reference to E. coli phage lambda, the term is sometimes written as "χ site", using the Greek letter chi; for E. coli and other bacteria the term "Chi" is proper. | 1 | Applied and Interdisciplinary Chemistry |
Design and fabrication of E-AB aptamers is consistent with methods used for previously reported aptamers. SELEX is a well known selection method for fabrication and selection of nucleotide aptamers. In 1990s, scientists introduced SELEX. Aptamers are chosen based on their in vitro target recognition through this process. In SELEX, aptamers are chosen based on their ability to recognize specific targets. This method involves three key steps: First, single-stranded nucleic acids are bound to the target. Next, the bound nucleic acids are separated from unbound ones. Finally, Polymerase Chain Reaction (PCR) amplifies the nucleic acids that have an affinity for the target, allowing for further screening or functional analysis. Following SELEX, high-throughput sequencing is used to identify sequences that have been enriched due to their target-binding abilities. SELEX is relatively limited by the amount of enrichment that can be achieved in a single round. A less-reported screening method for aptamer fabrication that overcomes this limitation is affinity-based library enrichment that has been termed Particle Display. | 0 | Theoretical and Fundamental Chemistry |
Robert Crabtree is renowned for his influential work on hydrogenation, particularly his contributions to the development of the Crabtree catalyst. This catalyst, utilizing iridium as the active metal, displays exceptional efficiency, regio- and stereoselectivity in hydrogenation reactions. Notably, when terpinen-4-ol undergoes hydrogenation, the Crabtree catalyst exhibits a remarkable preference of 1000:1 for adding hydrogen to the substrate face containing the OH group. In contrast, the hydrogenation reaction with Palladium on carbon only achieves a selectivity ratio of 20:80. The chelation of the alcohol to the catalyst is evident from the identification of a catalyst-substrate complex involving norbornene-2-ol.
During his early research, Crabtree also focused on C–H bond activation. Crabtree's groundbreaking contribution in this area was reversing the hydrogenation reactions he developed before, particularly in stoichiometric alkane dehydrogenation. He utilized tert-butylethylene as a hydrogen acceptor to facilitate the release of hydrogen during the dehydrogenation of cyclooctane, forming bound cyclooctadiene. This discovery demonstrated one of the earliest instances of intermolecular C–H activation using a homogeneous metal complex. This achievement played a significant role in his tenure award and academic success | 0 | Theoretical and Fundamental Chemistry |
The karyorelictid nuclear code (translation table 27) is a genetic code used by the nuclear genome of the Karyorelictea ciliate Parduczia sp. This code, along with translation tables 28 and 31, is remarkable in that every one of the 64 possible codons can be a sense codon. Translation termination probably relies on context, specifically proximity to the poly(A) tail. | 1 | Applied and Interdisciplinary Chemistry |
In the UK planning laws, applications and restrictions delay flood mitigation work. This can be counteracted by setting up Temporary Test Dams in watercourses that can then be monitored and valued. This does however require the landowners support. TTDs have proven to be a great way to get rapid action following a flood event and a way to get communities involved in the defence against future flood events. | 1 | Applied and Interdisciplinary Chemistry |
* Evalyn Bostock, (1917–1944) British actress who died from accidentally drinking carbon tetrachloride after mistaking it for her drink while working in a photographic darkroom.
* Harry Edwards (1887–1952), an American director who died from carbon tetrachloride poisoning shortly after directing his first television production.
* Zilphia Horton, (1910–1952) American musician and activist who died from accidentally drinking a glass full of carbon tetrachloride-based typewriter cleaning fluid that she mistook for water.
* Margo Jones, (1911–1955) American stage director who was exposed to the fumes of carbon tetrachloride that was used to clean off paint from a carpet. She died a week later from kidney failure.
* Jim Beck, (1919–1956), American record producer, died after exposure to carbon tetrachloride fumes that he was exposed to during cleaning recording equipment.
* Tommy Tucker, (1933–1982) American blues singer, died after using carbon tetrachloride in floor refinishing. | 1 | Applied and Interdisciplinary Chemistry |
In 2013, Russia and China banned ractopamine in pork, and Russia also in beef, deeming it unfit for human consumption. Because the traditional Chinese diet embraces pig offal, and because ractopamine is concentrated by the gastro-intestinal system of animals, Chinese officials have banned ractopamine. Other countries in Asia, whose traditional diet is similar to that of the Chinese, have had similar concerns, but the American use of tied trade access as a proxy for conflict has somewhat mitigated their reactions. | 0 | Theoretical and Fundamental Chemistry |
In the modern understanding, the superficially unoccupied p-orbital on a (meta)stable carbene is not, in fact, fully empty. Instead, the carbene Lewis structures are in resonance with dative bonds toward adjacent lone-pair or pi-bond orbitals.
Early workers attributed the stability of Arduengo carbenes to the bulky N-adamantyl substituents, which prevent the carbene from dimerising. But replacement of the N-adamantyl groups with methyl groups also affords 1,3,4,5-tetramethylimidazol-2‑ylidene (MeImC:), a thermodynamically stable unhindered NHC.
In 1995, Arduengo's group obtained a carbene derivative of dihydroimidazol-2-ylidene, proving that stability did not arise from the aromaticity of the conjugated imidazole backbone. The following year, the first acyclic persistent carbene demonstrated that stability did not even require a cyclic backbone. Unhindered derivatives of the hydrogenated and acyclic carbenes dimerized, suggesting that MeImC: might be exceptional, rather than paradigmatic. But the behavior of the acyclic carbenes offered a tantalizing clue to the stabilization mechanism.
Unlike the cyclic derivatives, acyclic carbenes are flexible and bonds to the carbenic atom admit rotation. But bond rotation in the compound appeared hindered, suggesting a double bond character that would place the positive charge on adjacent nitrogen atoms while preserving the octet rule. Indeed, most persistent carbenes are stabilized by two flanking nitrogen centers. The outliers include an aminothiocarbene and an aminooxycarbene, which use other heteroatoms, and room-temperature-stable bis(diisopropylamino)cyclopropenylidene, in which the carbene atom is connected to two carbon atoms in a three-member, aromatic, cyclopropenylidene ring. | 0 | Theoretical and Fundamental Chemistry |
The ERK1/2 pathway of mammals is probably the best-characterized MAPK system. The most important upstream activators of this pathway are the Raf proteins (A-Raf, B-Raf or c-Raf), the key mediators of response to growth factors (EGF, FGF, PDGF, etc.); but other MAP3Ks such as c-Mos and Tpl2/Cot can also play the same role. All these enzymes phosphorylate and thus activate the MKK1 and/or MKK2 kinases, that are highly specific activators for ERK1 and ERK2. The latter phosphorylate a number of substrates important for cell proliferation, cell cycle progression, cell division and differentiation (RSK kinases, Elk-1 transcription factor, etc.)
In contrast to the relatively well-insulated ERK1/2 pathway, mammalian p38 and JNK kinases have most of their activators shared at the MAP3K level (MEKK1, MEKK4, ASK1, TAK1, MLK3, TAOK1, etc.). In addition, some MAP2K enzymes may activate both p38 and JNK (MKK4), while others are more specific for either JNK (MKK7) or p38 (MKK3 and MKK6). Due to these interlocks, there are very few if any stimuli that can elicit JNK activation without simultaneously activating p38 or reversed. Both JNK and p38 signaling pathways are responsive to stress stimuli, such as cytokines, ultraviolet irradiation, heat shock, and osmotic shock, and are involved in adaptation to stress, apoptosis or cell differentiation. JNKs have a number of dedicated substrates that only they can phosphorylate (c-Jun, NFAT4, etc.), while p38s also have some unique targets (e.g. the MAPKAP kinases MK2 and MK3), ensuring the need for both in order to respond to stressful stimuli.
ERK5 is part of a fairly well-separated pathway in mammals. Its sole specific upstream activator MKK5 is turned on in response to the MAP3 kinases MEKK2 and MEKK3. The specificity of these interactions are provided by the unique architecture of MKK5 and MEKK2/3, both containing N-terminal PB1 domains, enabling direct heterodimerisation with each other. The PB1 domain of MKK5 also contributes to the ERK5-MKK5 interaction: it provides a special interface (in addition to the D-motif found in MKK5) through which MKK5 can specifically recognize its substrate ERK5. Although the molecular-level details are poorly known, MEKK2 and MEKK3 respond to certain developmental cues to direct endothel formation and cardiac morphogenesis. While also implicated in brain development, the embryonic lethality of ERK5 inactivation due to cardiac abnormalities underlines its central role in mammalian vasculogenesis. It is notable, that conditional knockout of ERK5 in adult animals is also lethal, due to the widespread disruption of endothelial barriers. Mutations in the upstream components of the ERK5 pathway (the CCM complex) are thought to underlie cerebral cavernous malformations in humans. | 1 | Applied and Interdisciplinary Chemistry |
The MCSGP process consists of several, at least two, chromatographic columns which are switched in position opposite to the flow direction. Most of the columns are equipped with a gradient pump to adjust the modifier concentration at the column inlet. Some columns are connected directly, so that non pure product streams are internally recycled. Other columns are short circuited, so that they operate in pure batch mode. The system is split into several sections, from which every section performs a tasks analogous to the tasks of a batch purification. These tasks are loading the feed, running the gradient elution, recycling of weakly adsorbing site fractions, fractionation of the purified product, recycling of strongly adsorbing site fractions, cleaning the column from strongly adsorbing impurities, cleaning in place and re-equilibration of the column to start the next purification run. All of the tasks mentioned here are carried out at the same time in one unit. Recycling of non-pure side fractions is performed in countercurrent movement. | 0 | Theoretical and Fundamental Chemistry |
In proteomics, MALDI is used for the rapid identification of proteins isolated by using gel electrophoresis: SDS-PAGE, size exclusion chromatography, affinity chromatography, strong/weak ion exchange, isotope coded protein labeling (ICPL), and two-dimensional gel electrophoresis. Peptide mass fingerprinting is the most popular analytical application of MALDI-TOF mass spectrometers. MALDI TOF/TOF mass spectrometers are used to reveal amino acid sequence of peptides using post-source decay or high energy collision-induced dissociation (further use see mass spectrometry).
MALDI-TOF have been used to characterise post-translational modifications. For example, it has been widely applied to study protein methylation and demethylation. However, care must be taken when studying post-translational modifications by MALDI-TOF. For example, it has been reported that loss of sialic acid has been identified in papers when dihydroxybenzoic acid (DHB) has been used as a matrix for MALDI MS analysis of glycosylated peptides. Using sinapinic acid, 4-HCCA and DHB as matrices, S. Martin studied loss of sialic acid in glycosylated peptides by metastable decay in MALDI/TOF in linear mode and reflector mode. A group at Shimadzu Corporation derivatized the sialic acid by an amidation reaction as a way to improve detection sensitivity and also demonstrated that ionic liquid matrix reduces a loss of sialic acid during MALDI/TOF MS analysis of sialylated oligosaccharides. THAP, DHAP, and a mixture of 2-aza-2-thiothymine and phenylhydrazine have been identified as matrices that could be used to minimize loss of sialic acid during MALDI MS analysis of glycosylated peptides. It has been reported that a reduction in loss of some post-translational modifications can be accomplished if IR MALDI is used instead of UV MALDI.
Besides proteins, MALDI-TOF has also been applied to study lipids. For example, it has been applied to study the catalytic reactions of phospholipases. In addition to lipids, oligonucleotides have also been characterised by MALDI-TOF. For example, in molecular biology, a mixture of 5-methoxysalicylic acid and spermine can be used as a matrix for oligonucleotides analysis in MALDI mass spectrometry, for instance after oligonucleotide synthesis. | 1 | Applied and Interdisciplinary Chemistry |
After CCNY, Haines taught elementary school science at the Ethical Culture Fieldston School. He then became a laboratory assistant to Richard Block at the Boyce Thompson Institute where he studied the microorganism Ochromonas danica. When Block died in a plane crash, Haines took over his research projects. In 1964 he obtained his Doctor of Philosophy degree in chemistry from Rutgers University.
Haines became assistant professor of chemistry at City College in 1964 and full professor of chemistry in 1972, a position he held until retiring in 2007. In 1972 he co-founded the Sophie Davis School of Biomedical Education with University President Robert Marshak. This remarkable program took new undergraduates directly into medical school. It continues today as The CUNY School of Medicine. Haines taught biochemistry to undergraduates and served as director of biochemistry at the school from 1974 to 2006. Deeply committed to his students, he also taught remedial summer school and regularly counseled struggling students and their parents. On many occasions he was voted most popular professor.
Haines simultaneously conducted laboratory research and taught as professor of biochemistry in the doctoral program of biochemistry at the Graduate Center of the City University of New York. He has published extensively on the structure and function of living membranes, including on the function of cholesterol in blocking sodium leakage through membranes, and most recently on the function of cardiolipin in the mitochondrial membrane.
From 1994 to 2001, Haines chaired the [https://www.prdi.org/ Partnership for Responsible Drug Information], which organized lectures and conferences to educate the public about alternatives to the "War on Drugs."
Haines served as visiting professor at the Mitsubishi Institute in Japan, at the University of California at Berkeley, and in many other universities. On his retirement from CCNY, he became a visiting professor of biochemistry at the [http://www.sakmarlab.org/Overview/ Sakmar Laboratory at Rockefeller University].
In 2020, Haines was elected a Fellow of the American Association for the Advancement of Science "For initiating and setting up the CUNY Medical School at City College of New York to educate minority and disadvantaged students." | 1 | Applied and Interdisciplinary Chemistry |
Synthetic salmon calcitonin may be used therapeutically in humans, as it is twenty times more active than human calcitonin and has a longer half-life. It is used as therapy for Paget's disease, severe hypercalcemia, and in some cases, gynecomastia. It is also used as a therapy against osteoporosis working as an inhibitor of osteoclastic resorption and production of osteoclast precursors), having an effectiveness of 40-50 times that of the human analogue. Studies have shown that treatment of with salcatonin can reduce the rate of new fractures in the lumbar spine and the forearm in postmenopausal women. They may also have analgesic effects, relieving bone pain. | 1 | Applied and Interdisciplinary Chemistry |
Several examples can be found in organic syntheses.
Below lithium–halogen exchange is a step in the synthesis of morphine. Here n-butyllithium is used to perform lithium–halogen exchange with bromide. The nucleophilic carbanion center quickly undergoes carbolithiation to the double bond, generating an anion stabilized by the adjacent sulfone group. An intramolecular S2 reaction by the anion forms the cyclic backbone of morphine.
Lithium–halogen exchange is a crucial part of Parham cyclization. In this reaction, an aryl halide (usually iodide or bromide) exchanges with organolithium to form a lithiated arene species. If the arene bears a side chain with an electrophillic moiety, the carbanion attached to the lithium will perform intramolecular nucleophilic attack and cyclize. This reaction is a useful strategy for heterocycle formation. In the example below, Parham cyclization was used to in the cyclization of an isocyanate to form isoindolinone, which was then converted to a nitrone. The nitrone species further reacts with radicals and can be used as "spin traps" to study biological radical processes. | 0 | Theoretical and Fundamental Chemistry |
The leucine synthesis pathway diverges from the valine pathway beginning with α-ketoisovalerate. α-Isopropylmalate synthase catalyzes this condensation with acetyl CoA to produce α-isopropylmalate. An isomerase converts α-isopropylmalate to β-isopropylmalate. The third step is the NAD-dependent oxidation of β-isopropylmalate catalyzed by a dehydrogenase. The final step is the transamination of the α-ketoisocaproate by the action of a glutamate-leucine transaminase.
Leucine, like valine, regulates the first step of its pathway by inhibiting the action of the α-Isopropylmalate synthase. Because leucine is synthesized by a diversion from the valine synthetic pathway, the feedback inhibition of valine on its pathway also can inhibit the synthesis of leucine. | 1 | Applied and Interdisciplinary Chemistry |
The technique works backwards from the target to identify a precursor molecule and an enzyme that converts it into the target, and then a second precursor that can produce the first and so on until a simple, inexpensive molecule becomes the beginning of the series. For each precursor, the enzyme is evolved using induced mutations and natural selection to produce a more productive version. The evolutionary process can be repeated over multiple generations until acceptable productivity is achieved. The process does not require high temperature, high pressure, the use of exotic catalysts or other elements that can increase costs. The enzyme "optimizations" that increase the production of one precursor from another are cumulative in that the same precursor productivity improvements can potentially be leveraged across multiple target molecules. | 0 | Theoretical and Fundamental Chemistry |
Bathochromic shift is typically demonstrated using a spectrophotometer, colorimeter, or spectroradiometer. | 0 | Theoretical and Fundamental Chemistry |
In Earth's atmosphere, the speed of sound varies greatly from about at high altitudes to about at high temperatures. | 1 | Applied and Interdisciplinary Chemistry |
Cresol red can be used in many common molecular biology reactions in place of other loading dyes. Cresol Red does not inhibit Taq polymerase to the same degree as other common loading dyes. | 0 | Theoretical and Fundamental Chemistry |
In cell adhesion laminin-111 and other isoforms are important proteins that anchor cells to the extracellular matrix (ECM). The linkage between cells and the ECM is formed by binding cell surface receptors to one end of the laminin α chain and binding ECM components to another region of the laminin. Globular domains (G-Domain) of the α chain are the regions on laminin-111 that allow the binding of integrins, glycoproteins, sulfated glycolipids and dystroglycan. | 0 | Theoretical and Fundamental Chemistry |
The consumption of polluted water leads to many deaths. In the year 2015, 1.8 million people world wide died because of water pollution and over 1 billion people became ill. Low-income and third-world communities are especially endangered, because they often live close to industries with high emission. Hazards like waterborne pathogens and diseases spread fast in water surface bodies like rivers and are especially threatening in third-world countries without sewage- and wastewater treatment systems. | 1 | Applied and Interdisciplinary Chemistry |
In 2010, AstraZeneca announced a co-promotion agreement with Daiichi Sankyo to distribute Nexium in Japan. In September 2011, Nexium was approved for sale and was launched by Daiichi Sankyo in Japan. Esomeprazole was approved for use in the United States in February 2001. | 0 | Theoretical and Fundamental Chemistry |
The mechanism for the conversion of an alcohol to the N-substituted thiocarbamate is shown below. The reaction proceeds under acidic conditions. The alcohol accepts a hydrogen ion from sulfuric acid to form a water, which then leaves, creating a carbocation. The mesomeric form of the cyanogroup reacts with the carbocation. The carbocation is attacked by a water, which then loses an hydrogen to form the product. The product then undergoes hydrolysis to form the N-substituted thiocarbamate.
The reaction requires the formation of a carbocation and does not work for primary alcohols. Only secondary and tertiary alcohols undergo the Riemschneider reaction. | 0 | Theoretical and Fundamental Chemistry |
Conformational isomerism is a form of isomerism that describes the phenomenon of molecules with the same structural formula but with different shapes due to rotations about one or more bonds. Different conformations can have different energies, can usually interconvert, and are very rarely isolatable. For example, there exists a variety of Cyclohexane conformations (which cyclohexane is an essential intermediate for the synthesis of nylon–6,6) including a chair conformation where four of the carbon atoms form the "seat" of the chair, one carbon atom is the "back" of the chair, and one carbon atom is the "foot rest"; and a boat conformation, the boat conformation represents the energy maximum on a conformational itinerary between the two equivalent chair forms; however, it does not represent the transition state for this process, because there are lower-energy pathways. The conformational inversion of substituted cyclohexanes is a very rapid process at room temperature, with a half-life of 0.00001 seconds.
There are some molecules that can be isolated in several conformations, due to the large energy barriers between different conformations. 2,2,6,6-Tetrasubstituted biphenyls can fit into this latter category. | 0 | Theoretical and Fundamental Chemistry |
Antimicrobial resistance is the driving force for the development of new antimicrobial agents. The complexity and diversity of resistance mechanisms has defined the need for new and improved β-lactam antibiotics. With their broad spectrum the cephalosporins have come to dominate β-lactam chemotherapy although they often lack oral bioavailability.
On 29 October 2010, a new cephalosporin agent - Ceftarolin - was approved by the food and drug administration (FDA). Teflaro (ceftaroline fosamil) is an injectable antibiotic prodrug to treat adults with acute bacterial skin and skin structure infections (ABSSI) and community acquired bacterial pneumonia (CABP).
Ceftobiprole has been approved for the treatment of adult patients with hospital acquired pneumonia (excluding VAP) and community acquired pneumonia in 12 European countries, Canada and Switzerland. | 1 | Applied and Interdisciplinary Chemistry |
While each country is free to choose its team by whatever means it seems appropriate, the selection process usually involves holding regional and national olympiad competitions. Many countries hold "training camps" for its top students, where mentors from the country give the students accelerated college-level courses in chemistry with an emphasis on the topics covered in that year's preparatory problems as well as practical training. It is agreed that such training programs must not exceed a total duration of two weeks but there are allegations every year that some countries exceed this limit by months or even years. Another concern is that some countries tend to bring the same students to the competition year after year, which helps them win better medals. Although some believe that this is against the spirit of the olympiad, many nations find it hard to justify leaving their best students at home. | 1 | Applied and Interdisciplinary Chemistry |
The atomic electron tomography technique is performed in transmission electron microscopes capable of reaching sub-Angstrom resolution. A collection of 2D images taken at numerous different tilt angles is acquired from the sample in question, and then used to reconstruct a 3D image. After image acquisition, a significant amount of processing must be done to correct for issues such as drift, noise, and scan distortion. High quality analysis and processing using atomic electron tomography results in a 3D reconstruction of an amorphous material detailing the atomic positions of the different species that are present. | 0 | Theoretical and Fundamental Chemistry |
The most common side effects patients experience are a headache or a chronic cough. The chronic cough develops in about 20% of people treated. | 0 | Theoretical and Fundamental Chemistry |
The first version of HMDB was released on January 1, 2007, followed by two subsequent versions on January 1, 2009 (version 2.0), August 1, 2009 (version 2.5), September 18, 2012 (version 3.0) and Jan. 1, 2013 (version 3.5), 2017 (version 4.0)., 2022 (version 5.0). Details for each of the major HMDB versions (up to version 5.0) is provided in Table 1. | 1 | Applied and Interdisciplinary Chemistry |
Molecular beams can be used to create nanocluster beams of virtually any element. They can be synthesized in high vacuum by with molecular beam techniques combined with a mass spectrometer for mass selection, separation and analysis. And finally detected with detectors. | 0 | Theoretical and Fundamental Chemistry |
The structure of a transcription factory appears to be determined by cell type, transcriptional activity of the cell and also the method of technique used to visualise the structure. The generalised view of a transcription factory would feature between 4 – 30 RNA polymerase molecules and it is thought that the more transcriptionally active a cell is, the more polymerases that will be present in a factory in order to meet the demands of transcription. The core of the factory is porous and protein rich, with the hyperphosphorylated, elongating form polymerases on the perimeter. The type of proteins present include: ribonucleoproteins, co-activators, transcription factors, RNA helicase and splicing and processing enzymes. A factory only contains one type of RNA polymerase and the diameter of the factory varies depending on the RNA polymerase featured; RNA polymerase I factories are roughly 500 nm in width whereas RNA polymerase II and III factories a magnitude smaller at 50 nm. It has been experimentally shown that the transcription factory is immobilised to a structure and it is postulated that this immobilisation is because of a tethering to the nuclear matrix; this is because it has been shown it is tied to a structure that is unaffected by restriction enzymes. Proteins that have been thought to be involved in the tethering includes spectrin, actin and lamins. | 1 | Applied and Interdisciplinary Chemistry |
Calcium looping is considered as potential promising solutions to reduce CO capture energy penalty. There are many advantages from the calcium looping methods. Firstly, the method has been proved to yield a low efficiency penalties (5-8% points) while other mature CO capture systems yield a higher efficiency penalties (8-12.5%). Moreover, the method is well suited for a wide range of flue gases. Calcium looping is applicable for new builds and retrofits to existing power stations or other stationary industrial CO sources because the method can be implemented using large-scale circulating fluidized beds while other methods such as amine scrubbing is required a vastly upscale solvent scrubbing towers. In addition, crushed limestone used in calcium looping as the sorbent is a natural product, which is well distributed all over the world, non-hazardous and inexpensive. Many cement manufacturers or power plants located close to limestone sources could conceivably employ Calcium looping for CO capture. The waste sorbent can be used in cement manufacture. | 1 | Applied and Interdisciplinary Chemistry |
The Avrami equation was applied in cancer biophysics in two aspects. First aspect is connected with tumor growth and cancer cells kinetics, which can be described by the sigmoidal curve. In this context the Avrami function was discussed as an alternative to the widely used Gompertz curve. In the second aspect the Avrami nucleation and growth theory was used together with multi-hit theory of carcinogenesis to show how the cancer cell is created. The number of oncogenic mutations in cellular DNA can be treated as nucleation particles which can transform whole DNA molecule into cancerous one (neoplastic transformation). This model was applied to clinical data of gastric cancer, and shows that Avramis constant n is between 4 and 5 which suggest the fractal geometry of carcinogenic dynamics. Similar findings were published for breast and ovarian cancers, where n'=5.3. | 0 | Theoretical and Fundamental Chemistry |
The separate condenser showed dramatic potential for improvements on the Newcomen engine but Watt was still discouraged by seemingly insurmountable problems before a marketable engine could be perfected. It was only after entering into partnership with Matthew Boulton that such became reality. Watt told Boulton about his ideas on improving the engine, and Boulton, an avid entrepreneur, agreed to fund development of a test engine at Soho, near Birmingham. At last Watt had access to facilities and the practical experience of craftsmen who were soon able to get the first engine working. As fully developed, it used about 75% less fuel than a similar Newcomen one.
In 1775, Watt designed two large engines: one for the Bloomfield Colliery at Tipton, completed in March 1776, and one for John Wilkinson's ironworks at Broseley in Shropshire, which was at work the following month. A third engine, at Stratford-le-Bow in east London, was also working that summer.
Watt had tried unsuccessfully for several years to obtain an accurately bored cylinder for his steam engines, and was forced to use hammered iron, which was out of round and caused leakage past the piston. Joseph Wickham Roe stated in 1916: "When [John] Smeaton saw the first engine he reported to the Society of Engineers that 'Neither the tools nor the workmen existed who could manufacture such a complex machine with sufficient precision.
In 1774, John Wilkinson invented a boring machine in which the shaft that held the cutting tool was supported on both ends and extended through the cylinder, unlike the cantilevered borers then in use. Boulton wrote in 1776 that "Mr. Wilkinson has bored us several cylinders almost without error; that of 50 inches diameter, which we have put up at Tipton, does not err on the thickness of an old shilling in any part".
Boulton and Watt's practice was to help mine-owners and other customers to build engines, supplying men to erect them and some specialised parts. However, their main profit from their patent was derived from charging a licence fee to the engine owners, based on the cost of the fuel they saved. The greater fuel efficiency of their engines meant that they were most attractive in areas where fuel was expensive, particularly Cornwall, for which three engines were ordered in 1777, for the Wheal Busy, Ting Tang, and Chacewater mines. | 0 | Theoretical and Fundamental Chemistry |
Water, air, alcohol, glycerol, and thin motor oil are all examples of Newtonian fluids over the range of shear stresses and shear rates encountered in everyday life. Single-phase fluids made up of small molecules are generally (although not exclusively) Newtonian. | 1 | Applied and Interdisciplinary Chemistry |
Previtamin D is an intermediate in the production of cholecalciferol (vitamin D).
It is formed by the action of UV light, most specifically UVB light of wavelengths between 295 and 300 nm, acting on 7-dehydrocholesterol in the epidermal layers of the skin.
The B ring of the steroid nucleus structure is broken open, making a secosteroid. This then undergoes spontaneous isomerization into cholecalciferol, the prohormone of the active form of vitamin D, calcitriol.
The synthesis of previtamin D is blocked effectively by sunscreens. | 0 | Theoretical and Fundamental Chemistry |
Hyper–Rayleigh scattering optical activity ( ), a form of chiroptical harmonic scattering, is a nonlinear optical physical effect whereby chiral scatterers (such as nanoparticles or molecules) convert light (or other electromagnetic radiation) to higher frequencies via harmonic generation processes, in a way that the intensity of generated light depends on the chirality of the scatterers. "Hyper–Rayleigh scattering" is a nonlinear optical counterpart to Rayleigh scattering. "Optical activity" refers to any changes in light properties (such as intensity or polarization) that are due to chirality. | 0 | Theoretical and Fundamental Chemistry |
In theoretical physics, the Mandelstam variables are numerical quantities that encode the energy, momentum, and angles of particles in a scattering process in a Lorentz-invariant fashion. They are used for scattering processes of two particles to two particles. The Mandelstam variables were first introduced by physicist Stanley Mandelstam in 1958.
If the Minkowski metric is chosen to be , the Mandelstam variables are then defined by
where p and p are the four-momenta of the incoming particles and p and p are the four-momenta of the outgoing particles.
is also known as the square of the center-of-mass energy (invariant mass) and as the square of the four-momentum transfer. | 0 | Theoretical and Fundamental Chemistry |
Friedel's salt is an anion exchanger mineral belonging to the family of the layered double hydroxides (LDHs). It has affinity for anions as chloride and iodide and is capable of retaining them to a certain extent in its crystallographical structure. | 0 | Theoretical and Fundamental Chemistry |
In 1947, scrolls were discovered in caves near the Dead Sea that proved to contain writing in Hebrew and Aramaic, most of which are thought to have been produced by the Essenes, a small Jewish sect. These scrolls are of great significance in the study of Biblical texts because many of them contain the earliest known version of books of the Hebrew bible. A sample of the linen wrapping from one of these scrolls, the Great Isaiah Scroll, was included in a 1955 analysis by Libby, with an estimated age of 1,917 ± 200 years. Based on an analysis of the writing style, palaeographic estimates were made of the age of 21 of the scrolls, and samples from most of these, along with other scrolls which had not been palaeographically dated, were tested by two AMS laboratories in the 1990s. The results ranged in age from the early 4th century BC to the mid 4th century AD. In all but two cases the scrolls were determined to be within 100 years of the palaeographically determined age. The Isaiah scroll was included in the testing and was found to have two possible date ranges at a 2σ confidence level, because of the shape of the calibration curve at that point: there is a 15% chance that it dates from 355 to 295 BC, and an 84% chance that it dates from 210 to 45 BC. Subsequently, these dates were criticized on the grounds that before the scrolls were tested, they had been treated with modern castor oil in order to make the writing easier to read; it was argued that failure to remove the castor oil sufficiently would have caused the dates to be too young. Multiple papers have been published both supporting and opposing the criticism. | 0 | Theoretical and Fundamental Chemistry |
Ordinary (non-time) crystals form through spontaneous symmetry breaking related to a spatial symmetry. Such processes can produce materials with interesting properties, such as diamonds, salt crystals, and ferromagnetic metals. By analogy, a time crystal arises through the spontaneous breaking of a time-translation symmetry. A time crystal can be informally defined as a time-periodic self-organizing structure. While an ordinary crystal is periodic (has a repeating structure) in space, a time crystal has a repeating structure in time. A time crystal is periodic in time in the same sense that the pendulum in a pendulum-driven clock is periodic in time. Unlike a pendulum, a time crystal "spontaneously" self-organizes into robust periodic motion (breaking a temporal symmetry). | 0 | Theoretical and Fundamental Chemistry |
The Molecular Kink Paradigm envisions a representative network chain as a series of vectors that follow the chain contour within its tube. Each vector represents the equilibrium end-to-end distance of a kink. The actual 3-dimensional path of the chain is not pertinent, since all elastic forces are assumed to operate along the chain contour. In addition to the chain's contour length, the only other important parameter is its tortuosity, the ratio of its contour length to its end-to-end distance. As the chain is extended, in response to an applied strain, the induced elastic force is assumed to propagate uniformly along its contour. Consider a network chain whose end points (network nodes) are more or less aligned with the tensile strain axis. As the initial strain is applied to the rubber sample, the network nodes at the ends of the chain begin to move apart and all of the kink vectors along the contour are stretched simultaneously. Physically, the applied strain forces the kinks to stretch beyond their thermal equilibrium end-to-end distances, causing a decrease in their entropy. The increase in free energy associated with this change in entropy, gives rise to a (linear) elastic force that opposes the strain. The force constant for the low strain regime can be estimated by sampling molecular dynamics (MD) trajectories of a kink, i.e. short chains, composed of 2–3 isoprene units, at relevant temperatures, e.g. 300K. By taking many samples of the coordinates over the course of the simulations, the probability distributions of end-to-end distance for a kink can be obtained. Since these distributions (which turn out to be approximately Gaussian) are directly related to the number of states, we may associate them with the entropy of the kink at any end-to-end distance. By numerically differentiating the probability distribution, the change in entropy, and hence free energy, with respect to the kink end-to-end distance can be found. The force model for this regime is found to be linear and proportional to the temperature divided by the chain tortuosity. | 0 | Theoretical and Fundamental Chemistry |
In most countries, sewage collection and treatment are subject to local and national regulations and standards. | 1 | Applied and Interdisciplinary Chemistry |
Retinyl esters from animal-sourced foods (or synthesized for dietary supplements for humans and domesticated animals) are acted upon by retinyl ester hydrolases in the lumen of the small intestine to release free retinol. Retinol enters intestinal absorptive cells by passive diffusion. Absorption efficiency is in the range of 70 to 90%. Humans are at risk for acute or chronic vitamin A toxicity because there are no mechanisms to suppress absorption or excrete the excess in urine. Within the cell, retinol is there bound to retinol binding protein 2 (RBP2). It is then enzymatically reesterified by the action of lecithin retinol acyltransferase and incorporated into chylomicrons that are secreted into the lymphatic system.
Unlike retinol, β-carotene is taken up by enterocytes by the membrane transporter protein scavenger receptor B1 (SCARB1). The protein is upregulated in times of vitamin A deficiency. If vitamin A status is in the normal range, SCARB1 is downregulated, reducing absorption. Also downregulated is the enzyme beta-carotene 15,15-dioxygenase (formerly known as beta-carotene 15,15-monooxygenase) coded for by the BCMO1 gene, responsible for symmetrically cleaving β-carotene into retinal. Absorbed β-carotene is either incorporated as such into chylomicrons or first converted to retinal and then retinol, bound to RBP2. After a meal, roughly two-thirds of the chylomicrons are taken up by the liver with the remainder delivered to peripheral tissues. Peripheral tissues also can convert chylomicron β-carotene to retinol.
The capacity to store retinol in the liver means that well-nourished humans can go months on a vitamin A deficient diet without manifesting signs and symptoms of deficiency. Two liver cell types are responsible for storage and release: hepatocytes and hepatic stellate cells (HSCs). Hepatocytes take up the lipid-rich chylomicrons, bind retinol to retinol-binding protein 4 (RBP4), and transfer the retinol-RBP4 to HSCs for storage in lipid droplets as retinyl esters. Mobilization reverses the process: retinyl ester hydrolase releases free retinol which is transferred to hepatocytes, bound to RBP4, and put into blood circulation. Other than either after a meal or when consumption of large amounts exceeds liver storage capacity, more than 95% of retinol in circulation is bound to RBP4. | 1 | Applied and Interdisciplinary Chemistry |
The Coulter Counter was created by Wallace H. Coulter in 1949. The Coulter counter consists of two electrolyte reservoirs that are connected by a small channel, through which a current of ions flow. Each particle drawn through the channel causes a brief change to the electrical resistance of the liquid. The change in the electrical resistance causes a disturbance in the electric field. The counter detects these changes in electrical resistance; the size of the particles in the field is proportional to magnitude of the disturbance in the electric field. | 0 | Theoretical and Fundamental Chemistry |
Hot-dip galvanizing deposits a thick, robust layer of zinc iron alloys on the surface of a steel item. In the case of automobile bodies, where additional decorative coatings of paint will be applied, a thinner form of galvanizing is applied by electrogalvanizing. The hot-dip process generally does not reduce strength to a measurable degree, with the exception of high-strength steels where hydrogen embrittlement can become a problem.
Thermal diffusion galvanizing, or Sherardizing, provides a zinc diffusion coating on iron- or copper-based materials. | 1 | Applied and Interdisciplinary Chemistry |
The distribution constant (or partition ratio) (K) is the equilibrium constant for the distribution of an analyte in two immiscible solvents.
In chromatography, for a particular solvent, it is equal to the ratio of its molar concentration in the stationary phase to its molar concentration in the mobile phase, also approximating the ratio of the solubility of the solvent in each phase.
The term is often confused with partition coefficient or distribution coefficient. | 0 | Theoretical and Fundamental Chemistry |
The atomic mass constant can also be expressed as its energy-equivalent, mc. The 2018 CODATA recommended values are:
The megaelectronvolt mass-equivalent (MeV/c) is commonly used as a unit of mass in particle physics, and these values are also important for the practical determination of relative atomic masses. | 0 | Theoretical and Fundamental Chemistry |
Liquids can interact with two main types of solid surfaces. Traditionally, solid surfaces have been divided into high-energy and low-energy solids. The relative energy of a solid has to do with the bulk nature of the solid itself. Solids such as metals, glasses, and ceramics are known as hard solids because the chemical bonds that hold them together (e.g., covalent, ionic, or metallic) are very strong. Thus, it takes a large amount of energy to break these solids (alternatively, a large amount of energy is required to cut the bulk and make two separate surfaces), so they are termed "high-energy". Most molecular liquids achieve complete wetting with high-energy surfaces.
The other type of solid is weak molecular crystals (e.g., fluorocarbons, hydrocarbons, etc.) where the molecules are held together essentially by physical forces (e.g., van der Waals forces and hydrogen bonds). Since these solids are held together by weak forces, a very low amount of energy is required to break them, thus they are termed "low-energy". Depending on the type of liquid chosen, low-energy surfaces can permit either complete or partial wetting.
Dynamic surfaces have been reported that undergo changes in surface energy upon the application of an appropriate stimuli. For example, a surface presenting photon-driven molecular motors was shown to undergo changes in water contact angle when switched between bistable conformations of differing surface energies. | 0 | Theoretical and Fundamental Chemistry |
A reducer reduces the pipe size from a larger to a smaller bore (inner diameter). Alternatively, reducer may refer to any fitting which causes a change in pipe diameter. This change may be intended to meet hydraulic flow requirements of the system or adapt to existing piping of a different size. The reduction length is usually equal to the average of the larger and smaller pipe diameters. Although reducers are usually concentric, eccentric reducers are used as needed to maintain the top- or bottom-of-pipe level.
A reducer can also be used either as a nozzle or diffuser, depending on the mach number of the flow. | 1 | Applied and Interdisciplinary Chemistry |
The initial discovery of this family of proteins is attributed to Adler et al. (1967). First identified as E. coli mutants that could not produce a properly localized septum, resulting in the generation of minicells
due to mislocalized cell division occurring near the bacterial poles. This caused miniature vesicles to pinch off, void of essential molecular constituents permitting it to exist as a viable bacterial cell. Minicells are achromosomal cells that are products of aberrant cell division, and contain RNA and protein, but little or no chromosomal DNA. This finding led to the identification of three interacting proteins involved in a dynamic system of localizing the mid-zone of the cell for properly controlled cell division. | 1 | Applied and Interdisciplinary Chemistry |
Porous crystalline solids consist of secondary building units (SBUs) which assemble to form a periodic and porous framework. An almost infinite number of frameworks can be formed through various SBU combinations leading to unique material properties for applications in separations, storage, and heterogeneous catalysis.
Types of porous crystalline solids include zeolites, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents. MOFs are a class of porous polymeric material, consisting of metal ions linked together by organic bridging ligands and are a new development on the interface between molecular coordination chemistry and materials science.
COFs are another class of porous polymeric materials, consisting of porous, crystalline, covalent bonds that usually have rigid structures, exceptional thermal stabilities (to temperatures up to 600 °C), are stable in water and low densities. They exhibit permanent porosity with specific surface areas surpassing those of well-known zeolites and porous silicates. | 0 | Theoretical and Fundamental Chemistry |
Solid solution strengthening increases yield strength of the material by increasing the shear stress, , to move dislocations:
where c is the concentration of the solute atoms, G is the shear modulus, b is the magnitude of the Burger's vector, and is the lattice strain due to the solute. This is composed of two terms, one describing lattice distortion and the other local modulus change.
Here, the term that captures the local modulus change, a constant dependent on the solute atoms and is the lattice distortion term.
The lattice distortion term can be described as:
, where a is the lattice parameter of the material.
Meanwhile, the local modulus change is captured in the following expression:
, where G is shear modulus of the solute material. | 1 | Applied and Interdisciplinary Chemistry |
Most ceramics are extremely hard and must be wet-sawed with a circular blade embedded with diamond particles. A metallography or lapidary saw equipped with a low-density diamond blade is usually suitable. The blade must be cooled by a continuous liquid spray. | 1 | Applied and Interdisciplinary Chemistry |
Advected contours, e.g. of trace gases (such as ozone) in the stratosphere,
can be validated with satellite remote sensing instruments using a method called isoline retrieval. | 1 | Applied and Interdisciplinary Chemistry |
Paper chromatography is one method for testing the purity of compounds and identifying substances. Paper chromatography is a useful technique because it is relatively quick and requires only small quantities of material. Separations in paper chromatography involve the principle of partition. In paper chromatography, substances are distributed between a stationary phase and a mobile phase. The stationary phase is the water trapped between the cellulose fibers of the paper. The mobile phase is a developing solution that travels up the stationary phase, carrying the samples with it. Components of the sample will separate readily according to how strongly they adsorb onto the stationary phase versus how readily they dissolve in the mobile phase.
When a colored chemical sample is placed on a filter paper, the colors separate from the sample by placing one end of the paper in a solvent. The solvent diffuses up the paper, dissolving the various molecules in the sample according to the polarities of the molecules and the solvent. If the sample contains more than one color, that means it must have more than one kind of molecule. Because of the different chemical structures of each kind of molecule, the chances are very high that each molecule will have at least a slightly different polarity, giving each molecule a different solubility in the solvent. The unequal solubility causes the various color molecules to leave solution at different places as the solvent continues to move up the paper. The more soluble a molecule is, the higher it will migrate up the paper. If a chemical is very non-polar it will not dissolve at all in a very polar solvent. This is the same for a very polar chemical and a very non-polar solvent.
It is very important to note that when using water (a very polar substance) as a solvent, the more polar the color, the higher it will rise on the papers. | 0 | Theoretical and Fundamental Chemistry |
The fim switch in Escherichia coli is the mechanism by which the fim gene cluster, encoding Type I Pili, is transcriptionally controlled.
These pili are virulence factors involved in adhesion, especially important in uropathogenic Escherichia coli. The gene undergoes phase variation mediated via two recombinases and is a model example of site specific inversion. | 1 | Applied and Interdisciplinary Chemistry |
In 1997, Roberts and Szostak showed that fusions between a synthetic mRNA and its encoded myc epitope could be enriched from a pool of random sequence mRNA-polypeptide fusions by immunoprecipitation.
Nine years later, Fukuda and colleagues chose mRNA display method for in vitro evolution of single-chain Fv (scFv) antibody fragments. They selected six different scFv mutants with five consensus mutations. However, kinetic analysis of these mutants showed that their antigen-specificity remained similar to that of the wild type. However, they have demonstrated that two of the five consensus mutations were within the complementarity determining regions (CDRs). And they concluded that mRNA display has the potential for rapid artificial evolution of high-affinity diagnostic and therapeutic antibodies by optimizing their CDRs.
Roberts and coworkers have demonstrated that unnatural peptide oligomers consisting of an N-substituted amino acid can be synthesized as mRNA-polypeptide fusions. N-substituted amino acid-containing peptides have been associated with good proteolytic stability and improved pharmacokinetic properties. This work indicates that mRNA display technology has the potential for selecting drug-like peptides for therapeutic usage resistant to proteolysis. | 1 | Applied and Interdisciplinary Chemistry |
The iconography of the tympanum and archivolts of the late 13th-century portal of Strasbourg Cathedral was inspired by Alberts writings. Albert is frequently mentioned by Dante, who made his doctrine of free will the basis of his ethical system. In his Divine Comedy, Dante places Albertus with his pupil Thomas Aquinas among the great lovers of wisdom (Spiriti Sapienti') in the Heaven of the Sun.
In The Concept of Anxiety, Søren Kierkegaard wrote that Albert, "arrogantly boasted of his speculation before the deity and suddenly became stupid." Kierkegaard cites Gotthard Oswald Marbach whom he quotes as saying "Albertus repente ex asino factus philosophus et ex philosopho asinus" [Albert was suddenly transformed from an ass into a philosopher and from a philosopher into an ass].
In Mary Shelleys Frankenstein', the titular Frankenstein studies the works of Albertus Magnus.
Johann Eduard Erdmann considers Albert greater and more original than his pupil Aquinas.
In Open All Hours, Arkwright invents St Albert's day so Grandville can check customers pockets. | 1 | Applied and Interdisciplinary Chemistry |
The lower gastrointestinal tract (GI), includes the small intestine and all of the large intestine. The intestine is also called the bowel or the gut. The lower GI starts at the pyloric sphincter of the stomach and finishes at the anus. The small intestine is subdivided into the duodenum, the jejunum and the ileum. The cecum marks the division between the small and large intestine. The large intestine includes the rectum and anal canal. | 1 | Applied and Interdisciplinary Chemistry |
During the assay, a fraction of the free receptor is captured by the solid phase ligand and subsequently labeled with a fluorescent secondary molecule (Figure 1). The short contact time with the solid phase does not allow significant dissociation of the pre-formed complexes in the solution. Solution dissociation is thus “kinetically excluded” from contributing to the captured receptor and the resulting signal provides a measure of the free receptor in the solution.
Measuring the free receptor as a function of total ligand in a series of equilibrated solutions enables calculation of the equilibrium dissociation constant (K). Measuring the free receptor with several points before equilibrium enables measurement of the association rate constant (k). The off rate (k) can also be directly measured, however it is usually calculated from the measured K and measured k, (k = K * k).
Kinetic exclusion assays have been used to measure K’s in the nanomolar to femtomolar range. | 1 | Applied and Interdisciplinary Chemistry |
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