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The equation of state for an ideal or perfect gas is the ideal gas law and reads
where P is the pressure, V is the volume, n is amount of gas (in mol units), R is the universal gas constant, 8.314 J/(mol K), and T is the temperature. Written this way, it is sometimes called the "chemists version", since it emphasizes the number of molecules n'. It can also be written as
where is the specific gas constant for a particular gas, in units J/(kg K), and ρ = m/V is density. This notation is the "gas dynamicist's" version, which is more practical in modeling of gas flows involving acceleration without chemical reactions.
The ideal gas law does not make an assumption about the specific heat of a gas. In the most general case, the specific heat is a function of both temperature and pressure. If the pressure-dependence is neglected (and possibly the temperature-dependence as well) in a particular application, sometimes the gas is said to be a perfect gas, although the exact assumptions may vary depending on the author and/or field of science.
For an ideal gas, the ideal gas law applies without restrictions on the specific heat. An ideal gas is a simplified "real gas" with the assumption that the compressibility factor Z is set to 1 meaning that this pneumatic ratio remains constant. A compressibility factor of one also requires the four state variables to follow the ideal gas law.
This approximation is more suitable for applications in engineering although simpler models can be used to produce a "ball-park" range as to where the real solution should lie. An example where the "ideal gas approximation" would be suitable would be inside a combustion chamber of a jet engine. It may also be useful to keep the elementary reactions and chemical dissociations for calculating emissions. | 7 | Physical Chemistry |
Redox gradients form in water columns and their sediments. Varying levels of oxygen (oxic, suboxic, hypoxic) within the water column alter redox chemistry and which redox reactions can occur. Development of oxygen minimum zones also contributes to formation of redox gradients.
Benthic sediments exhibit redox gradients produced by variations in mineral composition, organic matter availability, structure, and sorption dynamics. Limited transport of dissolved electrons through subsurface sediments, combined with varying pore sizes of sediments creates significant heterogeneity in benthic sediments. Oxygen availability in sediments determines which microbial respiration pathways can occur, resulting in a vertical stratification of redox processes as oxygen availability decreases with depth. | 7 | Physical Chemistry |
Reactive oxygen species or ROS are species such as superoxide, hydrogen peroxide, and hydroxyl radical, commonly associated with cell damage. ROS form as a natural by-product of the normal metabolism of oxygen and have important roles in cell signaling.
Two important oxygen-centered radicals are superoxide and hydroxyl radical. They derive from molecular oxygen under reducing conditions. However, because of their reactivity, these same radicals can participate in unwanted side reactions resulting in cell damage. Excessive amounts of these radicals can lead to cell injury and death, which may contribute to many diseases such as cancer, stroke, myocardial infarction, diabetes and major disorders. Many forms of cancer are thought to be the result of reactions between radicals and DNA, potentially resulting in mutations that can adversely affect the cell cycle and potentially lead to malignancy. Some of the symptoms of aging such as atherosclerosis are also attributed to radical induced oxidation of cholesterol to 7-ketocholesterol. In addition radicals contribute to alcohol-induced liver damage, perhaps more than alcohol itself. Radicals produced by cigarette smoke are implicated in inactivation of alpha 1-antitrypsin in the lung. This process promotes the development of emphysema.
Oxybenzone has been found to form radicals in sunlight, and therefore may be associated with cell damage as well. This only occurred when it was combined with other ingredients commonly found in sunscreens, like titanium oxide and octyl methoxycinnamate.
ROS attack the polyunsaturated fatty acid, linoleic acid, to form a series of 13-hydroxyoctadecadienoic acid and 9-hydroxyoctadecadienoic acid products that serve as signaling molecules that may trigger responses that counter the tissue injury which caused their formation. ROS attacks other polyunsaturated fatty acids, e.g. arachidonic acid and docosahexaenoic acid, to produce a similar series of signaling products.
Reactive oxygen species are also used in controlled reactions involving singlet dioxygen known as type II photooxygenation reactions after Dexter energy transfer (triplet-triplet annihilation) from natural triplet dioxygen and triplet excited state of a photosensitizer. Typical chemical transformations with this singlet dioxygen species involve, among others, conversion of cellulosic biowaste into new poylmethine dyes. | 2 | Environmental Chemistry |
Since EPIC-seq contains certain computational parts after the wet-lab portion for further processing, the following steps are summarized based on the developers' steps provided in the original paper. | 1 | Biochemistry |
Under sufficient tension and positive torque, DNA is thought to undergo a phase transition with the bases splaying outwards and the phosphates moving to the middle. This proposed structure for overstretched DNA has been called P-form DNA, in honor of Linus Pauling who originally presented it as a possible structure of DNA.
Evidence from mechanical stretching of DNA in the absence of imposed torque points to a transition or transitions leading to further structures which are generally referred to as S-form DNA. These structures have not yet been definitively characterised due to the difficulty of carrying out atomic-resolution imaging in solution while under applied force although many computer simulation studies have been made (for example,).
Proposed S-DNA structures include those which preserve base-pair stacking and hydrogen bonding (GC-rich), while releasing extension by tilting, as well as structures in which partial melting of the base-stack takes place, while base-base association is nonetheless overall preserved (AT-rich).
Periodic fracture of the base-pair stack with a break occurring once per three bp (therefore one out of every three bp-bp steps) has been proposed as a regular structure which preserves planarity of the base-stacking and releases the appropriate amount of extension, with the term "Σ-DNA" introduced as a mnemonic, with the three right-facing points of the Sigma character serving as a reminder of the three grouped base pairs. The Σ form has been shown to have a sequence preference for GNC motifs which are believed under the GNC hypothesis to be of evolutionary importance. | 4 | Stereochemistry |
From 1996 to 2004, researchers in the European Project for Ice Coring in Antarctica (EPICA) project were able to drill and analyze gases trapped in the ice cores in Antarctica to reconstruct GHG concentrations in the atmosphere over the past 800,000 years". They found that prior to approximately 900,000 years ago, the cycle of ice ages followed by relatively short warm periods lasted about 40,000 years, but by 800,000 years ago the time interval changed dramatically to cycles that lasted 100,000 years. There were low values of GHG in ice ages, and high values during the warm periods.
This 2016 EPA illustration above is a compilation of paleoclimatology showing methane concentrations over time based on analysis of gas bubbles from EPICA Dome C, Antarcticaapproximately 797,446 BCE to 1937 CE, Law Dome, Antarcticaapproximately 1008 CE to 1980 CE Cape Grim, Australia1985 CE to 2015 CE Mauna Loa, Hawaii1984 CE to 2015 CE and Shetland Islands, Scotland: 1993 CE to 2001 CE
The massive and rapid release of large volumes of methane gas from such sediments into the atmosphere has been suggested as a possible cause for rapid global warming events in the Earth's distant past, such as the Paleocene–Eocene Thermal Maximum, and the Great Dying.
In 2001, NASAs Goddard Institute for Space Studies and Columbia Universitys Center for Climate Systems Research scientists confirmed that other greenhouse gases apart from carbon dioxide were important factors in climate change in research presented at the annual meeting of the American Geophysical Union (AGU). They offered a theory on the 100,000-year long Paleocene–Eocene Thermal Maximum that occurred approximately 55 million years ago. They posited that there was a vast release of methane that had previously been kept stable through "cold temperatures and high pressure...beneath the ocean floor". This methane release into the atmosphere resulted in the warming of the earth. A 2009 journal article in Science, confirmed NASA research that the contribution of methane to global warming had previously been underestimated.
Early in the Earths history carbon dioxide and methane likely produced a greenhouse effect. The carbon dioxide would have been produced by volcanoes and the methane by early microbes. During this time, Earths earliest life appeared. According to a 2003 article in the journal Geology, these first, ancient bacteria added to the methane concentration by converting hydrogen and carbon dioxide into methane and water. Oxygen did not become a major part of the atmosphere until photosynthetic organisms evolved later in Earth's history. With no oxygen, methane stayed in the atmosphere longer and at higher concentrations than it does today. | 2 | Environmental Chemistry |
Rust is a commonly used metaphor for slow decay due to neglect, since it gradually converts robust iron and steel metal into a soft crumbling powder. A wide section of the industrialized American Midwest and American Northeast, once dominated by steel foundries, the automotive industry, and other manufacturers, has experienced harsh economic cutbacks that have caused the region to be dubbed the "Rust Belt".
In music, literature, and art, rust is associated with images of faded glory, neglect, decay, and ruin. | 8 | Metallurgy |
Several reuptake inhibitors of VMATs are known to exist, including reserpine (RES), tetrabenazine (TBZ), dihydrotetrabenazine (DTBZOH), and ketanserin (KET). It is thought that RES exhibits competitive inhibition, binding to the same site as the monoamine substrate, as studies have shown that it can be displaced via introduction of norepinephrine. TBZ, DTBZOH, and KET are thought to exhibit non-competitive inhibition, instead binding to allosteric sites and decreasing the activity of the VMAT rather than simply blocking its substrate binding site. It has been found that these inhibitors are less effective at inhibiting VMAT1 than VMAT2, and the inhibitory effects of the tetrabenazines on VMAT1 is negligible. | 1 | Biochemistry |
The deuteron wavefunction must be antisymmetric if the isospin representation is used (since a proton and a neutron are not identical particles, the wavefunction
need not be antisymmetric in general). Apart from their isospin, the two nucleons also have spin and spatial distributions of their wavefunction. The latter is symmetric if the deuteron is symmetric under parity (i.e. have an "even" or "positive" parity), and antisymmetric if the deuteron is antisymmetric under parity (i.e. have an "odd" or "negative" parity). The parity is fully determined by the total orbital angular momentum of the two nucleons: if it is even then the parity is even (positive), and if it is odd then the parity is odd (negative).
The deuteron, being an isospin singlet, is antisymmetric under nucleons exchange due to isospin, and therefore must be symmetric under the double exchange of their spin and location. Therefore, it can be in either of the following two different states:
*Symmetric spin and symmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (−1) from isospin exchange, (+1) from spin exchange and (+1) from parity (location exchange), for a total of (−1) as needed for antisymmetry.
*Antisymmetric spin and antisymmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (−1) from isospin exchange, (−1) from spin exchange and (−1) from parity (location exchange), again for a total of (−1) as needed for antisymmetry.
In the first case the deuteron is a spin triplet, so that its total spin s is 1. It also has an even parity and therefore even orbital angular momentum l ; The lower its orbital angular momentum, the lower its energy. Therefore, the lowest possible energy state has , .
In the second case the deuteron is a spin singlet, so that its total spin s is 0. It also has an odd parity and therefore odd orbital angular momentum l. Therefore, the lowest possible energy state has , .
Since gives a stronger nuclear attraction, the deuterium ground state is in the , state.
The same considerations lead to the possible states of an isospin triplet having , or , . Thus the state of lowest energy has , , higher than that of the isospin singlet.
The analysis just given is in fact only approximate, both because isospin is not an exact symmetry, and more importantly because the strong nuclear interaction between the two nucleons is related to angular momentum in spin–orbit interaction that mixes different s and l states. That is, s and l are not constant in time (they do not commute with the Hamiltonian), and over time a state such as , may become a state of , . Parity is still constant in time so these do not mix with odd l states (such as , ). Therefore, the quantum state of the deuterium is a superposition (a linear combination) of the , state and the , state, even though the first component is much bigger. Since the total angular momentum j is also a good quantum number (it is a constant in time), both components must have the same j, and therefore . This is the total spin of the deuterium nucleus.
To summarize, the deuterium nucleus is antisymmetric in terms of isospin, and has spin 1 and even (+1) parity. The relative angular momentum of its nucleons l is not well defined, and the deuteron is a superposition of mostly with some . | 9 | Geochemistry |
Nanofluidic circuitry is a nanotechnology aiming for control of fluids in nanometer scale. Due to the effect of an electrical double layer within the fluid channel, the behavior of nanofluid is observed to be significantly different compared with its microfluidic counterparts. Its typical characteristic dimensions fall within the range of 1–100 nm. At least one dimension of the structure is in nanoscopic scale. Phenomena of fluids in nano-scale structure are discovered to be of different properties in electrochemistry and fluid dynamics. | 7 | Physical Chemistry |
Since very little is known about the surface Gibbs energy of transition metal oxides, polarity of the surface and the degree of coordinative unsaturation of a surface cation are used to compare the stabilities of different surface structures. Also, defect sites can have a huge impact on the surface stability. | 7 | Physical Chemistry |
In practical sense, the most important reaction of metal acyls is their detachment by reductive elimination of aldehydes from acyl metal hydrides:
:LMC(O)R(H) → LM + RCHO
This reaction is the final step of hydroformylation.
Another important reaction is decarbonylation. This reaction requires that the acyl complex be coordinatively unsaturated:
:LMC(O)R → LM(CO)R + L
:LMC(O)R → LM(CO)R
The oxygen center of acyl ligands is basic. This aspect is manifested in O-alkylations, which converts acyl complexes to alkoxycarbene complexes: | 0 | Organic Chemistry |
With an FFT based spectrum analyzer, the frequency resolution is , the inverse of the time T over which the waveform is measured and Fourier transformed.
With Fourier transform analysis in a digital spectrum analyzer, it is necessary to sample the input signal with a sampling frequency that is at least twice the bandwidth of the signal, due to the Nyquist limit. A Fourier transform will then produce a spectrum containing all frequencies from zero to . This can place considerable demands on the required analog-to-digital converter and processing power for the Fourier transform, making FFT based spectrum analyzers limited in frequency range. | 7 | Physical Chemistry |
Space groups in 2 dimensions are the 17 wallpaper groups which have been known for several centuries, though the proof that the list was complete was only given in 1891, after the much more difficult classification of space groups had largely been completed.
In 1879 the German mathematician Leonhard Sohncke listed the 65 space groups (called Sohncke groups) whose elements preserve the chirality. More accurately, he listed 66 groups, but both the Russian mathematician and crystallographer Evgraf Fedorov and the German mathematician Arthur Moritz Schoenflies noticed that two of them were really the same. The space groups in three dimensions were first enumerated in 1891 by Fedorov (whose list had two omissions (I3d and Fdd2) and one duplication (Fmm2)), and shortly afterwards in 1891 were independently enumerated by Schönflies (whose list had four omissions (I3d, Pc, Cc, ?) and one duplication (P2m)). The correct list of 230 space groups was found by 1892 during correspondence between Fedorov and Schönflies. later enumerated the groups with a different method, but omitted four groups (Fdd2, I2d, P2d, and P2c) even though he already had the correct list of 230 groups from Fedorov and Schönflies; the common claim that Barlow was unaware of their work is incorrect. describes the history of the discovery of the space groups in detail. | 4 | Stereochemistry |
The Rare Earths Facility was a production plant for various chemicals and metals including thorium, uranium, and radium. It was located in West Chicago, Illinois, USA. | 8 | Metallurgy |
Lysophosphatidylserine is a lysophospholipid which triggers TLR 2.
A recent study showed that it does not stimulate normal leukocytes. It also enhances glucose transport, lowering blood glucose levels while leaving secretion of insulin unaffected. | 1 | Biochemistry |
FET framework was proposed to simplify classifications of psychiatric disorders (DSM, ICD) using 12 functional aspects of behaviour that this model highlights. Clinical studies showed good differential power of the FET framework for various diagnoses of psychopathology. For example, depressed people had low endurance and psychomotor slowdown in their temperament profiles. In contrast to them, patients with Generalized Anxiety Disorder had higher impulsivity and neuroticism. FET-developers suggested that every symptom in DSM/ICD diagnoses can be mapped into a specific FET code reflecting a disregulation within well-documented neurochemical systems. | 1 | Biochemistry |
Compatibility is a term used by geochemists to describe how elements partition themselves in the solid and melt within Earth's mantle. In geochemistry, compatibility is a measure of how readily a particular trace element substitutes for a major element within a mineral.
Compatibility of an ion is controlled by two things: its valence and its ionic radius. Both must approximate those of the major element for the trace element to be compatible in the mineral. For instance, olivine (an abundant mineral in the upper mantle) has the chemical formula . Nickel, with very similar chemical behaviour to iron and magnesium, substitutes readily for them and hence is very compatible in the mantle.
Compatibility controls the partitioning of different elements during melting. The compatibility of an element in a rock is a weighted average of its compatibility in each of the minerals present. By contrast, an incompatible element is one that is least stable within its crystal structure. If an element is incompatible in a rock, it partitions into a melt as soon as melting begins. In general, when an element is referred to as being “compatible” without mentioning what rock it is compatible in, the mantle is implied. Thus incompatible elements are those that are enriched in the continental crust and depleted in the mantle. Examples include: rubidium, barium, uranium, and lanthanum. Compatible elements are depleted in the crust and enriched in the mantle, with examples nickel and titanium.
Compatibility is commonly described by an elements distribution coefficient. A distribution coefficient describes how the solid and liquid phases of an element will distribute themselves in a mineral. Current studies of Earths rare trace elements seek to quantify and examine the chemical composition of elements in the Earths crust. There are still uncertainties in the understanding of the lower crust and upper mantle region of Earths interior. In addition, numerous studies have focused on looking at the partition coefficients of certain elements in the basaltic magma to characterize the composition of oceanic crust. By having a way to measure the composition of elements in the crust and mantle given a mineral sample, compatibility allows relative concentrations of a particular trace element to be determined. From a petrological point of view, the understanding of how major and rare trace elements differentiate in the melt provides deeper understanding of Earth's chemical evolution over the geologic time scale. | 9 | Geochemistry |
Sulfur assimilation is the process by which living organisms incorporate sulfur into their biological molecules. In plants, sulfate is absorbed by the roots and then be transported to the chloroplasts by the transipration stream where the sulfur are reduced to sulfide with the help of a series of enzymatic reactions. Furthermore, the reduced sulfur is incorporated into cysteine, an amino acid that is a precursor to many other sulfur-containing compounds. In animals, sulfur assimilation occurs primarily through the diet, as animals cannot produce sulfur-containing compounds directly. Sulfur is incorporated into amino acids such as cysteine and methionine, which are used to build proteins and other important molecules. | 1 | Biochemistry |
The primary advantage to hyperspectral imaging is that, because an entire spectrum is acquired at each point, the operator needs no prior knowledge of the sample, and postprocessing allows all available information from the dataset to be mined. Hyperspectral imaging can also take advantage of the spatial relationships among the different spectra in a neighbourhood, allowing more elaborate spectral-spatial models for a more accurate segmentation and classification of the image.
The primary disadvantages are cost and complexity. Fast computers, sensitive detectors, and large data storage capacities are needed for analyzing hyperspectral data. Significant data storage capacity is necessary since uncompressed hyperspectral cubes are large, multidimensional datasets, potentially exceeding hundreds of megabytes. All of these factors greatly increase the cost of acquiring and processing hyperspectral data. Also, one of the hurdles researchers have had to face is finding ways to program hyperspectral satellites to sort through data on their own and transmit only the most important images, as both transmission and storage of that much data could prove difficult and costly. As a relatively new analytical technique, the full potential of hyperspectral imaging has not yet been realized. | 7 | Physical Chemistry |
The genetic instructions of every replicating cell in a living organism are contained within its DNA. Throughout the cell's lifetime, this information is transcribed and replicated by cellular mechanisms to produce proteins or to provide instructions for daughter cells during cell division, and the possibility exists that the DNA may be altered during these processes. This is known as a mutation. At the molecular level, there are regulatory systems that correct most — but not all — of these changes to the DNA before it is replicated.
The functionality of a protein is highly dependent on its structure. Changing a single amino acid in a protein may reduce its ability to carry out this function, or the mutation may even change the function that the protein carries out. Changes like these may severely impact a crucial function in a cell, potentially causing the cell — and in extreme cases, the organism — to die. Conversely, the change may allow the cell to continue functioning albeit differently, and the mutation can be passed on to the organism's offspring. If this change does not result in any significant physical disadvantage to the offspring, the possibility exists that this mutation will persist within the population. The possibility also exists that the change in function becomes advantageous.
The 20 amino acids translated by the genetic code vary greatly by the physical and chemical properties of their side chains. However, these amino acids can be categorised into groups with similar physicochemical properties. Substituting an amino acid with another from the same category is more likely to have a smaller impact on the structure and function of a protein than replacement with an amino acid from a different category.
Sequence alignment is a fundamental research method for modern biology. The most common sequence alignment for protein is to look for similarity between different sequences in order to infer function or establish evolutionary relationships. This helps researchers better understand the origin and function of genes through the nature of homology and conservation. Substitution matrices are utilized in algorithms to calculate the similarity of different sequences of proteins; however, the utility of Dayhoff PAM Matrix has decreased over time due to the requirement of sequences with a similarity more than 85%. In order to fill in this gap, Henikoff and Henikoff introduced BLOSUM (BLOcks SUbstitution Matrix) matrix which led to marked improvements in alignments and in searches using queries from each of the groups of related proteins. | 1 | Biochemistry |
The typical process for creating ICCs in the lab involves ionisation of an elemental source, followed by confinement in an ion trap, where they are imaged via their fluorescence. Changing parameters such as the axial or radial confining potentials may lead to different observed geometries of the crystal, even if the number of ions does not change.
For measurements involving highly charged ions, these are typically observed as "dark" areas in the fluorescence of the Coulomb crystal, due to their different energy levels. This effect is also noticeable when ions in the Coulomb crystal appear to disappear, without changing the structure of the crystal, due to mixing with impurities in a non-ideal vacuum.
Heating effects are also important in the characterisation of Coulomb crystals, since thermal motion can cause the image to blur. This may be stimulated by the cooling laser being slightly off-resonance, and so needs to be carefully monitored. | 7 | Physical Chemistry |
In physical chemistry, Henrys law is a gas law that states that the amount of dissolved gas in a liquid is directly proportional to its partial pressure above the liquid. The proportionality factor is called Henrys law constant. It was formulated by the English chemist William Henry, who studied the topic in the early 19th century.
In simple words, we can say that the partial pressure of a gas in vapour phase is directly proportional to the mole fraction of a gas in solution.
An example where Henrys law is at play is the depth-dependent dissolution of oxygen and nitrogen in the blood of underwater divers that changes during decompression, going to decompression sickness. An everyday example is given by ones experience with carbonated soft drinks, which contain dissolved carbon dioxide. Before opening, the gas above the drink in its container is almost pure carbon dioxide, at a pressure higher than atmospheric pressure. After the bottle is opened, this gas escapes, moving the partial pressure of carbon dioxide above the liquid to be much lower, resulting in degassing as the dissolved carbon dioxide comes out of the solution. | 7 | Physical Chemistry |
Next, as a cleansing against different sequencing depths from different runs and other factors that can hinder the fragment length distribution sanity, Bayesian normalization via the Dirichlet-multinomial model should be done. Per every sample, based on the fragment lengths observed in that sample, a multinomial maximum likelihood estimation-based fragment length distribution is generated. Two intervals of 250 base pair length are used, located between -1000th base pair and -750th base pair, and between 750th base pair and 1000th base pair locations to the centre of TSS. This is done due to the prevention of the impact of gene expression on the generated distribution, as the selected intervals are relatively far away from TSS. Then, the fragment length densities from that distribution are sampled for each 201-fragment size and used as a parameter for Dirichlet distribution generation.
The initial parameter for Dirichlet distribution is set to 20. From the obtained Dirichlet distribution, 2000 fragments are sampled, and Shannon's entropy is calculated for those. The Shannon entropies are subsequently compared with the Shannon entropy values of five randomly selected background sets ( where ). | 1 | Biochemistry |
The Memorial Lecture Award was established in the year 1979 in the honour of Professor Kotcherlakota Rangadhama Rao by the students of Prof. K.Rangadhama Rao and Indian National Science Academy, formerly National Institute of Sciences of India, Calcutta. The lecture is awarded for outstanding contributions in the field of Spectroscopy. The award carries an honorarium of Rs. 25,000/- and a citation.
The below lists the recipients of the Memorial Award since its inception in the year 1979. | 7 | Physical Chemistry |
For MLL, two isomers exist. These isomers of MLL are cis, if the L ligands are mutually adjacent, and trans, if the L groups are situated 180° to each other. It was the analysis of such complexes that led Alfred Werner to the 1913 Nobel Prize–winning postulation of octahedral complexes. | 4 | Stereochemistry |
Pierre Sinaÿ's scientific work focuses on the chemistry of carbohydrates and the understanding of the role of oligosaccharides in the living world. In the mid-1970s, Pierre Sinaÿ discovered and developed an effective method for oligosaccharide synthesis known as imidate glycosylation. This, by now allowing access to increasingly complex carbohydrate structures, is not unrelated to the development of glycobiology, the aim of which is to decode the meaning of this third alphabet of saccharides, which is in addition to that of proteins and nucleic acids. He synthesized the antigenic determinants of substances in human blood groups and then synthesized a complexly structured pentasaccharide representing the active site of heparin responsible for its antithrombotic effect. This last achievement demonstrates for the first time, without any ambiguity, the molecular basis of such an activity, commonly used in hospital medicine. This breakthrough in glyco-chemistry has led to the concept of conformational flexibility, which is crucial in heparinology. First materialized by the use of nuclear magnetic resonance, this concept was studied in detail using the chemical synthesis of constrained sugars adopting unconventional conformations. Pierre Sinaÿ has also discovered and developed a whole series of conceptually new reactions. Selective examples include the synthesis of spiroorthoesters by using selenium chemistry, the development of organometallic chemistry of anomeric carbon, the pioneering synthesis of C-disaccharides, electrochemical glycosylation and, more recently, a novel functionalization of cyclodextrins through a kind of molecular microsurgery in which aluminium derivatives are said to be the scalpel. For the first time, the existence of the glycosyl cation, an intermediate conventionally postulated during glycosylation reactions, could be formally demonstrated through chemistry in a superacid environment. A 4-volume book covers many aspects of carbohydrate chemistry and biology. | 0 | Organic Chemistry |
The term total analysis system (TAS) describes a device that automates and includes all of the necessary steps for the chemical analysis of a sample (e.g. sampling, sample transport, filtration, dilution, chemical reactions, separation, and detection). Most of the current total analysis systems are "micro" total analysis systems that utilize the principles of microfluidics.
Total analysis systems shrink a whole laboratory to a chip-sized lab-on-a-chip and due to its extremely small size, can be placed close to a sampling site. It can be cost-effective taking into account chip technologies, sample sizes, and analysis time. It also reduces the exposure of lab personnel to toxic chemicals, which is an advantage compared to conventional techniques. This technology can be used in point-of-care testing or point-of-use diagnostics which do not require skilled technicians. During pandemics this can save the lives of medical providers. | 3 | Analytical Chemistry |
Selenenic acids derived from selenocysteine are involved in cell signaling and certain enzymatic processes. The best known selenoenzyme, glutathione peroxidase (GPx), catalyzes the reduction of peroxides by glutathione (GSH). The selenenic acid intermediate (E-SeOH) is formed upon oxidation of the catalytically active selenol (E-SeH) by hydrogen peroxide. This selenenic acid derivative of the peroxidase then reacts with a thiol-containing cofactor (GSH) to generate the key intermediate selenenyl sulfide (E-SeSG). This intermediate is subsequently attacked by a second GSH to regenerate the selenol and the glutathione cofactor is released in its oxidized form, GSSG. The catalytic mechanism of GPx, involves selenol (R-SeH), selenenyl sulfide (R1-SeS-R2), and selenenic acid intermediates.
:RSeH + HO → RSeOH + HO
:RSeOH + GSH → GS-SeR + HO
:GS-SeR + GSH → GS-SG + RSeH
In the absence of thiols, selenols tend to overoxidize to produce seleninic acids. Many organoselenium compounds (selenenamides, diaryl diselenides) contain "interesting" biological activities. Their activity is attributed to their mimicry of glutathione peroxidase activity. They reduce hydroperoxides that otherwise convert to toxic byproducts and/or reactive oxygen species that can cause further damage to the cell. | 0 | Organic Chemistry |
Collagen: Collagen is the primary structure of vertebrates and is the most abundant protein in mammals. Because of this, collagen is one of the most easily attainable biopolymers, and used for many research purposes. Because of its mechanical structure, collagen has high tensile strength and is a non-toxic, easily absorbable, biodegradable, and biocompatible material. Therefore, it has been used for many medical applications such as in treatment for tissue infection, drug delivery systems, and gene therapy.
Silk fibroin: Silk Fibroin (SF) is another protein rich biopolymer that can be obtained from different silkworm species, such as the mulberry worm Bombyx mori. In contrast to collagen, SF has a lower tensile strength but has strong adhesive properties due to its insoluble and fibrous protein composition. In recent studies, silk fibroin has been found to possess anticoagulation properties and platelet adhesion. Silk fibroin has been additionally found to support stem cell proliferation in vitro.
Gelatin: Gelatin is obtained from type I collagen consisting of cysteine, and produced by the partial hydrolysis of collagen from bones, tissues and skin of animals. There are two types of gelatin, Type A and Type B. Type A collagen is derived by acid hydrolysis of collagen and has 18.5% nitrogen. Type B is derived by alkaline hydrolysis containing 18% nitrogen and no amide groups. Elevated temperatures cause the gelatin to melts and exists as coils, whereas lower temperatures result in coil to helix transformation. Gelatin contains many functional groups like NH2, SH, and COOH which allow for gelatin to be modified using nanoparticles and biomolecules. Gelatin is an Extracellular Matrix protein which allows it to be applied for applications such as wound dressings, drug delivery and gene transfection.
Starch: Starch is an inexpensive biodegradable biopolymer and copious in supply. Nanofibers and microfibers can be added to the polymer matrix to increase the mechanical properties of starch improving elasticity and strength. Without the fibers, starch has poor mechanical properties due to its sensitivity to moisture. Starch being biodegradable and renewable is used for many applications including plastics and pharmaceutical tablets.
Cellulose: Cellulose is very structured with stacked chains that result in stability and strength. The strength and stability comes from the straighter shape of cellulose caused by glucose monomers joined together by glycogen bonds. The straight shape allows the molecules to pack closely. Cellulose is very common in application due to its abundant supply, its biocompatibility, and is environmentally friendly. Cellulose is used vastly in the form of nano-fibrils called nano-cellulose. Nano-cellulose presented at low concentrations produces a transparent gel material. This material can be used for biodegradable, homogeneous, dense films that are very useful in the biomedical field.
Alginate: Alginate is the most copious marine natural polymer derived from brown seaweed. Alginate biopolymer applications range from packaging, textile and food industry to biomedical and chemical engineering. The first ever application of alginate was in the form of wound dressing, where its gel-like and absorbent properties were discovered. When applied to wounds, alginate produces a protective gel layer that is optimal for healing and tissue regeneration, and keeps a stable temperature environment. Additionally, there have been developments with alginate as a drug delivery medium, as drug release rate can easily be manipulated due to a variety of alginate densities and fibrous composition. | 1 | Biochemistry |
Modulation of purine metabolism has pharmacotherapeutic value.
Purine synthesis inhibitors inhibit the proliferation of cells, especially leukocytes. These inhibitors include azathioprine, an immunosuppressant used in organ transplantation, autoimmune disease such as rheumatoid arthritis or inflammatory bowel disease such as Crohn's disease and ulcerative colitis.
Mycophenolate mofetil is an immunosuppressant drug used to prevent rejection in organ transplantation; it inhibits purine synthesis by blocking inosine monophosphate dehydrogenase (IMPDH).
Methotrexate also indirectly inhibits purine synthesis by blocking the metabolism of folic acid (it is an inhibitor of the dihydrofolate reductase).
Allopurinol is a drug that inhibits the enzyme xanthine oxidoreductase and, thus, lowers the level of uric acid in the body. This may be useful in the treatment of gout, which is a disease caused by excess uric acid, forming crystals in joints. | 1 | Biochemistry |
Chlorprothixene may increase the plasma-level of concomitantly given lithium. In order to avoid lithium intoxication, lithium plasma levels should be monitored closely.
If chlorprothixene is given concomitantly with opioids, the opioid dose should be reduced (by approx. 50%), because chlorprothixene amplifies the therapeutic actions and side effects of opioids considerably.
Avoid the concomitant use of chlorprothixene and tramadol (Ultram). Seizures may be encountered with this combination.
Consider additive sedative effects and confusional states to emerge, if chlorprothixene is given with benzodiazepines or barbiturates. Choose particular low doses of these drugs.
Exert particular caution in combining chlorprothixene with other anticholinergic drugs (tricyclic antidepressants and antiparkinsonian agents): Particularly the elderly may develop delirium, high fever, severe obstipation, even ileus and glaucoma . | 4 | Stereochemistry |
The radial distribution function is an important measure because several key thermodynamic properties, such as potential energy and pressure can be calculated from it.
For a 3-D system where particles interact via pairwise potentials, the potential energy of the system can be calculated as follows:
Where N is the number of particles in the system, is the number density, is the pair potential.
The pressure of the system can also be calculated by relating the 2nd virial coefficient to . The pressure can be calculated as follows:
Note that the results of potential energy and pressure will not be as accurate as directly calculating these properties because of the averaging involved with the calculation of . | 7 | Physical Chemistry |
Supplementation with vitamin D is a reliable method for preventing or treating rickets. On the other hand, the effects of vitamin D supplementation on non-skeletal health are uncertain. A review did not find any effect from supplementation on the rates of non-skeletal disease, other than a tentative decrease in mortality in the elderly. Vitamin D supplements do not alter the outcomes for myocardial infarction, stroke or cerebrovascular disease, cancer, bone fractures or knee osteoarthritis.
A US Institute of Medicine (IOM) report states: "Outcomes related to cancer, cardiovascular disease and hypertension, and diabetes and metabolic syndrome, falls and physical performance, immune functioning and autoimmune disorders, infections, neuropsychological functioning, and preeclampsia could not be linked reliably with intake of either calcium or vitamin D, and were often conflicting." Some researchers claim the IOM was too definitive in its recommendations and made a mathematical mistake when calculating the blood level of vitamin D associated with bone health. Members of the IOM panel maintain that they used a "standard procedure for dietary recommendations" and that the report is solidly based on the data. | 1 | Biochemistry |
Examination of this reaction's mechanism suggests that the formation of the silonate is all that is needed to activate addition of the organosilane to the palladium center. The presence of a pentavalent silicon is not needed and kinetic analysis has shown that this reaction has first order dependence on silonate concentration. This is due to the key bond being formed, the Pd-O bond during the transmetalation step, that then allows for transfer of the carbon fragment onto the palladium center. Based on this observation, it seems that the rate limiting step in this catalytic cycle is the Pd-O bond formation, in which increased silonate concentrations increase the rate of this reaction (indicative of faster reactions). | 0 | Organic Chemistry |
Enantiomers of chiral compounds have similar chemical and physical properties, but can be metabolized by the body differently. This was looked at in bowhead whales (Balaena mysticetus) for two main reasons: they are large animals with slow metabolisms (meaning PCBs will accumulate in fatty tissue) and few studies have measured chiral PCBs in cetaceans. They found that the average PCB concentrations in the blubber were approximately four times higher than the liver; however, this result is most likely age- and sex-dependent. As reproductively active females transferred PCBs and other poisonous substances to the fetus, the PCB concentrations in the blubber were significantly lower than males of the same body length (less than 13 meters). | 2 | Environmental Chemistry |
Some caries excavation methods lead to leaving caries-affected dentin behind to serve as the bonding substrate, mostly in indirect pulp capping.
It is reported that the immediate bond strengths to caries-affected dentin are 20-50% lower than to sound dentin, and even lower with caries-infected dentin. How does caries progression correlates with this? First, it reduces mineral content, increases porosity and changes the dentinal collagen structure and its distribution too. These changes can cause a significant reduction in the mechanical properties in dentin e.g. hardness, stiffness, tensile strength, modulus of elasticity, and shrinkage during drying, which makes dentin in and under hybrid layer more prone to cohesive failures under occlusal forces.
Lower mineral content of the caries-affected dentin will allow phosphoric acid or acidic monomers to demineralize matrix more deeply than in normal dentin, which results in even more residual water in exposed collagen matrix. | 7 | Physical Chemistry |
After a sufficiently large time frame to allow hybridization, the array is illuminated with fluorescent light. Those probes on the array that are hybridized to one of the labeled fragments emit a light signal that is captured by a camera. This image contains all raw data for the remaining part of the workflow.
This raw data, encoded as false-color image, needs to be converted to numerical values before the actual analysis can be done. The analysis and information extraction of the raw data often remains the most challenging part for ChIP-on-chip experiments. Problems arise throughout this portion of the workflow, ranging from the initial chip read-out, to suitable methods to subtract background noise, and finally to appropriate algorithms that normalize the data and make it available for subsequent statistical analysis, which then hopefully lead to a better understanding of the biological question that the experiment seeks to address. Furthermore, due to the different array platforms and lack of standardization between them, data storage and exchange is a huge problem. Generally speaking, the data analysis can be divided into three major steps:
During the first step, the captured fluorescence signals from the array are normalized, using control signals derived from the same or a second chip. Such control signals tell which probes on the array were hybridized correctly and which bound nonspecifically.
In the second step, numerical and statistical tests are applied to control data and IP fraction data to identify POI-enriched regions along the genome. The following three methods are used widely: median percentile rank, single-array error, and sliding-window. These methods generally differ in how low-intensity signals are handled, how much background noise is accepted, and which trait for the data is emphasized during the computation. In the recent past, the sliding-window approach seems to be favored and is often described as most powerful.
In the third step, these regions are analyzed further. If, for example, the POI was a transcription factor, such regions would represent its binding sites. Subsequent analysis then may want to infer nucleotide motifs and other patterns to allow functional annotation of the genome. | 1 | Biochemistry |
Aside from sharing the same absolute stereochemistry as leptomycin B, callystatin A was discovered to have similar biological activity with leptomycin B as well. The anti-tumor activity of leptomycin B and callystatin A arises because many NES-cargo molecules blocked by these antibiotics are those involved in the cellular processes of proliferation, differentiation, and development, learning and memory, and hormone action. These molecules include regulatory proteins such as Rev, MAPK/MEK1, c-Abl, Cyclin B1, MDM2/p53, IkB, MPF, and PKA.
The most important role of leptomycin B is its inhibitory effect on the NES-dependent nuclear export mechanism, leading to the cell cycle arrest during G1 and G2 phases in eukaryotic cells. In wild-type cells, macromolecules in the nucleus with the leucine-rich nuclear export signal (NES) can be transported to the cytoplasm by binding to a karyopherin protein called chromosome region maintenance 1 (CRM1)/exportin 1. This CRM1/exportin1/NES-cargo interaction is stabilized by Ran-GTP binding which forms a complex that can transport the cargo to the cytoplasm. There, the cargo will be released when the Ran-GTP protein is hydrolyzed by a cytoplasmic Ran-GTPase enzyme to form Ran-GDP. This step completes the transport process and CRM1/exportin1 reenters the nucleus for more cargo binding. Leptomycin B and callystatin A inhibit the action of CRM1/exportin1 by a likely Michael-type addition of the thiol group from a cysteine residue of CRM1/exportin1 to form a covalent bond. This interaction prevents CRM1/exportin1 from recognizing and binding the NES of the cargo molecules because it occurs within the same binding site. Thus, macromolecules intended to be transported out of the nucleus will accumulate there instead. | 0 | Organic Chemistry |
Spectrometer can determine chemical composition through its measure of spectrums. The common spectrometer used in analytical chemistry is Mass spectrometry. In a mass spectrometer, a small amount of sample is ionized and converted to gaseous ions, where they are separated and analyzed according to their mass-to-charge ratios.
NMR Spectroscopy involves exciting a NMR-active sample and then measuring the effects of this magnetic excitation. From this, the bonds present in a sample can be determined. | 3 | Analytical Chemistry |
The above equations of state suggest methods to experimentally measure changes in the thermodynamic potentials using physically measurable parameters. For example the free energy expressions
and
can be integrated at constant temperature and quantities to obtain:
can be integrated:
:<math>
\Delta H = \int_{S1}^{S2}T\,\mathrm{d}S = \Delta Q\,\,\,\,
:<math>
\Delta U = \int_{S1}^{S2}T\,\mathrm{d}S = \Delta Q\,\,\,\,
Note that these measurements are made at constant {N } and are therefore not applicable to situations in which chemical reactions take place. | 7 | Physical Chemistry |
On the evening of March 12, 2018, both Negishi and his wife were reported missing by family members. Police determined that, based on a purchase made earlier in the day, the couple had left their home in West Lafayette, Indiana, and headed north. At about 5 a.m. the next day, officers in Ogle County, Illinois, received a call to check on the welfare of an elderly man who was walking on a rural road south of Rockford. When he was taken to hospital, officers identified him as Negishi and found that police in Indiana were looking for him and his wife. A short time later, Suzukis body was found at the Orchard Hills Landfill in Davis Junction, along with the couples car.
According to a statement from the family, the couple was driving to Rockford International Airport for a trip when their car became stuck in a ditch on a road near the landfill. Negishi went looking for help and was said to be suffering from an "acute state of confusion and shock". The Ogle County Sheriff Department said there was no suspicion of foul play in Suzukis death, although the cause of her death was not immediately released. The family said Suzuki was near the end of her battle with Parkinsons disease.
In May 2018, an autopsy concluded that Suzuki died from hypothermia, but Parkinson's disease and hypertension were contributing factors. | 0 | Organic Chemistry |
To obtain the effect, it is necessary to achieve a phase separation, one of these phases works as the trigger for the temporary form, using a transition temperature that can be Tm or Tg and in this effect is called T. A second phase has the higher transition temperature and above this temperature the polymer melts and is processed by conventional methods.
The ratio of the elements forming the phase separation largely regulates the T transition temperature; this is much easier to control than in metallic alloys.
An example of this is the poly(ethylene oxide-ethylene terephthalate) or EOET copolymer. The polyethylene terephthalate (PET) segment has a relatively high Tg and its Tm is commonly referred to as the "hard" segment, whereas polyethylene ethylene oxide (PEO), has a relatively low Tm and Tg and is referred to as the "soft" segment. In the final polymer these segments separate into two phases in the solid state. PET has a high degree of crystallinity and the formation of these crystals provides for the flow and rearrangement of the PEO chains as they are stretched at temperatures higher than their Tm. | 7 | Physical Chemistry |
Water can be split into its constituent elements, hydrogen, and oxygen, by passing an electric current through it. This process is called electrolysis. The cathode half reaction is:
The anode half reaction is:
The gases produced bubble to the surface, where they can be collected or ignited with a flame above the water if this was the intention. The required potential for the electrolysis of pure water is 1.23 V at 25 °C. The operating potential is actually 1.48 V or higher in practical electrolysis. | 2 | Environmental Chemistry |
In his 1884 dissertation, Svante Arrhenius put forth his explanation of solid crystalline salts disassociating into paired charged particles when dissolved, for which he won the 1903 Nobel Prize in Chemistry. Arrheniuss explanation was that in forming a solution, the salt dissociates into charged particles, to which Michael Faraday (1791-1867) had given the name "ions" many years earlier. Faradays belief had been that ions were produced in the process of electrolysis. Arrhenius proposed that, even in the absence of an electric current, solutions of salts contained ions. He thus proposed that chemical reactions in solution were reactions between ions.
Shortly after Arrhenius's hypothesis of ions, Franz Hofmeister and Siegmund Lewith found that different ion types displayed different effects on such things as the solubility of proteins. A consistent ordering of these different ions on the magnitude of their effect arises consistently in many other systems as well. This has since become known as the Hofmeister series.
While the origins of these effects are not abundantly clear and have been debated throughout the past century, it has been suggested that the charge density of these ions is important and might actually have explanations originating from the work of Charles-Augustin de Coulomb over 200 years ago. | 7 | Physical Chemistry |
There are seven different kinds of lattice systems, and each kind of lattice system has four different kinds of centerings (primitive, base-centered, body-centered, face-centered). However, not all of the combinations are unique; some of the combinations are equivalent while other combinations are not possible due to symmetry reasons. This reduces the number of unique lattices to the 14 Bravais lattices.
The distribution of the 14 Bravais lattices into 7 lattice systems is given in the following table.
In geometry and crystallography, a Bravais lattice is a category of translative symmetry groups (also known as lattices) in three directions.
Such symmetry groups consist of translations by vectors of the form
:R = na + na + na,
where n, n, and n are integers and a, a, and a are three non-coplanar vectors, called primitive vectors.
These lattices are classified by the space group of the lattice itself, viewed as a collection of points; there are 14 Bravais lattices in three dimensions; each belongs to one lattice system only. They represent the maximum symmetry a structure with the given translational symmetry can have.
All crystalline materials (not including quasicrystals) must, by definition, fit into one of these arrangements.
For convenience a Bravais lattice is depicted by a unit cell which is a factor 1, 2, 3, or 4 larger than the primitive cell. Depending on the symmetry of a crystal or other pattern, the fundamental domain is again smaller, up to a factor 48.
The Bravais lattices were studied by Moritz Ludwig Frankenheim in 1842, who found that there were 15 Bravais lattices. This was corrected to 14 by A. Bravais in 1848. | 3 | Analytical Chemistry |
In vertebrates, the majority of gene promoters contain a CpG island with numerous CpG sites. When many of a gene's promoter CpG sites are methylated the gene becomes inhibited (silenced). Colorectal cancers typically have 3 to 6 driver mutations and 33 to 66 hitchhiker or passenger mutations. However, transcriptional inhibition (silencing) may be of more importance than mutation in causing progression to cancer. For example, in colorectal cancers about 600 to 800 genes are transcriptionally inhibited by CpG island methylation (see regulation of transcription in cancer). Transcriptional repression in cancer can also occur by other epigenetic mechanisms, such as altered production of microRNAs. In breast cancer, transcriptional repression of BRCA1 may occur more frequently by over-produced microRNA-182 than by hypermethylation of the BRCA1 promoter (see Low expression of BRCA1 in breast and ovarian cancers). | 1 | Biochemistry |
The period of the iconoclasts synchronised with the reign of the Frankish emperor Charlemagne, whose power was felt throughout western Europe. Some of the craftsmen who were forced to leave Byzantium were welcomed by him in his capitals of Cologne and Aix-la-Chapelle and their influence was also felt in France. Another stream passed by way of the Mediterranean to Italy, where the old classical art had decayed owing to the many national calamities, and here it brought about a revival. In the Rhineland and elsewhere in Europe the terms "Rhenish-Byzantine" and "Romanesque" applied to architecture and works of art generally, testify to the provenance of the style of this and the succeeding period. The bronze parapet of Aachen Cathedral is of classic design and probably dates from Charlemagne's time.
All through the Middle Ages the use of bronze continued on a great scale, particularly in the 11th and 12th centuries. Bernward, bishop of Hildesheim, a great patron of the arts, had bronze doors, the Bernward Doors, made for St Nicholas' church (afterwards removed to the cathedral) which were set up in 1015; great doors were made for Augsburg somewhere between 1060 and 1065, and for Mainz shortly after the year 1000. A prominent feature on several of these doors is seen in finely modelled lion jaws, with conventional manes and with ring hanging from their jaws. These have their counterpart in France and Scandinavia as well as in England, where they are represented by the so-called Sanctuary Knocker at Durham Cathedral.
Provision of elaborate tomb monuments and church furniture gave much work to German and Netherlandish founders. Mention may be made of the seven-branch candlestick at Essen Cathedral made for the Abbess Matilda about the year 1000, and another at Brunswick completed in 1223; also of the remarkable font of the 13th century made for Hildesheim Cathedral at the charge of Wilbernus, a canon of the cathedral. Other fonts are found at Brandenburg and Würzburg. Vast numbers of bronze and brass ewers, holy-water vessels, reliquaries and candelabra were produced in the Middle Ages. In general, most of the finest work was executed for the Church. An important centre of medieval copper and brass casting (Dutch: geelgieten; literally "yellow casting") was the Meuse Valley, especially in the 12th century. The city of Dinant gave its name to the French term for all types of artistic copper and brass work: dinanderie (see also section "Brass"). After the destruction of the town by Charles the Bold in 1466, many brass workers moved to Maastricht, Aachen and other towns in Germany and even England.
The end of the Gothic period saw some great craftsmen in Germany and the Habsburg Netherlands. The brass worker Aert van Tricht was based in Maastricht but worked in St. Johns Cathedral, s-Hertogenbosch and Xanten Cathedral. A bronze lectern for St. Peter's Church, Leuven is now in the collection of The Cloisters in New York. Peter Vischer of Nuremberg, and his sons, working on the bronze reliquary of Saint Sebald, a finely conceived monument of architectural form, with rich details of ornament and figures; among the latter appearing the artist in his working dress. The shrine was completed and set up in the year 1516. This great craftsman executed other fine works at Magdeburg, Römhild and Breslau. Reference should be made to the colossal monument at Innsbruck, the tomb of the Emperor Maximilian I, with its 28 bronze statues of more than life size. Large fountains in which bronze was freely employed were set up, such as those at Munich and Augsburg. The tendency was to use this metal for large works of an architectural or sculpturesque nature; while at the same time smaller objects were produced for domestic purposes. By the late 15th to 16th centuries, a style of ornamental brass bowls called Beckenschlägerschüssel had developed. | 8 | Metallurgy |
The increase of ocean acidity decelerates the rate of calcification in salt water, leading to smaller and slower growing coral reefs which supports approximately 25% of marine life. Impacts are far-reaching from fisheries and coastal environments down to the deepest depths of the ocean. The increase in ocean acidity in not only killing the coral, but also the wildly diverse population of marine inhabitants which coral reefs support. | 9 | Geochemistry |
Hexose transporters (HXT) are a group of proteins that are largely responsible for the uptake of glucose in yeast. In S. cerevisiae, 20 HXT genes have been identified and 17 encode for glucose transporters (HXT1-HXT17), GAL2 encodes for a galactose transporter, and SNF3 and RGT2 encode for glucose sensors. The number of glucose sensor genes have remained mostly consistent through the budding yeast lineage, however glucose sensors are absent from Schizosaccharomyces pombe. Sch. pombe is a Crabtree-positive yeast, which developed aerobic fermentation independently from Saccharomyces lineage, and detects glucose via the cAMP-signaling pathway. The number of transporter genes vary significantly between yeast species and has continually increased during the evolution of the S. cerevisiae lineage. Most of the transporter genes have been generated by tandem duplication, rather than from the WGD. Sch. pombe also has a high number of transporter genes compared to its close relatives. Glucose uptake is believed to be a major rate-limiting step in glycolysis and replacing S. cerevisiae<nowiki/>s HXT1-17 genes with a single chimera HXT' gene results in decreased ethanol production or fully respiratory metabolism. Thus, having an efficient glucose uptake system appears to be essential to ability of aerobic fermentation. There is a significant positive correlation between the number of hexose transporter genes and the efficiency of ethanol production. | 1 | Biochemistry |
A spot test in lichenology is a spot analysis used to help identify lichens. It is performed by placing a drop of a chemical reagent on different parts of the lichen and noting the colour change (or lack thereof) associated with application of the chemical. The tests are routinely encountered in dichotomous keys for lichen species, and they take advantage of the wide array of lichen products (secondary metabolites) produced by lichens and their uniqueness among taxa. As such, spot tests reveal the presence or absence of chemicals in various parts of a lichen. They were first proposed as a method to help identify species by the Finnish lichenologist William Nylander in 1866.
Three common spot tests use either 10% aqueous KOH solution (K test), saturated aqueous solution of bleaching powder or calcium hypochlorite (C test), or 5% alcoholic p-phenylenediamine solution (P test). The colour changes occur due to presence of particular secondary metabolites in the lichen. In identification key reference literature, the outcome of chemical spot tests serves as a primary characteristic for determining the species of lichens. There are several other less frequently used spot tests of more limited use that are employed in specific situations, such as to distinguish between certain species. Variations of the technique, including using filter paper to enhance visibility of reactions or examining under a microscope, accommodate different lichen types and pigmentations, with results typically summarised by a short code indicating the substance and reaction observed. Other diagnostic methods like ultraviolet (UV) light exposure can help identify lichen metabolites and distinguish between species, as some substances fluoresce under UV, aiding in the differentiation of closely related species. | 3 | Analytical Chemistry |
Since members of the type I and type II cytokine receptor families possess no catalytic kinase activity, they rely on the JAK family of tyrosine kinases to phosphorylate and activate downstream proteins involved in their signal transduction pathways. The receptors exist as paired polypeptides, thus exhibiting two intracellular signal-transducing domains.
JAKs associate with a proline-rich region in each intracellular domain that is adjacent to the cell membrane and called a box1/box2 region. After the receptor associates with its respective cytokine/ligand, it goes through a conformational change, bringing the two JAKs close enough to phosphorylate each other. The JAK autophosphorylation induces a conformational change within itself, enabling it to transduce the intracellular signal by further phosphorylating and activating transcription factors called STATs (Signal Transducer and Activator of Transcription, or Signal Transduction And Transcription). The activated STATs dissociate from the receptor and form dimers before translocating to the cell nucleus, where they regulate transcription of selected genes.
Some examples of the molecules that use the JAK/STAT signaling pathway are colony-stimulating factor, prolactin, growth hormone, and many cytokines. Janus Kinases have also been reported to have a role in the maintenance of X chromosome inactivation. | 1 | Biochemistry |
The sclerometer, also known as the Turner-sclerometer (from meaning "hard"), is an instrument used by metallurgists, material scientists and mineralogists to measure the scratch hardness of materials. It was invented in 1896 by Thomas Turner (1861–1951), the first Professor of metallurgy in Britain, at the University of Birmingham.
The Turner-Sclerometer test consists of measuring the amount of load required to make a scratch.
In test a weighted diamond point is drawn, once forward and once backward, over the smooth surface of the material to be tested. The hardness number is the weight in grams required to produce a standard scratch. The scratch selected is one which is just visible to the naked eye as a dark line on a bright reflecting surface. It is also the scratch which can just be felt with the edge of a quill when the latter is drawn over the smooth surface at right angles to a series of such scratches produced by regularly increasing weights. | 8 | Metallurgy |
In vertebrates, calcium ions, like many other ions, are of such vital importance to many physiological processes that its concentration is maintained within specific limits to ensure adequate homeostasis. This is evidenced by human plasma calcium, which is one of the most closely regulated physiological variables in the human body. Normal plasma levels vary between 1 and 2% over any given time. Approximately half of all ionized calcium circulates in its unbound form, with the other half being complexed with plasma proteins such as albumin, as well as anions including bicarbonate, citrate, phosphate, and sulfate.
Different tissues contain calcium in different concentrations. For instance, Ca (mostly calcium phosphate and some calcium sulfate) is the most important (and specific) element of bone and calcified cartilage. In humans, the total body content of calcium is present mostly in the form of bone mineral (roughly 99%). In this state, it is largely unavailable for exchange/bioavailability. The way to overcome this is through the process of bone resorption, in which calcium is liberated into the bloodstream through the action of bone osteoclasts. The remainder of calcium is present within the extracellular and intracellular fluids.
Within a typical cell, the intracellular concentration of ionized calcium is roughly 100 nM, but is subject to increases of 10- to 100-fold during various cellular functions. The intracellular calcium level is kept relatively low with respect to the extracellular fluid, by an approximate magnitude of 12,000-fold. This gradient is maintained through various plasma membrane calcium pumps that utilize ATP for energy, as well as a sizable storage within intracellular compartments. In electrically excitable cells, such as skeletal and cardiac muscles and neurons, membrane depolarization leads to a Ca transient with cytosolic Ca concentration reaching around 1 µM. Mitochondria are capable of sequestering and storing some of that Ca. It has been estimated that mitochondrial matrix free calcium concentration rises to the tens of micromolar levels in situ during neuronal activity. | 1 | Biochemistry |
Dexchlorpheniramine is an antihistamine, or an antagonist of the histamine H receptor. A study found that dexchlorpheniramine had a K value of 20 to 30 μM for the muscarinic acetylcholine receptors using rat brain tissue. | 4 | Stereochemistry |
Nanoscale iron can be directly into the subsurface because they are small enough to be distributed thoroughly. Because the particles are so small, they have a comparatively large reactive surface, providing a more effective reaction. As of now, nanoscale iron is the only material that has been used with this injection strategy, and it is probably the only material that is effective in injection. | 2 | Environmental Chemistry |
There are three widely used techniques for generating terahertz pulses, all based on ultrashort pulses from titanium-sapphire lasers or mode-locked fiber lasers. | 7 | Physical Chemistry |
Agricola describes parting silver from gold in this book by using acids. He also describes heating with antimony sulphide (stibium), which would give silver sulphide and a mixture of gold and antimony. The gold and silver can then be recovered with cupellation. Gold can also be parted using salts or using mercury. Large scale cupellation using a cupellation hearth is also covered in this book. | 8 | Metallurgy |
The C5 fragment 24 required for the synthesis of the C ring (scheme 3) was prepared from 2,3-dibromopropene (20) by reaction with ethyl acetate (21), n-butyllithium and a copper salt, followed by organic reduction of acetate 22 to alcohol 23 (lithium aluminium hydride) and its TES silylation. Michael addition of 24 with the cyclooctane 19 to 25 with t-BuLi was catalyzed by copper cyanide. After removal of the TES group (HCl, THF), the alcohol 26 was oxidized to aldehyde 27 (TPAP, NMO)which enabled the intramolecular Aldol reaction to bicycle 28. | 0 | Organic Chemistry |
Deviations from perfect absorption and perfect black body behavior lead to light losses. For selective emitters, any light emitted at wavelengths not matched to the bandgap energy of the photovoltaic may not be efficiently converted, reducing efficiency. In particular, emissions associated with phonon resonances are difficult to avoid for wavelengths in the deep infrared, which cannot be practically converted. An ideal emitter would emit no light at wavelengths other than at the bandgap energy, and much TPV research is devoted to developing emitters that better approximate this narrow emission spectrum. | 7 | Physical Chemistry |
In genetics, an enhancer is a short (50–1500 bp) region of DNA that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur. These proteins are usually referred to as transcription factors. Enhancers are cis-acting. They can be located up to 1 Mbp (1,000,000 bp) away from the gene, upstream or downstream from the start site. There are hundreds of thousands of enhancers in the human genome. They are found in both prokaryotes and eukaryotes.
The first discovery of a eukaryotic enhancer was in the immunoglobulin heavy chain gene in 1983. This enhancer, located in the large intron, provided an explanation for the transcriptional activation of rearranged Vh gene promoters while unrearranged Vh promoters remained inactive. Lately, enhancers have been shown to be involved in certain medical conditions, for example, myelosuppression. Since 2022, scientists have used artificial intelligence to design synthetic enhancers and applied them in animal systems, first in a cell line, and one year later also in vivo. | 1 | Biochemistry |
Piperacillin is a broad-spectrum β-lactam antibiotic of the ureidopenicillin class. The chemical structure of piperacillin and other ureidopenicillins incorporates a polar side chain that enhances penetration into Gram-negative bacteria and reduces susceptibility to cleavage by Gram-negative beta lactamase enzymes. These properties confer activity against the important hospital pathogen Pseudomonas aeruginosa. Thus piperacillin is sometimes referred to as an "anti-pseudomonal penicillin".
When used alone, piperacillin lacks strong activity against the Gram-positive pathogens such as Staphylococcus aureus, as the beta-lactam ring is hydrolyzed by the bacteria's beta-lactamase.
It was patented in 1974 and approved for medical use in 1981. Piperacillin is most commonly used in combination with the beta-lactamase inhibitor tazobactam (piperacillin/tazobactam), which enhances piperacillin's effectiveness by inhibiting many beta lactamases to which it is susceptible. However, the co-administration of tazobactam does not confer activity against MRSA, as penicillin (and most other beta lactams) do not avidly bind to the penicillin-binding proteins of this pathogen. The World Health Organization classifies piperacillin as critically important for human medicine. | 4 | Stereochemistry |
The concentrations of free calcium in the cell can regulate an array of reactions and is important for signal transduction in the cell. Mitochondria can transiently store calcium, a contributing process for the cell's homeostasis of calcium.
Their ability to rapidly take in calcium for later release makes them good "cytosolic buffers" for calcium. The endoplasmic reticulum (ER) is the most significant storage site of calcium, and there is a significant interplay between the mitochondrion and ER with regard to calcium. The calcium is taken up into the matrix by the mitochondrial calcium uniporter on the inner mitochondrial membrane. It is primarily driven by the mitochondrial membrane potential. Release of this calcium back into the cell's interior can occur via a sodium-calcium exchange protein or via "calcium-induced-calcium-release" pathways. This can initiate calcium spikes or calcium waves with large changes in the membrane potential. These can activate a series of second messenger system proteins that can coordinate processes such as neurotransmitter release in nerve cells and release of hormones in endocrine cells.
Ca influx to the mitochondrial matrix has recently been implicated as a mechanism to regulate respiratory bioenergetics by allowing the electrochemical potential across the membrane to transiently "pulse" from ΔΨ-dominated to pH-dominated, facilitating a reduction of oxidative stress. In neurons, concomitant increases in cytosolic and mitochondrial calcium act to synchronize neuronal activity with mitochondrial energy metabolism. Mitochondrial matrix calcium levels can reach the tens of micromolar levels, which is necessary for the activation of isocitrate dehydrogenase, one of the key regulatory enzymes of the Krebs cycle. | 1 | Biochemistry |
The most important industrial application is the nickel-catalyzed synthesis of adiponitrile () synthesis from buta-1,3-diene (). Adiponitrile is a precursor to hexamethylenediamine (), which is used for the production of certain kinds of Nylon. The DuPont ADN process to give adiponitrile is shown below:
This process consists of three steps: hydrocyanation of butadiene to a mixture of 2-methyl-butene-3-nitrile (2M3BM) and pentene-3-nitrile (3PN), an isomerization step from 2M3BM (not desired) to 3PN and a second hydrocyanation (aided by a Lewis acid cocatalyst such as aluminium trichloride or triphenylboron) to adiponitrile. | 0 | Organic Chemistry |
Plasmonic nanoparticles have demonstrated a wide potential for the establishment of innovative cancer treatments. Despite that, there are still not plasmonic nanomaterials employed in the clinical practice, because the associated metal persistence. Preliminary research indicates that some nanomaterials, among which gold nanorods and ultrasmall-in-nano architectures, can convert IR laser light into localized heat, also in combination with other established cancer treatments. | 7 | Physical Chemistry |
Dipen Sinha of the Los Alamos National Laboratory developed ARS in 1989. Most published work in acoustics has been in the ultrasonic region and their instrumentation has dealt with propagation through a medium and not a resonance effect. One of the first, if not the first publication related to acoustic resonance was in 1988 in the journal of Applied Spectroscopy. The researchers designed a V-shaped quartz rod instrument that utilized ultrasonic waves to obtain signatures of microliters of different liquids. The researchers did not have any type of classification statistics or identification protocols; the researchers simply observed ultrasonic resonance signatures with these different materials. Specifically, Sinha was working on developing an ARS instrument that can detect nuclear, chemical, and biological weapons. By 1996, he had successfully developed a portable ARS unit that can be used in a battlefield. The unit can detect and identify deadly chemicals that are stored in containers in matter of minutes. In addition, the instrument was further developed by a different research group (Dr. Robert Lodder, University of Kentucky) and their work was also published in Applied Spectroscopy. The researchers created a V-shaped instrument that could breach the sonic and ultrasonic regions creating more versatility. The term acoustic resonance spectrometer was coined for the V-shaped spectrometer as well. Since the study in 1994, the ARS has evolved and been used to differentiate wood species, differentiate pharmaceutical tablets, determine burn rates and determine dissolution rates of tablets. In 2007 Analytical Chemistry featured the past and current work of the lab of Dr. Lodder discussing the potential of acoustics in the analytical chemistry and engineering fields. | 7 | Physical Chemistry |
The electronic structure of diazo compounds is characterized by π electron density delocalized over the α-carbon and two nitrogen atoms, along with an orthogonal π system with electron density delocalized over only the terminal nitrogen atoms. Because all octet rule-satisfying resonance forms of diazo compounds have formal charges, they are members of a class of compounds known as 1,3-dipoles. Some of the most stable diazo compounds are α-diazo-β-diketones and α-diazo-β-diesters, in which the electron density is further delocalized into an electron-withdrawing carbonyl group. In contrast, most diazoalkanes without electron-withdrawing substituents, including diazomethane itself, are explosive. A commercially relevant diazo compound is ethyl diazoacetate (NCHCOOEt). A group of isomeric compounds with only few similar properties are the diazirines, where the carbon and two nitrogens are linked as a ring.
Four resonance structures can be drawn:
Compounds with the diazo moiety should be distinguished from diazonium compounds, which have the same terminal azo group but bear an overall positive charge, and azo compounds in which the azo group bridges two organic substituents. | 0 | Organic Chemistry |
* corresponding academician of the Spanish Royal Academy of Sciences (1934)
* Hero of Socialist Labor (06/10/1945)
* four Orders of Lenin (05/07/1940; 06/10/1945; 02/05/1946; 02/05/1951)
* two PrOrders of the Red Banner of Labor (03/29/1941; 04/03/1944)
* USSR State Prize from the seizure of the chemicalization of the national economy of the USSR (1934)
* USSR State Prize of the first degree (1942) - for outstanding scientific works on organic chemistry, published in the collection of selected works of the author in 1941
* USSR State Prize of the second degree (1946) - for the development of a new method for obtaining aromatic hydrocarbons
* USSR State Prize of the first degree (1948)
* A. M. Butlerov Prize of the Russian Physical and Chemical Society (1924) | 0 | Organic Chemistry |
The findings of the Apollo missions were the first articles of evidence to suggest the existence of a magma ocean on the Moon. The rocks in the samples acquired from the missions were found to be composed of a mineral called anorthite. Anorthite consists mostly of a variety of plagioclase feldspars, which are lower in density than magma. This discovery gave rise to the hypothesis that the rocks formed through an ascension to the surface of a magma ocean during the early life stages of the Moon. Additional evidence for the existence of the Lunar Magma Ocean includes the sources of mare basalts and KREEP (K for potassium, REE for rare-earth elements, and P for phosphorus). The existence of these components within the mostly anorthositic crust of the Moon are synonymous with the solidification of the Lunar Magma Ocean. Furthermore, the abundance of the trace element europium within the Moons crust suggests that it was absorbed from the magma ocean, leaving europium deficits in the mare basalt rock sources of the Moons crust. The lunar magma ocean was initially 200-300 km thick and the magma achieved a temperature of about 2000 K. After the early stages of the Moons accretion, the magma ocean was subjected to cooling caused by convection in the planets interior. | 9 | Geochemistry |
In 1899, Charles Ernest Overton and Hans Horst Meyer independently proposed that the tadpole toxicity of non-ionizable organic compounds depends on their ability to partition into lipophilic compartments of cells. They further proposed the use of the partition coefficient in an olive oil/water mixture as an estimate of this lipophilic associated toxicity. Corwin Hansch later proposed the use of n-octanol as an inexpensive synthetic alcohol that could be obtained in a pure form as an alternative to olive oil. | 7 | Physical Chemistry |
SOFIA has been used to rapidly detect the abnormal form of the prion protein (PrP) in samples of bodily fluids, such as blood or urine. PrP is the marker protein used in diagnostics for transmissible spongiform encephalopathies (TSEs), examples of which include bovine spongiform encephalopathy in cattle (i.e. “mad cow” disease), scrapie in sheep, and Creutzfeldt–Jakob disease in humans. Currently, no rapid means exists for the ante mortem detection of PrP in the dilute quantities in which it usually appears in bodily fluids. SOFIA has the advantages of requiring little sample preparation, and allowing for electronic diagnostic equipment to be placed outside the containment area. | 1 | Biochemistry |
DNA and RNA are broken down into mononucleotides by the nucleases deoxyribonuclease and ribonuclease (DNase and RNase) from the pancreas. | 1 | Biochemistry |
Red mud, now more frequently termed bauxite residue, is an industrial waste generated during the processing of bauxite into alumina using the Bayer process. It is composed of various oxide compounds, including the iron oxides which give its red colour. Over 95% of the alumina produced globally is through the Bayer process; for every tonne of alumina produced, approximately 1 to 1.5 tonnes of red mud are also produced. Annual production of alumina in 2020 was over 133 million tonnes resulting in the generation of over 175 million tonnes of red mud.
Due to this high level of production and the material's high alkalinity, if not stored properly, it can pose a significant environmental hazard. As a result, significant effort is being invested in finding better methods for safe storage and dealing with it such as waste valorization in order to create useful materials for cement and concrete.
Less commonly, this material is also known as bauxite tailings, red sludge, or alumina refinery residues. | 2 | Environmental Chemistry |
See also: Extremophile
The ocean is home to a variety of marine organisms known as extremophiles - organisms that thrive in extreme conditions of temperature, pressure, and light availability. Extremophiles inhabit many unique habitats in the ocean, such as hydrothermal vents, black smokers, cold seeps, hypersaline regions, and sea ice brine pockets. Some scientists have speculated that life may have evolved from hydrothermal vents in the ocean.In hydrothermal vents and similar environments, many extremophiles acquire energy through chemoautotrophy, using chemical compounds as energy sources, rather than light as in photoautotrophy. Hydrothermal vents enrich the nearby environment in chemicals such as elemental sulfur, H, HS, Fe, and methane. Chemoautotrophic organisms, primarily prokaryotes, derive energy from these chemicals through redox reactions. These organisms then serve as food sources for higher trophic levels, forming the basis of unique ecosystems.
Several different metabolisms are present in hydrothermal vent ecosystems. Many marine microorganisms, including Thiomicrospira, Halothiobacillus, and Beggiatoa, are capable of oxidizing sulfur compounds, including elemental sulfur and the often toxic compound HS. HS is abundant in hydrothermal vents, formed through interactions between seawater and rock at the high temperatures found within vents. This compound is a major energy source, forming the basis of the sulfur cycle in hydrothermal vent ecosystems. In the colder waters surrounding vents, sulfur-oxidation can occur using oxygen as an electron acceptor; closer to the vents, organisms must use alternate metabolic pathways or utilize another electron acceptor, such as nitrate. Some species of Thiomicrospira can utilize thiosulfate as an electron donor, producing elemental sulfur. Additionally, many marine microorganisms are capable of iron-oxidation, such as Mariprofundus ferrooxydans. Iron-oxidation can be oxic, occurring in oxygen-rich parts of the ocean, or anoxic, requiring either an electron acceptor such as nitrate or light energy. In iron-oxidation, Fe(II) is used as an electron donor; conversely, iron-reducers utilize Fe(III) as an electron acceptor. These two metabolisms form the basis of the iron-redox cycle and may have contributed to banded iron formations.
At another extreme, some marine extremophiles inhabit sea ice brine pockets where temperature is very low and salinity is very high. Organisms trapped within freezing sea ice must adapt to a rapid change in salinity up to 3 times higher than that of regular seawater, as well as the rapid change to regular seawater salinity when ice melts. Most brine-pocket dwelling organisms are photosynthetic, therefore, these microenvironments can become hyperoxic, which can be toxic to its inhabitants. Thus, these extremophiles often produce high levels of antioxidants. | 9 | Geochemistry |
Primase adds RNA primers onto the lagging strand, which allows synthesis of Okazaki fragments from 5 to 3. However, primase creates RNA primers at a much lower rate than that at which DNA polymerase synthesizes DNA on the leading strand. DNA polymerase on the lagging strand also has to be continually recycled to construct Okazaki fragments following RNA primers. This makes the speed of lagging strand synthesis much lower than that of the leading strand. To solve this, primase acts as a temporary stop signal, briefly halting the progression of the replication fork during DNA replication. This molecular process prevents the leading strand from overtaking the lagging strand. | 1 | Biochemistry |
Water vapor is common in the Solar System and by extension, other planetary systems. Its signature has been detected in the atmospheres of the Sun, occurring in sunspots. The presence of water vapor has been detected in the atmospheres of all seven extraterrestrial planets in the Solar System, the Earth's Moon, and the moons of other planets, although typically in only trace amounts.
Geological formations such as cryogeysers are thought to exist on the surface of several icy moons ejecting water vapor due to tidal heating and may indicate the presence of substantial quantities of subsurface water. Plumes of water vapor have been detected on Jupiters moon Europa and are similar to plumes of water vapor detected on Saturns moon Enceladus. Traces of water vapor have also been detected in the stratosphere of Titan. Water vapor has been found to be a major constituent of the atmosphere of dwarf planet, Ceres, largest object in the asteroid belt The detection was made by using the far-infrared abilities of the Herschel Space Observatory. The finding is unexpected because comets, not asteroids, are typically considered to "sprout jets and plumes." According to one of the scientists, "The lines are becoming more and more blurred between comets and asteroids." Scientists studying Mars hypothesize that if water moves about the planet, it does so as vapor.
The brilliance of comet tails comes largely from water vapor. On approach to the Sun, the ice many comets carry sublimes to vapor. Knowing a comets distance from the sun, astronomers may deduce the comets water content from its brilliance.
Water vapor has also been confirmed outside the Solar System. Spectroscopic analysis of HD 209458 b, an extrasolar planet in the constellation Pegasus, provides the first evidence of atmospheric water vapor beyond the Solar System. A star called CW Leonis was found to have a ring of vast quantities of water vapor circling the aging, massive star. A NASA satellite designed to study chemicals in interstellar gas clouds, made the discovery with an onboard spectrometer. Most likely, "the water vapor was vaporized from the surfaces of orbiting comets." Other exoplanets with evidence of water vapor include HAT-P-11b and K2-18b. | 2 | Environmental Chemistry |
He received his second Ph.D. degree at Duke University where he was a Fulbright Scholar from 1964 to 1968. He worked in the laboratory of Charles Tanford, Department of Biochemistry in the protein folding area focussing his career on the folding thermodynamics and
kinetics, properties of the native and the unfolded proteins. His early collaborative work in uncovering residual native protein structure, following treatment with heat, acid (low pH) experimentally in a number of model proteins in his lab was published in 1967. He actually performed equilibrium unfolding studies on ribonuclease protein in guanidine hydrochloride, the findings of which were acceptable for the aforementioned Ph.D. degree in biochemistry by Duke University (1968).
Salahuddin returned to AMU Aligarh and joined the Department of Biochemistry, Faculty of Medicine, J.N. Medical College in 1968 as a reader. Salahuddin was present at the foundation ceremony of the new IBU Building on 15 January 1986. The event was inaugurated by Abdus Salam. He performed a critical role toward the establishment of the Interdisciplinary Biotechnology Institute for Modern Biological and Biotechnological Education at Aligarh along with the AMU administration in 1984. | 1 | Biochemistry |
Electro-electrodialysis is an electromembrane process utilizing three compartments, which combines electrodialysis and electrolysis. It is commonly used to recover acid from a solution using AEM, CEM and electrolysis. The three compartments are separated by two barriers, which are the ion exchange membranes. The compartment in the middle has the water to be treated. The compartments located on the sides contain clean water. The anions pass through the AEM, while the cations pass through the CEM. The electricity creates H in the anions side and OH in the cations side, which react with the respective ions. | 1 | Biochemistry |
ATP consists of an adenine attached by the 9-nitrogen atom to the 1′ carbon atom of a sugar (ribose), which in turn is attached at the 5' carbon atom of the sugar to a triphosphate group. In its many reactions related to metabolism, the adenine and sugar groups remain unchanged, but the triphosphate is converted to di- and monophosphate, giving respectively the derivatives ADP and AMP. The three phosphoryl groups are labeled as alpha (α), beta (β), and, for the terminal phosphate, gamma (γ).
In neutral solution, ionized ATP exists mostly as ATP, with a small proportion of ATP. | 1 | Biochemistry |
The basic method is to produce sacrificial anodes through a casting process. However, two casting methods can be distinguished.
The high pressure die-casting process for sacrificial anodes is widespread. It is a fully automated machine process. In order for the manufacturing process to run reliably and in a repeatable manner, a modification of the processed sacrificial anode alloy is required. Alternatively, the gravity casting process is used for the production of the sacrificial anodes. This process is performed manually or partially automated. The alloy does not have to be adapted to the manufacturing process, but is designed for 100% optimum corrosion protection. | 7 | Physical Chemistry |
Function Maize gene for first step in biosynthesis of benzoxazin, which aids in resistance to insect pests, pathogenic fungi and bacteria.
First report Hamilton 1964, as a mutant sensitive to the herbicide atrazine, and lacking benzoxazinoids (less than 1% of non-mutant plants).
Molecular characterization reveals that the BX1 protein is a homologue to the alpha-subunit of tryptophan synthase. The reference mutant allele has a deletion of about 900 bp, located at the 5-terminus and comprising sequence upstream of the transcription start site and the first exon. Additional alleles are given by a Mu transposon insertion in the fourth exon (Frey et al. 1997 ) and a Ds' transposon insertion in the maize inbred line W22 genetic background (Betsiashvili et al. 2014). Gene sequence diversity analysis has been performed for 281 inbred lines of maize, and the results suggest that bx1 is responsible for much of the natural variation in DIMBOA (a benzoxazinoid compound) synthesis (Butron et al. 2010). Genetic variation in benzoxazinoid content influences maize resistance to several insect pests (Meihls et al. 2013; McMullen et al. 2009). | 1 | Biochemistry |
In the 1870s, the French industrialist Pierre Manhès began his first attempts with a small, ordinary Bessemer converter of 50 kg in his factory in Vedène, then in factories in Éguilles, near Avignon. He sought to refine a matte with 25 to 30% copper previously melted in a crucible. But like Hollway, he did not succeed in completely refining the matte. The oxidation of undesirable elements occurred as expected, but the operation was quickly disrupted by the appearance of metallic copper. The matte, which was an ionic compound, was immiscible with the slag, but also with the molten metal. The latter, which is denser (ρ ≈ 9), went to the bottom of the converter and clogged the tuyeres.
Pierre Manhès then patented the use of additives whose oxidation would release enough heat to avoid getting stuck. In the end, it was the Frenchman Paul David, then an engineer in his factory in 1880, who suggested the solution. He proposed horizontal tuyeres placed at a sufficient distance from the bottom of the converter so that the copper could gather below them and the air blow constantly in the matte. By 1881, their converter was both technically operational and cost-effective.
In the autumn of 1884, the process was adopted in the United States by the Parrot Silver and Copper Company in Butte, Montana. The two types became larger and larger, increasing from a capacity of one ton to eight tons in 1912, and even fifteen tons for cylindrical converters in 1920. | 8 | Metallurgy |
The electrical efficiency of thermal power plants is defined as the ratio between the input and output energy. It is typically only 33% when disregarding usefulness of the heat output for building heat. The images show cooling towers which allow power stations to maintain the low side of the temperature difference essential for conversion of heat differences to other forms of energy. Discarded or "Waste" heat that is lost to the environment may instead be used to advantage. | 7 | Physical Chemistry |
Suppose the original dataset D contains the n spectra in rows. The signals of the original dataset are generally preprocessed. The original spectra are compared to a reference spectrum. By subtracting a reference spectrum, often the average spectrum of the dataset, so called dynamic spectra are calculated which form the corresponding dynamic dataset E. The presence and interpretation may be dependent on the choice of reference spectrum. The equations below are valid for equally spaced measurements of the perturbation. | 7 | Physical Chemistry |
Phosphine is a worldwide constituent of the Earth's atmosphere at very low and highly variable concentrations. It may contribute significantly to the global phosphorus biochemical cycle. The most likely source is reduction of phosphate in decaying organic matter, possibly via partial reductions and disproportionations, since environmental systems do not have known reducing agents of sufficient strength to directly convert phosphate to phosphine.
It is also found in Jupiter's atmosphere. | 0 | Organic Chemistry |
In organosulfur chemistry, sulfenamides (also spelled sulphenamides) are a class of organosulfur compounds characterized by the general formula , where the R groups are hydrogen, alkyl, or aryl. Sulfenamides have been used extensively in the vulcanization of rubber using sulfur. They are related to the oxidized compounds known as sulfinamides () and sulfonamides (). | 0 | Organic Chemistry |
An important implication of encapsulation is that the guest behaves differently from the way it would when in solution. The guest molecule tends to be unreactive and often has distinctive spectroscopic signatures. Compounds normally highly unstable in solution, such as arynes or cycloheptatetraene, have been isolated at room temperature when molecularly encapsulated. | 6 | Supramolecular Chemistry |
Metrnl participates in the control of inflammatory responses and is a critical regulator of muscle regeneration. | 1 | Biochemistry |
In recombinant DNA technology, specific restriction endonucleases are used that will isolate a particular gene and cleave the sugar phosphate backbones at different points (retaining symmetry), so that the double-stranded restriction fragments have single-stranded ends. These short extensions, called sticky ends, can form hydrogen bonded base pairs with complementary sticky ends on any other DNA cut with the same enzyme (such as a bacterial plasmid).
In agarose gel electrophoresis, the restriction fragments yield a band pattern characteristic of the original DNA molecule and restriction enzyme used, for example the relatively small DNA molecules of viruses and plasmids can be identified simply by their restriction fragment patterns. If the nucleotide differences of two different alleles occur within the restriction site of a particular restriction enzyme, digestion of segments of DNA from individuals with different alleles for that particular gene with that enzyme would produce different fragments and that will each yield different band patterns in gel electrophoresis. | 1 | Biochemistry |
Hyperspectral remote sensing is used in a wide array of applications. Although originally developed for mining and geology (the ability of hyperspectral imaging to identify various minerals makes it ideal for the mining and oil industries, where it can be used to look for ore and oil), it has now spread into fields as widespread as ecology and surveillance, as well as historical manuscript research, such as the imaging of the Archimedes Palimpsest. This technology is continually becoming more available to the public. Organizations such as NASA and the USGS have catalogues of various minerals and their spectral signatures, and have posted them online to make them readily available for researchers. On a smaller scale, NIR hyperspectral imaging can be used to rapidly monitor the application of pesticides to individual seeds for quality control of the optimum dose and homogeneous coverage. | 7 | Physical Chemistry |
He obtained his undergraduate and graduate degrees from the University of Manitoba in Winnipeg, Canada. Dr. Wowk obtained his PhD in physics in 1997. His graduate studies included work in online portal imaging for radiotherapy at the Manitoba Cancer Treatment and Research Foundation (now Cancer Care Manitoba), and work on artifact reduction for functional magnetic resonance imaging at the National Research Council of Canada. His work in the latter field is cited by several text books, including
Functional MRI which includes an image he obtained of magnetic field changes inside the human body caused by respiration. | 1 | Biochemistry |
TET enzymes are dioxygenases in the family of alpha-ketoglutarate-dependent hydroxylases. A TET enzyme is an alpha-ketoglutarate (α-KG) dependent dioxygenase that catalyses an oxidation reaction by incorporating a single oxygen atom from molecular oxygen (O) into its substrate, 5-methylcytosine in DNA (5mC), to produce the product 5-hydroxymethylcytosine in DNA. This conversion is coupled with the oxidation of the co-substrate α-KG to succinate and carbon dioxide (see Figure).
The first step involves the binding of α-KG and 5-methylcytosine to the TET enzyme active site. The TET enzymes each harbor a core catalytic domain with a double-stranded β-helix fold that contains the crucial metal-binding residues found in the family of Fe(II)/α-KG- dependent oxygenases. α-KG coordinates as a bidentate ligand (connected at two points) to Fe(II) (see Figure), while the 5mC is held by a noncovalent force in close proximity. The TET active site contains a highly conserved triad motif, in which the catalytically-essential Fe(II) is held by two histidine residues and one aspartic acid residue (see Figure). The triad binds to one face of the Fe center, leaving three labile sites available for binding α-KG and O (see Figure). TET then acts to convert 5-methylcytosine to 5-hydroxymethylcytosine while α-ketoglutarate is converted to succinate and CO. | 1 | Biochemistry |
The self-ionization of water (also autoionization of water, and autodissociation of water, or simply dissociation of water) is an ionization reaction in pure water or in an aqueous solution, in which a water molecule, HO, deprotonates (loses the nucleus of one of its hydrogen atoms) to become a hydroxide ion, OH. The hydrogen nucleus, H, immediately protonates another water molecule to form a hydronium cation, HO. It is an example of autoprotolysis, and exemplifies the amphoteric nature of water. | 7 | Physical Chemistry |
This model suggests that enzymes exist in a variety of conformations, only some of which are capable of binding to a substrate. When a substrate is bound to the protein, the equilibrium in the conformational ensemble shifts towards those able to bind ligands (as enzymes with bound substrates are removed from the equilibrium between the free conformations). | 1 | Biochemistry |
There has been extensive research to discover treatment for DMD. The most common drug treated against DMD is known to be Deflazacort yielding the greatest benefits with the most acceptable side effects. Physical therapy consists of varying exercises that aim to increase muscle strength and durability so to facilitate normal physical activity and is recommended to begin as early as possible after diagnosis. Contracture intervention is recommended for patients in the middle ambulatory stage. However, surgical approach to DMD is declining as less invasive treatment becomes available. While treatment for DMD has been observed to improve muscle function and quality of life, a cure to the debilitating disease remains to be found. | 1 | Biochemistry |
According to Schlüter et al. (2004) chloride pore water profiles can be used to investigate submarine groundwater discharge. Chloride can be used as a conservative tracer, as it is enriched in seawater and depleted in groundwater. Three different shapes of chloride pore water profiles reflect three different transport modes within marine sediments. A chloride profile showing constant concentrations with depth indicates that no submarine groundwater is present. A chloride profile with a linear decline indicates a diffusive mixing between groundwater and seawater and a concave shaped chloride profile represents an advective admixture of submarine groundwater from below. Stable isotope ratios in the water molecule may also be used to trace and quantify the sources of a submarine groundwater discharge. | 9 | Geochemistry |
Organocatalysts for asymmetric synthesis can be grouped in several classes:
* Biomolecules: proline, phenylalanine. Secondary amines in general. The cinchona alkaloids, certain oligopeptides.
* Synthetic catalysts derived from biomolecules.
* Hydrogen bonding catalysts, including TADDOLS, derivatives of BINOL such as NOBIN, and organocatalysts based on thioureas
* Triazolium salts as next-generation Stetter reaction catalysts
Examples of asymmetric reactions involving organocatalysts are:
* Asymmetric Diels-Alder reactions
* Asymmetric Michael reactions
* Asymmetric Mannich reactions
* Shi epoxidation
* Organocatalytic transfer hydrogenation | 0 | Organic Chemistry |
Synapses function as ensembles within particular brain networks to control the amount of neuronal activity, which is essential for memory, learning, and behavior. Consequently, synaptic disruptions might have negative effects. In fact, alterations in cell-intrinsic molecular systems or modifications to environmental biochemical processes can lead to synaptic dysfunction. The synapse is the primary unit of information transfer in the nervous system, and correct synaptic contact creation during development is essential for normal brain function. In addition, several mutations have been connected to neurodevelopmental disorders, and that compromised function at different synapse locations is a hallmark of neurodegenerative diseases.
Synaptic defects are causally associated with early appearing neurological diseases, including autism spectrum disorders (ASD), schizophrenia (SCZ), and bipolar disorder (BP). On the other hand, in late-onset degenerative pathologies, such as Alzheimers (AD), Parkinsons (PD), and Huntington's (HD) diseases, synaptopathy is thought to be the inevitable end-result of an ongoing pathophysiological cascade. These diseases are identified by a gradual loss in cognitive and behavioral function and a steady loss of brain tissue. Moreover, these deteriorations have been mostly linked to the gradual build-up of protein aggregates in neurons, the composition of which may vary based on the pathology; all have the same deleterious effects on neuronal integrity. Furthermore, the high number of mutations linked to synaptic structure and function, as well as dendritic spine alterations in post-mortem tissue, has led to the association between synaptic defects and neurodevelopmental disorders, such as ASD and SCZ, characterized by abnormal behavioral or cognitive phenotypes.
Nevertheless, due to limited access to human tissue at late stages and a lack of thorough assessment of the essential components of human diseases in the available experimental animal models, it has been difficult to fully grasp the origin and role of synaptic dysfunction in neurological disorders. | 1 | Biochemistry |
A method for nitrogen fixation was first described by Henry Cavendish in 1784 using electric arcs reacting nitrogen and oxygen in air. This method was implemented in the Birkeland–Eyde process of 1903. The fixation of nitrogen by lightning is a very similar natural occurring process.
The possibility that atmospheric nitrogen reacts with certain chemicals was first observed by Desfosses in 1828. He observed that mixtures of alkali metal oxides and carbon react with nitrogen at high temperatures. With the use of barium carbonate as starting material, the first commercial process became available in the 1860s, developed by Margueritte and Sourdeval. The resulting barium cyanide reacts with steam, yielding ammonia. In 1898 Frank and Caro developed what is known as the Frank–Caro process to fix nitrogen in the form of calcium cyanamide. The process was eclipsed by the Haber process, which was discovered in 1909. | 1 | Biochemistry |
Each candidate CRM (cCRM) is cloned upstream of a reporter gene. Compared to traditional reporter assays, the main innovation is the use of fluorescence activated cell sorting (FACS) of dissociated cells, instead of microscopy, to screen for tissue-specific enhancers. This approach utilizes a two-marker system: in each embryo, one marker (here, the rat CD2 cell surface protein) is used to label cells of a specific tissue for being sorted by FACS, and the other marker (here, green fluorescent protein GFP) is used as a reporter of CRM activity.
Cells are sorted according to their tissue type and then by GFP fluorescence, and the cCRMs are recovered by PCR from double-positive sorted cells, and from total input cells. High-throughput sequencing of both populations then allows measuring the relative abundance of each cCRM in input and sorted populations; one can then assess the enrichment or depletion of each cCRM in double-positive cells versus input as a measure of activity in the CD2-positive cell type being tested. | 1 | Biochemistry |
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