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In organic chemistry, an aminomethyl group is a monovalent functional group with formula . It can be described as a methyl group substituted by an amino group . | 0 | Organic Chemistry |
KT5720 is a kinase inhibitor with specificity towards protein kinase A. It is a semi-synthetic derivative of K252a and analog of staurosporine. | 1 | Biochemistry |
In phase I, a variety of enzymes act to introduce reactive and polar groups into their substrates. One of the most common modifications is hydroxylation catalysed by the cytochrome P-450-dependent mixed-function oxidase system. These enzyme complexes act to incorporate an atom of oxygen into nonactivated hydrocarbons, which can result in either the introduction of hydroxyl groups or N-, O- and S-dealkylation of substrates. The reaction mechanism of the P-450 oxidases proceeds through the reduction of cytochrome-bound oxygen and the generation of a highly-reactive oxyferryl species, according to the following scheme:
:O + NADPH + H + RH → NADP + HO + ROH
Phase I reactions (also termed nonsynthetic reactions) may occur by oxidation, reduction, hydrolysis, cyclization, decyclization, and addition of oxygen or removal of hydrogen, carried out by mixed function oxidases, often in the liver. These oxidative reactions typically involve a cytochrome P450 monooxygenase (often abbreviated CYP), NADPH and oxygen. The classes of pharmaceutical drugs that utilize this method for their metabolism include phenothiazines, paracetamol, and steroids. If the metabolites of phase I reactions are sufficiently polar, they may be readily excreted at this point. However, many phase I products are not eliminated rapidly and undergo a subsequent reaction in which an endogenous substrate combines with the newly incorporated functional group to form a highly polar conjugate.
A common Phase I oxidation involves conversion of a C-H bond to a C-OH. This reaction sometimes converts a pharmacologically inactive compound (a prodrug) to a pharmacologically active one. By the same token, Phase I can turn a nontoxic molecule into a poisonous one (toxification). Simple hydrolysis in the stomach is normally an innocuous reaction, however there are exceptions. For example, phase I metabolism converts acetonitrile to HOCHCN, which rapidly dissociates into formaldehyde and hydrogen cyanide.
Phase I metabolism of drug candidates can be simulated in the laboratory using non-enzyme catalysts. This example of a biomimetic reaction tends to give products that often contains the Phase I metabolites. As an example, the major metabolite of the pharmaceutical trimebutine, desmethyltrimebutine (nor-trimebutine), can be efficiently produced by in vitro oxidation of the commercially available drug. Hydroxylation of an N-methyl group leads to expulsion of a molecule of formaldehyde, while oxidation of the O-methyl groups takes place to a lesser extent. | 1 | Biochemistry |
Twinning is crystallographically defined by its twin plane 𝑲, the mirror plane in the twin and parent material, and 𝜼 which is the twinning shear direction. Deformation twins in Zr are generally lenticular in shape, lengthening in the 𝜼 direction and thickening along the 𝑲 plane normal.
The twin plane, shear direction, and shear plane form the basis vectors of an orthogonal set. The axis-angle misorientation relationship between the parent and twin is a rotation of angle 𝜉 about the shear plane's normal direction 𝑷.
More generally, twinning can be described as a 180° rotation about an axis (𝑲 for type I twins or 𝜼 for type II twins normal direction) , or a mirror reflection in a plane (𝑲 or 𝜼 normal plane).
In addition to a homogeneous shear, atomic shuffles are sometimes required to reform the correct crystal structure in the twinned lattice. For each twin variant, a reciprocal twin with swapped 𝑲 and 𝑲 𝜼 and 𝜼 is possible, but one variant may appear more frequently in reality due to complexities with the required shuffles.
there are only two crystallographic planes in a shearing action that do not change their shape and size as a consequence of the shear. The first 𝑲 is the plane defining the upper and lower surfaces of the sheared volume. This plane contains the shear direction. The other plane, designated C. The shear direction is shown with an arrow and labelled with its customary designation 𝜼. It follows from the above that there are three ways that a crystal lattice can be sheared while still retaining its crystal structure and symmetry:
# When 𝑲 is a rational plane and 𝜼 a rational direction, a twin of the first kind
# When 𝑲 is a rational plane and 𝜼 a rational direction, a twin of the second kind, rare
# When all four elements 𝑲, 𝑲, 𝜼, and 𝜼 are rational, a compound twin | 3 | Analytical Chemistry |
Aerosol partitioning theory governs condensation on and evaporation from an aerosol surface, respectively. Condensation of mass causes the mode of the particle-size distributions of the aerosol to increase; conversely, evaporation causes the mode to decrease. Nucleation is the process of forming aerosol mass from the condensation of a gaseous precursor, specifically a vapor. Net condensation of the vapor requires supersaturation, a partial pressure greater than its vapor pressure. This can happen for three reasons:
# Lowering the temperature of the system lowers the vapor pressure.
# Chemical reactions may increase the partial pressure of a gas or lower its vapor pressure.
# The addition of additional vapor to the system may lower the equilibrium vapor pressure according to Raoult's law.
There are two types of nucleation processes. Gases preferentially condense onto surfaces of pre-existing aerosol particles, known as heterogeneous nucleation. This process causes the diameter at the mode of particle-size distribution to increase with constant number concentration. With sufficiently high supersaturation and no suitable surfaces, particles may condense in the absence of a pre-existing surface, known as homogeneous nucleation. This results in the addition of very small, rapidly growing particles to the particle-size distribution. | 7 | Physical Chemistry |
Boronic acids can be obtained via several methods. The most common way is reaction of organometallic compounds based on lithium or magnesium (Grignards) with borate esters. For example, phenylboronic acid is produced from phenylmagnesium bromide and trimethyl borate followed by hydrolysis
:PhMgBr + B(OMe) → PhB(OMe) + MeOMgBr
:PhB(OMe) + 2 HO → PhB(OH) + 2 MeOH
Another method is reaction of an arylsilane (RSiR) with boron tribromide (BBr) in a transmetallation to RBBr followed by acidic hydrolysis.
A third method is by palladium catalysed reaction of aryl halides and triflates with diboronyl esters in a coupling reaction known as the Miyaura borylation reaction. An alternative to esters in this method is the use of diboronic acid or tetrahydroxydiboron ([B(OH)]). | 0 | Organic Chemistry |
Neuromelanin gives specific brain sections, such as the substantia nigra or the locus coeruleus, distinct color. It is a type of melanin and similar to other forms of peripheral melanin. It is insoluble in organic compounds, and can be labeled by silver staining. It is called neuromelanin because of its function and the color change that appears in tissues containing it. It contains black/brown pigmented granules. Neuromelanin is found to accumulate during aging, noticeably after the first 2–3 years of life. It is believed to protect neurons in the substantia nigra from iron-induced oxidative stress. It is considered a true melanin due to its stable free radical structure and it avidly chelates metals. | 1 | Biochemistry |
The Krüppel associated box (KRAB) domain is a category of transcriptional repression domains present in approximately 400 human zinc finger protein-based transcription factors (KRAB zinc finger proteins). The KRAB domain typically consists of about 75 amino acid residues, while the minimal repression module is approximately 45 amino acid residues. It is predicted to function through protein-protein interactions via two amphipathic helices. The most prominent interacting protein is called TRIM28 initially visualized as SMP1, cloned as KAP1 and TIF1-beta. Substitutions for the conserved residues abolish repression.
Over 10 independently encoded KRAB domains have been shown to be effective repressors of transcription, suggesting this activity to be a common property of the domain. KRAB domains can be fused with dCas9 CRISPR tools to form even stronger repressors. | 1 | Biochemistry |
In some cases, chemical trap is used to detect or infer a compound when present at concentrations below its detection limit or is present in a mixture, where other components interfere with its detection. The trapping agent, for example a dye, reacts with the chemical to be detected, giving a product that is more easily detected. | 3 | Analytical Chemistry |
# Prepare standard concentrations of protein of 1, 5, 7.5 and 10 µg/mL. Prepare a blank of NaCl only. Prepare a series of sample dilutions.
# Add 100 µL of each of the above to separate tubes (use microcentrifuge tubes) and add 1.0 mL of Coomassie Blue to each tube.
# Turn on and adjust a spectrophotometer to a wavelength of 595 nm, and blank the spectrophotometer using 1.5 mL cuvettes or use a mobile smartphone camera (RGBradford method).
# Wait 2 minutes and read the absorbance of each standard and sample at 595 nm.
# Plot the absorbance of the standards vs. their concentration. Compute the extinction coefficient and calculate the concentrations of the unknown samples. | 3 | Analytical Chemistry |
Inhibitors of protein AMPylation with inhibitory constant (K) ranging from 6 - 50 μM and at least 30-fold selectivity versus HypE have been discovered. | 1 | Biochemistry |
TAD locations are defined by applying an algorithm to Hi-C data. For example, TADs are often called according to the so-called "directionality index". The directionality index is calculated for individual 40kb bins, by collecting the reads that fall in the bin, and observing whether their paired reads map upstream or downstream of the bin (read pairs are required to span no more than 2Mb). A positive value indicates that more read pairs lie downstream than upstream, and a negative value indicates the reverse. Mathematically, the directionality index is a signed chi-square statistic.
The development of specialized genome browsers and visualization tools such as Juicebox, HiGlass/HiPiler, The 3D Genome Browser, 3DIV, 3D-GNOME, and TADKB have enabled us to visualize the TAD organization of regions of interest in different cell types. | 1 | Biochemistry |
The single survivin gene can give rise to four different alternatively spliced transcripts:
# Survivin, which has a three-intron–four-exon structure in both the mouse and human.
# Survivin-2B, which has an insertion of an alternative exon 2.
# Survivin-Delta-Ex-3, which has exon 3 removed. The removal of exon 3 results in a frame shift that generates a unique carboxyl terminus with a new function. This new function may involve a nuclear localization signal. Moreover, a mitochondrial localization signal is also generated.
# Survivin-3B, which has an insertion of an alternative exon 3. | 1 | Biochemistry |
A clone is a group of identical cells that share a common ancestry, meaning they are derived from the same cell.
Clonality implies the state of a cell or a substance being derived from one source or the other. Thus there are terms like polyclonal—derived from many clones; oligoclonal—derived from a few clones; and monoclonal—derived from one clone. These terms are most commonly used in context of antibodies or immunocytes. | 1 | Biochemistry |
Near-field scanning optical microscopy (NSOM) was described in 1984, and used in many applications since then. The combination of Raman scattering and NSOM techniques was first realized in 1995, when it was used for imaging a Rb-doped KTP crystal at a spatial resolution of 250 nm.
NSOM employs two different methods for data collection and analysis: the fiber tip aperture approach and the apertureless metal tip approach. NSOM with aperture probes has a smaller aperture that can increase the spatial resolution of NSOM; however, the transmission of light to the sample and the collection efficiency of the scattered/emitted light is also diminished. The apertureless near-field scanning microscopy (ANSOM) was developed in the 1990s. ANSOM employs a metalized tip instead of an optical fiber probe. The performance of the ANSOM strongly depends on the electric field enhancement factor of the metalized tip. This technique is based on surface plasmon resonance (SPR) which is the precursor of tip-enhanced Raman scattering (TERS) and surface-enhanced Raman scattering (SERS).
In 1997, Martin and Girard demonstrated theoretically that electric field under a metallic or dielectric tip (belonging to NSOM apertureless technique) can be strongly enhanced if the incident field is along the tip axis. Since then a few groups have reported Raman or fluorescence enhancement in near field optical spectroscopy by apertureless microscopy. In 2000, T. Kalkbrenner et al. used a single gold particle as a probe for apertureless scanning and presented images of an aluminium film with 3 μm holes on a glass substrate. The resolution of this apertureless method was 100 nm, that is comparable to that of fiber-based systems Recently, a carbon nanotube (CNT) having a conical end, tagged with gold nanoparticles, was applied as a nanometer-resolution optical probe tip for NSOM. NSOM images were obtained with a spatial resolution of ~5 nm, demonstrating the potential of a composite CNT probe tip for nanoscale-resolution optical imaging. | 7 | Physical Chemistry |
Color superconductivity is a phenomenon where matter carries color charge without loss, on analogy to the way conventional superconductors can carry electric charge without loss. Color superconductivity is predicted to occur in quark matter if the baryon density is sufficiently high (i.e., well above the density and energies of an atomic nucleus) and the temperature is not too high (well below 10 kelvins). Color superconducting phases are to be contrasted with the normal phase of quark matter, which is just a weakly interacting Fermi liquid of quarks.
In theoretical terms, a color superconducting phase is a state in which the quarks near the Fermi surface become correlated in Cooper pairs, which condense. In phenomenological terms, a color superconducting phase breaks some of the symmetries of the underlying theory, and has a very different spectrum of excitations and very different transport properties from the normal phase. | 7 | Physical Chemistry |
Triglycerides are transported through the blood to appropriate tissues (adipose, muscle, etc.) by lipoproteins such as Very-Low-Density-Lipoproteins (VLDL). Triglycerides present on the VLDL undergo lipolysis by the cellular lipases of target tissues, which yields glycerol and free fatty acids. Free fatty acids released into the blood are then available for cellular uptake. Free fatty acids not immediately taken up by cells may bind to albumin for transport to surrounding tissues that require energy. Serum albumin is the major carrier of free fatty acids in the blood.
The glycerol also enters the bloodstream and is absorbed by the liver or kidney where it is converted to glycerol 3-phosphate by the enzyme glycerol kinase. Hepatic glycerol 3-phosphate is converted mostly into dihydroxyacetonephosphate (DHAP) and then glyceraldehyde 3-phosphate (GA3P) to rejoin the glycolysis and gluconeogenesis pathway. | 1 | Biochemistry |
Differential capacitance in physics, electronics, and electrochemistry is a measure of the voltage-dependent capacitance of a nonlinear capacitor, such as an electrical double layer or a semiconductor diode. It is defined as the derivative of charge with respect to potential. | 7 | Physical Chemistry |
Each of these mechanisms can act in isolation or in combination with others. Assuming each effect is independent, the observed line profile is a convolution of the line profiles of each mechanism. For example, a combination of the thermal Doppler broadening and the impact pressure broadening yields a Voigt profile.
However, the different line broadening mechanisms are not always independent. For example, the collisional effects and the motional Doppler shifts can act in a coherent manner, resulting under some conditions even in a collisional narrowing, known as the Dicke effect. | 7 | Physical Chemistry |
Leonard Adleman of the University of Southern California initially developed this field in 1994. Adleman demonstrated a proof-of-concept use of DNA as a form of computation which solved the seven-point Hamiltonian path problem. Since the initial Adleman experiments, advances have occurred and various Turing machines have been proven to be constructible.
Since then the field has expanded into several avenues. In 1995, the idea for DNA-based memory was proposed by Eric Baum who conjectured that a vast amount of data can be stored in a tiny amount of DNA due to its ultra-high density. This expanded the horizon of DNA computing into the realm of memory technology although the in vitro demonstrations were made almost after a decade.
The field of DNA computing can be categorized as a sub-field of the broader DNA nanoscience field started by [http://seemanlab4.chem.nyu.edu/ Ned Seeman] about a decade before Len Adlemans demonstration. Neds original idea in the 1980s was to build arbitrary structures using bottom-up DNA self-assembly for applications in crystallography. However, it morphed into the field of structural DNA self-assembly which as of 2020 is extremely sophisticated. Self-assembled structure from a few nanometers tall all the way up to several tens of micrometers in size have been demonstrated in 2018.
In 1994, Prof. Seemans group demonstrated early DNA lattice structures using a small set of DNA components. While the demonstration by Adleman showed the possibility of DNA-based computers, the DNA design was trivial because as the number of nodes in a graph grows, the number of DNA components required in Adlemans implementation would grow exponentially. Therefore, computer scientists and biochemists started exploring tile-assembly where the goal was to use a small set of DNA strands as tiles to perform arbitrary computations upon growth. Other avenues that were theoretically explored in the late 90's include DNA-based security and cryptography, computational capacity of DNA systems, DNA memories and disks, and DNA-based robotics.
Before 2002, Lila Kari showed that the DNA operations performed by genetic recombination in some organisms are Turing complete.
In 2003, [https://users.cs.duke.edu/~reif/ John Reif's group] first demonstrated the idea of a DNA-based walker that traversed along a track similar to a line follower robot. They used molecular biology as a source of energy for the walker. Since this first demonstration, a wide variety of DNA-based walkers have been demonstrated. | 1 | Biochemistry |
The pressure-fed engine is a class of rocket engine designs. A separate gas supply, usually helium, pressurizes the propellant tanks to force fuel and oxidizer to the combustion chamber. To maintain adequate flow, the tank pressures must exceed the combustion chamber pressure.
Pressure fed engines have simple plumbing and have no need for complex and occasionally unreliable turbopumps. A typical startup procedure begins with opening a valve, often a one-shot pyrotechnic device, to allow the pressurizing gas to flow through check valves into the propellant tanks. Then the propellant valves in the engine itself are opened. If the fuel and oxidizer are hypergolic, they burn on contact; non-hypergolic fuels require an igniter. Multiple burns can be conducted by merely opening and closing the propellant valves as needed. If the pressurization system also has activating valves, they can be operated electrically, or by gas pressure controlled by smaller electrically operated valves.
Care must be taken, especially during long burns, to avoid excessive cooling of the pressurizing gas due to adiabatic expansion. Cold helium won't liquify, but it could freeze a propellant, decrease tank pressures, or damage components not designed for low temperatures. The Apollo Lunar Module Descent Propulsion System was unusual in storing its helium in a supercritical but very cold state. It was warmed as it was withdrawn through a heat exchanger from the ambient temperature fuel.
Spacecraft attitude control and orbital maneuvering thrusters are almost universally pressure-fed designs.
Examples include the Reaction Control (RCS) and the Orbital Maneuvering (OMS) engines of the Space Shuttle orbiter; the RCS and Service Propulsion System (SPS) engines on the Apollo Command/Service Module; the SuperDraco (in-flight abort) and Draco (RCS) engines on the SpaceX Dragon 2; and the RCS, ascent and descent engines on the Apollo Lunar Module.
Some launcher upper stages also use pressure-fed engines. These include the Aerojet AJ10 and TRW TR-201 used in the second stage of Delta II launch vehicle,
and the Kestrel engine of the Falcon 1 by SpaceX.
The 1960s Sea Dragon concept by Robert Truax for a big dumb booster would have used pressure-fed engines.
Pressure-fed engines have practical limits on propellant pressure, which in turn limits combustion chamber pressure. High pressure propellant tanks require thicker walls and stronger materials which make the vehicle tanks heavier, thereby reducing performance and payload capacity. The lower stages of launch vehicles often use either solid fuel or pump-fed liquid fuel engines instead, where high pressure ratio nozzles are considered desirable.
Other vehicles or companies using pressure-fed engine:
*OTRAG (rocket)
*Quad (rocket) of Armadillo Aerospace
*XCOR EZ-Rocket of XCOR Aerospace
*Masten Space Systems
*Aquarius Launch Vehicle
*NASA's Project Morpheus prototype lander
*NASA Mighty Eagle mini lunar lander
*CONAE's Tronador II upper stage
*Copenhagen Suborbitals' Spica | 7 | Physical Chemistry |
Hydrophobic interactions in protein SEC are relatively weak at low ionic strength, electrostatic effects may contribute significantly to retention, and this allows us to use an SEC column as a weak ion exchanger. | 3 | Analytical Chemistry |
Arrhenius argued that for reactants to transform into products, they must first acquire a minimum amount of energy, called the activation energy E. At an absolute temperature T, the fraction of molecules that have a kinetic energy greater than E can be calculated from statistical mechanics. The concept of activation energy explains the exponential nature of the relationship, and in one way or another, it is present in all kinetic theories.
The calculations for reaction rate constants involve an energy averaging over a Maxwell–Boltzmann distribution with as lower bound and so are often of the type of incomplete gamma functions, which turn out to be proportional to . | 7 | Physical Chemistry |
Phreds approach to base calling and calculating quality scores was outlined by Ewing et al.'. To determine quality scores, Phred first calculates several parameters related to peak shape and peak resolution at each base. Phred then uses these parameters to look up a corresponding quality score in huge lookup tables. These lookup tables were generated from sequence traces where the correct sequence was known, and are hard coded in Phred; different lookup tables are used for different sequencing chemistries and machines. An evaluation of the accuracy of Phred quality scores for a number of variations in sequencing chemistry and instrumentation showed that Phred quality scores are highly accurate.
Phred was originally developed for "slab gel" sequencing machines like the ABI373. When originally developed, Phred had a lower base calling error rate than the manufacturers base calling software, which also did not provide quality scores. However, Phred was only partially adapted to the capillary DNA sequencers that became popular later. In contrast, instrument manufacturers like ABI continued to adapt their base calling software changes in sequencing chemistry, and have included the ability to create Phred-like quality scores. Therefore, the need to use Phred for base calling of DNA sequencing traces has diminished, and using the manufacturers current software versions can often give more accurate results. | 1 | Biochemistry |
Honorary Membership of the Czech Society for Mass Spectrometry; Lifetime Achievement Award in Chromatography by the LC-GC Magazine, Europe; Giorgio Nota Award, Italian Chemical Society; Heyrovsky Medal in Chemical Sciences, Prague, Czech Republic. | 3 | Analytical Chemistry |
This semiregular tiling is a member of a sequence of snubbed polyhedra and tilings with vertex figure (3.3.3.3.n) and Coxeter–Dynkin diagram . These figures and their duals have (n32) rotational symmetry, being in the Euclidean plane for n=6, and hyperbolic plane for any higher n. The series can be considered to begin with n=2, with one set of faces degenerated into digons.
From a Wythoff construction there are eight hyperbolic uniform tilings that can be based from the regular heptagonal tiling.
Drawing the tiles colored as red on the original faces, yellow at the original vertices, and blue along the original edges, there are 8 forms. | 4 | Stereochemistry |
Rokushō is used to treat a number of metals, including raw natural copper, which holds impurities, purified copper, and copper alloy mixes with two to five metals, to produce irogane metals, including: shakudō, an alloy of copper and gold, which becomes black to dark blue-violet; shibuichi, an alloy of fine silver and copper (in a higher percentage than sterling), which turns grey to misty aquamarine or other shades of blue to green; kuromido which becomes dark coppery black.
Rokushō was generally used to patinate all types of mokume-gane ("wood grain metal") as well.
Although other patination agents can be used on these metals, some artisans prefer the rich colors achieved with traditional rokushō in the niiro process.
These metals are becoming increasingly popular in high-end artistic jewelry, especially in bi-metals (a layer of the alloy fused to another metal such as sterling). Because rokushō has a dramatically different effect on sterling silver than on the alloys typically fused to it in bi-metals, a common technique in art jewelry is to engrave through the alloy layer in a pattern to reveal the silver underneath prior to patination. This provides a rich contrast in color, highlighting the pattern. | 8 | Metallurgy |
Lactate can be used to produce a bioplastic called polylactic acid (PLA). The properties of PLA depend on the ratio of the two optical isomers of lactate (D-lactate and L-lactate). D-lactate is produced by mixed acid fermentation in E. coli. Early experiments engineered the E. coli strain RR1 to produce either one of the two optical isomers of lactate.
Later experiments modified the E. coli strain KO11, originally developed to enhance ethanol production. Scientists were able to increase the yield of D-lactate from fermentation by performing several deletions. | 1 | Biochemistry |
Some species secrete gels that are effective in parasite control. For example, the long-finned pilot whale secretes an enzymatic gel that rests on the outer surface of this animal and helps prevent other organisms from establishing colonies on the surface of these whales' bodies.
Hydrogels existing naturally in the body include mucus, the vitreous humor of the eye, cartilage, tendons and blood clots. Their viscoelastic nature results in the soft tissue component of the body, disparate from the mineral-based hard tissue of the skeletal system. Researchers are actively developing synthetically derived tissue replacement technologies derived from hydrogels, for both temporary implants (degradable) and permanent implants (non-degradable). A review article on the subject discusses the use of hydrogels for nucleus pulposus replacement, cartilage replacement, and synthetic tissue models. | 7 | Physical Chemistry |
The broad scope of the available raw neuronal proteins to map requires that initial studies be focused on small areas of the neurons. When taking samples, there are a few places that interest neurologists most. The most important place to start for neurologists is the plasma membrane. This is where most of the communication between neurons takes place. The proteins being mapped here include ion channels, neurotransmitter receptors, and molecule transporters. Along the plasma membrane, the proteins involved in creating cholesterol-rich lipid rafts are being studied because they have been shown to be crucial for glutamate uptake during the initial stages of neuron formation. As mentioned before, vesicle proteins are also being studied closely because they are involved in disease.
Collecting samples to study, however, requires special consideration to ensure that the reproducibility of the samples is not compromised. When taking a global sample of one area of the brain for example, proteins that are ubiquitous and relatively unimportant show up very clear in the SDS PAGE. Other unexplored, more specific proteins barely show up and are therefore ignored. It is usually necessary to divide up the plasma membrane proteome, for example, into subproteomes characterized by specific function. This allows these more specific classes of peptides to show up more clearly. In a way, dividing into subproteomes is simply applying a magnifying lens to a specific section of a global proteome’s SDS PAGE map. This method seems to be most effective when applied to each cellular organelle separately. Mitochondrial proteins, for example, which are more effective at transporting electrons across its membrane, can be specifically targeted effectively in order to match their electron-transporting ability to their amino acid sequence. | 1 | Biochemistry |
The pyrolysis (thermal decomposition) of acetaldehyde, CHCHO (g) → CH (g) + CO (g), proceeds via the Rice-Herzfeld mechanism:
*Initiation (formation of free radicals):
: CHCHO (g) → •CH (g) + •CHO (g) k
The methyl and CHO groups are free radicals.
*Propagation (two steps):
: •CH (g) + CHCHO (g) → CH (g) + •CHCO (g) k
This reaction step provides methane, which is one of the two main products.
: •CHCO (g) → CO (g) + •CH (g) k
The product •CHCO (g) of the previous step gives rise to carbon monoxide (CO), which is the second main product.
The sum of the two propagation steps corresponds to the overall reaction CHCHO (g) → CH (g) + CO (g), catalyzed by a methyl radical •CH.
*Termination:
: •CH (g) + •CH (g) → CH (g) k
This reaction is the only source of ethane (minor product) and it is concluded to be the main chain ending step.
Although this mechanism explains the principal products, there are others that are formed in a minor degree, such as acetone (CHCOCH) and propanal (CHCHCHO).
Applying the Steady State Approximation for the intermediate species CH(g) and CHCO(g), the rate law for the formation of methane and the order of reaction are found:
The rate of formation of the product methane is
For the intermediates
and
Adding (2) and (3), we obtain
so that
Using (4) in (1) gives the rate law , which is order 3/2 in the reactant CHCHO. | 7 | Physical Chemistry |
Biliproteins found in plants and algae serve as a system of pigments whose purpose is to detect and absorb light needed for photosynthesis. The absorption spectra of biliproteins complements that of other photosynthetic pigments such as chlorophyll or carotene. The pigments detect and absorb energy from sunlight; the energy later being transferred to chlorophyll via internal energy transfer. According to a 2002 article written by Takashi Hirata et al., the chromophores of certain phycobiliproteins are responsible for antioxidant activities in these biliproteins, and phycocyanin also possesses anti-inflammatory qualities due to its inhibitory apoprotein. When induced by both collagen and adenosine triphosphate (ADP), the chromophore phycocyanobilin suppresses platelet aggregation in phycocyanin, its corresponding phycobiliprotein. | 1 | Biochemistry |
Percoll does not notably diffuse over time, resulting in the formation of very stable gradients. Therefore, both discontinuous and continuous Percoll density gradients can be prepared weeks in advance, allowing great reproducibility & ease of use. | 1 | Biochemistry |
The internal heating within terrestrial planets powers tectonic and volcanic activities. Of the terrestrial planets in the Solar System, Earth has the most internal heating because it is the largest. Mercury and Mars have no ongoing visible surface effects of internal heating because they are only 5 and 11% the mass of Earth respectively; they are nearly "geologically dead" (however, see Mercury's magnetic field and Geological history of Mars). Earth, being more massive, has a great enough ratio of mass to surface area for its internal heating to drive plate tectonics and volcanism. | 7 | Physical Chemistry |
An acid–alkali reaction is a special case of an acid–base reaction, where the base used is also an alkali. When an acid reacts with an alkali salt (a metal hydroxide), the product is a metal salt and water. Acid–alkali reactions are also neutralization reactions.
In general, acid–alkali reactions can be simplified to
by omitting spectator ions.
Acids are in general pure substances that contain hydrogen cations () or cause them to be produced in solutions. Hydrochloric acid () and sulfuric acid () are common examples. In water, these break apart into ions:
The alkali breaks apart in water, yielding dissolved hydroxide ions: | 7 | Physical Chemistry |
Broad-base adoption of mass timber and their role in substituting steel and concrete in new mid-rise construction projects over the next few decades has the potential to turn timber buildings into carbon sinks, as they store the carbon dioxide taken up from the air by trees that are harvested and used as mass timber. This could result in storing between 10 million tons of carbon per year in the lowest scenario and close to 700 million tons in the highest scenario. For this to happen, the harvested forests would need to be sustainably managed and wood from demolished timber buildings would need to be reused or preserved on land in various forms. | 5 | Photochemistry |
Selegiline belongs to the phenethylamine and amphetamine chemical families. It is also known as -deprenyl, as well as (R)-(–)-N,α-dimethyl-N-(2-propynyl)phenethylamine or (R)-(–)-N-methyl-N-2-propynylamphetamine. The compound is a derivative of levomethamphetamine (-methamphetamine) with a propargyl group attached to the nitrogen atom. This detail is borrowed from pargyline, an older MAO-B inhibitor of the phenylalkylamine group. Selegiline is the levorotatory enantiomer of the racemic mixture deprenyl.
Selegiline is synthesized by the alkylation of (–)-methamphetamine using propargyl bromide.
Another clinically used MAOI of the amphetamine class is tranylcypromine. | 4 | Stereochemistry |
Molecular machines are molecules or molecular assemblies that can perform functions such as linear or rotational movement, switching, and entrapment. These devices exist at the boundary between supramolecular chemistry and nanotechnology, and prototypes have been demonstrated using supramolecular concepts. Jean-Pierre Sauvage, Sir J. Fraser Stoddart and Bernard L. Feringa shared the 2016 Nobel Prize in Chemistry for the design and synthesis of molecular machines. | 6 | Supramolecular Chemistry |
Changes in AOU are not consistent across spatial domains. Notably, the Northern Hemisphere AOU spikes in the mid-1990s, while Southern Hemisphere AOU significantly decreases in the mid-2000s. This could be due to less dense data in the Southern Hemisphere. Since the 80s, regions of major O decrease (AOU increase) include the subpolar North Pacific, equatorial Atlantic, and eastern equatorial Pacific. Regions of O increase (AOU decrease) include the western subtropical North Pacific and eastern subpolar North Atlantic. | 9 | Geochemistry |
EDMR has been demonstrated on a single electron from a quantum dot. Measurements of less than 100 donors and theoretical analyses of such a measurement have been published, relying on the P interface defect to act as the acceptor. | 7 | Physical Chemistry |
In the phosphatidylinositol signal pathway, the extracellular signal molecule binds with the G-protein receptor (G) on the cell surface and activates phospholipase C, which is located on the plasma membrane. The lipase hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) into two second messengers: inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 binds with the IP3 receptor in the membrane of the smooth endoplasmic reticulum and mitochondria to open Ca channels. DAG helps activate protein kinase C (PKC), which phosphorylates many other proteins, changing their catalytic activities, leading to cellular responses.
The effects of Ca are also remarkable: it cooperates with DAG in activating PKC and can activate the CaM kinase pathway, in which calcium-modulated protein calmodulin (CaM) binds Ca, undergoes a change in conformation, and activates CaM kinase II, which has unique ability to increase its binding affinity to CaM by autophosphorylation, making CaM unavailable for the activation of other enzymes. The kinase then phosphorylates target enzymes, regulating their activities. The two signal pathways are connected together by Ca-CaM, which is also a regulatory subunit of adenylyl cyclase and phosphodiesterase in the cAMP signal pathway. | 1 | Biochemistry |
In chemistry, the tricapped trigonal prismatic molecular geometry describes the shape of compounds where nine atoms, groups of atoms, or ligands are arranged around a central atom, defining the vertices of a triaugmented triangular prism (a trigonal prism with an extra atom attached to each of its three rectangular faces).
It is very similar to the capped square antiprismatic molecular geometry, and there is some dispute over the specific geometry exhibited by certain molecules. | 4 | Stereochemistry |
CTD is a unique resource where biocurators read the scientific literature and manually curate four types of core data:
* Chemical-gene interactions
* Chemical-disease associations
* Gene-disease associations
* Chemical-phenotype associations | 1 | Biochemistry |
The Geochemical Society is a nonprofit scientific organization founded to encourage the application of chemistry to solve problems involving geology and cosmology. The society promotes understanding of geochemistry through the annual Goldschmidt Conference, publication of a peer-reviewed journal and electronic newsletter, awards programs recognizing significant accomplishments in the field, and student development programs. The society's offices are located on the campus of the Carnegie Institution for Science in Washington, DC. | 9 | Geochemistry |
Despite its major advantages, RT-PCR is not without drawbacks. The exponential growth of the reverse transcribed complementary DNA (cDNA) during the multiple cycles of PCR produces inaccurate end point quantification due to the difficulty in maintaining linearity. In order to provide accurate detection and quantification of RNA content in a sample, qRT-PCR was developed using fluorescence-based modification to monitor the amplification products during each cycle of PCR. The extreme sensitivity of the technique can be a double edged sword since even the slightest DNA contamination can lead to undesirable results. A simple method for elimination of false positive results is to include anchors, or tags, to the 5' region of a gene specific primer. Additionally, planning and design of quantification studies can be technically challenging due to the existence of numerous sources of variation including template concentration and amplification efficiency. Spiking in a known quantity of RNA into a sample, adding a series of RNA dilutions generating a standard curve, and adding in a no template copy sample (no cDNA) may used as controls. | 1 | Biochemistry |
These groups may contain only two-fold axes, mirror planes, and/or an inversion center. These are the crystallographic point groups 1 and (triclinic crystal system), 2, m, and (monoclinic), and 222, , and mm2 (orthorhombic). (The short form of is mmm.) If the symbol contains three positions, then they denote symmetry elements in the x, y, z direction, respectively. | 3 | Analytical Chemistry |
Dexibuprofen is a nonsteroidal anti-inflammatory drug (NSAID). It is the active dextrorotatory enantiomer of ibuprofen. Most ibuprofen formulations contain a racemic mixture of both isomers.
Dexibuprofen is a chiral switch of racemic ibuprofen. The chiral carbon in dexibuprofen is assigned an absolute configuration of (S) per the Cahn–Ingold–Prelog rules. Dexibuprofen is also called as [https://pubchem.ncbi.nlm.nih.gov/compound/Dexibuprofen S(+)Ibuprofen].
Ibuprofen is an α-arylpropionic acid used largely in the treatment of rheumatoid arthritis and widely used over-the counter drug for headache and minor pains. This drug has a chiral center and exists as a pair of enantiomers. (S)-Ibuprofen, the eutomer, is responsible for the desired therapeutic effect. The inactive (R)-enantiomer, the distomer, undergoes a unidirectional chiral inversion to give the active (S)-enantiomer, the former acting as a prodrug for the latter. That is, when the ibuprofen is administered as a racemate the distomer is converted in vivo into the eutomer while the latter is unaffected. | 4 | Stereochemistry |
In addition to its role in synaptic plasticity described above, PI3K-AKT signaling pathway also has an important role in brain growth, which is altered when PI3K signaling is disturbed. For example, intracranial volume is also associated with this pathway, in particular with AKT3 intronic variants. Thyroid hormone was originally identified as the primary regulator of brain growth and cognition, and recent evidence has demonstrated that thyroid hormone produces some of its effects on the maturation and plasticity of synapses through PI3K. | 1 | Biochemistry |
The endocannabinoid system (ECS) is a biological system composed of endocannabinoids, which are endogenous lipid-based retrograde neurotransmitters that bind to cannabinoid receptors, and cannabinoid receptor proteins that are expressed throughout the vertebrate central nervous system (including the brain) and peripheral nervous system. The endocannabinoid system remains under preliminary research, but may be involved in regulating physiological and cognitive processes, including fertility, pregnancy, pre- and postnatal development, various activity of immune system, appetite, pain-sensation, mood, and memory, and in mediating the pharmacological effects of cannabis. The ECS plays an important role in multiple aspects of neural functions, including the control of movement and motor coordination, learning and memory, emotion and motivation, addictive-like behavior and pain modulation, among others.
Two primary cannabinoid receptors have been identified: CB1, first cloned (or isolated) in 1990; and CB2, cloned in 1993. CB1 receptors are found predominantly in the brain and nervous system, as well as in peripheral organs and tissues, and are the main molecular target of the endogenous partial agonist, anandamide, as well as exogenous tetrahydrocannabinol, the most known active component of cannabis. Endocannabinoid 2-arachidonoylglycerol (2-AG), which was found to be two and three orders of magnitude more abundant in mammalian brain than anandamide, acts as a full agonist at both CB receptors.
The endocannabinoid system is sometimes referred to as the endocannabinoidome or expanded endocannabinoid system. | 1 | Biochemistry |
Carbon-14 can also be produced by other neutron reactions, including in particular Carbon-13|(n,γ) and Oxygen-17|(n,α) with thermal neutrons, and Nitrogen-15|(n,d) and Oxygen-16|(n,) with fast neutrons. The most notable routes for production by thermal neutron irradiation of targets (e.g., in a nuclear reactor) are summarized in the table.
Carbon-14 may also be radiogenic (cluster decay of , , ). However, this origin is extremely rare. | 9 | Geochemistry |
It is anecdotally said that hot peppers help people in the tropics “cool off.” This theory is consistent with the peripheral vasodilatory effect of capsaicin that has been shown to lower skin temperature in humans exposed to a hot environment. Capsaicin feels hot in the mouth because it activates sensory receptors on the tongue otherwise used to detect thermal heat. This receptor is called Transient Receptor Potential Vanilloid 1 (TRPV1). TRPV1 receptors are also located in the gut and in other organs. Stimulation of TRPV1 receptors is known to bring about activation of the sympathetic nervous system (SNS). Capsaicin has been shown to increase fat burning in humans and animals through stimulation of the SNS.
Like capsaicin, capsinoids activate TRPV1 receptors, although they are not hot in the mouth. Capsinoids cannot reach the TRPV1 oral cavity receptors, located slightly below the surface in the mouth, because of structural differences from capsaicin. On the other hand, both capsaicin and capsinoids activate TRPV1 receptors in the same manner. Research has indicated that the TRPV1 receptors in the gut are important for the metabolic effects of capsaicin and capsinoids.
Both energy metabolism and body temperature increases are observed in humans following extracted capsinoids or CH-19 Sweet administration. Animal studies also demonstrate these increases, as well as suppressed in body fat accumulation following capsinoids intake. The exact mechanisms and the relative importance of each remain under investigation, as are the effects of capsinoids on appetite and satiation. | 1 | Biochemistry |
This is to give an overview of the evolving chirality nomenclature system commonly employed to distinguish enantiomers of a chiral drug. In the beginning, enantiomers were distinguished based on their ability to rotate the plane of plane-polarized light. The enantiomer that rotates the plane-polarized light to the right is named "dextro-rotatory", abbreviated as "dextro" or "d" and the counterpart as "levo" or "l". A racemic mixture is denoted as "(±)", "rac", or "dl". Now the d/l system of naming based on optical rotation is falling into disuse.
Later, the Fischer convention was introduced to specify the configuration of a stereogenic center and uses the symbols D and L. The use of capital letters is to differentiate from the "d" / "l" notation (optical descriptor) described earlier. In this system, the enantiomers are named with reference to D- and L-glyceraldehyde which is taken as the standard for comparison. The structure of the chiral molecule should be represented in the Fischer projection formula. If the hydroxyl group attached to the highest chiral carbon is on the right-hand side it is referred to as D-series and if on the left-hand side it is called L-series. This nomenclature system has also become obsolete. But D-/L-system of naming is still employed to designate the configuration of amino acids and sugars. In general the D/L system of nomenclature is superseded by the Cahn-Ingold-Prelog (CIP) rule to describe the configuration of a stereogenic/chiral center.
In the CIP or R/S convention, or sequence rule, the configuration, spatial arrangements of ligands/substituents around a chiral center, is labeled as either "R" or "S". This convention is now almost worldwide in use and become a part of the IUPAC (International Union of Pure and Applied Chemistry) rules of nomenclature. In this approach: identify the chiral center, label the four atoms directly attached to the stereogenic center in question, assign priorities according to the sequence rule ( from 1 to 4), rotate the molecule until the lowest priority (number 4) substituent is away from the observer/viewer, draw a curve from number 1 to number 2 to number 3 substituent. If the curve is clockwise, the chiral center is of R-absolute configuration, "R" (Latin, rectus = right). If the curve is counterclockwise, the chiral center is of S-absolute configuration, "S" (Latin, sinister = left). Refer to figure, the Cahn-Ingold-Prelog rule.
An overview of the nomenclature system is presented in the table below. | 4 | Stereochemistry |
Collision frequency describes the rate of collisions between two atomic or molecular species in a given volume, per unit time. In an ideal gas, assuming that the species behave like hard spheres, the collision frequency between entities of species A and species B is:
which has units of [volume][time].
Here,
* is the number of A molecules in the gas,
* is the number of B molecules in the gas,
* is the collision cross section, the "effective area" seen by two colliding molecules, simplified to , where the radius of A and the radius of B.
* is the Boltzmann constant,
* is the temperature,
* is the reduced mass of the reactants A and B, | 7 | Physical Chemistry |
Unlike the human body, typical chemical reactions are unable to regenerate the cofactor for further use. Synthetic cofactors have been researched to solve this problem. The analogues have been synthesized from similar compounds such as 1,4-dihydronicotinamide. These synthetic cofactors have since been used to better understand the mechanisms of reactions especially when it comes to stereospecificity, which may be enhanced by metal ions. Analogues serve as an alternative to traditional regeneration techniques. | 1 | Biochemistry |
Curing is a chemical process employed in polymer chemistry and process engineering that produces the toughening or hardening of a polymer material by cross-linking of polymer chains. Even if it is strongly associated with the production of thermosetting polymers, the term "curing" can be used for all the processes where a solid product is obtained from a liquid solution, such as with PVC plastisols. | 7 | Physical Chemistry |
In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is or where the R represents substituents or hydrogen atoms.
The term "carbene" may also refer to the specific compound , also called methylene, the parent hydride from which all other carbene compounds are formally derived.
There are two types of carbenes: singlets or triplets, depending upon their electronic structure. The different classes undergo different reactions.
Most carbenes are extremely reactive and short-lived. A small number (the dihalo<nowiki/>carbenes, carbon monoxide, and carbon monosulfide) can be isolated, and can stabilize as metal ligands, but otherwise cannot be stored in bulk. A rare exception are the persistent carbenes, which have extensive application in modern organometallic chemistry. | 0 | Organic Chemistry |
Hypothermia is often defined as any body temperature below . With this method it is divided into degrees of severity based on the core temperature.
Another classification system, the Swiss staging system, divides hypothermia based on the presenting symptoms which is preferred when it is not possible to determine an accurate core temperature.
Other cold-related injuries that can be present either alone or in combination with hypothermia include:
*Chilblains: condition caused by repeated exposure of skin to temperatures just above freezing. The cold causes damage to small blood vessels in the skin. This damage is permanent and the redness and itching will return with additional exposure. The redness and itching typically occurs on cheeks, ears, fingers, and toes.
*Frostbite: the freezing and destruction of tissue, which happens below the freezing point of water
*Frostnip: a superficial cooling of tissues without cellular destruction
*Trench foot or immersion foot: a condition caused by repetitive exposure to water at non-freezing temperatures
The normal human body temperature is often stated as . Hyperthermia and fever, are defined as a temperature of greater than . | 1 | Biochemistry |
The Geneva Rules are the rules established by the International Chemistry Committee in 1892. These rules were the beginning of international cooperation for organic chemistry nomenclature. They were decided upon by a group of 34 of leading chemists from 9 different European nations. Their goal was to provide rules for the naming of aliphatic compounds, some of which are still in place today such as the longest chain provides the parent name and a functional group is indicated by a suffix. They also intended to extend the rules to include naming schemes for cyclic compounds however this did not occur. | 0 | Organic Chemistry |
Photosystem I operates with the functions of producing NADPH, the reduced form of NADP(Fd + NADH + 2 NADP + H = Fd + NAD + 2 NADPH.)[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2944534/#:~:text=It%20was%20found%20that%20the,%2B%20NAD%2B%20%2B%202%20NADPH.], at the end of the photosynthetic reaction through electron transfer, and of providing energy to a [https://chem.libretexts.org/Bookshelves/General_Chemistry/Book%3A_Structure_and_Reactivity_in_Organic_Biological_and_Inorganic_Chemistry_(Schaller)/V%3A__Reactivity_in_Organic_Biological_and_Inorganic_Chemistry_3/09%3A_Photosynthesis/9.06%3A_Adding_a_Proton_Pump-_Cytochrome_b6f_Complex proton pump] and eventually ATP, for instance in cyclic electron transport. | 5 | Photochemistry |
SINEs are much shorter (300bp) than LINEs. They share similarity with genes transcribed by RNA polymerase II, the enzyme that transcribes genes into mRNA transcripts, and the initiation sequence of RNA polymerase III, the enzyme that transcribes genes into ribosomal RNA, tRNA and other small RNA molecules. SINEs such as mammalian MIR elements have tRNA gene at the start and adenine-rich at the end like in LINEs.
SINEs do not encode a functional reverse transcriptase protein and rely on other mobile transposons, especially LINEs. SINEs exploit LINE transposition components despite LINE-binding proteins prefer binding to LINE RNA. SINEs cannot transpose by themselves because they cannot encode SINE transcripts. They usually consist of parts derived from tRNA and LINEs. The tRNA portion contains an RNA polymerase III promoter which the same kind of enzyme as RNA polymerase II. This makes sure the LINE copies would be transcribed into RNA for further transposition. The LINE component remains so LINE-binding proteins can recognise the LINE part of the SINE. | 1 | Biochemistry |
Greek prefixes in alphabetical order indicate ring size.
Lactones are usually named according to the precursor acid molecule (aceto = 2 carbon atoms, propio = 3, butyro = 4, valero = 5, capro = 6, etc.), with a -lactone suffix and a Greek letter prefix that specifies the number of carbon atoms in the heterocycle — that is, the distance between the relevant -OH and the -COOH groups along said backbone. The first carbon atom after the carbon in the -COOH group on the parent compound is labelled α, the second will be labeled β, and so forth. Therefore, the prefixes also indicate the size of the lactone ring: α-lactone = 3-membered ring, β-lactone = 4-membered, γ-lactone = 5-membered, δ-lactone = 6-membered, etc. Macrocyclic lactones are known as macrolactones.
The other suffix used to denote a lactone is -olide, used in substance class names like butenolide, macrolide, cardenolide or bufadienolide.
To obtain the preferred IUPAC names, lactones are named as heterocyclic pseudoketones by adding the suffix one, dione, thione, etc. and the appropriate multiplicative prefixes to the name of the heterocyclic parent hydride. | 0 | Organic Chemistry |
A major breakthrough that allowed the large scale manufacture of fluorocarbons was the Fowler process. In this process, cobalt trifluoride is used as the source of fluorine. Illustrative is the synthesis of perfluorohexane:
The resulting cobalt difluoride is then regenerated, sometimes in a separate reactor:
Industrially, both steps are combined, for example in the manufacture of the Flutec range of fluorocarbons by F2 chemicals Ltd, using a vertical stirred bed reactor, with hydrocarbon introduced at the bottom, and fluorine introduced halfway up the reactor. The fluorocarbon vapor is recovered from the top. | 2 | Environmental Chemistry |
An optical isomer can be named by the spatial configuration of its atoms. The system (named after Latin dexter and laevus, right and left), not to be confused with the d- and l-system, see above, does this by relating the molecule to glyceraldehyde. Glyceraldehyde is chiral itself and its two isomers are labeled and (typically typeset in small caps in published work). Certain chemical manipulations can be performed on glyceraldehyde without affecting its configuration, and its historical use for this purpose (possibly combined with its convenience as one of the smallest commonly used chiral molecules) has resulted in its use for nomenclature. In this system, compounds are named by analogy to glyceraldehyde, which, in general, produces unambiguous designations, but is easiest to see in the small biomolecules similar to glyceraldehyde. One example is the chiral amino acid alanine, which has two optical isomers, and they are labeled according to which isomer of glyceraldehyde they come from. On the other hand, glycine, the amino acid derived from glyceraldehyde, has no optical activity, as it is not chiral (it's achiral).
The labeling is unrelated to (+)/(−) it does not indicate which enantiomer is dextrorotatory and which is levorotatory. Rather, it indicates the compound's stereochemistry relative to that of the dextrorotatory or levorotatory enantiomer of glyceraldehyde. The dextrorotatory isomer of glyceraldehyde is, in fact, the isomer. Nine of the nineteen -amino acids commonly found in proteins are dextrorotatory (at a wavelength of 589 nm), and -fructose is also referred to as levulose because it is levorotatory. A rule of thumb for determining the isomeric form of an amino acid is the "CORN" rule. The groups
:COOH, R, NH and H (where R is the side-chain)
are arranged around the chiral center carbon atom. With the hydrogen atom away from the viewer, if the arrangement of the CO→R→N groups around the carbon atom as center is counter-clockwise, then it is the form. If the arrangement is clockwise, it is the form. As usual, if the molecule itself is oriented differently, for example, with H towards the viewer, the pattern may be reversed. The form is the usual one found in natural proteins. For most amino acids, the form corresponds to an S absolute stereochemistry, but is R instead for certain side-chains. | 4 | Stereochemistry |
Heteroatom-promoted lateral lithiation is the site-selective replacement of a benzylic hydrogen atom for lithium for the purpose of further functionalization. Heteroatom-containing substituents may direct metalation to the benzylic site closest to the heteroatom or increase the acidity of the ring carbons via an inductive effect. | 0 | Organic Chemistry |
The following have received a medal:
*2022: Michael Tarbutt, for pioneering experimental and theoretical work on the production of ultracold molecules by laser cooling, and the applications of those molecules to quantum science and tests of fundamental physics.
*2021: Carla Faria, for distinguished contributions to the theory of strong-field laser-matter interactions.
*2020: Michael Charlton, for scientific leadership in antimatter science.
*2019: , for outstanding contributions to experiments on ultra-cold atoms and molecules
*2016: Jeremy M. Hutson, for his pioneering work on the theory of ultracold molecules
*2014: Charles S Adams, for his imaginative experiments which have pioneered the field of Rydberg quantum optics
*2012: , for his pioneering experimental work in Bose-Einstein condensates and cold Fermi gases
*2010: , for her contributions to the development of the worlds only positronium beam'
*2008: Edward Hinds, for his important and elegant experimental investigations in the fields of atomic physics and quantum optics | 7 | Physical Chemistry |
Early studies of quasi-1-D conductors were motivated by a proposal, in 1964, that certain types of polymer chain compounds could exhibit superconductivity with a high critical temperature T. The theory was based on the idea that pairing of electrons in the BCS theory of superconductivity could be mediated by interactions of conducting electrons in one chain with nonconducting electrons in some side chains. (By contrast, electron pairing is mediated by phonons, or vibrating ions, in the BCS theory of conventional superconductors.) Since light electrons, instead of heavy ions, would lead to the formation of Cooper pairs, their characteristic frequency and, hence, energy scale and T would be enhanced. Organic materials, such as TTF-TCNQ were measured and studied theoretically in the 1970s. These materials were found to undergo a metal-insulator, rather than superconducting, transition. It was eventually established that such experiments represented the first observations of the Peierls transition.
The first evidence for CDW transport in inorganic linear chain compounds, such as transition metal trichalcogenides, was reported in 1976 by Monceau et al., who observed enhanced electrical conduction at increased electric fields in NbSe. The nonlinear contribution to the electrical conductivity σ vs. field E was fit to a Landau-Zener tunneling characteristic ~ exp[-E/E] (see Landau–Zener formula), but it was soon realized that the characteristic Zener field E was far too small to represent Zener tunneling of normal electrons across the Peierls gap. Subsequent experiments showed a sharp threshold electric field, as well as peaks in the noise spectrum (narrow band noise) whose fundamental frequency scales with the CDW current. These and other experiments (e.g.,) confirm that the CDW collectively carries an electric current in a jerky fashion above the threshold field. | 7 | Physical Chemistry |
Fluorogenic describes a property of chemical compounds which are initially not fluorescent, but become fluorescent through a chemical reaction, typically through an intermolecular covalent reaction which binds the now fluorescent compound to a target molecule. IUPAC uses a broader definition of fluorogenic, wherein a enhancement of fluorescence via a chemical reaction is not required, however in contrast to the IUPAC definition common use of fluorogenic does not refer to non-reaction effects like the enhancement of fluorescence from a fluorophore being in different solvents. Fluorogenic labeling reagents are often used in analytical chemistry procedures, particularly in HPLC or CE to derivative target compounds (e.g. labeling the primary amines of polypeptides), thereby allowing enhanced sensitivity through fluorescence based detection. | 3 | Analytical Chemistry |
The durability and life of dynamically loaded, welded steel structures is determined in many cases by the welds, in particular the weld transitions. Through selective treatment of the transitions (grinding (abrasive cutting), abrasive blasting, hammering, etc.), the durability of many designs increase significantly. Hammering methods have proven to be particularly effective treatment methods and were within the joint project REFRESH extensively studied and developed. The HiFIT (High-Frequency Impact Treatment (also called HFMI (High Frequency Mechanical Impact))) process is such a hammering method that is universally applicable, requires only a low tech equipment and still offers high reproducibility and the possibility for quality control. | 8 | Metallurgy |
The EBF intends to stimulate further harmonization of industry practices in bioanalysis, to bring a common understanding of the interpretation of regulatory issues and more clarity to the implementation of procedures in order to achieve best practices in the world of bioanalysis. The forum currently hosts two types of meetings: | 3 | Analytical Chemistry |
Hemoglycin is a completely abiotic molecule that forms in molecular clouds going on to protoplanetary disks, way before biochemistry on exoplanets like Earth begins. Hemoglycin via its glycine could seed an exoplanet (one able to support early biochemistry) but its main function appears to be the accretion of matter via formation of an extensive low-density lattice in space in a protoplanetary disk. Besides being present in carbonaceous meteorites, hemoglycin has also been extracted and crystallized from a fossil stromatolite that formed on Earth 2.1 billion years ago. Potentially this fossil hemoglycin was delivered during the Late Heavy Bombardment (LHB) to Earth. Data to support this being the hemoglycin in the fossil has extraterrestrial isotopes similar to that in meteorites.
The polymer on the precambrian Earth could have functioned to drive the Great Oxygenation Event (GOE) beginning 2.4 Gya by splitting water in response to ultraviolet irradiation. Also, it could provide an energy source to early biochemistry and/or it simply delivered a source of polymer glycine. | 9 | Geochemistry |
There are examples of a new class of compounds that, on the basis of their chemical formulae, would appear to be Zintl phases, e.g., KIn, which is metallic and paramagnetic. Molecular orbital calculations have shown that the anion is (In) and that the extra electron is distributed over the cations and, possibly, the anion antibonding orbitals. Another exception is the metallic InBi. InBi fulfills the Zintl phase requisite of element-element bonds but not the requisite of the polyanionic structure fitting a normal valence compound, i.e., the Bi–Bi polyanionic structure does not correspond to a normal valence structure such as the diamond Tl in NaTl. | 7 | Physical Chemistry |
Dextromethorphan (DXM) is a cough suppressant used in many cough and cold medicines. It affects serotonin, norepinephrine, NMDA, and sigma-1 receptors in the brain, all of which have been implicated in the pathophysiology of depression. In 2022, the FDA approved the combination dextromethorphan/bupropion to serve as a rapid acting antidepressant in patients with major depressive disorder.
It is in the morphinan class of medications with sedative, dissociative, and stimulant properties (at lower doses). Dextromethorphan does not have a significant affinity for the mu-opioid receptor activity typical of morphinan compounds and exerts its therapeutic effects through several other receptors. In its pure form, dextromethorphan occurs as a white powder.
When exceeding approved dosages, dextromethorphan acts as a dissociative hallucinogen. It has multiple mechanisms of action, including actions as a nonselective serotonin reuptake inhibitor and a sigma-1 receptor agonist. Dextromethorphan and its major metabolite, dextrorphan, also block the NMDA receptor at high doses, which produces effects similar to other dissociative anesthetics such as ketamine, nitrous oxide, and phencyclidine.
It was patented in 1949 and approved for medical use in 1953. | 4 | Stereochemistry |
E3 ubiquitin-protein ligase TRIM33, also known as (ectodermin homolog and tripartite motif-containing 33) is a protein encoded in the human by the gene TRIM33, a member of the tripartite motif family.
TRIM33 is thought to be a transcriptional corepressor. However unlike the related TRIM24 and TRIM28 proteins, few transcription factors such as SMAD4 that interact with TRIM33 have been identified. | 1 | Biochemistry |
A simple example illustrates the principle. Ozone (O) dissociates following ultraviolet excitation to yield an oxygen atom and an oxygen molecule. Although there are (at least) two possible channels, the principle products are O(D) and O(Δ); that is, both the atom and the molecule are in their first excited electronic state (see atomic term symbol and molecular term symbol for further explanation). At a wavelength of 266 nm, the photon has enough energy to dissociate ozone to these two products, to excite the O(Δ) vibrationally to a maximum level of v = 3, and to provide some energy to the recoil velocity between the two fragments. Of course, the more energy that is used to excite the O vibrations, the less will be available for the recoil. The O(1D) atom's REMPI, combined with the product imaging technique, yields an image that can be used to calculate the O(1D) three-dimensional velocity distribution. A slice through this cylindrically symmetric distribution is shown in the figure, where an O(D) atom that has zero velocity in the center-of-mass frame would arrive at the center of the figure.D) three-dimensional velocity distribution -->
Note that there are four rings, corresponding to four main groups of O(D) speeds. These [https://www.tilakastro.com/which-planet-is-responsible-for-fame-in-astrology/ correspond] to O2(1) production at vibrational levels v = 0, 1, 2, and 3. The ring corresponding to v = 0 is the outer one, since production of the O(Δ) in this level leaves the most energy for recoil between the O(D) and O(Δ). Thus, the product imaging technique immediately shows the vibrational distribution of the O(Δ).
Note that the angular distribution of the O(D) is not uniform – more of the atoms fly toward the north or south pole than to the equator. In this case, the north-south axis is parallel to the polarization direction of the light that dissociated the ozone. Ozone molecules that absorb the polarized light are those in a particular alignment distribution, with a line connecting the end oxygen atoms in O roughly parallel to the polarization. Because the ozone dissociates more rapidly than it rotates, the O and O products recoil predominantly along this polarization axis. But there is more detail as well. A close examination shows that the peak in the angular distribution is not actually exactly at the north or south pole, but rather at an angle of about 45 degrees. This has to do with the polarization of the laser that ionizes the O(D), and can be analyzed to show that the angular momentum of this atom (which has 2 units) is aligned relative to the velocity of recoil. More detail can be found elsewhere.
There are other dissociation channels available to ozone following excitation at this wavelength. One produces O(P) and O(Σ), indicating that both the atom and molecule are in their ground electronic state. The image above has no information on this channel, since only the O(D) is probed. However, by tuning the ionization laser to the REMPI wavelength of O(P) one finds a completely different image that provides information about the internal energy distribution of O(Σ). | 7 | Physical Chemistry |
It has also been discovered that GLD2 has medical uses.
For example, such enzyme is overexpressed in patients who suffer from cancer; that's why it can be used as a prognostic factor for early appearance in breast cancer patients. Moreover, PAP activity is used to measure the effect of anticancer drugs as etoposide and cordycepin in two carcinoma cell lines: HeLa, which is the human epithelioid cervix carcinoma, and MCF-7 (human breast cancer).
However, in spite its utilities it can also be involved in the expression of several common diseases such as: leukemia, liver cirrhosis, brain injuries, hepatitis and in some cases infertility in male patients. | 1 | Biochemistry |
The adiabatic (no heat exchanged) expansion of a gas may be carried out in a number of ways. The change in temperature experienced by the gas during expansion depends not only on the initial and final pressure, but also on the manner in which the expansion is carried out.
*If the expansion process is reversible, meaning that the gas is in thermodynamic equilibrium at all times, it is called an isentropic expansion. In this scenario, the gas does positive work during the expansion, and its temperature decreases.
*In a free expansion, on the other hand, the gas does no work and absorbs no heat, so the internal energy is conserved. Expanded in this manner, the temperature of an ideal gas would remain constant, but the temperature of a real gas decreases, except at very high temperature.
*The method of expansion discussed in this article, in which a gas or liquid at pressure P flows into a region of lower pressure P without significant change in kinetic energy, is called the Joule–Thomson expansion. The expansion is inherently irreversible. During this expansion, enthalpy remains unchanged (see proof below). Unlike a free expansion, work is done, causing a change in internal energy. Whether the internal energy increases or decreases is determined by whether work is done on or by the fluid; that is determined by the initial and final states of the expansion and the properties of the fluid.
The temperature change produced during a Joule–Thomson expansion is quantified by the Joule–Thomson coefficient, . This coefficient may be either positive (corresponding to cooling) or negative (heating); the regions where each occurs for molecular nitrogen, N, are shown in the figure. Note that most conditions in the figure correspond to N being a supercritical fluid, where it has some properties of a gas and some of a liquid, but can not be really described as being either. The coefficient is negative at both very high and very low temperatures; at very high pressure it is negative at all temperatures. The maximum inversion temperature (621 K for N) occurs as zero pressure is approached. For N gas at low pressures, is negative at high temperatures and positive at low temperatures. At temperatures below the gas-liquid coexistence curve, N condenses to form a liquid and the coefficient again becomes negative. Thus, for N gas below 621 K, a Joule–Thomson expansion can be used to cool the gas until liquid N forms. | 7 | Physical Chemistry |
Stainless steel is a material which is difficult to solder because of its stable, self-healing surface oxide layer and its low thermal conductivity. A solution of zinc chloride in hydrochloric acid is a common flux for stainless steels; it has however to be thoroughly removed afterwards as it would cause pitting corrosion. Another highly effective flux is phosphoric acid; its tendency to polymerize at higher temperatures however limits its applications. | 8 | Metallurgy |
There are four levels of multimedia fugacity Models applied for prediction of fate and transport of organic chemicals in the multicompartmental environment:
Depending on the number of phases and complexity of processes different level models are applied. Many of the models apply to steady-state conditions and can be reformulated to describe time-varying conditions by using differential equations. The concept has been used to assess the relative propensity for chemicals to transform from temperate zones and “condense out” at the polar regions.
The multicompartmental approach has been applied to the “quantitative water air sediment interaction" or "QWASI" model designed to assist in understanding chemical fate in lakes. Another application found in POPCYCLING-BALTIC model, which is describing fate of persistent organic pollutants in Baltic region. | 7 | Physical Chemistry |
The oxidation of a methyl group occurs widely in nature and industry. The oxidation products derived from methyl are hydroxymethyl group , formyl group , and carboxyl group . For example, permanganate often converts a methyl group to a carboxyl () group, e.g. the conversion of toluene to benzoic acid. Ultimately oxidation of methyl groups gives protons and carbon dioxide, as seen in combustion. | 0 | Organic Chemistry |
Aggressiveness of treatment is matched to the degree of hypothermia. Treatment ranges from noninvasive, passive external warming to active external rewarming, to active core rewarming. In severe cases resuscitation begins with simultaneous removal from the cold environment and management of the airway, breathing, and circulation. Rapid rewarming is then commenced. Moving the person as little and as gently as possible is recommended as aggressive handling may increase risks of a dysrhythmia.
Hypoglycemia is a frequent complication and needs to be tested for and treated. Intravenous thiamine and glucose is often recommended, as many causes of hypothermia are complicated by Wernicke's encephalopathy.
The UK National Health Service advises against putting a person in a hot bath, massaging their arms and legs, using a heating pad, or giving them alcohol. These measures can cause a rapid fall in blood pressure and potential cardiac arrest. | 1 | Biochemistry |
Foldits toolbox is mainly for the design of protein molecules. The games creator announced the plan to add, by 2013, the chemical building blocks of organic subcomponents to enable players to design small molecules. The small molecule design system termed Drugit was tested on the Von Hippel-Lindau tumor suppressor (VHL). Results of the VHL experiment were presented in a March 2023 preprint paper and at an August 2023 American Chemical Society conference session. | 1 | Biochemistry |
The and pH of a solution are related by the Nernst equation as commonly represented by a Pourbaix diagram . explicitly denotes expressed versus the standard hydrogen electrode (SHE). For a half cell equation, conventionally written as a reduction reaction (i.e., electrons accepted by an oxidant on the left side):
The equilibrium constant of this reduction reaction is:
where curly braces { } indicate activities (), rectangle braces [ ] denote molar or molal concentrations (), represent the activity coefficients, and the stoichiometric coefficients are shown as exponents.
Activities correspond to thermodynamic concentrations and take into account the electrostatic interactions between ions present in solution. When the concentrations are not too high, the activity () can be related to the measurable concentration () by a linear relationship with the activity coefficient ():
The half-cell standard reduction potential is given by
where is the standard Gibbs free energy change, is the number of electrons involved, and is the Faraday's constant. The Nernst equation relates pH and as follows:
In the following, the Nernst slope (or thermal voltage) is used, which has a value of 0.02569... V at STP. When base-10 logarithms are used, V λ = 0.05916... V at STP where λ = ln[10] = 2.3026.
This equation is the equation of a straight line for as a function of pH with a slope of volt (pH has no units).
This equation predicts lower at higher pH values. This is observed for the reduction of O into HO, or OH, and for reduction of H into H. is then often noted as to indicate that it refers to the standard hydrogen electrode (SHE) whose = 0 by convention under standard conditions (T = 298.15 K = 25 °C = 77 F, P = 1 atm (1.013 bar), concentrations = 1 M and thus pH = 0). | 7 | Physical Chemistry |
The van der Waals force between two molecules, in this context, is the sum of the attractive or repulsive forces between them; these forces are primarily electrostatic in nature, and in their simplest form might consist of a force between two charges, two dipoles, or between a charge and a dipole. Thus, the strength of the force may often depend on the net charge, electric dipole moment, or the electric polarizability () (see for example London force) of the molecules, with highly polarizable molecules contributing to stronger forces, and so on.
The total force between two bodies, each consisting of many molecules in the van der Waals theory is simply the sum of the intermolecular van der Waals forces, where pairwise additivity is assumed. That is to say, the forces are summed as though each pair of molecules interacts completely independently of their surroundings (See Van der Waals forces between Macroscopic Objects for an example of such a treatment). This assumption is usually correct for gasses, but presents a problem for many condensed materials, as it is known that the molecular interactions may depend strongly on their environment and neighbors. For example, in a conductor, a point-like charge might be screened by the electrons in the conductance band, and the polarizability of a condensed material may be vastly different from that of an individual molecule. In order to correctly predict the van der Waals forces of condensed materials, a theory that takes into account their total electrostatic response is needed. | 7 | Physical Chemistry |
Metastable metallic hydrogen may have potential as a highly efficient rocket propellant, with a theoretical specific impulse of up to 1700 seconds (for reference, the current most efficient chemical rocket propellants have an less than 500 s), although a metastable form suitable for mass-production and conventional high-volume storage may not exist. Another significant issue is the heat of the reaction, which at over 6000 K is too high for any known engine materials to be used. This would necessitate diluting the metallic hydrogen with water or liquid hydrogen, a mixture that would still provide a significant performance boost from current propellants. | 7 | Physical Chemistry |
Aquatic invertebrates, most popularly the larvae of the caddis fly sp., are responsive to climate change, low levels of pollution and temperature change. As a result, they have the longest history of use in biomonitoring programs. Additionally, macroscopic species: frogs, fish, and some plant species, as well as, many forms of microscopic life, like bacteria and protozoa are used as indicator organisms in a variety of applications, storm water run-off among them.
Many species of Macroalgae (including Cyanobacteria, though not technically a true algae) are also used in biomonitoring for both aquatic and marine environments, as their short lifespan makes them very reactive to changes. | 2 | Environmental Chemistry |
In Mendelian disorders of large effect, findings thus far suggest one or a very small number of variants within coding genes underlie the entire condition. Because of the severity of these disorders, the few causal variants are presumed to be extremely rare or novel in the population, and would be missed by any standard genotyping assay. Exome sequencing provides high coverage variant calls across coding regions, which are needed to separate true variants from noise. A successful model of Mendelian gene discovery involves the discovery of de novo variants using trio sequencing, where parents and proband are genotyped. | 1 | Biochemistry |
Studies for the use of ESL as an anticonvulsant for children are under way .
Like oxcarbazepine, ESL has potential uses for the treatment of trigeminal neuralgia and bipolar disorder. A 2015 assessment showed no statistical difference to placebo for the latter disorder. | 4 | Stereochemistry |
Gastroesophageal reflux disease (GERD) is a condition in which the digestive acid in the stomach comes in contact with the esophagus. The irritation caused by this disorder is known as heartburn. Long-term contact between gastric acids and the esophagus can cause permanent damage to the esophagus and is associated with Barrett's esophagus. Esomeprazole reduces the production of digestive acids, thus reducing their effect on the esophagus. | 4 | Stereochemistry |
Interleukin 19 is produced mainly in monocytes, and can be found in big concentrations in patients with allergic disorders and psoriasis. IL-19 plays a big role in the CNS by regulating the inflammation process through a delayed production of it. | 1 | Biochemistry |
Dry water or empty water, a form of "powdered liquid", is an air–water emulsion in which water droplets are surrounded by a silica coating. Dry water consists of 95% liquid water, but the silica coating prevents the water droplets from combining and turning back into a bulk liquid. The result is a white powder. | 7 | Physical Chemistry |
In the direct enantiomer separation the most popular approach is use of chiral stationary phases. In this case the site of the chiral selector is on the stationary phase. Stationary phase consist of an inert solid support (usually silica microparticles) on to the surface of which a single enantiomer of a chiral molecule (selector) is either coated/adsorbed or chemically linked and that forms the chiral stationary phase. Commonly used chiral selectors include polysaccharides, proteins, cyclodextrins, etc. An interesting review of chiral stationary phase development and application in chiral analysis appeared in [https://www.chromatographyonline.com/view/review-chiral-stationary-phase-development-and-chiral-applications LCGC] magazine, 2011. | 4 | Stereochemistry |
Cheon enrolled in Yonsei University in 1981 majoring in chemistry. He later obtained a Bachelor of Science and Master of Science in 1985 and 1987, respectively. Studying under Professor Gregory S. Girolami, Cheon received a Ph.D. in chemistry from the University of Illinois at Urbana-Champaign in 1993. Staying in the U.S., he did postdoc work in the University of California Berkeley | 0 | Organic Chemistry |
Due to the electronegativity difference between carbon and nitrogen, the nitroso group has a relatively strong -I effect, but not as strong as the nitro group. (Positively charged nitrogen atoms on alkylammonium cations and on nitro groups have a much stronger -I effect) | 0 | Organic Chemistry |
Spectral bands are regions of a given spectrum, having a specific range of wavelengths or frequencies. Most often, it refers to electromagnetic bands, regions of the electromagnetic spectrum.
More generally, spectral bands may also be means in the spectra of other types of signals, e.g., noise spectrum.
A frequency band is an interval in the frequency domain, limited by a lower frequency and an upper frequency. For example, it may refer to a radio band, such as wireless communication standards set by the International Telecommunication Union. | 7 | Physical Chemistry |
Under prebiotic conditions, imidazole-4-acetaldehyde can be synthesized from erythrose, formamidine, formaldehyde, and ammonia. | 1 | Biochemistry |
The primary mutualistic interaction between transposon and host organism is in the formation of epialleles. True to the name, an epiallele is a kind of epigenetic mutant of a certain allelic type that produces distinct morphological differences from the wild type. The predominant research into this subject has been conducted on Arabidopsis thaliana, which has the dual disadvantages of being both TE-poor and an overly genetically stable organism. The manner of formation of epialleles is somewhat unclear, but it is thought to be due to the fact that some transposable elements, in stealing pieces of genetic code from their host organism, blend in so well as to confuse the host cellular machinery into thinking that its own genes are the transposons, which leads to epigenetic silencing of certain alleles, forming an epiallele. Some examples of this are:
* FWA, a dominant allele in arabidopsis, turned off by transposon regulation elements. The overall effect of this heritable silencing is to delay flowering.
* BNS, a recessive allele in arabiopsis, hypermethylated via siRNA co-opting of RISC complex, which results in silencing. The overall effect of this is the loss of a putative anaphase promoting complex gene.
* FLC, the flowering locus C gene, which represses flowering time in arabidopsis, can be partially inactivated by the insertion of a Mu-like element (MULE) into the first intron of the gene, resulting in earlier flowering time.
There is also evidence to suggest that trasposons play a more general role than was previously thought in the formation of miRNAs as well as in the silencing of centromeres. | 1 | Biochemistry |
Bland and Altman drive the point that any two methods that are designed to measure the same parameter (or property) should have good correlation when a set of samples are chosen such that the property to be determined varies considerably. A high correlation for any two methods designed to measure the same property could thus in itself just be a sign that one has chosen a widespread sample. A high correlation does not necessarily imply that there is good agreement between the two methods. | 3 | Analytical Chemistry |
Following a suggestion by Jöns Jacob Berzelius, Mulder used the term protein in his 1838 paper, "On the composition of some animal substances" (originally in French but translated in 1839 to German). In the same publication, he also proposed that animals draw most of their protein from plants.
Mulder "was the first to propose a theory concerning the causes of the differences between albumin, casein, and fibrin, and other substances more or less similar to them in physical properties and in their chemical behavior when exposed to reagents. Analyses of these substances showed that their percentage contribution with respect to carbon, hydrogen, nitrogen and oxygen were so similar as to suggest that they contain one common radical."
This radical, a macromolecule, had formula and was known as protein. The variations in albuminous substances were attributed to peripheral bonds of protein to sulfur and/or phosphorus. Justus Liebig and his students sought to determine the structure of proteins, but until the methods of Emil Fischer and Franz Hofmeister became available, the amino acid decompositions were unknown.
Augustus Voelcker was Mulder's assistant for a year from 1846.
In 1850, Mulder was elected a foreign member of the Royal Swedish Academy of Sciences. He died in Bennekom. | 0 | Organic Chemistry |
Ceramide-1-phosphate (C1P) is formed by the action of ceramide kinase (CK) enzymes on Cer. C1P carry ionic charge at neutral pH and contain two hydrophobic chains making it relatively insoluble in aqueous environment. Thus, C1P reside in the organelle where it was formed and is unlikely to spontaneously flip-flop across membrane bilayers.
C1P activate phospholipase A2 and is found, along with CK, to be a mediator of arachidonic acid released in cells in response to a protein called interleukin-1β (IL-1β) and a lipid-soluble molecule that transports calcium ions (Ca) across the bilayer, also known as calcium ionophore. C1P was also previously reported to encourage cell division (mitogenic) in fibroblasts, block apoptosis by inhibiting acid SMase in white blood cells within tissues (macrophages) and increase intracellular free calcium concentrations in thyroid cells. C1P also has known roles in vesicular trafficking, cell survival, phagocytosis ("cell eating") and macrophage degranulation. | 1 | Biochemistry |
One improvement over the standard design of ceramic vacuum filter is to use serialized pore size distributions of non-fibrous porous ceramic filters. The porosity of this type of ceramic can be varied from 20% to 60% by volume, which allows a low-pressure drop of liquid and gas flow. Custom sizes from 1 mm diameter/0.5 mm bore of porous ceramic filters are available for a range of designs. A non-fibrous porous ceramic filter is more resistant in alkaline and acidic conditions compared to fibrous ceramic filters. Thus, it has a longer service life as it has good wearing and erosion resistance as well as being able to withstand high temperatures.
Another improvement is applied at the regeneration stage when the residual filter cake is removed by back-flushing the clean plant water to wash the internal ceramic filter. Filter cake dewatering of ceramic filters produces low final cake moistures at minimum operation and maintenance costs. The residuals moisture are removed from the filter cake due to capillary action within the ceramic elements, which rotate above the slurry level. This process gives maximum filtration, and the final cake can be maintained at the lowest moisture content due to the effective cleaning of both ceramic sectors. In addition, performance can be optimized by using an ultrasonic cleaning system to achieve efficient operation conditions for regeneration of plates. The use of filtrate in looped water cycle in the design operation can reduce the water consumption up to 30-50%. High filtrate purity can be obtained, as there is only 0.001-0.005 g/L solids in the filtrate produced from this process. This eventually results in the reduction of polymer flocculant consumption in thickeners.
Ceramic scraper knives have been introduced to this design as they are able to shave through the mass formed in filter cake dewatering. The remaining layer of solid residue on the filter provides protection from mechanical abrasion. Therefore, the maintenance costs can be reduced while the service life of the ceramic filter increases. | 3 | Analytical Chemistry |
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