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A PV diagram plots the change in pressure P with respect to volume V for some process or processes. Typically in thermodynamics, the set of processes forms a cycle, so that upon completion of the cycle there has been no net change in state of the system; i.e. the device returns to the starting pressure and volume.
The figure shows the features of an idealized PV diagram. It shows a series of numbered states (1 through 4). The path between each state consists of some process (A through D) which alters the pressure or volume of the system (or both).
A key feature of the diagram is that the amount of energy expended or received by the system as work can be measured because the net work is represented by the area enclosed by the four lines.
In the figure, the processes 1-2-3 produce a work output, but processes from 3-4-1 require a smaller energy input to return to the starting position / state; so the net work is the difference between the two.
This figure is highly idealized, in so far as all the lines are straight and the corners are right angles. A diagram showing the changes in pressure and volume in a real device will show a more complex shape enclosing the work cycle. (). | 7 | Physical Chemistry |
Flora on Pandora are of a tropical type several times taller than that existing on Earth. Many, if not all, plant and animal species have bioluminescent properties. The flora specimens seen in the film were all designed by Jodie Holt, a professor of botany at the University of California, Riverside. According to Holt, Pandoran flora are able to communicate with each other through signal transduction and are larger in size than Earth flora due to greater atmospheric thickness, weaker gravity, and stronger magnetism on Pandora. | 1 | Biochemistry |
The scalar approach defines flux density as a scalar-valued function of a direction and sense in space prescribed by the investigator at a point prescribed by the investigator. Sometimes this approach is indicated by the use of the term hemispheric flux. For example, an investigator of thermal radiation, emitted from the material substance of the atmosphere, received at the surface of the earth, is interested in the vertical direction, and the downward sense in that direction. This investigator thinks of a unit area in a horizontal plane, surrounding the prescribed point. The investigator wants to know the total power of all the radiation from the atmosphere above in every direction, propagating with a downward sense, received by that unit area. For the flux density scalar for the prescribed direction and sense, we may write
where with the notation above, indicates that the integration extends only over the solid angles of the relevant hemisphere, and denotes the angle between and the prescribed direction. The term is needed on account of Lambert's law. Mathematically, the quantity is not a vector because it is a positive scalar-valued function of the prescribed direction and sense, in this example, of the downward vertical. In this example, when the collected radiation is propagating in the downward sense, the detector is said to be "looking upwards". The measurement can be made directly with an instrument (such as a pyrgeometer) that collects the measured radiation all at once from all the directions of the imaginary hemisphere; in this case, Lambert-cosine-weighted integration of the spectral radiance (or specific intensity) is not performed mathematically after the measurement; the Lambert-cosine-weighted integration has been performed by the physical process of measurement itself. | 7 | Physical Chemistry |
Solvophobic theory attempts to explain interactions between polar solvents and non-polar solutes. In the pure solvent, there are relatively strong cohesive forces between the solvent molecules due to hydrogen bonding or other polar interactions. Hence, non-polar solutes tend not to be soluble in polar solvents because these solvent-solvent binding interactions must be overcome first. When applied to liquid chromatography (LC), solvophobic theory attributes the retention of solutes on the stationary phase partly to the rejection of solute molecules by the solvent, and partly to the attraction of the solute molecules by the stationary phase. | 7 | Physical Chemistry |
An important disadvantage of polycrystalline NiAl-based alloys are their room-temperature and high-temperature brittleness, which interferes with potential structural applications. This brittleness is generally attributed to the inability of dislocations to move in the highly ordered lattices. The introduction of small amount of boron can drastically increase the ductility by suppressing intergranular fracture.
Ni-based superalloys derive their strength from the formation of γ precipitates (NiAl) in the γ phase (Ni) which strengthen the alloys through precipitation hardening. In these alloys the volume fraction of the γ precipitates is as high as 80%. Because of this high volume fraction, the evolution of these γ precipitates during the alloys life cycles is important: a major concern is the coarsening of these γ precipitates at high temperature (800 to 1000 °C), which greatly reduces the alloys strength. This coarsening is due to the balance between interfacial and elastic energy in the γ + γ phase and is generally inevitable over long durations of time. This coarsening problem is addressed by introducing other elements such as Fe, Cr and Mo, which generate multiphase configurations that can significantly increase the creep resistance. This creep resistance is attributed to the formation of inhomogeneous precipitate CrMoNi, which pins dislocations and prevents further coarsening of the γ phase. The addition of Fe and Cr also drastically increases the weldability of the alloy. | 8 | Metallurgy |
4,5-Dihydroxy-2,3-pentanedione (DPD) is an organic compound that occurs naturally but exists as several related structures. The idealized formula for this species is CHC(O)C(O)CH(OH)CHOH, but it is known to exist as several other forms resulting from cyclization. It is not stable at room temperature as a pure material, which has further complicated its analysis. The (S)-stereoisomer occurs naturally. It is typically hydrated, i.e., one keto group has added water to give the geminal diol.
DPD is produced by degradation of S-adenosylhomocysteine by the action of the enzyme S-ribosylhomocysteinase. The compound probably does not exist as depicted above, but as an equilibrium mixture of three hydrates.
DPD is a precursor to borate diester, which is known as autoinducer-2 (AI-2). AI-2 is a signaling molecules found in quorum sensing. It is produced and recognized by many Gram-negative and Gram-positive bacteria. AI-2 is synthesized by the reaction of DPD with boric acid and is recognized by the two-component sensor kinase LuxPQ in Vibrionaceae. | 0 | Organic Chemistry |
The term backscatter in photography refers to light from a flash or strobe reflecting back from particles in the lenss field of view causing specks of light to appear in the photo. This gives rise to what are sometimes referred to as orb artifacts'. Photographic backscatter can result from snowflakes, rain or mist, or airborne dust. Due to the size limitations of the modern compact and ultra-compact cameras, especially digital cameras, the distance between the lens and the built-in flash has decreased, thereby decreasing the angle of light reflection to the lens and increasing the likelihood of light reflection off normally sub-visible particles. Hence, the orb artifact is commonplace with small digital or film camera photographs. | 7 | Physical Chemistry |
Macromolecular Chemistry and Physics is a biweekly peer-reviewed scientific journal covering polymer science. It publishes full papers, talents, trends, and highlights in all areas of polymer science, from chemistry to physical chemistry, physics, and materials science. | 7 | Physical Chemistry |
The theoretical SV of a pure triglyceride molecule can be calculated by the following equation (where MW is its molecular weight):
:where:
:3 is the number of fatty acids residues per triglyceride
:1000 is the conversion factor for milligrams to grams
:56.1 is the molar mass of KOH.
For instance, triolein, a triglyceride occurring in many fats and oils, has three oleic acid residues esterified to a molecule of glycerol with a total MW of 885.4 (g / mol). Therefore, its SV equals 190 mg KOH / g sample. In comparison, trilaurin with three shorter fatty acid residues (lauric acid) has a MW of 639 and an SV of 263.
As it can be seen from equation (2), the SV of a given fat is inversely proportional to its molecular weight. Actually, as fats and oils contain a mix of different triglycerides species, the average MW can be calculated according to the following relation:
This means that coconut oil with an abundance of medium chain fatty acids (mainly lauric acid) contain more fatty acids per unit of weight than, for example, olive oil (mainly oleic acid). Consequently, more ester saponifiable functions were present per g of coconut oil, which means more KOH is required to saponify the same amount of matter, and thus a higher SV. The calculated molecular weight (Eq. 3) is not applicable to fats and oils containing high amounts of unsaponifiable material, free fatty acids (> 0.1%), or mono- and diacylglycerols (> 0.1%). | 3 | Analytical Chemistry |
An explicit distinction between thermal equilibrium and thermodynamic equilibrium is made by B. C. Eu. He considers two systems in thermal contact, one a thermometer, the other a system in which there are several occurring irreversible processes, entailing non-zero fluxes; the two systems are separated by a wall permeable only to heat. He considers the case in which, over the time scale of interest, it happens that both the thermometer reading and the irreversible processes are steady. Then there is thermal equilibrium without thermodynamic equilibrium. Eu proposes consequently that the zeroth law of thermodynamics can be considered to apply even when thermodynamic equilibrium is not present; also he proposes that if changes are occurring so fast that a steady temperature cannot be defined, then "it is no longer possible to describe the process by means of a thermodynamic formalism. In other words, thermodynamics has no meaning for such a process." This illustrates the importance for thermodynamics of the concept of temperature.
Thermal equilibrium is achieved when two systems in thermal contact with each other cease to have a net exchange of energy. It follows that if two systems are in thermal equilibrium, then their temperatures are the same.
Thermal equilibrium occurs when a system's macroscopic thermal observables have ceased to change with time. For example, an ideal gas whose distribution function has stabilised to a specific Maxwell–Boltzmann distribution would be in thermal equilibrium. This outcome allows a single temperature and pressure to be attributed to the whole system. For an isolated body, it is quite possible for mechanical equilibrium to be reached before thermal equilibrium is reached, but eventually, all aspects of equilibrium, including thermal equilibrium, are necessary for thermodynamic equilibrium. | 7 | Physical Chemistry |
There is very little known about the mechanism of action of these drugs. However, it was shown in 2015 that a possible mechanism of action of these drugs in colorectal cancer-initiating cells is through activating dsRNA expression which leads to the activation of the MDA5/MAVS RNA recognition pathway inducing some sort of viral mimicry inside the cell. | 1 | Biochemistry |
A database storing the sequence alignments of the most conserved regions of protein families. These alignments are used to derive the BLOSUM matrices. Only the sequences with a percentage of identity lower than the threshold are used.
By using the block, counting the pairs of amino acids in each column of the multiple alignment. | 1 | Biochemistry |
~90% of the organic sulfur in plants is concentrated in the amino acids cysteine and methionine. Cysteine acts as the direct or indirect precursor to any other organic sulfur compounds in plants such as coenzyme-A, methionine, biotin, lipoic acid and glutathione. The carbon skeleton necessary for sulfur assimilation are provided by glycolysis (acetyl-CoA), respiration (aspartic acid, Asp, which derives from oxaloacetate) and photorespiration (serine, Ser). Because cysteine is a direct precursor to methionine, methionine is naturally S-depleted in comparison to cysteine. The majority of sulfur is generally in the organic form but, when excess sulfur is available in the environment, inorganic sulfate becomes the major sulfur form. In most plants, S discrimination is minimal, and in a study of rice plants it was observed that discrimination takes place in the uptake stage, depleting imported sulfate by 1–2‰ from the source. This effect is through the expression of SO transporter genes (SULTR), 14 of which have been identified – which are expressed dependent on the availability of sulfate in the environment. When sulfate is plentiful low affinity transporters are expressed and when sulfate is scarce high affinity genes with greater S discrimination are expressed. | 9 | Geochemistry |
Viral transport medium (VTM) is a solution used to preserve virus specimens after collection so that they can be transported and analysed in a laboratory at a later time. Unless stored in an ultra low temperature freezer or in liquid nitrogen, virus samples, and especially RNA virus samples, are prone to degradation. However, such cooling equipment is seldom available in the field due to their cumbersome size, weight, and in the case of freezers, high energy consumption. Hence, there is a need for VTM; a chemical preservative that can be used at ambient temperature. Chemical components may include saline solution, phosphate-buffered saline (PBS), or fetal bovine serum (FBS). VTM must be sterile to avoid introducing contamination to the specimen.
In the United States, the FDA and CDC publish guidelines for VTM production. | 1 | Biochemistry |
Evolutionary simulations are performed by reproduction-mutation-selection life cycle. Populations are fixed at size and they will not go extinct. Non-overlapping generations are employed. In a typical evolutionary simulation, a single random viable individual that can produce a stable gene expression pattern is chosen as the founder. Cloned individuals are generated to create a population of identical individuals. According to the asexual or sexual reproductive mode, offspring are produced by randomly choosing (with replacement) parent individual(s) from current generation. Mutations can be acquired with probability μ and survive with probability equal to their fitness. This process is repeated until N individuals are produced that go on to found the following generation. | 1 | Biochemistry |
* The light-protective carotenoid pigments (present in photosynthetic organisms such as plants, algae, cyanobacteria and in some bacteria and archaea) have been classified as high priority targets for biosignature models on Mars due to their stability and easy identification by Raman spectroscopy. In this experiment, the light-protective carotenoids in two organisms (cyanobacterium Nostoc sp. and the green alga cf. Sphaerocystis sp.) were still detectable at relatively high levels after being exposed for 15 months.
* Dried biofilms of three desert strains of Chroococcidiopsis showed overall higher viability and lower amounts of DNA damage when compared to multi-layer films of the planktonic counterpart, and were consistent with ground Mars simulation experiments. The strains tested were CCMEE 029 from the Negev Desert, where they live beneath the surface of rocks (endoliths) and strains CCMEE 057 and CCMEE 064 from the Sinai Desert where they are both endoliths and hypoliths (within rocks or on the ground sheltered beneath rocks).
* Other results are expected to be published in Frontiers in Microbiology under the research topic title: "Habitability Beyond Earth", and in an upcoming special collection of Astrobiology journal.
* In March 2019, scientists reported that life-forms from Earth survived 18 months living in outer space outside the International Space Station (ISS), as part of the BIOMEX studies related to the EXPOSE-R2 mission, suggesting that life could survive, theoretically, on the planet Mars. | 1 | Biochemistry |
All seven STAT proteins share a common structural motif consisting of an N-terminal domain followed by a coiled-coil, DNA-binding domain, linker, Src homology 2 (SH2), and a C-terminal transactivation domain. Much research has focused on elucidating the roles each of these domains play in regulating different STAT isoforms. Both the N-terminal and SH2 domains mediate homo or heterodimer formation, while the coiled-coil domain functions partially as a nuclear localization signal (NLS). Transcriptional activity and DNA association are determined by the transactivation and DNA-binding domains, respectively. | 1 | Biochemistry |
In fMRS, depending on the focus of the study, either single-voxel or multi-voxel spectroscopic technique can be used.
In single-voxel fMRS the selection of the volume of interest (VOI) is often done by running a functional magnetic resonance imaging (fMRI) study prior to fMRS to localize the brain region activated by the task. Single-voxel spectroscopy requires shorter acquisition times; therefore it is more suitable for fMRS studies where high temporal resolution is needed and where the volume of interest is known.
Multi-voxel spectroscopy provides information about group of voxels and data can be presented in 2D or 3D images, but it requires longer acquisition times and therefore temporal resolution is decreased. Multi-voxel spectroscopy usually is performed when the specific volume of interest is not known or it is important to study metabolite dynamics in a larger brain region. | 7 | Physical Chemistry |
Enhanced Atmospheric Methane Oxidation is the concept of enhancing the overall oxidative methane sink in the atmosphere, through generating additional hydroxyl or chlorine atmospheric radicals. | 2 | Environmental Chemistry |
Porphyrin complexes consist of a square planar MN core. The periphery of the porphyrins, consisting of sp-hybridized carbons, generally display only small deviations from planarity. Additionally, the metal is often not centered in the N plane.
Large metals such as zirconium, tantalum, and molybdenum tend to bind two porphyrin ligands. Some [M(OEP)] feature a multiple bonds between the metals. | 1 | Biochemistry |
Aminosulfuranes compare favorably with many of the other fluorination methods available. They are easier to handle than sulfur tetrafluoride; however SF does not promote cationic rearrangements. With respect to carboxylic acids, aminosulfuranes and SF are complementary: the former gives acid fluorides, while the latter gives trifluoromethyl compounds.
Perfluorinated alkylamines, such as Ishikawas reagent (N,N'-diethyl-1,1,2,3,3,3-hexafluoropropylamine WRONG MOLECULE IN SCHEME BELOW), are highly selective for hydroxyl groups and do not react with aldehydes and ketones. The amide byproducts of these reagents, however, are harder to separate from the desired products than aminosulfurane byproducts.
Alkali and tetraalkylammonium fluorides can be used to displace sulfonate esters; however, these reactions require higher temperatures than aminosulfurane fluorination of the corresponding free alcohols. | 0 | Organic Chemistry |
Pyridine is diamagnetic. Its critical parameters are: pressure 5.63 MPa, temperature 619 K and volume 248 cm·mol. In the temperature range 340–426 °C its vapor pressure p can be described with the Antoine equation
where T is temperature, A = 4.16272, B = 1371.358 K and C = −58.496 K. | 0 | Organic Chemistry |
Histidine-tryptophan-ketoglutarate, or Custodiol HTK solution, is a high-flow, low-potassium preservation solution used for organ transplantation. The solution was initially developed by Hans-Jürgen Bretschneider.
HTK solution is intended for perfusion and flushing of donor liver, kidney, heart, lung and pancreas prior to removal from the donor and for preserving these organs during hypothermic storage and transport to the recipient. HTK solution is based on the principle of inactivating organ function by withdrawal of extracellular sodium and calcium, together with intensive buffering of the extracellular space by means of histidine/histidine hydrochloride, so as to prolong the period during which the organs will tolerate interruption of oxygenated blood. The composition of HTK is similar to that of intracellular fluid. All of the components of HTK occur naturally in the body. The osmolarity of HTK is 310 mOsm/L. | 1 | Biochemistry |
Examination in 2004 of Meridiani rocks, showed the first strong in situ evidence for past water by detecting the mineral jarosite, which only forms in water. This discovery proved that water once existed in Meridiani Planum. In addition, some rocks showed small laminations (layers) with shapes that are only made by gently flowing water. The first such laminations were found in a rock called "The Dells." Geologists would say that the cross-stratification showed festoon geometry from transport in subaqueous ripples. A picture of cross-stratification, also called cross-bedding, is shown on the left.
Box-shaped holes in some rocks were caused by sulfates forming large crystals, and then when the crystals later dissolved, holes, called vugs, were left behind. The concentration of the element bromine in rocks was highly variable probably because it is very soluble. Water may have concentrated it in places before it evaporated. Another mechanism for concentrating highly soluble bromine compounds is frost deposition at night that would form very thin films of water that would concentrate bromine in certain spots. | 9 | Geochemistry |
The classical limit of non-linear inverse Compton scattering, also called non-linear Thomson scattering and multiphoton Thomson scattering, is a special case of classical synchrotron emission driven by the force exerted on a charged particle by intense electric and magnetic fields. Practically, a moving charge emits electromagnetic radiation while experiencing the Lorentz force induced by the presence of these electromagnetic fields. The calculation of the emitted spectrum in this classical case is based on the solution of the Lorentz equation for the particle and the substitution of the corresponding particle trajectory in the Liénard-Wiechert fields. In the following, the considered charged particles will be electrons, and gaussian units will be used.
The component of the Lorentz force perpendicular to the particle velocity is the component responsible for the local radial acceleration and thus of the relevant part of the radiation emission by a relativistic electron of charge , mass and velocity . In a simplified picture, one can suppose a local circular trajectory for a relativistic particle and can assume a relativistic centripetal force equal to the magnitude of the perpendicular Lorentz force acting on the particle: <math display="block">
\gamma \dfrac{m v^2}{\rho}=e\sqrt{\left(\mathbf{E}+\dfrac{\mathbf{v}}{c}\times\mathbf{B}\right)^2-\left(\dfrac{\mathbf{E}\cdot\mathbf{v}}{v}\right)^2}
and are the electric and magnetic fields respectively, is the magnitude of the electron velocity and is the Lorentz factor . This equation defines a simple dependence of the local radius of curvature on the particle velocity and on the electromagnetic fields felt by the particle. Since the motion of the particle is relativistic, the magnitude can be substituted with the speed of light to simplify the expression for . Given an expression for , the model given in Example 1: bending magnet can be used to approximately describe the classical limit of non-linear inverse Compton scattering. Thus, the power distribution in frequency of non-linear Thomson scattering by a relativistic charged particle can be seen as equivalent to the general case of synchrotron emission with the main parameters made explicitly dependent on the particle velocity and on the electromagnetic fields. | 7 | Physical Chemistry |
The Small Molecule Interaction Database is a database containing protein domain-small molecule interactions. It uses a domain-based approach to identify domain families, found in the Conserved Domain Database (CDD), which interact with a query small molecule. The CDD from NCBI amalgamates data from several different sources; Protein FAMilies (PFAM), Simple Modular Architecture Research Tool (SMART), Cluster of Orthologous Genes (COGs), and NCBI's own curated sequences. The data in SMID is derived from the Protein Data Bank (PDB), a database of known protein crystal structures.
SMID can be queried by entering a protein GI, domain identifier, PDB ID or SMID ID. The results of a search provide small molecule, protein, and domain information for each interaction identified in the database. Interactions with non-biological contacts are normally screened out by default.
SMID-BLAST is a tool developed to annotate known small-molecule binding sites as well as to predict binding sites in proteins whose crystal structures have not yet been determined. The prediction is based on extrapolation of known interactions, found in the PDB, to interactions between an uncrystallized protein with a small molecule of interest. SMID-BLAST was validated against a test set of known small molecule interactions from the PDB. It was shown to be an accurate predictor of protein-small molecule interactions; 60% of predicted interactions identically matched the PDB annotated binding site, and of these 73% had greater than 80% of the binding residues of the protein correctly identified. Hogue, C et al. estimated that 45% of predictions that were not observed in the PDB data do in fact represent true positives. | 1 | Biochemistry |
Enzymatic synthesis of HMOs through transgalactosylation is an efficient way for production. Various donors, including p-nitrophenyl-β-galactopyranoside, uridine diphosphate galactose and lactose, can be used in transgalactosylation. In particular, lactose may act as either a donor or an acceptor in a variety of enzymatic reactions and is available in large quantities from the whey produced as a co-processing product from cheese production. There is a lack of published data, however, describing the large-scale production of such galacto-oligosaccharides. | 0 | Organic Chemistry |
Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons. Photosystems are found in the thylakoid membranes of plants, algae, and cyanobacteria. These membranes are located inside the chloroplasts of plants and algae, and in the cytoplasmic membrane of photosynthetic bacteria. There are two kinds of photosystems: PSI and PSII.
PSII will absorb red light, and PSI will absorb far-red light. Although photosynthetic activity will be detected when the photosystems are exposed to either red or far-red light, the photosynthetic activity will be the greatest when plants are exposed to both wavelengths of light. Studies have actually demonstrated that the two wavelengths together have a synergistic effect on the photosynthetic activity, rather than an additive one.
Each photosystem has two parts: a reaction center, where the photochemistry occurs, and an antenna complex, which surrounds the reaction center. The antenna complex contains hundreds of chlorophyll molecules which funnel the excitation energy to the center of the photosystem. At the reaction center, the energy will be trapped and transferred to produce a high energy molecule.
The main function of PSII is to efficiently split water into oxygen molecules and protons. PSII will provide a steady stream of electrons to PSI, which will boost these in energy and transfer them to NADP and H to make NADPH. The hydrogen from this NADPH can then be used in a number of different processes within the plant. | 5 | Photochemistry |
Eshelby was born at Puddington, Cheshire, the son of Captain Alan Douglas Eshelby and Phoebe Mason Hutchinson. He was educated at St Cyprian's School, Eastbourne and was due to go to Charterhouse School but developed rheumatic fever and received his secondary education privately at home. At about this time the family moved to Manor House at Farrington Gurney, Somerset where his tutors were the village schoolmaster and a local clergyman. He relied extensively on self-instruction and obtained a place in the Physics Department of Bristol University and was awarded a first class honours in physics in 1937. He then worked in a research laboratory under H W B Skinner and W Sucksmith on magnetism and the soft X-ray spectra of solids. | 8 | Metallurgy |
Lipofuscin is the name given to fine yellow-brown pigment granules composed of lipid-containing residues of lysosomal digestion. It is considered to be one of the aging or "wear-and-tear" pigments, found in the liver, kidney, heart muscle, retina, adrenals, nerve cells, and ganglion cells. | 1 | Biochemistry |
* A regularly updated repository of hundreds of computational analysis modules that support data preprocessing, gene expression analysis, proteomics, single nucleotide polymorphism (SNP) analysis, flow cytometry, and short-read sequencing.
* A programmatic interface that makes analysis modules available to computational biologists and developers from Python, Java, MATLAB, and R.
* The GenePattern Notebook Environment: Built on the Jupyter Notebook environment, GenePattern Notebook allows researchers to run GenePattern analyses within notebooks that interleave text, graphics, and executable code, creating a single "research narrative."
* GParc: Repository and community for GenePattern users to share and discuss their own GenePattern modules | 1 | Biochemistry |
The development of orthogonal protecting groups is a problem in organic synthesis because these protecting groups allow each instance of a common functional group, such as the hydroxyl group, to be distinguished during the synthesis of a complex molecule. A very common protecting group for the hydroxyl functional group is the para-methoxy benzyl (PMB) ether. This protecting group is chemically similar to the less electron-rich benzyl ether. Typically, selective cleavage of a PMB ether in the presence of a benzyl ether uses strong stoichiometric oxidants such as 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) or ceric ammonium nitrate (CAN). PMB ethers are far more susceptible to oxidation than benzyl ethers since they are more electron-rich. The selective deprotection of PMB ethers can be achieved through the use of bis-(2-(2,4-difluorophenyl)-5-trifluoromethylpyridine)-(4,4'-ditertbutylbipyridine)iridium(III) hexafluorophosphate (Ir[dF(CF)ppy](dtbbpy)PF) and a mild stoichiometric oxidant such as bromotrichloromethane, BrCCl. The photoexcited iridium catalyst is reducing enough to fragment the bromotrichloromethane to form a trichloromethyl radical, bromide anion, and the Ir(IV) complex. The electron-poor fluorinated ligands makes the iridium complex oxidising enough to accept an electron from an electron-rich arene such as a PMB ether. After the arene is oxidized, it will readily participate in hydrogen atom transfer with trichloromethyl radical to form chloroform and an oxocarbenium ion, which is readily hydrolyzed to reveal the free hydroxide. This reaction was demonstrated to be orthogonal to many common protecting groups when a base was added to neutralise the HBr produced. | 5 | Photochemistry |
The light-producing chemistry behind bioluminescence varies across the lineages of bioluminescent organisms. Based on this observation, bioluminescence is believed to have evolved independently at least 40 times. In bioluminescent bacteria, the reclassification of the members ofVibrio fischeri species group as a new genus, Aliivibrio, has led to increased interest in the evolutionary origins of bioluminescence. Among bacteria, the distribution of bioluminescent species is polyphyletic. For instance, while all species in the terrestrial genus Photorhabdus are luminescent, the genera Aliivibrio, Photobacterium, Shewanella and Vibrio contain both luminous and non-luminous species. Despite bioluminescence in bacteria not sharing a common origin, they all share a gene sequence in common. The appearance of the highly conserved lux operon in bacteria from very different ecological niches suggests a strong selective advantage despite the high energetic costs of producing light. DNA repair is thought to be the initial selective advantage for light production in bacteria. Consequently, the lux operon may have been lost in bacteria that evolved more efficient DNA repair systems but retained in those where visible light became a selective advantage. The evolution of quorum sensing is believed to have afforded further selective advantage for light production. Quorum sensing allows bacteria to conserve energy by ensuring that they do not synthesize light-producing chemicals unless a sufficient concentration are present to be visible. | 1 | Biochemistry |
tert-Butanesulfinamide (also known as 2-methyl-2-propanesulfinamide or Ellmans sulfinamide) is an organosulfur compound and a member of the class of sulfinamides. Both enantiomeric forms are commercially available and are used in asymmetric synthesis as chiral auxiliaries, often as chiral ammonia equivalents for the synthesis of amines. tert-Butanesulfinamide and the associated synthetic methodology was introduced in 1997 by Jonathan A. Ellman et al'. | 0 | Organic Chemistry |
Under these criteria, we can propose a model for the fractions of incident light that are absorbed (), remitted (), and transmitted () by one representative layer.
in which:
• is the fraction of cross-sectional surface area that is occupied by particles of type .
• is the effective absorption coefficient for particles of type .
• is the remission coefficient for particles of type .
• is the thickness of a particle of type in the direction of the incident beam.
• The summation is carried out over all of the distinct “types” of particle.
In effect, represents the fraction of light that will interact with a particle of type , and and quantify the likelihood of that interaction resulting in absorption and remission, respectively.
Surface area fractions and volume fractions for each type of particle can be defined as follows:
in which:
• is the mass fraction of particles of type i in the sample.
• is the fraction of occupied volume composed of particles of type i.
• is the fraction of particle surface area that is composed of particles of type i.
• is the fraction of total volume composed of particles of type i.
• is the fraction of cross-sectional surface area that is composed of particles of type i.
• is the density of particles of type i.
• is the void fraction of the sample.
This is a logical way of relating the spectroscopic behavior of a “representative layer” to the properties of the individual particles that make up the layer. The values of the absorption and remission coefficients represent a challenge in this modeling approach. Absorption is calculated from the fraction of light striking each type of particle and a “Beer’s law”-type calculation of the absorption by each type of particle, so the values of used should ideally model the ability of the particle to absorb light, independent of other processes (scattering, remission) that also occur. We referred to this as the absorbing power in the section above. | 7 | Physical Chemistry |
The runaway success of DNA microarrays has generated much enthusiasm for protein microarrays. However, protein microarrays have not quite taken off as expected, even with the necessary tools and know-how from DNA microarrays being in place and ready for adaptation. One major reason is that protein microarrays are much more laborious and technically challenging to construct than DNA microarrays.
The traditional methods of producing protein arrays require the separate in vivo expression of hundreds or thousands of proteins, followed by separate purification and immobilization of the proteins on a solid surface. Cell-free protein array technology attempts to simplify protein microarray construction by bypassing the need to express the proteins in bacteria cells and the subsequent need to purify them. It takes advantage of available cell-free protein synthesis technology which has demonstrated that protein synthesis can occur without an intact cell as long as cell extracts containing the DNA template, transcription and translation raw materials and machinery are provided. Common sources of cell extracts used in cell-free protein array technology include wheat germ, Escherichia coli, and rabbit reticulocyte. Cell extracts from other sources such as hyperthermophiles, hybridomas, Xenopus oocytes, insect, mammalian and human cells have also been used.
The target proteins are synthesized in situ on the protein microarray, directly from the DNA template, thus skipping many of the steps in traditional protein microarray production and their accompanying technical limitations. More importantly, the expression of the proteins can be done in parallel, meaning all the proteins can be expressed together in a single reaction. This ability to multiplex protein expression is a major time-saver in the production process. | 1 | Biochemistry |
After a BSc and a MSc in organic chemistry he worked for the Department of Scientific and Industrial Research, before earning a scholarship to go to the University of Liverpool for a PhD under Thomas Percy Hilditch, studying fish liver oils and fats from farm animals.
After his retirement in 1969, he held several honorary posts at Victoria University of Wellington. He died on 8 June 1999 and was cremated at Karori Crematorium. | 0 | Organic Chemistry |
The stereochemistry involved in the reactions of five-membered rings can be predicted by an envelope transition state model. Nucleophiles favor addition from the "inside" of the envelope, or from the top of the figure on the right. The "inside" addition produces a results in a staggered conformation, rather than the eclipsed conformation that results from the "outside" addition. | 0 | Organic Chemistry |
In many countries, pesticides must be approved for sale and use by a government agency.
Worldwide, 85% of countries have pesticide legislation for the proper storage of pesticides and 51% include provisions to ensure proper disposal of all obsolete pesticides.
Though pesticide regulations differ from country to country, pesticides, and products on which they were used are traded across international borders. To deal with inconsistencies in regulations among countries, delegates to a conference of the United Nations Food and Agriculture Organization adopted an International Code of Conduct on the Distribution and Use of Pesticides in 1985 to create voluntary standards of pesticide regulation for different countries. The Code was updated in 1998 and 2002. The FAO claims that the code has raised awareness about pesticide hazards and decreased the number of countries without restrictions on pesticide use.
Three other efforts to improve regulation of international pesticide trade are the United Nations London Guidelines for the Exchange of Information on Chemicals in International Trade and the United Nations Codex Alimentarius Commission. The former seeks to implement procedures for ensuring that prior informed consent exists between countries buying and selling pesticides, while the latter seeks to create uniform standards for maximum levels of pesticide residues among participating countries. | 2 | Environmental Chemistry |
is synonymous to "the relative abundance of elements" in any object, either in weight ratio or in atomic (number of atoms) ratio, regardless of how "Earth's crust" is defined, and denotation is not restricted to percents. | 9 | Geochemistry |
Depending on the marker, it can take between 2 and 24 hours for the level to increase in the blood. Additionally, determining the levels of cardiac markers in the laboratory - like many other lab measurements - takes substantial time. Cardiac markers are therefore not useful in diagnosing a myocardial infarction in the acute phase. The clinical presentation and results from an ECG are more appropriate in the acute situation.
However, in 2010, research at the Baylor College of Medicine revealed that, using diagnostic nanochips and a swab of the cheek, cardiac biomarker readings from saliva can, with the ECG readings, determine within minutes whether someone is likely to have had a heart attack. | 1 | Biochemistry |
As of 2021, new laws do not directly include Armodafinil as a doping agent, but they do include Modafinil, as Armodafinil is an enantiomer of Modafinil it will show up on lab tests, but it can be debated if it is or not the same substance.
New laws state that simple possession is not a criminal offence and is punished with a fine and confiscation. Importing into Romania and exporting from Romania of the substance, without a valid medical prescription, is a criminal offence and is punished with jail time between two and seven years. | 4 | Stereochemistry |
The energy U stored in an electrostatic field distribution is:Knowing the magnitude of the electric field of an ion in a medium of dielectric constant ε is and the volume element can be expressed as , the energy can be written as: Thus, the energy of solvation of the ion from gas phase (ε =1) to a medium of dielectric constant ε is: | 7 | Physical Chemistry |
A DNA transcription unit encoding for a protein may contain both a coding sequence, which will be translated into the protein, and regulatory sequences, which direct and regulate the synthesis of that protein. The regulatory sequence before (upstream from) the coding sequence is called the five prime untranslated regions (5UTR); the sequence after (downstream from) the coding sequence is called the three prime untranslated regions (3UTR).
As opposed to DNA replication, transcription results in an RNA complement that includes the nucleotide uracil (U) in all instances where thymine (T) would have occurred in a DNA complement.
Only one of the two DNA strands serves as a template for transcription. The antisense strand of DNA is read by RNA polymerase from the 3 end to the 5 end during transcription (3 → 5). The complementary RNA is created in the opposite direction, in the 5 → 3 direction, matching the sequence of the sense strand except switching uracil for thymine. This directionality is because RNA polymerase can only add nucleotides to the 3 end of the growing mRNA chain. This use of only the 3 → 5' DNA strand eliminates the need for the Okazaki fragments that are seen in DNA replication. This also removes the need for an RNA primer to initiate RNA synthesis, as is the case in DNA replication.
The non-template (sense) strand of DNA is called the coding strand, because its sequence is the same as the newly created RNA transcript (except for the substitution of uracil for thymine). This is the strand that is used by convention when presenting a DNA sequence.
Transcription has some proofreading mechanisms, but they are fewer and less effective than the controls for copying DNA. As a result, transcription has a lower copying fidelity than DNA replication. | 1 | Biochemistry |
With termination collisions restricted, the concentration of active polymerizing chains and simultaneously the consumption of monomer rises rapidly. Assuming abundant unreacted monomer, viscosity changes affect the macromolecules but do not prove high enough to prevent smaller molecules – such as the monomer – from moving relatively freely. Therefore, the propagation reaction of the free-radical polymerization process is relatively insensitive to changes in viscosity. This also implies that at the onset of autoacceleration the overall rate of reaction increases relative to the rate of unautoaccelerated reaction given by the overall rate of reaction equation for free-radical polymerization:
Approximately, as the termination decreases by a factor of 4, the overall rate of reaction will double. The decrease of termination reactions also allows radical chains to add monomer for longer time periods, raising the mass-average molecular mass dramatically. However, the number-average molecular mass only increases slightly, leading to broadening of the molecular mass distribution (high dispersity, very polydispersed product). | 7 | Physical Chemistry |
Diphenylamine is an organic compound with the formula (CH)NH. The compound is a derivative of aniline, consisting of an amine bound to two phenyl groups. The compound is a colorless solid, but commercial samples are often yellow due to oxidized impurities. Diphenylamine dissolves well in many common organic solvents, and is moderately soluble in water. It is used mainly for its antioxidant properties. Diphenylamine is widely used as an industrial antioxidant, dye mordant and reagent and is also employed in agriculture as a fungicide and antihelmintic. | 3 | Analytical Chemistry |
When setting up their new comparative qPCR systems titled "Dots in Boxes" in 2017, New England Biolabs stated that they had designed the data collection portion around the MIQE guidelines so that the data fit all the minimum parameter checklists in the protocols. Other scientific instrument companies have assisted in guideline compliance by purposefully tailoring their devices for them, including Bio-Rad creating a mobile app that allows for active marking of the MIQE checklist as each step is completed.
An overview of the 10th anniversary since the publication of the MIQE guidelines was conducted in June 2020 and discussed the scientific studies that had produced better and more organized results when following the guidelines. In August 2020, an updated version of the guidelines for the digital PCR method was published to account for improvement in machinery, technologies, and techniques since the original 2013 release. Additional guideline steps were added for data analysis, while also providing a more simplified checklist table for researchers to use. An RT-qPCR targeting assay was developed alongside Stephen Bustin using the MIQE guidelines for clinical biomarkers in December 2020 in order to identify the clinical presence of COVID-19 viral particles during the COVID-19 pandemic. | 1 | Biochemistry |
Certain parent materials also contribute to soil acidification. Granites and their allied igneous rocks are called "acidic" because they have a lot of free quartz, which produces silicic acid on weathering. Also, they have relatively low amounts of calcium and magnesium. Some sedimentary rocks such as shale and coal are rich in sulfides, which, when hydrated and oxidized, produce sulfuric acid which is much stronger than silicic acid. Many coal soils are too acidic to support vigorous plant growth, and coal gives off strong precursors to acid rain when it is burned. Marine clays are also sulfide-rich in many cases, and such clays become very acidic if they are drained to an oxidizing state. | 9 | Geochemistry |
Water vapor, water vapour or aqueous vapor is the gaseous phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Water vapor is transparent, like most constituents of the atmosphere. Under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is less dense than most of the other constituents of air and triggers convection currents that can lead to clouds and fog.
Being a component of Earths hydrosphere and hydrologic cycle, it is particularly abundant in Earths atmosphere, where it acts as a greenhouse gas and warming feedback, contributing more to total greenhouse effect than non-condensable gases such as carbon dioxide and methane. Use of water vapor, as steam, has been important for cooking, and as a major component in energy production and transport systems since the industrial revolution.
Water vapor is a relatively common atmospheric constituent, present even in the solar atmosphere as well as every planet in the Solar System and many astronomical objects including natural satellites, comets and even large asteroids. Likewise the detection of extrasolar water vapor would indicate a similar distribution in other planetary systems. Water vapor can also be indirect evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects. | 2 | Environmental Chemistry |
Several important measures are used to characterize solar cells. The most obvious is the total amount of electrical power produced for a given amount of solar power shining on the cell. Expressed as a percentage, this is known as the solar conversion efficiency. Electrical power is the product of current and voltage, so the maximum values for these measurements are important as well, J and V respectively. Finally, in order to understand the underlying physics, the "quantum efficiency" is used to compare the chance that one photon (of a particular energy) will create one electron.
In quantum efficiency terms, DSSCs are extremely efficient. Due to their "depth" in the nanostructure there is a very high chance that a photon will be absorbed, and the dyes are very effective at converting them to electrons. Most of the small losses that do exist in DSSC's are due to conduction losses in the TiO and the clear electrode, or optical losses in the front electrode. The overall quantum efficiency for green light is about 90%, with the "lost" 10% being largely accounted for by the optical losses in the top electrode. The quantum efficiency of traditional designs vary, depending on their thickness, but are about the same as the DSSC.
In theory, the maximum voltage generated by such a cell is simply the difference between the (quasi-)Fermi level of the TiO and the redox potential of the electrolyte, about 0.7 V under solar illumination conditions (V). That is, if an illuminated DSSC is connected to a voltmeter in an "open circuit", it would read about 0.7 V. In terms of voltage, DSSCs offer slightly higher V than silicon, about 0.7 V compared to 0.6 V. This is a fairly small difference, so real-world differences are dominated by current production, J.
Although the dye is highly efficient at converting absorbed photons into free electrons in the TiO, only photons absorbed by the dye ultimately produce current. The rate of photon absorption depends upon the absorption spectrum of the sensitized TiO layer and upon the solar flux spectrum. The overlap between these two spectra determines the maximum possible photocurrent. Typically used dye molecules generally have poorer absorption in the red part of the spectrum compared to silicon, which means that fewer of the photons in sunlight are usable for current generation. These factors limit the current generated by a DSSC, for comparison, a traditional silicon-based solar cell offers about 35 mA/cm, whereas current DSSCs offer about 20 mA/cm.
Overall peak power conversion efficiency for current DSSCs is about 11%. Current record for prototypes lies at 15%. | 5 | Photochemistry |
Structural symmetry of a molecule can be defined mathematically as a permutation of the atoms that exchanges at least two atoms but does not change the molecule's structure. Two atoms then can be said to be structurally equivalent if there is a structural symmetry that takes one to the other.
Thus, for example, all four hydrogen atoms of methane are structurally equivalent, because any permutation of them will preserve all the bonds of the molecule.
Likewise, all six hydrogens of ethane () are structurally equivalent to each other, as are the two carbons; because any hydrogen can be switched with any other, either by a permutation that swaps just those two atoms, or by a permutation that swaps the two carbons and each hydrogen in one methyl group with a different hydrogen on the other methyl. Either operation preserves the structure of the molecule. That is the case also for the hydrogen atoms cyclopentane, allene, 2-butyne, hexamethylenetetramine, prismane, cubane, dodecahedrane, etc.
On the other hand, the hydrogen atoms of propane are not all structurally equivalent. The six hydrogens attached to the first and third carbons are equivalent, as in ethane, and the two attached to the middle carbon are equivalent to each other; but there is no equivalence between these two equivalence classes. | 4 | Stereochemistry |
Sharpless is a two-time Nobel Laureate. He is a recipient of the 2001 and 2022 Nobel Prize in Chemistry for his work on "chirally catalysed oxidation reactions", and "click chemistry", respectively.
In 2019, Sharpless was awarded the Priestley medal, the American Chemical Society's highest honor, for "the invention of catalytic, asymmetric oxidation methods, the concept of click chemistry and development of the copper-catalyzed version of the azide-acetylene cycloaddition reaction.". He received the Gold Medal of the American Institute of Chemists in 2023.
He is Distinguished University Professor at Kyushu University. He holds honorary degrees from the KTH Royal Institute of Technology (1995), Technical University of Munich (1995), Catholic University of Louvain (1996) and Wesleyan University (1999). | 4 | Stereochemistry |
In chemistry, pyramidal inversion (also umbrella inversion) is a fluxional process in compounds with a pyramidal molecule, such as ammonia (NH) "turns inside out". It is a rapid oscillation of the atom and substituents, the molecule or ion passing through a planar transition state. For a compound that would otherwise be chiral due to a stereocenter, pyramidal inversion allows its enantiomers to racemize. The general phenomenon of pyramidal inversion applies to many types of molecules, including carbanions, amines, phosphines, arsines, stibines, and sulfoxides. | 4 | Stereochemistry |
*Hardware architecture: At the core of HIVE there exists a solid backbone hardware made of few redundant critical components and scalable compute and storage units. The diagram at the right demonstrates the connectivity and components assignations for such HIVE cluster. Core components providing the vital functions for HIVE cloud include
**web servers facing outside through the high-end secure firewall to support web-portal functionality;
**cloud servers are the core functional units orchestrating distributed storage and computations workflows through complex queuing and prioritization schemas;
**high availability drone hardware serves as a computational unit for scientific visualization and user interface support functionalities;
**ultra-fast inter-process communication storage units organize distributed computations data interchange staging arena.
**switches and firewall hardware organize the secure high performance network environment for HIVE cloud.
**permanent storage units each are designed to store hundreds of terabytes of NGS data and reference genomes as well as storage for computational results and personal user files.
Sub-clusters of scalable high performance high density compute cores are there to serve as a powerhouse for extra-large distributed parallelized computations of NGS algorithmics. System is extremely scalable and has deployment instances ranging from a single HIVE in a box appliance to massive enterprise level systems of thousands of compute units.
*Software architecture: HIVE software infrastructure consists of layers incrementally providing more functionality.
**The Kernel backbone layer provides integration with heterogeneous hardware and operating system platforms.
**HIVE cloud backbone supports distributed storage, security and computing environment.
**Science backbone represents set of low level scientific libraries to perform variety of scientific computations, mathematical apparatus for chemical, biological, statistical and other purely scientific concepts
**CGI and Java-script layers provide web-portal and web-application compatibility layers.
**Low level libraries provide Application Programming Interface (API) for developing tools and utilities.
**Integrated apps provide major NGS tool arsenal
**Web-apps and HIVE –portal provide web-portal functionality | 1 | Biochemistry |
Virilization can occur in childhood in both males and females due to excessive amounts of androgens. Typical effects of virilization in children are pubic hair, accelerated growth and bone maturation, increased muscle strength, acne, and adult body odor. In males, virilization may signal precocious puberty, while congenital adrenal hyperplasia and androgen producing tumors (usually) of the gonads or adrenals are occasional causes in both sexes. | 1 | Biochemistry |
The property of photoconverted fluorescence Kaede protein was serendipitously discovered and first reported by Ando et al. in Proceedings of the United States National Academy of Sciences. An aliquot of Kaede protein was discovered to emit red fluorescence after being left on the bench and exposed to sunlight. Subsequent verification revealed that Kaede, which is originally green fluorescent, after exposure to UV light is photoconverted, becoming red fluorescent. It was then named Kaede. | 1 | Biochemistry |
Söllner was the son of lawyer Anton Maria Söllner and his wife Julie ( Karplus). He grew up in Vienna and began studying chemistry and philosophy at the University of Vienna in 1921. From his third semester he was a student assistant (Demonstrator) at the university. He completed his dissertation with Alfons Klemenc. In 1928 he entered the service of the Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry in Berlin, where he worked as a scientific assistant alongside Herbert Freundlich. In May 1933, Söllner began a habilitation thesis in the field of osmosis which was reviewed by Fritz Haber, Max Bodenstein and Herbert Freundlich.
Unfortunately, in the same year the Nazi party seized power. According to the national socialist definition he was of Jewish heritage and was therefore forced him to leave his position at the institute in June 1933. He then emigrated to Great Britain, where he found a position in the chemistry department of University College London, where he worked from 1933 to 1937. He was also a visiting researcher and consultant at Imperial Chemical Industries.
In 1937 Söllner moved to the United States. There he took a position as a chemist with the Department of Agronomy at Cornell University in Ithaca with support from the “Emergency Committee in Aid of Displaced German Scholars“. In 1938 he moved to the Department of Physiological Chemistry at the University of Minnesota School of Medicine in Minneapolis. There he was initially employed as an Associate Chemist. He was promoted to "Regular Chemist" in 1939, Associate Professor in 1943 and Full Professor in 1947.
Söllner was labelled as an enemy of the state by Nazi authorities. In the spring of 1940, the Reich Security Main Office in Berlin put him on a special Great Britain wanted list, a list of people who, in the event of a successful invasion and occupation of the British Isles by the Wehrmacht, should be identified and arrested as a priority by the SS special forces that followed the occupation forces.
Later Söllner moved to the Institute of Health in Bethesda, Maryland where he worked in the laboratory of National Institute of Arthritis Metabolism and Digestive Diseases, initially at the rank of Principal Research Analyst, from 1948 as a senior physical biochemist and from 1965 as head of the section for electrochemistry and colloid chemistry. In 1973 he officially retired, but continued to work as a consultant and visiting researcher for the institute until 1975.
Söllner was a specialist in ultrasound for colloid systems. In this context, he focused his research on the study of membranes and their electrophysical properties and on "Studies of Dispersion of Solids, Coagulation, and Fog Formation". Söllner published about 120 scientific papers in specialist journals. He was also a member of the American Association for the Advancement of Science, the American Institute of Chemistry and the New York Academy of Sciences, the American Chemical Society, the Society of General Physiologists and the Electrochemical Society. | 7 | Physical Chemistry |
Global paleoclimate indicators are the proxies sensitive to global paleoclimatic environment changes. They are mostly derived from marine sediments. Paleoclimate indicators derived from terrestrial sediments, on the other hand, are commonly influenced by local tectonic movements and paleogeographic variations. Factors governing the Earths climate system include plate tectonics, which controls the configuration of continents, the interplay between the atmosphere and the ocean, and the Earths orbital characteristics (Milankovitch cycles). Global paleoclimate indicators are established based on the information extracted from the analyses of geologic materials, including biological, geochemical and mineralogical data preserved in marine sediments. Indicators are generally grouped into three categories; paleontological, geochemical and lithological. | 9 | Geochemistry |
The purpose of studying the proteome is to better understand the activity of cells at the single cells level. Since proteins are responsible for determining how the cell acts, understanding the proteome of single cell gives the best understanding of how a cell operates, and how gene expression changes in a cell due to different environmental stimuli. Although transcriptomics has the same purpose as proteomics it is not as accurate at determining gene expression in cells as it does not take into account post-transcriptional regulation. Transcriptomics is still important as studying the difference between RNA levels and protein levels could give insight on which genes are post-transcriptionally regulated. | 1 | Biochemistry |
An abiogenic substance or process does not result from the present or past activity of living organisms. Abiogenic products may, e.g., be minerals, other inorganic compounds, as well as simple organic compounds (e.g. extraterrestrial methane, see also abiogenesis). | 0 | Organic Chemistry |
Prior to the widespread use of herbicides, cultural controls, such as altering soil pH, salinity, or fertility levels, were used to control weeds. Mechanical control including tillage and flooding were also used to control weeds. In the late 19th and early 20th centuries, inorganic chemicals such as sulfuric acid, arsenic, copper salts, kerosene and sodium chlorate were used to control weeds, but these chemicals were either toxic, flammable or corrosive and were expensive and ineffective at controlling weeds. | 2 | Environmental Chemistry |
Inelastic scattering of light caused by acoustic phonons was first predicted by Léon Brillouin in 1914
. Leonid Mandelstam is believed to have recognised the possibility of such scattering as early as 1918, but he published his idea only in 1926.
In order to credit Mandelstam, the effect is also called Brillouin-Mandelstam scattering (BMS). Other commonly used names are Brillouin light scattering (BLS) and Brillouin-Mandelstam light scattering (BMLS).
The process of stimulated Brillouin scattering (SBS) was first observed by Chiao et al. in 1964. The optical phase conjugation aspect of the SBS process was discovered by Boris Yakovlevich Zeldovich et al. in 1972. | 7 | Physical Chemistry |
In all organisms, two steps are required to read the information encoded in a genes DNA and produce the protein it specifies. First, the genes DNA is transcribed to messenger RNA (mRNA). Second, that mRNA is translated to protein. RNA-coding genes must still go through the first step, but are not translated into protein. The process of producing a biologically functional molecule of either RNA or protein is called gene expression, and the resulting molecule is called a gene product. | 1 | Biochemistry |
*1930s – first reports of the use of sucrose for gel electrophoresis; moving-boundary electrophoresis (Tiselius)
*1950 – introduction of "zone electrophoresis" (Tiselius); paper electrophoresis
*1955 – introduction of starch gels, mediocre separation (Smithies)
*1959 – introduction of acrylamide gels; discontinuous electrophoresis (Ornstein and Davis); accurate control of parameters such as pore size and stability; and (Raymond and Weintraub)
*1965 – introduction of free-flow electrophoresis (Hannig)
*1966 – first use of agar gels
*1969 – introduction of denaturing agents especially SDS separation of protein subunit (Weber and Osborn)
*1970 – Lämmli separated 28 components of T4 phage using a stacking gel and SDS
*1972 – agarose gels with ethidium bromide stain
*1975 – 2-dimensional gels (O’Farrell); isoelectric focusing, then SDS gel electrophoresis
*1977 – sequencing gels (Sanger)
*1981 – introduction of capillary electrophoresis (Jorgenson and Lukacs)
*1983 – pulsed-field gel electrophoresis enables separation of large DNA molecules (Sweeley)
*2004 – introduction of a standardized polymerization time for acrylamide gel solutions to optimize gel properties, in particular thermodynamic stability, during electrophoresis (Kastenholz)
A 1959 book on electrophoresis by Milan Bier cites references from the 1800s. However, Oliver Smithies made significant contributions. Bier states: "The method of Smithies ... is finding wide application because of its unique separatory power." Taken in context, Bier clearly implies that Smithies' method is an improvement. | 1 | Biochemistry |
The Blastocrithidia nuclear code (translation table 31) is a genetic code used by the nuclear genome of the trypanosomatid genus Blastocrithidia. This code, along with translation tables 27 and 28, is remarkable in that every one of the 64 possible codons can be a sense codon. | 1 | Biochemistry |
Physical methods are the conceptually simplest, using some physical means to force the transfected material into the target cell's nucleus. The most widely used physical method is electroporation, where short electrical pulses disrupt the cell membrane, allowing the transfected nucleic acids to enter the cell. Other physical methods use different means to poke holes in the cell membrane: Sonoporation uses high-intensity ultrasound (attributed mainly to the cavitation of gas bubbles interacting with nearby cell membranes), optical transfection uses a highly focused laser to form a ~1 µm diameter hole.
Several methods use tools that force the nucleic acid into the cell, namely: microinjection of nucleic acid with a fine needle; biolistic particle delivery, in which nucleic acid is attached to heavy metal particles (usually gold) and propelled into the cells at high speed; and magnetofection, where nucleic acids are attached to magnetic iron oxide particles and driven into the target cells by magnets.
Hydrodynamic delivery is a method used in mice and rats, in which nucleic acids can be delivered to the liver by injecting a relatively large volume in the blood in less than 10 seconds; nearly all of the DNA is expressed in the liver by this procedure. | 1 | Biochemistry |
Porphyrins have conjugated molecular ring systems (macrocycles) that appear in many enzymes of biological systems. As a ligand, porphyrin forms numerous complexes with metallic ions like iron in hemoglobin that colors blood red. Hemoglobin transports oxygen to the cells of our bodies. Porphyrin–metal complexes often have strong colors. A similar molecular structural ring unit called chlorin is similarly complexed with magnesium instead of iron when forming part of the most common forms of chlorophyll molecules, giving them a green color. Another similar macrocycle unit is corrin, which complexes with cobalt when forming part of cobalamin molecules, constituting Vitamin B12, which is intensely red. The corrin unit has six conjugated double bonds but is not conjugated all the way around its macrocycle ring. | 7 | Physical Chemistry |
The S-N bond in sulfenamides are labile in a variety of ways. The sulfur atom tends to be the more electrophilic center of the S-N bond. Nucleophilic attack on sulfur can occur by amines, by thiols, and by alkyl-magnesium halides which leads to either new sulfenamide compounds or back to starting compounds such as sulfides and disulfides respectively. Both the nitrogen and sulfur atoms comprising the S-N bond in sulfenamides have lone pairs of electrons in their outer shells, one and two for nitrogen and sulfur respectively. These lone pairs allow for the possibility of forming either higher order bonds(double, triple) or adding new substituent groups to the compound For instance the nitrogen in the S-N bond of 2-hydroxysulfenanilides can oxidized to an imine species with sodium dichromate.
Sulfenamides react with amino-azaheterocycles to form heterocyclic systems (often used as amino protecting groups in various other synthesis reactions). Chlorocarbonylsulfenyl chloride (ClCOSCl) also readily forms S-N bonds with 2-amino-azaheterocycles, but always of a cyclical nature.
A novel variant of the Appel reaction has been noted for sulfenamides. Reaction of o-nitrobenzenesulfenamide with PPh and CCl leads the formation of o-nitro-N-(triphenylphosphorany1idene)-benzenesulfenamide. In this variant reaction the triphenyl phosphine forms a double bonded linkage with nitrogen in the sulfenamide instead of oxygen as is customary in the Appel reaction. Additionally in the traditional Apple reaction the R-OH bond is cleaved leaving oxygen attached to triphenylphosphine. In this variant the S-N bond is not cleaved. | 0 | Organic Chemistry |
The detector (5) of AFM measures the deflection (displacement with respect to the equilibrium position) of the cantilever and converts it into an electrical signal. The intensity of this signal will be proportional to the displacement of the cantilever.
Various methods of detection can be used, e.g. interferometry, optical levers, the piezoelectric method, and STM-based detectors (see section "AFM cantilever deflection measurement"). | 6 | Supramolecular Chemistry |
Cavitation is the unstable unhindered expansion of a microscopic void in a solid elastomer under the action of tensile hydrostatic stresses. This can occur whenever the hydrostatic tension exceeds 5/6 of Young's modulus.
The cavitation phenomenon may manifest in any of the following situations:
* imposed hydrostatic tensile stress acting on a pre-existing void
* void pressurization due to gases that are generated due to chemical action (as in volatilization of low-molecular weight waxes or oils: blowpoint for insufficiently cured rubber, or thermal blowout for systems operating at very high temperature)
* void pressurization due to gases that come out of solution (as in gases dissolved at high pressure) | 7 | Physical Chemistry |
Coverage (read depth or depth) is the average number of reads representing a given nucleotide in the reconstructed sequence. It can be calculated from the length of the original genome (G), the number of reads(N), and the average read length(L) as . For example, a hypothetical genome with 2,000 base pairs reconstructed from 8 reads with an average length of 500 nucleotides will have 2x redundancy. This parameter also enables one to estimate other quantities, such as the percentage of the genome covered by reads (sometimes also called coverage). A high coverage in shotgun sequencing is desired because it can overcome errors in base calling and assembly. The subject of DNA sequencing theory addresses the relationships of such quantities.
Sometimes a distinction is made between sequence coverage and physical coverage. Sequence coverage is the average number of times a base is read (as described above). Physical coverage is the average number of times a base is read or spanned by mate paired reads. | 1 | Biochemistry |
Translation is carried out by more than one ribosome simultaneously. Because of the relatively large size of ribosomes, they can only attach to sites on mRNA 35 nucleotides apart. The complex of one mRNA and a number of ribosomes is called a polysome or polyribosome. | 1 | Biochemistry |
The conversion efficiency of biological photovoltaic devices is presently too low for scaled-up versions to achieve grid parity. Genetic engineering approaches are being employed to increase the current output from photosynthetic organisms for use in biological photovoltaic systems. | 7 | Physical Chemistry |
Ion channels may be classified by gating, i.e. what opens and closes the channels. For example, voltage-gated ion channels open or close depending on the voltage gradient across the plasma membrane, while ligand-gated ion channels open or close depending on binding of ligands to the channel. | 1 | Biochemistry |
Alanine is produced by the transamination of one molecule of pyruvate using two alternate steps: 1) conversion of glutamate to α-ketoglutarate using a glutamate-alanine transaminase, and 2) conversion of valine to α-ketoisovalerate via Transaminase C.
Not much is known about the regulation of alanine synthesis. The only definite method is the bacteriums ability to repress Transaminase C activity by either valine or leucine (see ilvEDA' operon). Other than that, alanine biosynthesis does not seem to be regulated. | 1 | Biochemistry |
The Calvin cycle accounts for 90% of biological carbon fixation. Consuming ATP and NADPH, the Calvin cycle in plants accounts for the preponderance of carbon fixation on land. In algae and cyanobacteria, it accounts for the preponderance of carbon fixation in the oceans. The Calvin cycle converts carbon dioxide into sugar, as triose phosphate (TP), which is glyceraldehyde 3-phosphate (GAP) together with dihydroxyacetone phosphate (DHAP):
:3 CO + 12 e + 12 H + P → TP + 4 HO
An alternative perspective accounts for NADPH (source of e) and ATP:
:3 CO + 6 NADPH + 6 H + 9 ATP + 5 HO → TP + 6 NADP + 9 ADP + 8 P
The formula for inorganic phosphate (P) is HOPO + 2H. Formulas for triose and TP are CHO-CHOH and CHO-CHOPO + 2H | 5 | Photochemistry |
The SK channel gating mechanism is controlled by intracellular calcium levels. Calcium enters the cell via voltage activated calcium channels as well as through NMDA receptors. Calcium does not directly bind to the SK channel. Even in the absence of calcium, the SK channel binds to the C-lobe of the protein calmodulin (CaM). When the N-lobe binds calcium, it traps the S4-S5 linker on the intracellular subunit of the SK channel. When each of the four S4-S5 linkers are bound to the N-lobe of calmodulin, the SK channel changes conformation. Calmodulin pushes the S4-S5 linker to allow the expansion of the S6 bundle crossing, leading to opening of the pore. The idea that this transitions the channel from a tetramer of monomers to a folded dimer of dimers, which results in rotation of the CaM-binding domains is now abandoned, and the most recent observations are not compatible with the proposal that this rotation causes the mechanical opening of the channel gate. The time constant of SK channel activation is approximately 5 ms. When calcium levels are depleted, the time constant for channel deactivation ranges from 15–60 ms. | 1 | Biochemistry |
Toluene hydrodealkylation converts toluene to benzene. In this hydrogen-intensive process, toluene is mixed with hydrogen, then passed over a chromium, molybdenum, or platinum oxide catalyst at 500–650 °C and 20–60 atm pressure. Sometimes, higher temperatures are used instead of a catalyst (at the similar reaction condition). Under these conditions, toluene undergoes dealkylation to benzene and methane:
This irreversible reaction is accompanied by an equilibrium side reaction that produces
biphenyl (aka diphenyl) at higher temperature:
If the raw material stream contains much non-aromatic components (paraffins or naphthenes), those are likely decomposed to lower hydrocarbons such as methane, which increases the consumption of hydrogen.
A typical reaction yield exceeds 95%. Sometimes, xylenes and heavier aromatics are used in place of toluene, with similar efficiency.
This is often called "on-purpose" methodology to produce benzene, compared to conventional BTX (benzene-toluene-xylene) extraction processes. | 2 | Environmental Chemistry |
NPPs have been implicated in several biological processes, including bone mineralization, purine nucleotide and insulin signaling, and cell differentiation and motility. They are generally regulated at the transcriptional level. | 1 | Biochemistry |
The RNA polymerase II transcribes U1, U2, U4, U5 and the less abundant U11, U12 and U4atac (snRNAs) acquire a m7G-cap which serves as an export signal. Nuclear export is mediated by CRM1. | 1 | Biochemistry |
Recently thiourea has been investigated for its multiple desirable properties as a fertilizer especially under conditions of environmental stress. It may be applied in various capacities, such as a seed pretreatment (for priming), foliar spray or medium supplementation. | 0 | Organic Chemistry |
In his book Chance and Necessity, Jacques Monod described the functions of proteins and other molecules capable of recognizing with elective discrimination a substrate or ligand or other molecule. In describing these molecules he introduced the term cognitive functions, the same cognitive functions that Maxwell attributed to his demon. Werner Loewenstein goes further and names these molecules molecular demon<nowiki/> or demon in short.
Naming the biological molecular machines in this way makes it easier to understand the similarities between these molecules and Maxwell's demon.
Because of this real discriminative if not cognitive property, Jacques Monod attributed a teleonomic function to these biological complexes. Teleonomy implies the idea of an oriented, coherent and constructive activity. Proteins therefore must be considered essential molecular agents in the teleonomic performances of all living beings. | 6 | Supramolecular Chemistry |
N-Linked glycans are attached in the endoplasmic reticulum to the nitrogen (N) in the side chain of asparagine (Asn) in the sequon. The sequon is an Asn-X-Ser or Asn-X-Thr sequence, where X is any amino acid except proline and the glycan may be composed of N-acetylgalactosamine, galactose, neuraminic acid, N-acetylglucosamine, fucose, mannose, and other monosaccharides. | 0 | Organic Chemistry |
The structure, properties, and reactivity of a molecule are dependent on straightforward bonding interactions including covalent bonds, ionic bonds, hydrogen bonds, and other forms of bonding. This bonding supplies a basic molecular skeleton that is modified by repulsive forces generally considered steric effects. Basic bonding and steric effects are at times insufficient to explain many structures, properties, and reactivity. Thus, steric effects are often contrasted and complemented by electronic effects, implying the influence of effects such as induction, conjunction, orbital symmetry, electrostatic interactions, and spin state. There are more esoteric electronic effects but these are among the most important when considering chemical structure and reactivity.
Special computational procedure was developed to separate steric and electronic effects of an arbitrary group in the molecule and to reveal their influence on structure and reactivity. | 7 | Physical Chemistry |
The most common F-gases are hydrofluorocarbons (HFCs), which contain hydrogen, fluorine, and carbon. They are used in a multitude of applications including commercial refrigeration, industrial refrigeration, air-conditioning systems, heat pump equipment, and as blowing agents for foams, fire extinguishants, aerosol propellants, and solvents. HFC-134a (1,1,1,2-Tetrafluoroethane) has grown to become the most abundant HFC in Earth's atmosphere as of year 2015.
Perfluorocarbons (PFCs) are the compounds consisting of fluorine and carbon. They are widely used in the electronics, cosmetics, and pharmaceutical industries, as well as in refrigeration when combined with other gases. PFCs were commonly used as fire extinguishants in the past and are still found in older fire protection systems. They are also a by-product of the aluminium smelting process. PFC-14 (Carbon tetrafluoride - CF) has grown to become the most abundant PFC in earth's atmosphere as of year 2015.
Sulphur hexafluoride (SF) is used primarily as an arc suppression and insulation gas. It can be found in high-voltage switchgear and is used in the production of magnesium.
Nitrogen trifluoride (NF) is used primarily as an etchant for microelectronics fabrication. | 2 | Environmental Chemistry |
In fluorescence microscopy, fluorescence confocal laser scanning microscopy, as well as in molecular biology, FRET is a useful tool to quantify molecular dynamics in biophysics and biochemistry, such as protein-protein interactions, protein–DNA interactions, and protein conformational changes. For monitoring the complex formation between two molecules, one of them is labeled with a donor and the other with an acceptor. The FRET efficiency is measured and used to identify interactions between the labeled complexes. There are several ways of measuring the FRET efficiency by monitoring changes in the fluorescence emitted by the donor or the acceptor. | 1 | Biochemistry |
Like the major spliceosome, the minor spliceosome had an early origin: several of its characteristic constituents are present in representative organisms from all eukaryotic supergroups for which there is any substantial genome sequence information. In addition, functionally important sequence elements contained within U12-type introns and snRNAs are highly conserved during evolution. | 1 | Biochemistry |
The ability to fix nitrogen in nodules is present in actinorhizal plants such as alder and bayberry, with the help of Frankia bacteria. They are found in 25 genera in the orders Cucurbitales, Fagales and Rosales, which together with the Fabales form a nitrogen-fixing clade of eurosids. The ability to fix nitrogen is not universally present in these families. For example, of 122 Rosaceae genera, only four fix nitrogen. Fabales were the first lineage to branch off this nitrogen-fixing clade; thus, the ability to fix nitrogen may be plesiomorphic and subsequently lost in most descendants of the original nitrogen-fixing plant; however, it may be that the basic genetic and physiological requirements were present in an incipient state in the most recent common ancestors of all these plants, but only evolved to full function in some of them.
In addition, Trema (Parasponia), a tropical genus in the family Cannabaceae, is unusually able to interact with rhizobia and form nitrogen-fixing nodules. | 1 | Biochemistry |
Vasilis Gregoriou (born 1965, Trikala, Greece) is a researcher, inventor, technology entrepreneur and former Director and Chairman of the Board of Directors at National Hellenic Research Foundation (NHRF) in Athens, Greece. During his career, he has achieved international recognition by serving in research and administrative positions both in Greece and the US. His studies in Greece began at the University of Patras (BSc. Chemistry) while his studies in the United States took place at Duke University where he received a PhD degree in Physical Chemistry. He was also a National Research Service Award recipient at Princeton University. | 7 | Physical Chemistry |
The safety of cosmetic products is constantly in question as the components are always changing or being discovered as a possibly harmful substance. The sulfite components of cosmetic ingredients, such as sodium bisulfite, underwent clinical trials to find out their safety in cosmetic formulations. Sodium bisulfite functions as a reducing agent and furthermore as a hair-waiving/straightening agent. As of 1998, sodium bisulfite was used in 58 different cosmetic products including hair conditioners, moisturizers, and hair dyes.
In a cosmetic context, the reducing ability of sodium bisulfite is used to prevent discoloration, bleach food starches, and delay spoilage of the product. Since the sulfite molecule was used in so many compounds in the 1990s, the EPA, FDA, and American Conference of Governmental Industrial Hygienists established a working place threshold limit value for sulfur dioxide of 2ppm averaged over 8 hours, and a 3-hour level of 5ppm. Even with this threshold established, the FDA recognized sodium bisulfite as a "generally recognized as safe" compound.
A final examination on the carcinogenicity, genotoxicity, oral toxicity, and cellular toxicity on consumed sodium bisulfite was conducted using living subjects such as mice and rats. The International Agency for Research on Cancer concluded that there was inadequate evidence that sodium bisulfite was carcinogenic. Under specific conditions such as acidity and concentration level, sodium bisulfite was able to cause negative alterations to the genome such as catalyzing transamination, and induce sister-chromatid exchanges suggesting possible genotoxicity. In a study using Osbourne-Mendel strain rats, it was concluded that oral toxicity was not significant if the consumed concentration was less than 0.1% (615ppm as SO2). A study done by Servalli, Lear, and Cottree in 1984 found that sodium bisulfite did not produce membrane fusion in hepatic and murine glial cells and human fibroblasts so there is no oral toxicity. These clinical studies concluded that sodium bisulfite was safe to use in cosmetic formulations. | 0 | Organic Chemistry |
During its intraerythrocytic asexual reproduction cycle Plasmodium falciparum consumes up to 80% of the host cell hemoglobin. The digestion of hemoglobin releases monomeric α-hematin (ferriprotoporphyrin IX). This compound is toxic, since it is a pro-oxidant and catalyzes the production of reactive oxygen species. Oxidative stress is believed to be generated during the conversion of heme (ferroprotoporphyrin) to hematin (ferriprotoporphyrin). Free hematin can also bind to and disrupt cell membranes, damaging cell structures and causing the lysis of the host erythrocyte. The unique reactivity of this molecule has been demonstrated in several in vitro and in vivo experimental conditions.
The malaria parasite, therefore, detoxifies the hematin, which it does by biocrystallization—converting it into insoluble and chemically inert β-hematin crystals (called hemozoin). In Plasmodium the food vacuole fills with hemozoin crystals, which are about 100–200 nanometres long and each contain about 80,000 heme molecules. Detoxification through biocrystallization is distinct from the detoxification process in mammals, where an enzyme called heme oxygenase instead breaks excess heme into biliverdin, iron, and carbon monoxide.
Several mechanisms have been proposed for the production of hemozoin in Plasmodium, and the area is highly controversial, with membrane lipids, histidine-rich proteins, or even a combination of the two, being proposed to catalyse the formation of hemozoin. Other authors have described a heme detoxification protein, which is claimed to be more potent than either lipids or histidine-rich proteins. It is possible that many processes contribute to the formation of hemozoin.
The formation of hemozoin in other blood-feeding organisms is not as well-studied as in Plasmodium. However, studies on Schistosoma mansoni have revealed that this parasitic worm produces large amounts of hemozoin during its growth in the human bloodstream. Although the shapes of the crystals are different from those produced by malaria parasites, chemical analysis of the pigment showed that it is made of hemozoin. In a similar manner, the crystals formed in the gut of the kissing bug Rhodnius prolixus during digestion of the blood meal also have a unique shape, but are composed of hemozoin. Hz formation in R. prolixus midgut occurs at physiologically relevant physico-chemical conditions and lipids play an important role in heme biocrystallization. Autocatalytic heme crystallization to Hz is revealed to be an inefficient process and this conversion is further reduced as the Hz concentration increases.
Several other mechanisms have been developed to protect a large variety of hematophagous organisms against the toxic effects of free heme. Mosquitoes digest their blood meals
extracellularly and do not produce hemozoin. Heme is retained in the peritrophic matrix, a layer of protein and polysaccharides that covers the midgut and separates gut cells from the blood bolus.
Although β-hematin can be produced in assays spontaneously at low pH, the development of a simple and reliable method to measure the production of hemozoin has been difficult. This is in part due to the continued uncertainty over what molecules are involved in producing hemozoin, and partly from the difficulty in measuring the difference between aggregated or precipitated heme, and genuine hemozoin. Current assays are sensitive and accurate, but require multiple washing steps so are slow and not ideal for high-throughput screening. However, some screens have been performed with these assays. | 1 | Biochemistry |
Four of the main types of molecular biomarkers are genomic biomarkers, transcriptomic biomarkers, proteomic biomarkers and metabolic biomarkers. | 1 | Biochemistry |
The majority of observed interactions between promoters and enhancers do not cross TAD boundaries. Removing a TAD boundary (for example, using CRISPR to delete the relevant region of the genome) can allow new promoter-enhancer contacts to form. This can affect gene expression nearby - such misregulation has been shown to cause limb malformations (e.g. polydactyly) in humans and mice.
Computer simulations have shown that transcription-induced supercoiling of chromatin fibres can explain how TADs are formed and how they can assure very efficient interactions between enhancers and their cognate promoters located in the same TAD. | 1 | Biochemistry |
TCF7L2 is a transcription factor influencing the transcription of several genes thereby exerting a large variety of functions within the cell. It is a member of the TCF family that can form a bipartite transcription factor (β-catenin/TCF) alongside β-catenin. Bipartite transcription factors can have large effects on the Wnt signalling pathway. Stimulation of the Wnt signaling pathway leads to the association of β-catenin with BCL9, translocation to the nucleus, and association with TCF7L2, which in turn results in the activation of Wnt target genes. The activation of the Wnt target genes specifically represses proglucagon synthesis in enteroendocrine cells. The repression of TCF7L2 using HMG-box repressor (HBP1) inhibits Wnt signalling. Therefore, TCF7L2 is an effector in the Wnt signalling pathway. TCF7L2's role in glucose metabolism is expressed in many tissues such as gut, brain, liver, and skeletal muscle. However, TCF7L2 does not directly regulate glucose metabolism in β-cells, but regulates glucose metabolism in pancreatic and liver tissues. That said, TCF7L2 directly regulates the expression of multiple transcription factors, axon guidance cues, cell adhesion molecules and ion channels in the thalamus.
The TCF7L2 gene encoding the TCF7L2 transcription factor, exhibits multiple functions through its polymorphisms and thus, is known as a pleiotropic gene. Type 2 diabetes T2DM susceptibility is exhibited in carriers of TCF7L2 rs7903146C>T and rs290481T>C polymorphisms. TCF7L2 rs290481T>C polymorphism, however, has shown no significant correlation to the susceptibility to gestational diabetes mellitus (GDM) in a Chinese Han population, whereas the T alleles of rs7903146 and rs1799884 increase susceptibility to GDM in the Chinese Han population. The difference in effects of the different polymorphisms of the gene indicate that the gene is indeed pleiotropic. | 1 | Biochemistry |
Although a number of surrogate biomarkers exist for measuring the metabolic products of bone resorption, the serum CTX marker was chosen because it is both highly correlated to bone turnover rate and already available for detection in a laboratory test carried out by a major lab testing corporation.
The CTX test measures for the presence and concentration of a crosslink peptide sequence of type I collagen, found, among other tissues, in bone. This specific peptide sequence relates to bone turnover because it is the portion that is cleaved by osteoclasts during bone resorption, and its serum levels are therefore proportional to osteoclastic activity at the time the blood sample is drawn. Serum levels in healthy patients not taking bisphosphonates tends to hover above 300 pg/mL.
Patients who are placed on a 6-month drug holiday exhibit marked improvements in their serum CTX values; in one study, patients showed an improvement of 155.3 pg/mL over 6 months or a rate of 25.9 pg/mL each month.
Initially, urinary CTX levels were sought, but this proved to offer no greater value than urinary NTX values—both tests suffered from large spontaneous fluctuations unrelated to therapy or intervention, and were therefore largely unreliable. In contrast, the monoclonal antibody test for detecting serum CTX levels features minimal spontaneous disruption yet remarkable change to antiresorptive therapy, making the serum CTX assay both highly sensitive and specific. | 1 | Biochemistry |
In photosynthetic organisms, Mg has the additional vital role of being the coordinating ion in the chlorophyll molecule. This role was discovered by Richard Willstätter, who received the Nobel Prize in Chemistry 1915 for the purification and structure of chlorophyll binding with sixth number of carbon | 1 | Biochemistry |
The Okorokov effect () or resonant coherent excitation, occurs when heavy ions move in crystals under channeling conditions. V. Okorokov predicted this effect in 1965 and it was first observed by Sheldon Datz in 1978. | 7 | Physical Chemistry |
There is very little known about the surface structures of transition metal oxides, but their bulk crystal structures are well researched. The approach to determine the surface structure is to assume the oxides are ideal crystal, where the bulk atomic arrangement is maintained up to and including the surface plane. The surfaces will be generated by cleavages along the planes of the bulk crystal structure. However, when a crystal is cleaved along a particular plane, the position of surface ions will differ from the bulk structure. Newly created surfaces will tend to minimize the surface Gibbs energy, through reconstruction, to obtain the most thermodynamically stable surface. The stability of these surface structures are evaluated by surface polarity, the degree of coordinative unsaturation and defect sites. | 7 | Physical Chemistry |
2-Furoic acid crystals are highly transparent in the 200–2000 nm wavelength region, are stable up to 130 °C, and generally have low absorption in the UV, visible, and IR ranges. In optical and dielectric studies, 2-furoic acid crystals may act as paraelectrics in the temperature range < 318 K and ferroelectrics in temperature ranges > 318 K. | 0 | Organic Chemistry |
There are at least 25 enzymes and specific transport proteins in the β-oxidation pathway. Of these, 18 have been associated with human disease as inborn errors of metabolism.
Furthermore, studies indicate that lipid disorders are involved in diverse aspects of tumorigenesis, and fatty acid metabolism makes malignant cells more resistant to a hypoxic environment. Accordingly, cancer cells can display irregular lipid metabolism with regard to both fatty acid synthesis and mitochondrial fatty acid oxidation (FAO) that are involved in diverse aspects of tumorigenesis and cell growth. Several specific β-oxidation disorders have been identified. | 1 | Biochemistry |
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