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Gene therapy may be classified into two types by the type of cell it affects: somatic cell and germline gene therapy.
In somatic cell gene therapy (SCGT), the therapeutic genes are transferred into any cell other than a gamete, germ cell, gametocyte, or undifferentiated stem cell. Any such modifications affect the individual patient only, and are not inherited by offspring. Somatic gene therapy represents mainstream basic and clinical research, in which therapeutic DNA (either integrated in the genome or as an external episome or plasmid) is used to treat disease. Over 600 clinical trials utilizing SCGT are underway in the US. Most focus on severe genetic disorders, including immunodeficiencies, haemophilia, thalassaemia, and cystic fibrosis. Such single gene disorders are good candidates for somatic cell therapy. The complete correction of a genetic disorder or the replacement of multiple genes is not yet possible. Only a few of the trials are in the advanced stages.
In germline gene therapy (GGT), germ cells (sperm or egg cells) are modified by the introduction of functional genes into their genomes. Modifying a germ cell causes all the organism's cells to contain the modified gene. The change is therefore heritable and passed on to later generations. Australia, Canada, Germany, Israel, Switzerland, and the Netherlands prohibit GGT for application in human beings, for technical and ethical reasons, including insufficient knowledge about possible risks to future generations and higher risks versus SCGT. The US has no federal controls specifically addressing human genetic modification (beyond FDA regulations for therapies in general). | 1 | Biochemistry |
NP-40 (also known as Tergitol-type NP-40 and nonyl phenoxypolyethoxylethanol) is a commercially available detergent with CAS Registry Number 9016-45-9. NP-40 is an ethoxylated nonylphenol for non-ionic surfactants and can act as emulsifier and demulsifier agent.
NP-40 is often used to break open all membranes within a cell, including the nuclear membrane . To break only the cytoplasmic membrane, other detergents such as digitonin can be used.
NP-40 has applications in paper and textile processing, in paints and coatings, and in agrochemical manufacturing.
Care should be taken to avoid confusing NP-40 with Nonidet P-40 (octyl phenoxypolyethoxylethanol) which is currently out of production. Nonidet P-40 ("Non-Ionic Detergent") was originally manufactured and trademarked by the Shell Chemical Company, but was phased out of production in the early 2000s. Confusingly, biochemical protocols published between the 1960s and 2000s refer to Shells Nonidet P-40 as NP-40. Shells original Nonidet P-40 had a hydrophilic-lipophilic balance (HLB) value of 13.5, as opposed to 12.9 for the currently available IGEPAL CA-630, indicating that the currently available compound is more potent than the compound used in older publications. Indeed, according to a 2017 report, an additional dilution factor of 10 was required for the currently available NP-40 ("Nonidet P-40 substitutes") to match the activity of the previously available, and now discontinued, Shell's Nonidet P-40. | 1 | Biochemistry |
There are several experimental techniques for the determination of transport numbers. The Hittorf method is based on measurements of ion concentration changes near the electrodes. The moving boundary method involves measuring the speed of displacement of the boundary between two solutions due to an electric current. | 7 | Physical Chemistry |
The principle of detailed balance can be used in kinetic systems which are decomposed into elementary processes (collisions, or steps, or elementary reactions). It states that at equilibrium, each elementary process is in equilibrium with its reverse process. | 7 | Physical Chemistry |
* Thomas H. Lowry & Kathleen Schueller Richardson, 1987, Mechanism and Theory in Organic Chemistry, 3rd Edn., New York, NY, US: Harper & Row, , see [https://books.google.com/books?isbn=0060440848], accessed 20 June 2015.
* Francis A. Carey & Richard J. Sundberg, 2006, "Title Advanced Organic Chemistry: Part A: Structure and Mechanisms," 4th Edn., New York, NY, US: Springer Science & Business Media, , see [https://books.google.com/books?isbn=0306468565], accessed 19 June 2015.
* Michael B. Smith & Jerry March, 2007, "March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure," 6th Ed., New York, NY, US: Wiley & Sons, , see [https://books.google.com/books?isbn=0470084944], accessed 19 June 2015. | 7 | Physical Chemistry |
The cause of Tay–Sachs disease is a genetic defect that is passed from parent to child. This genetic defect is located in the HEXA gene, which is found on chromosome 15.
The HEXA gene makes part of an enzyme called beta-hexosaminidase A, which plays a critical role in the nervous system. This enzyme helps break down a fatty substance called GM2 ganglioside in nerve cells.
Mutations in the HEXA gene disrupt the activity of beta-hexosaminidase A, preventing the breakdown of the fatty substances. As a result, the fatty substances accumulate to deadly levels in the brain and spinal cord. The buildup of GM2 ganglioside causes progressive damage to the nerve cells. This is the cause of the signs and symptoms of Tay-Sachs disease. | 1 | Biochemistry |
A hydrogencarbonate indicator (hydrogencarbonate indicator) is a type of pH indicator that is sensitive enough to show a color change as the concentration of carbon dioxide gas in an aqueous solution increases. The indicator is used in photosynthesis and respiration experiments to find out whether carbon dioxide is being liberated. It is also used to test the carbon dioxide content during gaseous exchange of organisms. When the carbon dioxide content is higher than 0.04%, the initial red colour changes to yellow as the pH becomes more acidic. If the carbon dioxide content is lower than 0.04%, it changes from red to magenta and, in relatively very low carbon dioxide concentrations, to purple. Carbon dioxide, even in the concentrations found in exhaled air, will dissolve in the indicator to form carbonic acid, a weak acid, which will lower the pH and give the characteristic colour change. A colour change to purple during photosynthesis shows a reduction in the percentage of carbon dioxide and is sometimes inferred as production of oxygen, but there is not actually any direct evidence for it.
Great care must be taken to avoid acidic or alkaline contamination of the apparatus in such experiments, since the test is not directly specific to gases like carbon dioxide. | 3 | Analytical Chemistry |
Terrestrial and marine ecosystems are chiefly connected through riverine transport, which acts as the main channel through which erosive terrestrially derived substances enter into oceanic systems. Material and energy exchanges between the terrestrial biosphere and the lithosphere as well as organic carbon fixation and oxidation processes together regulate ecosystem carbon and dioxygen (O) pools.
Riverine transport, being the main connective channel of these pools, will act to transport net primary productivity (primarily in the form of dissolved organic carbon (DOC) and particulate organic carbon (POC)) from terrestrial to oceanic systems. During transport, part of DOC will rapidly return to the atmosphere through redox reactions, causing "carbon degassing" to occur between land-atmosphere storage layers. The remaining DOC and dissolved inorganic carbon (DIC) are also exported to the ocean. In 2015, inorganic and organic carbon export fluxes from global rivers were assessed as 0.50–0.70 Pg C y and 0.15–0.35 Pg C y respectively. On the other hand, POC can remain buried in sediment over an extensive period, and the annual global terrestrial to oceanic POC flux has been estimated at 0.20 Gg C y. | 5 | Photochemistry |
Photo-methionine can be used to label recombinant proteins in Escherichia coli cells; though methionine in general is a rare amino acid so that means it could only give limited structural data. Nevertheless, photo-methionine was incorporated into Ca regulating protein calmodulin (CaM that was 17-kDa) that has nine methionines and studied via mass spectrometry (MS). What makes this method different is the use of mineral salts medium instead of DMEM (Dulbeccos Modified Eagle's Limiting Medium) or dialyzed fetal bovine serum for the incorporation into the cells. Using the mineral salt medium allowed the cells to be grown from the beginning in order to eliminate complicated steps with other protocols (incubating the cells in LB medium, followed by washing, and further incubating in the depleted medium), meaning that photo-methionine could be incorporated at the very beginning of the cell growth that had a high yield above 30%. Photo-methionine had shown no damage during the cell growth process and once photo-activated by UV-A light, CaM had nine distinct cross-link sites once MS had determined there was peaks of photo-methionine labeled CaM. Not only can photo-methionine be used for mapping 3D protein structure, studying protein-protein interactions, but now hydrophobic regions in the protein. | 5 | Photochemistry |
The thiol-yne reaction (also known as alkyne hydrothiolation) is an organic reaction between a thiol and an alkyne. The reaction product is an alkenyl sulfide. The reaction was first reported in 1949 with thioacetic acid as reagent and rediscovered in 2009. It is used in click chemistry and in polymerization, especially with dendrimers.
This addition reaction is typically facilitated by a radical initiator or UV irradiation and proceeds through a sulfanyl radical species. With monoaddition a mixture of (E/Z)-alkenes form. The mode of addition is anti-Markovnikov. The radical intermediate can engage in secondary reactions such as cyclisation. With diaddition the 1,2-disulfide or the 1,1- dithioacetal forms. Reported catalysts for radical additions are triethylborane, indium(III) bromide and AIBN. The reaction is also reported to be catalysed by cationic rhodium and iridium complexes, by thorium and uranium complexes, by rhodium complexes, by caesium carbonate and by gold.
Diphenyl disulfide reacts with alkynes to a 1,2-bis(phenylthio)ethylene. Reported alkynes are ynamides. A photoredox thiol-yne reaction has been reported. | 0 | Organic Chemistry |
The term gerontoplast was first introduced in 1977 to define the unique features of the plastid formed during leaf senescence. The process of senescence brings about regulated dismantling of cellular organelles involved in photosynthesis. Chloroplasts responsible for gas exchange in stomata are the last organelles to degrade during senescence, and give plants the green color. The formation of gerontoplasts from chloroplasts during senescence involves extensive structural modifications of the thylakoid membrane with the concomitant formation of a large number of plastoglobuli with lipophilic materials. The envelope of the plastid, however, remains intact. | 5 | Photochemistry |
Viscosity, a physical property, is a measure of how well adjacent molecules stick to one another. A solid can withstand a shearing force due to the strength of these sticky intermolecular forces. A fluid will continuously deform when subjected to a similar load. While a gas has a lower value of viscosity than a liquid, it is still an observable property. If gases had no viscosity, then they would not stick to the surface of a wing and form a boundary layer. A study of the delta wing in the Schlieren image reveals that the gas particles stick to one another (see Boundary layer section). | 7 | Physical Chemistry |
Each plastid creates multiple copies of its own unique genome, or plastome, (from plastid genome)which for a chlorophyll plastid (or chloroplast) is equivalent to a chloroplast genome, or a chloroplast DNA. The number of genome copies produced per plastid is variable, ranging from 1000 or more in rapidly dividing new cells, encompassing only a few plastids, down to 100 or less in mature cells, encompassing numerous plastids.
A plastome typically contains a genome that encodes transfer ribonucleic acids (tRNA)s and ribosomal ribonucleic acids (rRNAs). It also contains proteins involved in photosynthesis and plastid gene transcription and translation. But these proteins represent only a small fraction of the total protein set-up necessary to build and maintain any particular type of plastid. Nuclear genes (in the cell nucleus of a plant) encode the vast majority of plastid proteins; and the expression of nuclear and plastid genes is co-regulated to coordinate the development and differention of plastids.
Many plastids, particularly those responsible for photosynthesis, possess numerous internal membrane layers. Plastid DNA exists as protein-DNA complexes associated as localized regions within the plastids inner envelope membrane; and these complexes are called plastid nucleoids. Unlike the nucleus of a eukaryotic cell, a plastid nucleoid is not' surrounded by a nuclear membrane. The region of each nucleoid may contain more than 10 copies of the plastid DNA.
Where the proplastid (undifferentiated plastid) contains a single nucleoid region located near the centre of the proplastid, the developing (or differentiating) plastid has many nucleoids localized at the periphery of the plastid and bound to the inner envelope membrane. During the development/ differentiation of proplastids to chloroplastsand when plastids are differentiating from one type to anothernucleoids change in morphology, size, and location within the organelle. The remodelling of plastid nucleoids is believed to occur by modifications to the abundance of and the composition of nucleoid proteins.
In normal plant cells long thin protuberances called stromules sometimes formextending from the plastid body into the cell cytosol while interconnecting several plastids. Proteins and smaller molecules can move around and through the stromules. Comparatively, in the laboratory, most cultured cellswhich are large compared to normal plant cellsproduce very long and abundant stromules that extend to the cell periphery.
In 2014, evidence was found of the possible loss of plastid genome in Rafflesia lagascae, a non-photosynthetic parasitic flowering plant, and in Polytomella, a genus of non-photosynthetic green algae. Extensive searches for plastid genes in both taxons yielded no results, but concluding that their plastomes are entirely missing is still disputed. Some scientists argue that plastid genome loss is unlikely since even these non-photosynthetic plastids contain genes necessary to complete various biosynthetic pathways including heme biosynthesis.
Even with any loss of plastid genome in Rafflesiaceae, the plastids still occur there as "shells" without DNA content, which is reminiscent of hydrogenosomes in various organisms. | 5 | Photochemistry |
Shpolskii systems are low-temperature host–guest systems – they are typically rapidly frozen solutions of polycyclic aromatic hydrocarbons in suitable low molecular weight normal alkanes. The emission and absorption spectra of lowest energy electronic transitions in the Shpolskii systems exhibit narrow lines instead of the inhomogeneously broadened features normally associated with spectra of chromophores in liquids and amorphous solids. The effect was first described by Eduard Shpolskii in the 1950s and 1960s in the journals Transactions of the U.S.S.R. Academy of Sciences and Soviet Physics Uspekhi'.
Subsequent detailed studies of concentration and speed of cooling behavior of Shpolskii systems by L. A. Nakhimovsky and coauthors led to a hypothesis that these systems are metastable segregational solid solutions formed when one or more chromophores replace two or more molecules in the host crystalline lattice. The solid state quasi-equilibrium solubility in most Shpolskii systems is very low. When the Shpolskii effect is manifested, the solid state solubility increases two to three orders of magnitude. Isothermic annealing of the supersaturated rapidly frozen solutions of dibenzofuran in heptane was performed, and it was shown that the return of the metastable system to equilibrium in time reasonable for laboratory observation required the annealing temperature to be close to the melting temperature of the metastable frozen solution. Thus the Shpolskii systems are an example of a persistent metastable state.
A good match between the chromophore and the host lattice leads to a uniform environment for all the chromophores and hence greatly reduces the inhomogeneous broadening of the electronic transition's pure electronic and vibronic lines. In addition to the weak inhomogeneous broadening of the transitions, the quasi-lines observed at very low temperatures are phonon-less transitions. Since phonons originate in the lattice, an additional requirement is weak chromophore-lattice coupling. Weak coupling increases the probability of phonon-less transitions and hence favors the narrow zero phonon lines. The weak coupling is usually expressed in terms of the Debye-Waller factor, where a maximum value of one indicates no coupling between the chromophore and the lattice phonons. The narrow lines characteristic of the Shpolskii systems are only observed at cryogenic temperatures because at higher temperatures many phonons are active in the lattice and all of the amplitude of the transition shifts to the broad phonon sideband. The original observation of the Shpolskii effect was made at liquid nitrogen temperature (77 kelvins), but using temperatures close to that of liquid helium (4.2 K) yields much sharper spectral lines and is the usual practice.
Low molecular weight normal alkanes absorb light at energies higher than the absorption of all pi-pi electronic transitions of aromatic hydrocarbons. They interact weakly with the chromophores and crystallize when frozen. The length of the alkanes is often chosen to approximately match at least one of the dimensions of the chromophore, and are usually in the size range between n-pentane and n-dodecane. | 7 | Physical Chemistry |
The equivalence of the two formulations can also be seen by a simple parity argument without appeal to case analysis.
Proposition. The following formulations of the Woodward–Hoffmann rules are equivalent:
(A) For a pericyclic reaction, if the sum of the number of suprafacial 4q + 2 components and antarafacial 4r components is odd then it is thermally allowed; otherwise the reaction is thermally forbidden.
(B) For a pericyclic reaction, if the total number of antarafacial components of a (4n + 2)-electron reaction is even or the total number of antarafacial components of a 4n-electron reaction is odd then it is thermally allowed; otherwise the reaction is thermally forbidden.
Proof of equivalence: Index the components of a k-component pericyclic reaction and assign component i with Woodward-Hoffmann symbol N the electron count and topology parity symbol according to the following rules:<blockquote><math>n_i = \begin{cases} 0, & N\equiv 0\ (\mathrm{mod}\ 4)\\ 1, & N\equiv 2\ (\mathrm{mod}\ 4) \end{cases}\quad\mathrm{and}\quad
p_i = \begin{cases} 0, & i\text{ is supra}\\ 1, & i\text{ is antara} \end{cases}.We have a mathematically equivalent restatement of (A):
(A) A collection of symbols is thermally allowed if and only if the number of symbols with the property is odd.'
Since the total electron count is 4n + 2 or 4n precisely when (the number of (4q + 2)-electron components) is odd or even, respectively, while gives the number of antarafacial components, we can also restate (B):
(B) A collection of symbols is thermally allowed if and only if exactly one of or is odd.'
It suffices to show that (A) and (B) are equivalent. Exactly one of or is odd if and only if is odd. If , holds; hence, omission of symbols with the property from a collection will not change the parity of . On the other hand, when , we have , but simply enumerates the number of components with the property . Therefore, <blockquote><math>\sum_i n_i+p_i\equiv\sum_{n_i\neq p_i} n_i+p_i=
\sum_{n_i\neq p_i} 1=\#\{(n_i,p_i,i)\ |\ n_i\neq p_i\}\
(\mathrm{mod}\ 2)Thus, and the number of symbols in a collection with the property have the same parity. Since formulations (A) and (B) are equivalent, so are (A) and (B), as claimed.
To give a concrete example, a hypothetical reaction with the descriptor [6 + 4 + 2] would be assigned the collection {(1, 0, 1), (0, 1, 2), (1, 1, 3)} in the scheme above. There are two components, (1, 0, 1) and (0, 1, 2), with the property , so the reaction is not allowed by (A). Likewise, and are both even, so (B) yields the same conclusion (as it must): the reaction is not allowed. | 7 | Physical Chemistry |
Bulk metallic glasses have been modeled using atomic scale simulations (within the density functional theory framework) in a similar manner to high entropy alloys. This has allowed predictions to be made about their behavior, stability and many more properties. As such, new bulk metallic glass systems can be tested and tailored for a specific purpose (e.g. bone replacement or aero-engine component) without as much empirical searching of the phase space or experimental trial and error. Ab-initio molecular dynamics (MD) simulation confirmed that the atomic surface structure of a Ni-Nb metallic glass observed by scanning tunneling microscopy is a kind of spectroscopy. At negative applied bias it visualizes only one soft of atoms (Ni) owing to the structure of electronic density of states calculated using ab-initio MD simulation.
One common way to try and understand the electronic properties of amorphous metals is by comparing them to liquid metals, which are similarly disordered, and for which established theoretical frameworks exist. For simple amorphous metals, good estimations can be reached by semi-classical modelling of the movement of individual electrons using the Boltzmann equation and approximating the scattering potential as the superposition of the electronic potential of each nucleus in the surrounding metal. To simplify the calculations, the electronic potentials of the atomic nuclei can be truncated to give a muffin-tin pseudopotential. In this theory, there are two main effects that govern the change of resistivity with increasing temperatures. Both are based on the induction of vibrations of the atomic nuclei of the metal as temperatures increase. One is, that the atomic structure gets increasingly smeared out as the exact positions of the atomic nuclei get less and less well defined. The other is the introduction of phonons. While the smearing out generally decreases the resistivity of the metal, the introduction of phonons generally adds scattering sites and therefore increases resistivity. Together, they can explain the anomalous decrease of resistivity in amorphous metals, as the first part outweighs the second. In contrast to regular crystalline metals, the phonon contribution in an amorphous metal does not get frozen out at low temperatures. Due to the lack of a defined crystal structure, there are always some phonon wavelengths that can be excited. While this semi-classical approach holds well for many amorphous metals, it generally breaks down under more extreme conditions. At very low temperatures, the quantum nature of the electrons leads to long range interference effects of the electrons with each other in what is called "weak localization effects". In very strongly disordered metals, impurities in the atomic structure can induce bound electronic states in what is called "Anderson localization", effectively binding the electrons and inhibiting their movement. | 8 | Metallurgy |
Functional Ensemble of Temperament (FET) is a neurochemical model suggesting specific functional roles of main neurotransmitter systems in the regulation of behaviour. | 1 | Biochemistry |
In 1895 he left MIT to become the fourth president of Lehigh University. Lehighs endowment was predominantly in the stock of the major company of its founder, Asa Packers Lehigh Valley Railroad. The Panic of 1893 crashed the market, brought the country into depression that lasted years, and nearly brought the university to financial insolvency. Many prominent railroads such as the Northern Pacific Railway, the Union Pacific Railroad and the Atchison, Topeka & Santa Fe Railroad went into bankruptcy, and over 15,000 companies and 500 banks failed. In order to gain new sources of funding, President Drown broke the university's ties with the Episcopal Church in 1897, qualifying the university for aid from the Commonwealth of Pennsylvania. During his term, which started during a major financial crisis, he was able to save Lehigh from bankruptcy, grow enrollment, which had dipped seriously, grow academics, and even have one major building erected.
A broad intellectual with interests in various fields, he nonetheless thought the key to Lehighs success would be the school of technology. There he sought to broaden and deepen the offerings, increase the quality and quantity of laboratory space, equipment and apparatus, as funding permitted. Additionally, and in consultation with the faculty and the board of trustees, he created many new tiers of teaching, including the associate and assistant professorships. His idea was that this would create resources for top professors to be invited to Lehigh, and so help enlarge the curricula. During his tenure, the universitys first emeritus professorship was granted (Harding of Physics), and first doctorate awarded (Joseph W. Richards). Many new degrees in the technical school were now being offered, such as Metallurgy (1891), Electrometallurgy, and Chemical Engineering (1902). The curriculum leading to a degree in arts and engineering was established, as was the department of zoology and biology. New courses (majors, that is, or degree offerings, as it is now known) were also adopted in geology, and physics.
Dr. Drown eventually gained in popularity on campus, with his forward ideas, success, idiosyncratic pince-nez glasses and mustache. Faculty members eventually came to refer to Dr. Drown as "chief". Unfortunately, T. M. Drown would not live long enough to see all his ideas to fruition, as he died in office, following abdominal surgery, November 16, 1904, effectively ending his term.
Williams Hall (1903), a Beaux Arts inspired Brick structure, was erected to house the growing departments of Biology and Geology, among other functions.
In 1908, Lehigh University opened up Drown Hall which now houses Lehigh's English Department. | 3 | Analytical Chemistry |
Spectroradiometers are used in many applications, and can be made to meet a wide variety of specifications. Example applications include:
*Solar UV and UVB radiation
*LED measurement
*Display measurement and calibration
*CFL testing
*Remote detection of oil slicks
*Plant research and development
*Earth and planetary remote sensing | 7 | Physical Chemistry |
Some invertebrates use calcium compounds for building their exoskeleton (shells and carapaces) or endoskeleton (echinoderm plates and poriferan calcareous spicules). | 1 | Biochemistry |
A second Fe species apart from the ferrate(VI) ion, [(Mecy-ac)FeN](PF), has been reported. This species, is formed by oxidation followed by photolysis to yield the Fe(VI) species. Characterization of the Fe(VI) complex was done by Mossbauer, EXAFS, IR, and DFT calculations. Unlike the ferrate(VI) ion, compound 5 is diamagnetic. | 7 | Physical Chemistry |
James Marrow was born on 23 November 1966 in Bromborough, Wirral to John Williams Marrow and Mary Elizabeth Marrow. He attended Wirral Grammar School for Boys, then graduated with a 1st Class Honours Master of Arts (M.A) in Natural Sciences (Materials Science) from the University of Cambridge in 1988, where he was a student at Clare College, Cambridge before pursuing and completing a Doctor of Philosophy degree in 1991. During his PhD, he studied the Fatigue mechanisms in embrittled duplex stainless steel and was supervised by Julia King. | 8 | Metallurgy |
Add master mix which contains buffer, dNTP mix, MgCl, Taq polymerase and nuclease-free water to each PCR tube. Then add the necessary primer to the tubes. Next, place the PCR tubes in a thermal cycler for 30 cycles of the amplification program. This includes: denaturation, annealing, and elongation. The products of RT-PCR can be analyzed with gel electrophoresis. | 1 | Biochemistry |
Lithium-containing NASICON-type crystals are described by the general formula , in which M stands for a metal or a metalloid (Ti, Zr, Hf, Sn, Ge), and display a complex three-dimensional network of corner-sharing octahedra and phosphate tetrahedra. Lithium ions are hosted in voids in between, which can be subdivided into three kinds of sites:
* Li(1) 6-fold coordinated sites at Wyckoff 6b position;
* Li(2) sites at Wyckoff 18e position;
* Li(3) sites at Wyckoff 36f position.
In order to promote lithium conductivity at sufficiently high rates, Li(1) sites should be fully occupied and Li(2) sites should be fully empty. Li(3) sites are located between Li(1) and Li(2) sites and are occupied only when large tetravalent cations are present in the structure, such as Zr, Hf, and Sn. If some Ge cations in the (LGP) structure are partially replaced by Al cations, the LAGP material is obtained with the general formula . The single-phase NASICON structure is stable with x between 0.1 and 0.6; when this limit is exceeded, a solid solution is no more possible and secondary phases tend to be formed. Although Ge and Al cations have very similar ionic radii (0.53 Å for Ge vs. 0.535 Å for Al), cationic substitution leads to compositional disorder and promotes the incorporation of a larger amount of lithium ions to achieve electrical neutrality. Additional lithium ions can be incorporated in either Li(2) or Li(3) empty sites.
In the available scientific literature, there is not a unique description of the sites available for lithium ions and of their atomic coordination, as well as of the sites directly involved during the conduction mechanism. For example, only two available sites, namely Li(1) and Li(2), are mentioned in some cases, while the Li(3) site is neither occupied nor involved in the conduction process. This results in the lack of unambiguous description of LAGP local crystal structure, especially concerning the arrangement of lithium ions and site occupancy when germanium is partially replaced by aluminium.
LAGP displays a rhombohedral unit cell with a space group Rc. | 7 | Physical Chemistry |
Plants have many protection mechanisms to cope with stresses from the environment, which include ultraviolet light, cold or hot weather, windy days, and mechanical wounding. There are multiple pathways, but one pathway that plants have been able to develop is a self-defense mechanism by recognize pathogens through pathogen-associated molecular patterns (PAMPs) via cell surface-located pathogen-recognition receptors. These receptors induce intracellular signal pathways within the plant cells, while also resulting in PAMP-triggered immunity. Responses to PAMPs target broadly instead of specifically. This immunity requires downstream components via the MAPK cascade to activate the MAP kinases. The flagellin, a peptide of flg22, triggers a rapid and strong activation of MPK3, MPK4, and MPK6. MPK4 and MPK6 can be activated by harpin proteins. MPK3 and MPK6 are very similar proteins and have a function as regulators in abscission, stomatal development, signaling various abiotic stresses, and defense responses to certain pathogens. Experimentation has proposed that the MAPK module MEKK1-MKK4/MKK5-MPK3/MPK6 may be responsible for flg22 signal transmission. All of the proposed modules appear to be correct expect for MEKK1 because plants with mekk1 mutated have a compromised flg22-triggered activation of MPK4, yet they have normal activation of MPK3 and MPK6. Data has shown that MAPK cascade is composed of MKK4/MKK5 and MPK3/MPK6 in response to fungal pathogens. The observation shows that the activation of MPK3/MPK6 in conditional gain-of-function plants for MKK4/MKK5 or MEKK1/MKKKa is sufficient to induce camalexin, which is a major phytoalexin in Arabidopsis. The stomata are considered to be the entry point for pathogenic invaders because microbial invaders enter the plant at the stomata. A recent study has shown that MAPK cascades play a role in abiotic and biotic stress responses. The main pathways in stomatal development and dynamics are MPK3 and MPK6. During a drought, the stomata closes and is believed to be mediated by the phytohormone, abscisic acid, and involves MKK1, MPK3, and MPK6. Another way of closing the stomata is through a closing process that is called pathogen-induced, which is an innate response from the plant. Campestris (Xcc) excretes a chemical that reverts stomatal closure that was caused by bacteria and abscisic acid (ABA). Most stomata close in the presence of ABA, but some are unresponsive to bacteria. In Arabidopsis Xcc does not revert bacteria-induced or ABA-induced stomatal closure. Scientists are not certain if MAPK cascades are responsible for the signaling, so further investigation is needed for this. | 1 | Biochemistry |
This can be the case when studying a bimolecular reaction and a simultaneous hydrolysis (which can be treated as pseudo order one) takes place: the hydrolysis complicates the study of the reaction kinetics, because some reactant is being "spent" in a parallel reaction. For example, A reacts with R to give our product C, but meanwhile the hydrolysis reaction takes away an amount of A to give B, a byproduct: and . The rate equations are: and , where is the pseudo first order constant.
The integrated rate equation for the main product [C] is , which is equivalent to . Concentration of B is related to that of C through
The integrated equations were analytically obtained but during the process it was assumed that . Therefore, previous equation for [C] can only be used for low concentrations of [C] compared to [A] | 7 | Physical Chemistry |
Synthesis of organoberyllium compounds is limited but literature have shown that beryllium can react with halides, alkyls, alloxides and other organic compounds. Alkylation of beryllium halide is one of the most widely-used method in beryllium chemistry. | 0 | Organic Chemistry |
The detector used in a spectroradiometer is determined by the wavelength over which the light is being measured, as well as the required dynamic range and sensitivity of the measurements. Basic spectroradiometer detector technologies generally fall into one of three groups: photoemissive detectors (e.g. photomultiplier tubes), semiconductor devices (e.g. silicon), or thermal detectors (e.g. thermopile).
The spectral response of a given detector is determined by its core materials. For example, photocathodes found in photomultiplier tubes can be manufactured from certain elements to be solar-blind – sensitive to UV and non-responsive to light in the visible or IR.
CCD (Charge Coupled Device) arrays typically one dimensional (linear) or two dimensional (area) arrays of thousands or millions of individual detector elements (also known as pixels) and CMOS sensors. They include a silicon or InGaAs based multichannel array detector capable of measuring UV, visible and near-infra light.
CMOS (Complementary Metal Oxide Semiconductor) sensors differs from a CCD in that they add an amplifier to each photodiode. This is called an active pixel sensor because the amplifier is part of the pixel. Transistor switches connect each photodiode to the intrapixel amplifier at the time of readout. | 7 | Physical Chemistry |
An example of a publication using live IGSNs can be found here:
This paper contains several samples identified by IGSN. One of them is IGSN: 10.58052/SSH000SUA. Information about this sample can be obtained by resolving the IGSN by adding the URL of the resolver before the IGSN: https://doi.org/10.58052/SSH000SUA.
IGSN can be used to identify samples and sampling features, such as boreholes or outcrops. The IGSN [https://doi.org/10.60510/ICDP5054ESYI201 10.60510/ICDP5054ESYI201] identifies a core section from core [https://doi.org/10.60510/ICDP5054ECYD101 5054_1_A_658_Z (IGSN 10.60510/ICDP5054ECYD101)] of the COSC Expedition of the International Continental Scientific Drilling Program. The corresponding drill hole (sampling feature) [https://doi.org/10.60510/ICDP5054EEW1001 5054_1_A] is identified by IGSN [https://doi.org/10.60510/ICDP5054EEW1001 10.60510/ICDP5054EEW1001]. | 9 | Geochemistry |
1,3-Propanedithiol reacts with metal ions to form chelate rings. Illustrative is the synthesis of the derivative diiron propanedithiolate hexacarbonyl upon reaction with triiron dodecacarbonyl:
:Fe(CO) + CH(SH) → Fe(SCH)(CO) + H + Fe(CO) + CO | 0 | Organic Chemistry |
Alexander Butlerov showed in 1861 that the formose reaction created sugars including tetroses, pentoses, and hexoses when formaldehyde is heated under basic conditions with divalent metal ions like calcium. R. Breslow proposed that the reaction was autocatalytic in 1959. | 9 | Geochemistry |
With the help of the Lifshitz Theory on Casimir, respectively van der Waals, interactions of macroscopic bodies premelting can be viewed from an electrodynamical perspective.
A good example for determining the difference between complete and incomplete premelting is ice. From vacuum ultraviolet (VUV) frequencies upwards the polarizability of ice is greater than that of water, at lower frequencies this is reversed. Assuming there is already a film of thickness on the solid it is easy for any components of electromagnetic waves to travel through the film in the direction perpendicular to the solid surface as long is small. Hence as long as the film is thin compared to the frequency interaction from the solid to the whole film is possible. But when gets large compared to typical VUV frequencies the electronic structure of the film will be too slow to pass the high frequencies to the other end of the liquid phase. Thus this end of the liquid phase feels only a retarded van der Waals interaction with the solid phase. Hence the attraction between the liquid molecules themselves will predominate and they will start forming droplets instead of thickening the film further. So the speed of light limits complete premelting. This makes it a question of solid and surface free energies whether complete premelting occurs. Complete surface melting will occur when is monotonically decreasing. If instead shows a global minimum at finite than the premelting will be incomplete. This implies: When the long range interactions in the system are attractive than there will be incomplete premelting — assuming the film thickness is larger than any repulsive interactions. Is the film thickness small compared to the range of the repulsive interactions present and the repulsive interactions are stronger than the attractive ones than complete premelting can occur.
For van der Waals interactions Lifshitz theory can now calculate which type of premelting should occur for a special system. In fact small differences in systems can affect the type of premelting. For example, ice in an atmosphere of water vapour shows incomplete premelting, whereas the premelting of ice in air is complete.
For solid–solid interfaces it cannot be predicted in general whether the premelting is complete or incomplete when only considering van der Waals interactions. Here other types of interactions become very important. This also accounts for grain boundaries. | 7 | Physical Chemistry |
After 125 years of study, 1,3,5-trinitrobenzene yielded a second polymorph. The usual form has the space group Pbca, but in 2004, a second polymorph was obtained in the space group Pca2 when the compound was crystallised in the presence of an additive, trisindane. This experiment shows that additives can induce the appearance of polymorphic forms. | 3 | Analytical Chemistry |
In 2011 Eremets and Troyan reported observing the liquid metallic state of hydrogen and deuterium at static pressures of . This claim was questioned by other researchers in 2012.
It is recently proposed that the hydrogen in stars has an electric conductivity of . | 7 | Physical Chemistry |
A travel symmetry operation for an object is a symmetry operation f for which no point p has the property p = f(p).
Table 2. Travel symmetry operations in three dimensions.
a R and i are numbers ≥ 1. | 7 | Physical Chemistry |
Archaeal translation is the process by which messenger RNA is translated into proteins in archaea. Not much is known on this subject, but on the protein level it seems to resemble eukaryotic translation.
Most of the initiation, elongation, and termination factors in archaea have homologs in eukaryotes. Shine-Dalgarno sequences only are found in a minority of genes for many phyla, with many leaderless mRNAs probably initiated by scanning. The process of ABCE1 ATPase-based recycling is also shared with eukaryotes.
Being a prokaryote without a nucleus, archaea do perform transcription and translation at the same time like bacteria do. | 1 | Biochemistry |
Mycoestrogens are produced by various strains of fungi, many of which fall under the genus Fusarium. Fusarium fungi are filamentous fungi that are found in the soil and are associated with plants and some crops, especially cereals. Zearalenone is mainly produced by F. graminearum and F. culmorum strains, which inhabit different areas depending on temperature and humidity. F. graminearum prefers to inhabit warmer and more humid locations such as Eastern Europe, Northern America, Eastern Australia, and Southern China in comparison to F. colmorum which is found in colder Western Europe. | 1 | Biochemistry |
Although multicomponent working fluids have significant thermodynamic advantages over pure (single-component) ones, research and application keep focusing on pure working fluids. However, there are some typical examples for multicomponent based technologies such as Kalina cycle which uses water and ammonia mixture, or absorption refrigerators which also use water and ammonia mixture besides water, ammonia and hydrogen, lithium bromide or lithium chloride mixtures in a majority. Some scientific papers deal with the application of multicomponent working fluids in Organic Rankine cycles as well. These are mainly binary mixtures of hydrocarbons, fluorocarbons, hydrofluorocarbons, siloxanes and inorganic substances. | 7 | Physical Chemistry |
DNA digital data storage is the process of encoding and decoding binary data to and from synthesized strands of DNA.
While DNA as a storage medium has enormous potential because of its high storage density, its practical use is currently severely limited because of its high cost and very slow read and write times.
In June 2019, scientists reported that all 16 GB of text from the English Wikipedia had been encoded into synthetic DNA. In 2021, scientists reported that a custom DNA data writer had been developed that was capable of writing data into DNA at 18 Mbps. | 1 | Biochemistry |
Diphosphorus is an old target of chemists since it is the heavy analogue of N. Its fleeting existence is inferred by the controlled degradation of certain niobium complexes in the presence of trapping agents. Again, a Diels-Alder strategy is employed in the trapping: | 3 | Analytical Chemistry |
SPIKE (Signaling Pathways Integrated Knowledge Engine) is a database of highly curated interactions for particular human pathways. | 1 | Biochemistry |
Real gases can be characterized by their difference from ideal. This is done by writing the mechanical equation of state in the form where , called the compressibility factor, is usually expressed either as a function of pressure and temperature, or density and temperature, and in each case in the limit or , , the ideal gas value.
In the second case . Thus for a van der Waals fluid the compressibility factor is , or in terms of reduced variables
where . At the critical point, , .
In the limit , (for finite ); the fluid behaves like an ideal gas, a point noted several times earlier. Note additionally that the derivative for , and when this is . The slope is positive or negative depending on whether is greater than or less than , and becomes infinitely large negative as approaches .
Figure 6 shows a plot of various isotherms of vs . Also shown are the spinodal and coexistence curves described previously. The subcritical isotherm consists of stable, metastable, and unstable segments, and are identified the same as they were in Fig. 1. Also included are the zero initial slope isotherm and the one corresponding to infinite temperature.
By plotting vs using as a parameter, one obtains the generalized compressibility chart for a vdW gas, which is shown in Fig. 7. Like all other vdW properties, this is not quantitatively correct for most gases but it has the correct qualitative features as can be seen by comparison with this figure which was produced from data using real gases. The two graphs are similar, including the caustic generated by the crossing isotherms; they are qualitatively very much alike. | 7 | Physical Chemistry |
Since fish emulsion is naturally derived, it is considered an organic fertilizer appropriate for use in organic horticulture. In addition to having a typical N-P-K analysis of 5-2-2, fish emulsion adds micronutrients.
Fish emulsion, applied as a liquid fertilizer, is also used when growing roses to enhance the bloom color of the flowers. | 9 | Geochemistry |
Nitrifying bacteria are present in distinct taxonomical groups and are found in highest numbers where considerable amounts of ammonia are present (such as areas with extensive protein decomposition, and sewage treatment plants). Nitrifying bacteria thrive in lakes, streams, and rivers with high inputs and outputs of sewage, wastewater and freshwater because of the high ammonia content. | 1 | Biochemistry |
FAM227B is most highly expressed in the testis at 1.983 +/- 0.404 RPKM, in the kidney at 1.408 +/- 0.152 RPKM, in the adrenal at 1.177 +/- 0.088 RPKM, and in the thyroid 1.133 +/- 0.165 RPKM. It is also expressed to a lesser degree in the appendix, bone marrow, brain, colon, duodenum, endometrium, esophagus, fat, gall bladder, heart, liver, lung, lymph node, ovary, pancreas, placenta, prostate, salivary gland, skin, small intestine, spleen, stomach, and urinary bladder | 1 | Biochemistry |
With the invention of hollow casting bronze became the most important medium of monumental sculpture, largely because of its strength and lightness, which admitted poses that would not be possible in stone. But the value of the metal in later ages has involved the destruction of nearly all such statues. The few complete figures that survive, and a somewhat more numerous series of detached heads and portrait-busts, attest the excellence of ancient work in this material. The earliest statuettes are chiselled, wrought and welded; next in time come solid castings, but larger figures were composed of hammered sections, like domestic utensils, each part worked separately in repoussé and the whole assembled with rivets (σφυρήλατα). Very little of this flimsy fabric is extant, but chance has preserved one bust entire, in the Polledrara Tomb at Vulci. This belongs to the early 6th century BC, the age of repoussé work.
The process was soon superseded in such subjects by hollow casting, but beaten reliefs, the household craft from which Greek bronze work sprang, persisted in some special and highly perfected forms, as handle-plates on certain vases, emblemata on mirror-cases, and particularly as ornaments of armour, where light weight was required. The Siris bronzes in the British Museum are shoulder-pieces from a 4th-century cuirass. Casting was done by the cire perdue process in clay moulds, but a great deal of labour was spent on finishing. The casts are very finely chased, and most large pieces contain patches, inserted to make good the flaws. Heads and limbs of statues were cast separately and adjusted to the bodies: besides the evidence of literature and of the actual bronzes, there is an illustration of a dismembered statue in the making on a painted vase in Berlin.
Pliny and other ancient writers have much to say in regard to various alloys of bronze — Corinthian, Delian, Aeginetan, Syracusan — in regard to their composition and uses and particularly to their colour effects, but their statements have not been confirmed by modern analyses and are sometimes manifestly false. Corinthian bronze is said to have been first produced by accident in the Roman burning of the city (146 BC) when streams of molten copper, gold and silver mingled. Similar tales are told by Plutarch and Pliny about the artists' control of colour: Silanion made a pale-faced Jocasta by mixing silver with his bronze, Aristonidas made Athamas blush with an alloy of iron. There is good evidence that Greek and Roman bronzes were not artificially patinated, though many were gilt or silvered. Plutarch admires the blue colour of some very ancient statues at Delphi, and wonders how it was produced; Pliny mentions a bitumen wash, but this was doubtless a protective lacquer; and a 4th-century inscription from Chios records the regulations made there for keeping a public statue clean and bright. | 8 | Metallurgy |
After protein amino acid sequences have been translated from nucleic acid chains, they can be edited by appropriate enzymes. Although this is a form of protein affecting protein sequence, not explicitly covered by the central dogma, there are not many clear examples where the associated concepts of the two fields have much to do with each other. | 1 | Biochemistry |
The idea of a database to document all known molecular interactions was originally put forth by Tony Pawson in the 1990s and was later developed by scientists at the University of Toronto in collaboration with the University of British Columbia. The development of the Biomolecular Interaction Network Database (BIND) has been supported by grants from the Canadian Institutes of Health Research (CIHR), Genome Canada, the Canadian Foundation for Innovation and the Ontario Research and Development Fund. BIND was originally designed to be a constantly growing depository for information regarding biomolecular interactions, molecular complexes and pathways. As proteomics is a rapidly advancing field, there is a need to have information from scientific journals readily available to researchers. BIND facilitates the understanding of molecular interactions and pathways involved in cellular processes and will eventually give scientists a better understanding of developmental processes and disease pathogenesis
The major goals of the BIND project are: to create a public proteomics resource that is available to all; to create a platform to enable datamining from other sources (PreBIND); to create a platform capable of presenting visualizations of complex molecular interactions. From the beginning, BIND has been open access and software can be freely distributed and modified. Currently, BIND includes a data specification, a database and associated data mining and visualization tools. Eventually, it is hoped that BIND will be a collection of all the interactions occurring in each of the major model organisms. | 1 | Biochemistry |
Accepted nomenclature is to designate the number of components of the rotaxane in brackets as a prefix. Therefore, the a rotaxane consisting of a single dumbbell-shaped axial molecule with a single macrocycle around its shaft is called a [2]rotaxane, and two cyanostar molecules around the central phosphate group of dialkylphosphate is a [3]rotaxane. | 6 | Supramolecular Chemistry |
A typical LFER relation for predicting the equilibrium concentration of a compound or solute in the vapor phase to a condensed (or solvent) phase can be defined as follows (following M.H. Abraham and co-workers):
where is some free-energy related property, such as an adsorption or absorption constant, , anesthetic potency, etc. The lowercase letters (, , , , ) are system constants describing the contribution of the aerosol phase to the sorption process. The capital letters (, , , , ) are solute descriptors representing the complementary properties of the compounds. Specifically,
* is the gas–liquid partition constant on n-hexadecane at 298 K;
* = the excess molar refraction ( for n-alkanes).
* = the ability of a solute to stabilize a neighbouring dipole by virtue of its capacity for orientation and induction interactions;
* = the solute's effective hydrogen bond acidity; and
* = the solute's effective hydrogen-bond basicity.
The complementary system constants are identified as
* = the contribution from cavity formation and dispersion interactions;
* = the contribution from interactions with solute n-electrons and pi electrons;
* = the contribution from dipole-type interactions;
* = the contribution from hydrogen-bond basicity (because a basic sorbent will interact with an acidic solute); and
* = the contribution from hydrogen-bond acidity to the transfer of the solute from air to the aerosol phase.
Similarly, the correlation of solvent–solvent partition coefficients as , is given by
where is McGowan's characteristic molecular volume in cubic centimeters per mole divided by 100. | 7 | Physical Chemistry |
A carbon sink is a natural or artificial process that "removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas from the atmosphere". These sinks form an important part of the natural carbon cycle. An overarching term is carbon pool, which is all the places where carbon on Earth can be, i.e. the atmosphere, oceans, soil, plants, and so forth. A carbon sink is a type of carbon pool that has the capability to take up more carbon from the atmosphere than it releases.
Globally, the two most important carbon sinks are vegetation and the ocean. Soil is an important carbon storage medium. Much of the organic carbon retained in the soil of agricultural areas has been depleted due to intensive farming. Blue carbon designates carbon that is fixed via certain marine ecosystems. Coastal blue carbon includes mangroves, salt marshes and seagrasses. These make up a majority of ocean plant life and store large quantities of carbon. Deep blue carbon is located in international waters and includes carbon contained in "continental shelf waters, deep-sea waters and the sea floor beneath them".
For climate change mitigation purposes, the enhancement of natural carbon sinks, mainly soils and forests, is important. In the past, human practices like deforestation and industrial agriculture have depleted natural carbon sinks. This kind of land use change has been one of the causes of climate change. | 5 | Photochemistry |
With certain polar substituents, hydrogen bonding can occur in the allylic system between the substituents. Rather than the strain that would normally occur in the close group proximity, the hydrogen bond stabilizes the conformation and makes it energetically much more favorable. This scenario occurs when the allylic substituent at the 1 position is a hydrogen bond donor (usually a hydroxyl) and the substituent at the 3 position is a hydrogen bond acceptor (usually an ether). Even in cases where the allylic system could conform to put a much smaller hydrogen in the hydrogen bond acceptor’s position, it is much more favorable to allow the hydrogen bond to form. | 4 | Stereochemistry |
She graduated from Pierre and Marie Curie University. She studied the price of land in the 1700s and the Riverstrahler model of river nutrient transfer. | 9 | Geochemistry |
The threat of acidification includes a decline in commercial fisheries and the coast-based tourism industry. Several ocean goods and services are likely to be undermined by future ocean acidification potentially affecting the livelihoods of some 400 to 800 million people, depending upon the greenhouse gas emission scenario.
Some 1 billion people are wholly or partially dependent on the fishing, tourism, and coastal management services provided by coral reefs. Ongoing acidification of the oceans may therefore threaten future food chains linked with the oceans. | 9 | Geochemistry |
Per IUPAC, the term biaryl refers to an assembly of two aromatic rings joined by a single bond, starting with the simplest, biphenyl. Biaryls constitute an important structural motif of physical organic, synthetic, and catalytic interest—for instance, underlying the area of atropisomers in enantioselective synthesis—and they appear in many pharmaceutical, agrochemical, and materials (e.g. LCD) applications. The example of a coupling reaction reaction used in their preparation is an alternative to the traditional Suzuki and Stille cross-coupling reactions, and various catalysts have been employed for this transformation; Goossen et al. reported the formation of biaryls from palladium and copper-catalzyed cross-coupling reactions of an aryl or heteroaryl carboxylic acid and an aryl halide (I, Br, or Cl) in the presence of a base. | 0 | Organic Chemistry |
In most countries, a separate definition of VOCs is used with regard to indoor air quality that comprises each organic chemical compound that can be measured as follows: adsorption from air on Tenax TA, thermal desorption, gas chromatographic separation over a 100% nonpolar column (dimethylpolysiloxane). VOC (volatile organic compounds) are all compounds that appear in the gas chromatogram between and including n-hexane and n-hexadecane. Compounds appearing earlier are called VVOC (very volatile organic compounds); compounds appearing later are called SVOC (semi-volatile organic compounds).
France, Germany (AgBB/DIBt), Belgium, Norway (TEK regulation), and Italy (CAM Edilizia) have enacted regulations to limit VOC emissions from commercial products. European industry has developed numerous voluntary ecolabels and rating systems, such as EMICODE, M1, Blue Angel, GuT (textile floor coverings), Nordic Swan Ecolabel, EU Ecolabel, and Indoor Air Comfort. In the United States, several standards exist; California Standard CDPH Section 01350 is the most common one. These regulations and standards changed the marketplace, leading to an increasing number of low-emitting products. | 0 | Organic Chemistry |
Select filter cloth to obtain good wear and solid binding characteristics. Use moderate blowback pressure to avoid high wear. Adjust duration of blow back pressure short enough to remove the cake from the filter cloth. The tuning of valve body is important for the blow back to prevent the excess filtrated being force back out of the pipe to with the release cake solid as this minimises wear and filter media maintenance. | 3 | Analytical Chemistry |
In regards to rhythmicity of the clock in a free running setting PRR9 and PRR5 are associated with longer and shorter periods respectively. For each gene, the double mutant with PRR7 exacerbates observed trends in rhythmicity. The triple mutant renders the plant arrhythmic. | 1 | Biochemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2020 impact factor of 2.408. | 7 | Physical Chemistry |
In northern Europe, France, Germany, England and the Netherlands, bellfounding has been an enormous industry since the early part of the Middle Ages. Unfortunately a large number of medieval bells have been melted down and recast, and in times of warfare many were seized to be cast into guns. Early bells are of graceful outline, and often have simple but well-designed ornaments and very decorative inscriptions; for the latter a separate stamp or die was used for each letter or for a short group of letters. In every country bell-founders were an important group of the community; in England a great many of their names are known and the special character of their work is recognizable. Old bells exist in the French cathedrals of Amiens, Beauvais, Chartres and elsewhere; in Germany at Erfurt, Cologne and Halberstadt. The bell-founding industry has continued all through the centuries, one of its later achievements being the casting of "Big Ben" at Westminster in 1858, a bell of between 13 and 14 tons in weight.
In more recent years, bronze has to some extent replaced iron for railings, balconies and staircases, in connection with architecture; the style adopted is stiffly classical, which does not call for a very large amount of ornamentation, and the metal has the merit of pleasant appearance and considerable durability. | 8 | Metallurgy |
The chemical and biochemical properties of Mg present the cellular system with a significant challenge when transporting the ion across biological membranes. The dogma of ion transport states that the transporter recognises the ion then progressively removes the water of hydration, removing most or all of the water at a selective pore before releasing the ion on the far side of the membrane. Due to the properties of Mg, large volume change from hydrated to bare ion, high energy of hydration and very low rate of ligand exchange in the inner coordination sphere, these steps are probably more difficult than for most other ions. To date, only the ZntA protein of Paramecium has been shown to be a Mg channel. The mechanisms of Mg transport by the remaining proteins are beginning to be uncovered with the first three-dimensional structure of a Mg transport complex being solved in 2004.
The hydration shell of the Mg ion has a very tightly bound inner shell of six water molecules and a relatively tightly bound second shell containing 12–14 water molecules (Markham et al., 2002). Thus, it is presumed that recognition of the Mg ion requires some mechanism to interact initially with the hydration shell of Mg, followed by a direct recognition/binding of the ion to the protein. Due to the strength of the inner sphere complexation between Mg and any ligand, multiple simultaneous interactions with the transport protein at this level might significantly retard the ion in the transport pore. Hence, it is possible that much of the hydration water is retained during transport, allowing the weaker (but still specific) outer sphere coordination.
In spite of the mechanistic difficulty, Mg must be transported across membranes, and a large number of Mg fluxes across membranes from a variety of systems have been described. However, only a small selection of Mg transporters have been characterised at the molecular level. | 1 | Biochemistry |
Previous efforts to understand how sulfur metabolism and biosynthetic pathways relied on expensive labeling experiments using radioactive S. By leveraging natural assimilatory processes, stable isotope ratios can be used to track the sources of sulfur for plants, plant organs used in sulfur acquisition, the movement of sulfur through plants.
Sulfur (S) stable isotope composition measurements are often performed using an Elemental Analysis-Isotope Ratio Mass Spectrometer, (EA-IRMS) in which organic sulfur from biological samples is oxidized to sulfur dioxide (SO) and analyzed on a mass spectrometer. The mass spectrometer is used to quantify the ratio of the lighter (SO) to the heavier (SO) isotopologue of SO, and this ratio is then compared to sulfur isotope standards in order to standardize data to the VSMOW scale. In biological materials, sulfur is scarce relative to other organic elements like carbon and oxygen, introducing some additional difficulty in measuring its stable isotope composition. The elemental S composition of plant matter is ≈0.2%, accounting for approximately 2 mmol/m in most leaf tissue. In order to reach detectable levels of 30 ng to 3 µg of elemental S to calculate reliable δS values, leaf tissue samples need to be between 2–5 mg.
Improvements in detection have been made in recent years in the utilization of gas chromatography coupled with multicollector ICP-MS (GC/MC-ICP-MS) to be able to measure pmol quantities of organic S. Additionally, ICP-MS has been used to measure nanomolar quantities of dissolved sulfate. Most studies have focused on measuring the bulk δS value of plant tissues and few studies have been performed on measuring the δS values of individual S-containing compounds. The coupling of high-performance liquid chromatography (HPLC) with ICP-MS has been proposed as a way to test individual S-containing compounds. | 9 | Geochemistry |
Heavy meromyosin (HMM) is the larger of the two fragments obtained from the muscle protein myosin II following limited proteolysis by trypsin or chymotrypsin. HMM contains two domains S-1 and S-2, S-1 contains is the globular head that can bind to actin while the S-2 domain projects at and angle from light meromyosin (LMM) connecting the two meromyosin fragments.
HMM is used to determine the polarity of actin filaments by decorating them with HMM then viewing them under the electron microscope. | 1 | Biochemistry |
2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (or DDQ) is the chemical reagent with formula CCl(CN)O. This oxidant is useful for the dehydrogenation of alcohols, phenols, and steroid ketones. DDQ decomposes in water, but is stable in aqueous mineral acid. | 0 | Organic Chemistry |
Transannular strain can be eliminated by the simple addition of a carbon bridge. E,Z,E,Z,Z-[10]-annulene is quite unstable; while it has the requisite number of π-electrons to be aromatic, they are for the most part isolated. Ultimately, the molecule itself is very difficult to observe. However, by the simple addition of a methylene bridge between the 1 and 6 positions, a stable, flat, aromatic molecule can be made and observed. | 4 | Stereochemistry |
Surface diffusion may be studied by a variety of techniques, including both direct and indirect observations. Two experimental techniques that have proved very useful in this area of study are field ion microscopy and scanning tunneling microscopy. By visualizing the displacement of atoms or clusters over time, it is possible to extract useful information regarding the manner in which the relevant species diffuse-both mechanistic and rate-related information. In order to study surface diffusion on the atomistic scale it is unfortunately necessary to perform studies on rigorously clean surfaces and in ultra high vacuum (UHV) conditions or in the presence of small amounts of inert gas, as is the case when using He or Ne as imaging gas in field-ion microscopy experiments. | 7 | Physical Chemistry |
The first stereoselective synthesis was reported by Rajender Reddy Leleti and E. J.Corey. Later several routes to the total synthesis of salinosporamide A have been reported. | 0 | Organic Chemistry |
One category of reactions under Curtin–Hammett control includes transformations in which the more stable conformer reacts more quickly. This occurs when the transition state from the major intermediate to its respective product is lower in energy than the transition state from the minor intermediate to the other possible product. The major product is then derived from the major conformer, and the product distribution does not mirror the equilibrium conformer distribution. | 7 | Physical Chemistry |
Thomas Henry Haines (born August 9, 1933) was an American author, social activist, biochemist and academic. He was a professor of chemistry at City College of New York and of Biochemistry at the Sophie Davis School of Biomedical Education. He was a visiting professor in the Laboratory of Thomas Sakmar at Rockefeller University. He also served on the board of the Graham School, a social services and foster care agency in New York City. His scientific research focused on the structure and function of the living cell membrane. He is the father of Avril Haines, the seventh Director of National Intelligence. | 1 | Biochemistry |
A reduction–oxidation (redox) equilibrium can be handled in exactly the same way as any other chemical equilibrium. For example,
:Fe + Ce Fe + Ce;
However, in the case of redox reactions it is convenient to split the overall reaction into two half-reactions. In this example
:Fe + e Fe
:Ce + e Ce
The standard free energy change, which is related to the equilibrium constant by
can be split into two components,
The concentration of free electrons is effectively zero as the electrons are transferred directly from the reductant to the oxidant. The standard electrode potential, E for the each half-reaction is related to the standard free energy change by
where n is the number of electrons transferred and F is the Faraday constant. Now, the free energy for an actual reaction is given by
where R is the gas constant and Q a reaction quotient. Strictly speaking Q is a quotient of activities, but it is common practice to use concentrations instead of activities. Therefore:
For any half-reaction, the redox potential of an actual mixture is given by the generalized expression
This is an example of the Nernst equation. The potential is known as a reduction potential. Standard electrode potentials are available in a table of values. Using these values, the actual electrode potential for a redox couple can be calculated as a function of the ratio of concentrations.
The equilibrium potential for a general redox half-reaction (See #Equilibrium constant above for an explanation of the symbols)
:α A + β B... + n e σ S + τ T...
is given by
Use of this expression allows the effect of a species not involved in the redox reaction, such as the hydrogen ion in a half-reaction such as
: + 8 H + 5 e Mn + 4 HO
to be taken into account.
The equilibrium constant for a full redox reaction can be obtained from the standard redox potentials of the constituent half-reactions. At equilibrium the potential for the two half-reactions must be equal to each other and, of course, the number of electrons exchanged must be the same in the two half reactions.
Redox equilibrium play an important role in the electron transport chain. The various cytochromes in the chain have different standard redox potentials, each one adapted for a specific redox reaction. This allows, for example, atmospheric oxygen to be reduced in photosynthesis. A distinct family of cytochromes, the cytochrome P450 oxidases, are involved in steroidogenesis and detoxification. | 7 | Physical Chemistry |
The conjugate base of a sulfinic acid is a sulfinate anion. The enzyme cysteine dioxygenase converts cysteine into the corresponding sulfinate. One product of this catabolic reaction is the sulfinic acid hypotaurine. Sulfinite also describes esters of sulfinic acid. Cyclic sulfinite esters are called sultines. | 0 | Organic Chemistry |
The exact size of the GPCR superfamily is unknown, but at least 831 different human genes (or about 4% of the entire protein-coding genome) have been predicted to code for them from genome sequence analysis. Although numerous classification schemes have been proposed, the superfamily was classically divided into three main classes (A, B, and C) with no detectable shared sequence homology between classes.
The largest class by far is class A, which accounts for nearly 85% of the GPCR genes. Of class A GPCRs, over half of these are predicted to encode olfactory receptors, while the remaining receptors are liganded by known endogenous compounds or are classified as orphan receptors. Despite the lack of sequence homology between classes, all GPCRs have a common structure and mechanism of signal transduction. The very large rhodopsin A group has been further subdivided into 19 subgroups (A1-A19).
According to the classical A-F system, GPCRs can be grouped into six classes based on sequence homology and functional similarity:
*Class A (or 1) (Rhodopsin-like)
*Class B (or 2) (Secretin receptor family)
*Class C (or 3) (Metabotropic glutamate/pheromone)
*Class D (or 4) (Fungal mating pheromone receptors)
*Class E (or 5) (Cyclic AMP receptors)
*Class F (or 6) (Frizzled/Smoothened)
More recently, an alternative classification system called GRAFS (Glutamate, Rhodopsin, Adhesion, Frizzled/Taste2, Secretin) has been proposed for vertebrate GPCRs. They correspond to classical classes C, A, B2, F, and B.
An early study based on available DNA sequence suggested that the human genome encodes roughly 750 G protein-coupled receptors, about 350 of which detect hormones, growth factors, and other endogenous ligands. Approximately 150 of the GPCRs found in the human genome have unknown functions.
Some web-servers and bioinformatics prediction methods have been used for predicting the classification of GPCRs according to their amino acid sequence alone, by means of the pseudo amino acid composition approach. | 1 | Biochemistry |
Barbara McClintock discovered the first TEs in maize (Zea mays) at the Cold Spring Harbor Laboratory in New York. McClintock was experimenting with maize plants that had broken chromosomes.
In the winter of 1944–1945, McClintock planted corn kernels that were self-pollinated, meaning that the silk (style) of the flower received pollen from its own anther. These kernels came from a long line of plants that had been self-pollinated, causing broken arms on the end of their ninth chromosomes. As the maize plants began to grow, McClintock noted unusual color patterns on the leaves. For example, one leaf had two albino patches of almost identical size, located side by side on the leaf. McClintock hypothesized that during cell division certain cells lost genetic material, while others gained what they had lost. However, when comparing the chromosomes of the current generation of plants with the parent generation, she found certain parts of the chromosome had switched position. This refuted the popular genetic theory of the time that genes were fixed in their position on a chromosome. McClintock found that genes could not only move but they could also be turned on or off due to certain environmental conditions or during different stages of cell development.
McClintock also showed that gene mutations could be reversed. She presented her report on her findings in 1951, and published an article on her discoveries in Genetics in November 1953 entitled "Induction of Instability at Selected Loci in Maize".
At the 1951 Cold Spring Harbor Symposium where she first publicized her findings, her talk was met with dead silence. Her work was largely dismissed and ignored until the late 1960s–1970s when, after TEs were found in bacteria, it was rediscovered. She was awarded a Nobel Prize in Physiology or Medicine in 1983 for her discovery of TEs, more than thirty years after her initial research. | 1 | Biochemistry |
Acid–base imbalance occurs when a significant insult causes the blood pH to shift out of the normal range (7.32 to 7.42). An abnormally low pH in the extracellular fluid is called an acidemia and an abnormally high pH is called an alkalemia.
Acidemia and alkalemia unambiguously refer to the actual change in the pH of the extracellular fluid (ECF). Two other similar sounding terms are acidosis and alkalosis. They refer to the customary effect of a component, respiratory or metabolic. Acidosis would cause an acidemia on its own (i.e. if left "uncompensated" by an alkalosis). Similarly, an alkalosis would cause an alkalemia on its own. In medical terminology, the terms acidosis and alkalosis should always be qualified by an adjective to indicate the etiology of the disturbance: respiratory (indicating a change in the partial pressure of carbon dioxide), or metabolic (indicating a change in the Base Excess of the ECF). There are therefore four different acid-base problems: metabolic acidosis, respiratory acidosis, metabolic alkalosis, and respiratory alkalosis. One or a combination of these conditions may occur simultaneously. For instance, a metabolic acidosis (as in uncontrolled diabetes mellitus) is almost always partially compensated by a respiratory alkalosis (hyperventilation). Similarly, a respiratory acidosis can be completely or partially corrected by a metabolic alkalosis. | 7 | Physical Chemistry |
Prior to the discovery of rasagiline, a closely related analog called [https://pubchem.ncbi.nlm.nih.gov/compound/SU-11739 SU-11739] (AGN 1133) was patented. At first, the N-methyl was necessary for the agent to be considered a ring cyclized analog of pargyline with ca. twenty-times the potency. However, the N-methyl compound was a non-selective MAOI.
Racemic rasagiline was discovered and patented by Aspro Nicholas in the 1970s as a drug candidate for treatment of hypertension.
Moussa B. H. Youdim, a biochemist, had been involved in developing selegiline as a drug for Parkinsons, in collaboration with Peter Reiderer. He wanted to find a similar compound that would have fewer side effects, and around 1977, at about the same time he moved from London to Haifa to join the faculty of Technion, he noticed that rasagiline could potentially be such a compound. He called that compound, AGN 1135.
In 1996 Youdim, in collaboration with scientists from Technion and the US National Institutes of Health, and using compounds developed with Teva Pharmaceuticals, published a paper in which the authors wrote that they were inspired by the racemic nature of deprenyl and the greater activity of one of its stereoisomers, L-deprenyl, which became selegiline, to explore the qualities of the isomers of the Aspro compound, and they found that the R-isomer had almost all the activity; this is the compound that became rasagiline. They called the mesylate salt of the R-isomer TVP-1012 and the hydrochloride salt, TVP-101.
Teva and Technion filed patent applications for this racemically pure compound, methods to make it, and methods to use it to treat Parkinsons and other disorders, and Technion eventually assigned its rights to Teva.
Teva began development of rasagiline, and by 1999 was in Phase III trials, and entered into a partnership with Lundbeck in which Lundbeck agreed to share the costs and obtained the joint right to market the drug in Europe. In 2003 Teva partnered with Eisai, giving Eisai the right to jointly market the drug for Parkinson's in the US, and to co-develop and co-market the drug for Alzheimers and other neurological diseases.
It was approved by the European Medicines Agency for Parkinson's in 2005 and in the US in 2006. | 4 | Stereochemistry |
The use of highly reactive metals in chemical synthesis was popularized in the 1960s. One development in this theme is the use of metal vapor synthesis, as described by Skell, Timms, Ozin, and others. All of these methods relied on elaborate instrumentation to vaporize the metals, releasing an atomic form of these reactants.
In 1972, Reuben D. Rieke, a professor of chemistry at the University of North Carolina, published the method that now bears his name. In contrast to previous methods, it did not require special equipment, and the main challenges were only the handling of pyrophoric reagents and/or products, and the need for anhydrous reagents and air-free techniques. Thus his discovery gained much attention because of its simplicity and the reactivity of the activated metals.
Rieke continued this work at the University of Nebraska-Lincoln. He and his wife Loretta founded Rieke Metals LLC in 1991, based on these materials. | 0 | Organic Chemistry |
Spatially resolve acoustic spectroscopy (SRAS) is an optical technique that uses optically generated high frequency surface acoustic waves to probe
the direction elastic parameters of the surface and, as such, it can vividly reveal the surface microstructure of metals.
It can also image the crystallographic orientation and determine the single crystal elasticity matrix of the material. | 8 | Metallurgy |
For cellular organisms, the transport of specific molecules across compartmentalizing membrane barriers is essential in order to exchange content with their environment and with other individuals. For example, content exchange between individuals enables the exchange of genes between individuals (horizontal gene transfer), an important factor in the evolution of cellular life. While modern cells can rely on complicated protein machineries to catalyze these crucial processes, protocells must have accomplished this using more simple mechanisms.
Protocells composed of fatty acids would have been able to easily exchange small molecules and ions with their environment. Modern phospholipid bilayer cell membranes exhibit low permeability, but contain complex molecular assemblies which both actively and passively transport relevant molecules across the membrane in a highly specific manner. In the absence of these complex assemblies, simple fatty acid based protocell membranes would be more permeable and allow for greater non-specific transport across membranes. Molecules that would be highly permeable across protocell membranes include nucleoside monophosphate (NMP), nucleoside diphosphate (NDP), and nucleoside triphosphate (NTP), and may withstand millimolar concentrations of Mg. Osmotic pressure can also play a significant role regarding this passive membrane transport.
Environmental effects have been suggested to trigger conditions under which a transport of larger molecules, such as DNA and RNA, across the membranes of protocells is possible. For example, it has been proposed that electroporation resulting from lightning strikes could enable such transport. Electroporation is the rapid increase in bilayer permeability induced by the application of a large artificial electric field across the membrane. During electroporation, the lipid molecules in the membrane shift position, opening up a pore (hole) that acts as a conductive pathway through which hydrophobic molecules like nucleic acids can pass the lipid bilayer. A similar transfer of content across protocells and with the surrounding solution can be caused by freezing and subsequent thawing. This could, for instance, occur in an environment in which day and night cycles cause recurrent freezing. Laboratory experiments have shown that such conditions allow an exchange of genetic information between populations of protocells. This can be explained by the fact that membranes are highly permeable at temperatures slightly below their phase transition temperature. If this point is reached during the freeze-thaw cycle, even large and highly charged molecules can temporarily pass the protocell membrane.
Some molecules or particles are too large or too hydrophilic to pass through a lipid bilayer even under these conditions, but can be moved across the membrane through fusion or budding of vesicles, events which have also been observed for freeze-thaw cycles. This may eventually have led to mechanisms that facilitate movement of molecules to the inside of the protocell (endocytosis) or to release its contents into the extracellular space (exocytosis). | 9 | Geochemistry |
Knowledge of which genes (when non-functional) cause which disorders will simplify diagnosis of patients and provide insights into the functional characteristics of the mutation. The advent of modern-day high-throughput sequencing technologies combined with insights provided from the growing field of genomics is resulting in more rapid disease gene identification, thus allowing scientists to identify more complex mutations. | 1 | Biochemistry |
A way to identify aglycone is proposed to extract it from Agave spp. by using H-NMR and Heteronuclear multiple bond correlation (HMBC) experiments. The HMBC experiment can be combined with other techniques such as mass spectrometry to further examine the structure and the function of aglycone.
Samples of glycones and glycosides from limonoids can be simultaneously quantified through a high performance liquid chromatography (HPLC) method, where a binary solvent system and a diode array detector separate and detect them at a sensitivity of 0.25-0.50 μg. | 0 | Organic Chemistry |
The front-end optics of a spectroradiometer includes the lenses, diffusers, and filters that modify the light as it first enters the system. For Radiance an optic with a narrow field of view is required. For total flux an integrating sphere is required. For Irradiance cosine correcting optics are required. The material used for these elements determines what type of light is capable of being measured. For example, to take UV measurements, quartz rather than glass lenses, optical fibers, Teflon diffusers, and barium sulphate coated integrating spheres are often used to ensure accurate UV measurement. | 7 | Physical Chemistry |
The flammable nature of the exhalations of wine was already known to ancient natural philosophers such as Aristotle (384–322 BCE), Theophrastus (–287 BCE), and Pliny the Elder (23/24–79 CE). However, this did not immediately lead to the isolation of alcohol, even despite the development of more advanced distillation techniques in second- and third-century Roman Egypt. An important recognition, first found in one of the writings attributed to Jābir ibn Ḥayyān (ninth century CE), was that by adding salt to boiling wine, which increases the wines relative volatility, the flammability of the resulting vapors may be enhanced. The distillation of wine is attested in Arabic works attributed to al-Kindī (–873 CE) and to al-Fārābī (–950), and in the 28th book of al-Zahrāwīs (Latin: Abulcasis, 936–1013) Kitāb al-Taṣrīf (later translated into Latin as Liber servatoris). In the twelfth century, recipes for the production of aqua ardens ("burning water", i.e., alcohol) by distilling wine with salt started to appear in a number of Latin works, and by the end of the thirteenth century, it had become a widely known substance among Western European chemists.
The works of Taddeo Alderotti (1223–1296) describe a method for concentrating alcohol involving repeated fractional distillation through a water-cooled still, by which an alcohol purity of 90% could be obtained. The medicinal properties of ethanol were studied by Arnald of Villanova (1240–1311 CE) and John of Rupescissa (–1366), the latter of whom regarded it as a life-preserving substance able to prevent all diseases (the aqua vitae or "water of life", also called by John the quintessence of wine). | 0 | Organic Chemistry |
Beatriz Roldán Cuenya (born 1976 in Oviedo) is a Spanish physicist working in surface science and catalysis. Since 2017 she has been director of the Department of Interface Science at the Fritz Haber Institute of the Max Planck Society in Berlin, Germany. Since April 2023, she has also been interim director of the Department of Inorganic Chemistry, also at the Fritz Haber Institute. | 7 | Physical Chemistry |
#"Walter, Filip Neriusz", in Stanley S. Sokol, The Polish Biographical Dictionary, Bolchazy-Carducci Publishers, 1992.
#Stefan Sękowski, Stefan Szostkiewicz, Serce i retorta (The Heart and the Retort), Warsaw, Wiedza Powszechna, 1957.
#Aleksander Jełowicki, Wspomnienia (Memoirs), Paris, 1839.
#Stanisław Wodzicki, Wspomnienia z przeszłości (Memoirs of the Past). Kraków, 1873.
#Adolphe Wurz, Historia poglądów chemicznych (A History of Chemical Views), Warsaw, 1886. | 0 | Organic Chemistry |
Increased risk might be posed by the expected rise in total sulphur emissions from 4,400 kilotonnes (kt) in 1990 to 6,500 kt in 2000, 10,900 kt in 2010 and 18,500 in 2020. | 2 | Environmental Chemistry |
Comparing the two contributing structures of benzene, all single and double bonds are interchanged. Bond lengths can be measured, for example using X-ray diffraction. The average length of a C–C single bond is 154 pm; that of a C=C double bond is 133 pm. In localized cyclohexatriene, the carbon–carbon bonds should be alternating 154 and 133 pm. Instead, all carbon–carbon bonds in benzene are found to be about 139 pm, a bond length intermediate between single and double bond. This mixed single and double bond (or triple bond) character is typical for all molecules in which bonds have a different bond order in different contributing structures. Bond lengths can be compared using bond orders. For example, in cyclohexane the bond order is 1 while that in benzene is 1 + (3 ÷ 6) = . Consequently, benzene has more double bond character and hence has a shorter bond length than cyclohexane. | 7 | Physical Chemistry |
Binders promote the binding of pigment particles between themselves and the coating layer of the paper. Binders are spherical particles less than 1 µm in diameterr. Common binders are styrene maleic anhydride copolymer or styrene-acrylate copolymer. The surface chemical composition is differentiated by the adsorption of acrylic acid or an anionic surfactant, both of which are used for stabilization of the dispersion in water. Co-binders, or thickeners, are generally water-soluble polymers that influence the paper's color viscosity, water retention, sizing, and gloss. Some common examples are carboxymethyl cellulose (CMC), cationic and anionic hydroxyethyl cellulose (EHEC), modified starch, and dextrin. | 7 | Physical Chemistry |
The GUS system is not the only available gene reporter system for the analysis of promoter activity. Other competing systems are based on e.g. luciferase, GFP, beta-galactosidase, chloramphenicol acetyltransferase (CAT), alkaline phosphatase. The use of one or the other system is mainly dependent on the organism of interest and the imaging and microscopy technologies available to the laboratories conducting the research. | 1 | Biochemistry |
Toluene derivatives with heteroatom-containing substituents in the ortho position undergo site-selective benzylic lithiation in the presence of organolithium compounds (either alkyllithiums or lithium dialkylamides). Coordination of the Lewis acidic lithium atom to the Lewis basic heteroatom, as well as inductive effects derived from the electronegativity of the heteroatom, encourage selective deprotonation at the benzylic position. Competitive ring metalation (directed ortho-metalation) is an important side reaction, but a judicious choice of base often allows for selective benzylic metalation. Useful heteroatom-containing directing groups include dialkylamines, amides (secondary or tertiary), ketone enolates, carbamates, and sulfonates. Lateral lithiation of alkyl-substituted heterocycles incorporating heteroatom-containing substituents is also possible, although ring lithiation α to the ring heteroatom may compete with lateral lithiation. The products of lateral lithiation react with a variety of electrophiles, including reactive alkyl halides (allylic, benzylic, and primary), carbonyl compounds, silyl and stannyl chlorides, disulfides and diselenides, and others. A general, highly selective method for benzylic metalation using a mixed lithium and potassium metal amide (LiNK chemistry) has been developed which permits metalation regardless of the relative position (ortho, meta or para) of the methyl group to the heteroatom containing substituent | 0 | Organic Chemistry |
Mant et al. reported that HILIC/CEX offered unique selectivity, stronger separation power and wider range of applications compared to RPLC for peptide separations. | 3 | Analytical Chemistry |
Amine oxides exhibit many kinds of reactions.
*Pyrolytic elimination. Amine oxides, when heated to 150–200 °C undergo a Cope reaction to form a hydroxylamine and an alkene. The reaction requires the alkyl groups to have hydrogens at the beta-carbon (i.e. works with ethyl and above, but not methyl)
*Reduction to amines. Amine oxides are readily converted to the parent amine by common reduction reagents including lithium aluminium hydride, sodium borohydride, catalytic reduction, zinc / acetic acid, and iron / acetic acid. Pyridine N-oxides can be deoxygenated by phosphorus oxychloride
* Sacrificial catalysis. Oxidants can be regenerated by reduction of N-oxides, as in the case of regeneration of osmium tetroxide by N-methylmorpholine N-oxide in the Upjohn dihydroxylation.
* O-Alkylation. Pyridine N-oxides react with alkyl halides to the O-alkylated product
* Bis-ter-pyridine derivatives adsorbed on silver surfaces are discussed to react with oxygen to bis-ter-pyridine N-oxide. This reaction can be followed by video-scanning tunneling microscopy with sub-molecular resolution.
* In the Meisenheimer rearrangement (after Jakob Meisenheimer) certain N-oxides rearrange to hydroxylamines
: in a 1,2-rearrangement:
:or a 2,3-rearrangement:
* In the Polonovski reaction a tertiary N-oxide is cleaved by acetic acid anhydride to the corresponding acetamide and aldehyde: | 0 | Organic Chemistry |
The Cotton effect in physics, is the characteristic change in optical rotatory dispersion and/or circular dichroism in the vicinity of an absorption band of a substance.
In a wavelength region where the light is absorbed, the absolute magnitude of the optical rotation at first varies rapidly with wavelength, crosses zero at absorption maxima and then again varies rapidly with wavelength but in the opposite direction. This phenomenon was discovered in 1895 by the French physicist Aimé Cotton (1869–1951).
The Cotton effect is called positive if the optical rotation first increases as the wavelength decreases (as first observed by Cotton), and negative if the rotation first decreases.
A protein structure such as a beta sheet shows a negative Cotton effect. | 7 | Physical Chemistry |
Poolman has received numerous awards, including the Biochemistry Award (1989) of the Dutch Biochemistry and Molecular Biology Organisation (NVBMB), a Royal Netherlands Academy of Arts and Sciences fellowship (1989), a Human Frontiers Science Program Organization award (1992), the SON ‘Jonge Chemici’ award (1997), the Federation European Biochemical Society Lecturer Award (2014), and the Joel Mandelstam Memorial Lecture award (2016).
He obtained four TOP program grants from the Netherlands Organisation for Scientific Research (NWO)(2001, 2007, 2010, 2014)., two program grants from the Netherlands Proteomics Centre (2005 en 2008), and coordinated three large European networks (1996, 1999 and 2012). In 2015 he received an ERC Advanced Grant and in 2019 an ERC Proof-of-Concept Grant, and in 2017 the BaSyC consortium (with Poolman as one of the lead principal investigators) was awarded a multimillion Dutch Gravitation grant. | 0 | Organic Chemistry |
Photochlorination is one of the largest implementations of photochemistry to organic synthesis. The photon is however not absorbed by the organic compound, but by chlorine. Photolysis of Cl gives chlorine atoms, which abstract H atoms from hydrocarbons, leading to chlorination. | 5 | Photochemistry |
Nitrogen can be fixed by lightning converting nitrogen gas () and oxygen gas () in the atmosphere into (nitrogen oxides). The molecule is highly stable and nonreactive due to the triple bond between the nitrogen atoms. Lightning produces enough energy and heat to break this bond allowing nitrogen atoms to react with oxygen, forming . These compounds cannot be used by plants, but as this molecule cools, it reacts with oxygen to form , which in turn reacts with water to produce (nitrous acid) or (nitric acid). When these acids seep into the soil, they make (nitrate), which is of use to plants. | 1 | Biochemistry |
The Langelier saturation index (sometimes Langelier stability index) is a calculated number used to predict the calcium carbonate stability of water. It indicates whether the water will precipitate, dissolve, or be in equilibrium with calcium carbonate. In 1936, Wilfred Langelier developed a method for predicting the pH at which water is saturated in calcium carbonate (called pH). The LSI is expressed as the difference between the actual system pH and the saturation pH:
:LSI = pH (measured) − pH
* For LSI > 0, water is supersaturated and tends to precipitate a scale layer of CaCO.
* For LSI = 0, water is saturated (in equilibrium) with CaCO. A scale layer of CaCO is neither precipitated nor dissolved.
* For LSI .
If the actual pH of the water is below the calculated saturation pH, the LSI is negative and the water has a very limited scaling potential. If the actual pH exceeds pHs, the LSI is positive, and being supersaturated with CaCO, the water tends to form scale. At increasing positive index values, the scaling potential increases.
In practice, water with an LSI between −0.5 and +0.5 will not display enhanced mineral dissolving or scale-forming properties. Water with an LSI below −0.5 tends to exhibit noticeably increased dissolving abilities while water with an LSI above +0.5 tends to exhibit noticeably increased scale-forming properties.
The LSI is temperature-sensitive. The LSI becomes more positive as the water temperature increases. This has particular implications in situations where well water is used. The temperature of the water when it first exits the well is often significantly lower than the temperature inside the building served by the well or at the laboratory where the LSI measurement is made. This increase in temperature can cause scaling, especially in cases such as water heaters. Conversely, systems that reduce water temperature will have less scaling.
: Water analysis:
:: pH = 7.5
:: TDS = 320 mg/L
:: Calcium = 150 mg/L (or ppm) as CaCO
:: Alkalinity = 34 mg/L (or ppm) as CaCO
: LSI formula:
:: LSI = pH − pH
:: pH = (9.3 + A + B) − (C + D) where:
:: A = = 0.15
:: B = −13.12 × log(°C + 273) + 34.55 = 2.09 at 25 °C and 1.09 at 82 °C
:: C = log[Ca as CaCO] - 0.4 = 1.78
::: (Ca as CaCO is also called calcium hardness, and is calculated as 2.5[Ca])
:: D = log[alkalinity as CaCO] = 1.53 | 3 | Analytical Chemistry |
Sulfuric acid created by John Roebuck's process approached a 65% concentration. Later refinements to the lead chamber process by French chemist Joseph Louis Gay-Lussac and British chemist John Glover improved concentration to 78%. However, the manufacture of some dyes and other chemical processes require a more concentrated product. Throughout the 18th century, this could only be made by dry distilling minerals in a technique similar to the original alchemical processes. Pyrite (iron disulfide, ) was heated in air to yield iron(II) sulfate, , which was oxidized by further heating in air to form iron(III) sulfate, , which, when heated to 480 °C, decomposed to iron(III) oxide and sulfur trioxide, which could be passed through water to yield sulfuric acid in any concentration. However, the expense of this process prevented the large-scale use of concentrated sulfuric acid. | 7 | Physical Chemistry |
Nickel titanium, also known as nitinol, is a metal alloy of nickel and titanium, where the two elements are present in roughly equal atomic percentages. Different alloys are named according to the weight percentage of nickel; e.g., nitinol 55 and nitinol 60.
Nitinol alloys exhibit two closely related and unique properties: the shape memory effect and superelasticity (also called pseudoelasticity). Shape memory is the ability of nitinol to undergo deformation at one temperature, stay in its deformed shape when the external force is removed, then recover its original, undeformed shape upon heating above its "transformation temperature." Superelasticity is the ability for the metal to undergo large deformations and immediately return to its undeformed shape upon removal of the external load. Nitinol can deform 10 to 30 times as much as ordinary metals and return to its original shape. Whether nitinol behaves with the shape memory effect or superelasticity depends on whether it is above its transformation temperature. Below the transformation temperature it exhibits the shape memory effect, and above that temperature it behaves superelastically. | 8 | Metallurgy |
Soil E is also largely a function of hydrological conditions. In the event of a flood, saturated soils can shift from oxic to anoxic, creating a reducing environment as anaerobic microbial processes dominate. Moreover, small anoxic hotspots may develop within soil pore spaces, creating reducing conditions. With time, the starting E of a soil can be restored as water drains and the soil dries out. Soils with redox gradients formed by ascending groundwater are classified as gleysols, while soils with gradients formed by stagnant water are classified as stagnosols and planosols.
Soil E generally ranges from −300 to +900 mV. The table below summarizes typical E values for various soil conditions:
Generally accepted E limits that are tolerable by plants are +300 mV ) is also closely tied to pH, and both have significant influence on the function of soil-plant-microorganism systems. The main source of electrons in soil is organic matter. Organic matter consumes oxygen as it decomposes, resulting in reducing soil conditions and lower E. | 7 | Physical Chemistry |
In physics, absorption of electromagnetic radiation is the way by which the energy of a photon is taken up by matter, typically the electrons of an atom. Thus, the electromagnetic energy is transformed to other forms of energy, for example, to heat. The absorption of light during wave propagation is often called attenuation. Usually, the absorption of waves does not depend on their intensity (linear absorption), although in certain conditions (usually, in optics), the medium changes its transparency dependently on the intensity of waves going through, and the Saturable absorption (or nonlinear absorption) occurs. | 7 | Physical Chemistry |
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