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When an acid catalyst is used, the initial step in the reaction mechanism involves acid-catalyzed tautomerization of the carbonyl compound to the enol. The acid also serves to activate the carbonyl group of another molecule by protonation, rendering it highly electrophilic. The enol is nucleophilic at the α-carbon, allowing it to attack the protonated carbonyl compound, leading to the aldol after deprotonation.
This under the right conditions can then dehydrate to give the unsaturated carbonyl compound, the aldol condensation product.
# Acid-catalyzed aldol addition
# Acid-catalyzed aldol dehydration | 0 | Organic Chemistry |
Following the initial synthesis of phosphaethyne, it was realized that the same compound can be prepared more expeditiously via the flash pyrolysis of methyldichlorophosphine (CHPCl), resulting in the loss of two equivalents of hydrogen chloride. This methodology has been utilized to synthesize numerous substituted phosphaalkynes, including the methyl, vinyl, chloride, and fluoride derivatives. Fluoromethylidynephosphane (F-C≡P) can also be prepared via the potassium hydroxide promoted dehydrofluorination of trifluoromethylphosphine (CFPH). It is speculated that these reactions generally proceed via an intermediate phosphaethylene with general structure RClC=PH. This hypothesis has found experimental support in the observation of FC=PH by P NMR spectroscopy during the synthesis of F-C≡P. | 0 | Organic Chemistry |
A heterogeneous catalyst consisting of Pd supported by silica-coated FeO/FeO nanoparticles allows the reaction to be heated by electrical induction, and also allows facile magnetic separation of catalyst and product post-reaction. Copper ferrite has been reported as a heterocycle arylation catalyst and can be similarly separated from the reaction with a magnet. | 0 | Organic Chemistry |
Polyamine-based cryptands can be converted to polyammonium cages, which exhibit high affinities for anions. | 6 | Supramolecular Chemistry |
-Malic acid is the naturally occurring form, whereas a mixture of - and -malic acid is produced synthetically.
Malate plays an important role in biochemistry. In the C4 carbon fixation process, malate is a source of CO in the Calvin cycle. In the citric acid cycle, (S)-malate is an intermediate, formed by the addition of an -OH group on the si face of fumarate. It can also be formed from pyruvate via anaplerotic reactions.
Malate is also synthesized by the carboxylation of phosphoenolpyruvate in the guard cells of plant leaves. Malate, as a double anion, often accompanies potassium cations during the uptake of solutes into the guard cells in order to maintain electrical balance in the cell. The accumulation of these solutes within the guard cell decreases the solute potential, allowing water to enter the cell and promote aperture of the stomata. | 1 | Biochemistry |
Pre-implantation genetic diagnosis (PGD) is criticised for giving select demographic groups disproportionate access to a means of creating a child possessing characteristics that they consider "ideal". Many fertile couples now demand equal access to embryonic screening so that their child can be just as healthy as one created through IVF. Mass use of PGD, especially as a means of population control or in the presence of legal measures related to population or demographic control, can lead to intentional or unintentional demographic effects such as the skewed live-birth sex ratios seen in China following implementation of its one-child policy.
While PGD was originally designed to screen for embryos carrying hereditary genetic diseases, the method has been applied to select features that are unrelated to diseases, thus raising ethical questions. Examples of such cases include the selection of embryos based on histocompatibility (HLA) for the donation of tissues to a sick family member, the diagnosis of genetic susceptibility to disease, and sex selection.
These examples raise ethical issues because of the morality of eugenics. It becomes frowned upon because of the advantage of being able to eliminate unwanted traits and selecting desired traits. By using PGD, individuals are given the opportunity to create a human life unethically and rely on science and not by natural selection.
For example, a deaf British couple, Tom and Paula Lichy, have petitioned to create a deaf baby using IVF. Some medical ethicists have been very critical of this approach. Jacob M. Appel wrote that "intentionally culling out blind or deaf embryos might prevent considerable future suffering, while a policy that allowed deaf or blind parents to select for such traits intentionally would be far more troublesome." | 1 | Biochemistry |
When Eric Cornell and Carl Wieman produced a Bose–Einstein condensate from rubidium atoms in 1995, there naturally arose the prospect of creating a similar sort of condensate made from fermionic atoms, which would form a superfluid by the BCS mechanism. However, early calculations indicated that the temperature required for producing Cooper pairing in atoms would be too cold to achieve. In 2001, Murray Holland at JILA suggested a way of bypassing this difficulty. He speculated that fermionic atoms could be coaxed into pairing up by subjecting them to a strong magnetic field.
In 2003, working on Holland's suggestion, Deborah Jin at JILA, Rudolf Grimm at the University of Innsbruck, and Wolfgang Ketterle at MIT managed to coax fermionic atoms into forming molecular bosons, which then underwent Bose–Einstein condensation. However, this was not a true fermionic condensate. On December 16, 2003, Jin managed to produce a condensate out of fermionic atoms for the first time. The experiment involved 500,000 potassium-40 atoms cooled to a temperature of 5×10 K, subjected to a time-varying magnetic field. | 7 | Physical Chemistry |
The (temporal) autocorrelation function is the correlation of a time series with itself shifted by time , as a function of :
where is the deviation from the mean intensity. The normalization (denominator) here is the most commonly used for FCS, because then the correlation at , G(0), is related to the average number of particles in the measurement volume.
As an example, raw FCS data and its autocorrelation for freely diffusing Rhodamine 6G are shown in the figure to the right. The plot on top shows the fluorescent intensity versus time. The intensity fluctuates as Rhodamine 6G moves in and out of the focal volume. In the bottom plot is the autocorrelation on the same data. Information about the diffusion rate and concentration can be obtained using one of the models described below.
For a Gaussian illumination profile , the autocorrelation function is given by the general master formula
where the vector denotes the stochastic displacement in space of a fluorophore after time .
The expression is valid if the average number of fluorophores in the focal volume is low and if dark states, etc., of the fluorophore can be ignored. In particular, no assumption was made on the type of diffusive motion under investigation. The formula allows for an interpretation of as (i) a return probability for small beam parameters and (ii) the moment-generating function of if are varied. | 7 | Physical Chemistry |
The Shapiro–Senapathy algorithm has been used to determine the various aberrant splicing mechanisms in genes due to deleterious mutations in the splice sites, which cause numerous diseases. Deleterious splice site mutations impair the normal splicing of the gene transcripts, and thereby make the encoded protein defective. A mutant splice site can become “weak” compared to the original site, due to which the mutated splice junction becomes unrecognizable by the spliceosomal machinery. This can lead to the skipping of the exon in the splicing reaction, resulting in the loss of that exon in the spliced mRNA (exon-skipping). On the other hand, a partial or complete intron could be included in the mRNA due to a splice site mutation that makes it unrecognizable (intron inclusion). A partial exon-skipping or intron inclusion can lead to premature termination of the protein from the mRNA, which will become defective leading to diseases. The S&S has thus paved the way to determine the mechanisms by which a deleterious mutation could lead to a defective protein, resulting in different diseases depending on which gene is affected. | 1 | Biochemistry |
Noncovalent intermolecular interactions, albeit individually small, collectively alter chemical reactions in major ways. Listed below are common intermolecular forces that chemists have used to design foldamers.
* Hydrogen bonding (especially with peptide bonds)
* Pi stacking
* Solvophobic effects, which lead to hydrophobic collapse
* Van der Waals forces
* Electrostatic attraction | 6 | Supramolecular Chemistry |
The allyloxycarbonyl (alloc) protecting group is sometimes used to protect an amino group (or carboxylic acid or alcohol group) when an orthogonal deprotection scheme is required. It is also sometimes used when conducting on-resin cyclic peptide formation, where the peptide is linked to the resin by a side-chain functional group. The Alloc group can be removed using tetrakis(triphenylphosphine)palladium(0).
For special applications like synthetic steps involving protein microarrays, protecting groups sometimes termed "lithographic" are used, which are amenable to photochemistry at a particular wavelength of light, and so which can be removed during lithographic types of operations. | 1 | Biochemistry |
The most common adverse effects of esketamine for depression (≥5% incidence) include dissociation, dizziness, sedation, nausea, vomiting, vertigo, numbness, anxiety, lethargy, increased blood pressure, and feelings of drunkenness. Long-term use of esketamine has been associated with bladder disease. | 4 | Stereochemistry |
Carboxylic acids are commonly identified by their trivial names. They often have the suffix -ic acid. IUPAC-recommended names also exist; in this system, carboxylic acids have an -oic acid suffix. For example, butyric acid () is butanoic acid by IUPAC guidelines. For nomenclature of complex molecules containing a carboxylic acid, the carboxyl can be considered position one of the parent chain even if there are other substituents, such as 3-chloropropanoic acid. Alternately, it can be named as a "carboxy" or "carboxylic acid" substituent on another parent structure, such as 2-carboxyfuran.
The carboxylate anion ( or ) of a carboxylic acid is usually named with the suffix -ate, in keeping with the general pattern of -ic acid and -ate for a conjugate acid and its conjugate base, respectively. For example, the conjugate base of acetic acid is acetate.
Carbonic acid, which occurs in bicarbonate buffer systems in nature, is not generally classed as one of the carboxylic acids, despite that it has a moiety that looks like a COOH group. | 0 | Organic Chemistry |
Administered to patients whose pituitary glands generate insufficient quantities to support normal growth and development. Before recombinant HGH became available, HGH for therapeutic use was obtained from pituitary glands of cadavers. This unsafe practice led to some patients developing Creutzfeldt–Jakob disease. Recombinant HGH eliminated this problem, and is now used therapeutically. It has also been misused as a performance-enhancing drug by athletes and others. | 1 | Biochemistry |
In Japan, pesticide residues are regulated by the Food Safety Act.
Pesticide tolerances are set by the Ministry of Health, Labour and Welfare through the Drug and Food Safety Committee. Unlisted residue amounts are restricted to 0.01ppm. | 2 | Environmental Chemistry |
Synapses are typically formed where two neurons come in very close proximity. Ephaptic coupling may therefore arise across the synaptic cleft. Prominent examples are the fish Mauthner cell, the chick ciliary ganglion, the mammalian cerebellar basket synapse, and the mammalian, developing calyx of Held synapse. | 1 | Biochemistry |
The metabolic (catabolic fate) of propionyl-CoA depends on what environment it is being synthesized in. Therefore, propionyl-CoA in an anaerobic environment could have a different fate than that in an aerobic organism. The multiple pathways, either catabolism by propionyl-CoA carboxylase or methylcitrate synthase, also depend on the presence of various genes. | 1 | Biochemistry |
The Scythians emerged as a people prior to the 7th Century BC, when they were first mentioned in historical records. The Scythian civilization consisted of a number of distinct tribal groups scattered across the Pontic Steppes, Caucasus, and Central Asia. Though primarily a nomadic people, the Scythians established a number of settlements across their territory; these establishments in turn allowed for the development of a sedentary society and the accompanying development of trade skills, including metalworking.
Scythian knowledge of metalworking likely originated with the peoples of Iran and China, with this knowledge spreading along trade routes and arriving in the steppes from the 2nd to 1st Millennium BC. Early Scythian metallurgy was centered around bronzeworking, as these skills had already been widely adopted by the Scythians neighbors. The Minusinsk Basin of Siberia has been speculated as the origin point for the raw materials used in Bronze-age Scythian metallurgy, and Scythian access to this region fueled the peoples later centuries of expansion. During the 8th Century BC Scythians were often employed by nations in the Near East and these returning soldiers may have brought knowledge of iron-working back to their homeland, and by the start of the 6th-century BC the practice was widespread in the Pontic steppes. In addition to bronze and iron working, gold and copper-working were also present in Scythian society; in his commentary on the Scythian people, Greek historian Herodotus remarked on their fondness for making things from gold and copper.
Metallurgy held a major place in Scythian society as metalworkers were needed to produce material goods to support the Scythian way of life. As a nomadic society with broad borders, the Scythians often raided neighboring peoples and as such required metal weaponry - particularly iron swords and bronze arrowheads. It has been speculated that the Scythian's use of stylized metal adornments may have been copied from their opponents during these conflicts. In addition, jewelry and other adornment was in demand among all classes of society, as can be seen with the discovery of metal adornments in the burial tombs attributed to the Scythians. One notable aspect of Scythian clothing was the widespread use of metal belts.
Other signs of Scythian metalworking can be found throughout sites attributed to the people. Several notable Scythian archeological sites contain the remnants of metalworking operations; at one settlement along the Dnieper, remnants of blast furnaces and slag have been found, implying the existence of a large metallurgical center. Studies of other Scythian sites have also led to the remains of metal workshops and tools being found, further supporting the theory that the Scythians were organized craftspeople. Scythian metalworkers were particularly renowned for the high quality of their copper crafting. During war, portable molds were brought to forge arrowheads for the Scythian cavalry. Scythian metallurgy also influenced the metallurgy of the Koban people of the North Caucasus. | 8 | Metallurgy |
Metallabenzene complexes have been classified into three varieties; in such compounds, the parent acyclic hydrocarbon ligand is viewed as the anion CH. The 6 π electrons in the metallacycle conform to the Hückel (4n+2) theory. | 0 | Organic Chemistry |
Once they are identified along the z-axis, individual layers of DVD-like data may be accessed and tracked in similar ways to DVDs. The possibility of using parallel or page-based addressing has also been demonstrated. This allows much faster data transfer rates, but requires the additional complexity of spatial light modulators, signal imaging, more powerful lasers, and more complex data handling. | 5 | Photochemistry |
The Sherman function describes the dependence of electron-atom scattering events on the spin of the scattered electrons. It was first evaluated theoretically by the physicist Noah Sherman and it allows the measurement of polarization of an electron beam by Mott scattering experiments. A correct evaluation of the Sherman function associated to a particular experimental setup is of vital importance in experiments of spin polarized photoemission spectroscopy, which is an experimental technique which allows to obtain information about the magnetic behaviour of a sample. | 7 | Physical Chemistry |
The Society for Applied Spectroscopy was selected by Kowalskis family to administer an award in Kowalskis name, the Bruce R. Kowalski Award in Chemometrics - Administered by the Society for Applied Spectroscopy, "to honor the legacy of Professor Kowalski by recognizing outstanding young researchers in the field of chemometrics and by extension, for advanced mathematical and/or statistical methods in chemistry."
The University of Washington has three scholarships set up in Kowalskis honor, the Kowalski Excellence in Graduate Education Fund, Bruce Kowalski Endowed Fund for Graduate Student Support, and the chemistry departments Bruce R. Kowalski Endowed Fund in Chemistry.
In 2015 the American Chemical Society published a symposium series in Kowalskis honor, 40 Years of Chemometrics – From Bruce Kowalski to the Future.'
The Kowalski Prize, worth $1,000, is given annually by the Journal of Chemometrics, alternating between "the best theoretical paper and best applied paper published in the journal in the previous two years." | 3 | Analytical Chemistry |
RNAa has been used to study gene function in lieu of vector-based gene overexpression. Studies have demonstrated RNAa in vivo and its potential therapeutic applications in treating cancer and non-cancerous diseases.
In June 2016, UK-based MiNA Therapeutics announced the initiation of a phase I trial of the first-ever saRNA drug MTL-CEBPA in patients with liver cancer, in an attempt to activate CEBPA gene. | 1 | Biochemistry |
Synthetic repellents tend to be more effective and/or longer lasting than "natural" repellents.
For protection against mosquito bites, the U.S. Centers for Disease Control (CDC) recommends DEET, icaridin (picaridin, KBR 3023), oil of lemon eucalyptus (para-menthane-diol or PMD), IR3535 and 2-undecanone with the caveat that higher percentages of the active ingredient provide longer protection.
In 2015, Researchers at New Mexico State University tested 10 commercially available products for their effectiveness at repelling mosquitoes. On the mosquito Aedes aegypti, the vector of Zika virus, only one repellent that did not contain DEET had a strong effect for the duration of the 240 minutes test: a lemon eucalyptus oil repellent. All DEET-containing mosquito repellents were active.
In one comparative study from 2004, IR3535 was as effective or better than DEET in protection against Aedes aegypti and Culex quinquefasciatus mosquitoes. Other sources (official publications of the associations of German physicians as well as of German druggists) suggest the contrary and state DEET is still the most efficient substance available and the substance of choice for stays in malaria regions, while IR3535 has little effect. However, some plant-based repellents may provide effective relief as well. Essential oil repellents can be short-lived in their effectiveness.
A test of various insect repellents by an independent consumer organization found that repellents containing DEET or icaridin are more effective than repellents with "natural" active ingredients. All the synthetics gave almost 100% repellency for the first 2 hours, where the natural repellent products were most effective for the first 30 to 60 minutes, and required reapplication to be effective over several hours.
Although highly toxic to cats, permethrin is recommended as protection against mosquitoes for clothing, gear, or bed nets. In an earlier report, the CDC found oil of lemon eucalyptus to be more effective than other plant-based treatments, with a similar effectiveness to low concentrations of DEET. However, a 2006 published study found in both cage and field studies that a product containing 40% oil of lemon eucalyptus was just as effective as products containing high concentrations of DEET. Research has also found that neem oil is mosquito repellent for up to 12 hours. Citronella oils mosquito repellency has also been verified by research, including effectiveness in repelling Aedes aegypti', but requires reapplication after 30 to 60 minutes.
There are also products available based on sound production, particularly ultrasound (inaudibly high-frequency sounds) which purport to be insect repellents. However, these electronic devices have been shown to be ineffective based on studies done by the United States Environmental Protection Agency and many universities. | 1 | Biochemistry |
The MP-SPR optical setup measures at multiple wavelengths simultaneously (similarly to spectroscopic SPR), but instead of measuring at a fixed angle, it rather scans across a wide range of θ angles (for instance 40 degrees). This results in measurements of full SPR curves at multiple wavelengths providing additional information about structure and dynamic conformation of the film. | 7 | Physical Chemistry |
Mixed alkyl/aryl-halide compounds, which contain a single C-M bond and a C-X bond, are typically prepared by oxidative addition. Magnesium-containing compounds of this configuration are known as the Grignard reagents, though some calcium Grignards are known and more reactive and sensitive to decomposition. Calcium grignards must be pre-activated prior to synthesis.
There are three key reaction pathways for dialkyl and diaryl group 2 metal compounds.
*metathesis:
:MX + R-Y → MR + Y-X'
*transmetallation:
:MR + M → MR + M
*via the Schlenk equilibrium:
:2 RMX → MR + MX | 0 | Organic Chemistry |
Carnobacterium pleistocenium is a recently discovered bacterium from the arctic part of Alaska. It was found in permafrost, seemingly frozen there for 32,000 years. Melting the ice, however, brought these extremophiles back to life. This is the first case of an organism "coming back to life" from ancient ice. These bacterial cells were discovered in a tunnel dug by the Army Corps of Engineers in the 1960s to allow scientists to study the permafrost in preparation for the construction of the Trans-Alaska pipeline system.
The discovery of this bacterium is of particular interest for NASA, for it may be possible for such life to exist in the permafrost of Mars or on the surface of Europa. It is also of interest for scientists investigating the potential for cryogenically freezing life forms to reduce the transportation costs (in terms of life support systems) that would be associated with long-duration space travel. | 1 | Biochemistry |
Glide planes are noted in the Hermann–Mauguin notation by a, b or c, depending on which axis the glide is along. (The orientation of the plane is determined by the position of the symbol in the Hermann–Mauguin designation.) If the axis is not defined, then the glide plane may be noted by g. When the glide plane is parallel to the screen, these planes may be indicated by a bent arrow in which the arrowhead indicates the direction of the glide. When the glide plane is perpendicular to the screen, these planes can be represented either by dashed lines when the glide is parallel to the plane of the screen or dotted lines when the glide is perpendicular to the plane of the screen. Additionally, a centered lattice can cause a glide plane to exist in two directions at the same time. This type of glide plane may be indicated by a bent arrow with an arrowhead on both sides when the glide plan is parallel to the plane of the screen or a dashed and double-dotted line when the glide plane is perpendicular to the plane of the screen. There is also the n glide, which is a glide along the half of a diagonal of a face, and the d glide, which is along a fourth of either a face or space diagonal of the unit cell . The latter is often called the diamond glide plane as it features in the diamond structure. The n glide plane may be indicated by diagonal arrow when it is parallel to the plane of the screen or a dashed-dotted line when the glide plane is perpendicular to the plane of the screen. A d glide plane may be indicated by a diagonal half-arrow if the glide plane is parallel to the plane of the screen or a dashed-dotted line with arrows if the glide plane is perpendicular to the plane of the screen. If a d glide plane is present in a crystal system, then that crystal must have a centered lattice.
In todays version of Hermann–Mauguin notation, the symbol e is used in cases where there are two possible ways of designating the glide direction because both are true. For example if a crystal has a base-centered Bravais lattice centered on the C face, then a glide of half a cell unit in the a direction gives the same result as a glide of half a cell unit in the b' direction.
The isometry group generated by just a glide reflection is an infinite cyclic group. Combining two equal glide plane operations gives a pure translation with a translation vector that is twice that of the glide reflection, so the even powers of the glide reflection form a translation group.
In the case of glide-reflection symmetry, the symmetry group of an object contains a glide reflection and the group generated by it. For any symmetry group containing a glide reflection, the glide vector is one half of an element of the translation group. If the translation vector of a glide plane operation is itself an element of the translation group, then the corresponding glide plane symmetry reduces to a combination of reflection symmetry and translational symmetry. | 3 | Analytical Chemistry |
Computational methods have been increasing in popularity as a method to test possible root because they do not need to sacrifice a component to prove a root cause. Common cases where computational methods are used are for failures due to erosion, failures of components under complex stress states, and for predictive analyses. Computational fluid dynamics is used to determine the flow pattern and shear stresses on a component that had failed due to erosive wear. Finite element analysis is used to model components under complex stress states. Finite element analysis as well as phase field models can be used for predicting crack propagation and failure, which are then used to prevent failure by influencing component design. | 8 | Metallurgy |
The primary structure (amino acid sequence) is highly conserved among OCP sequences, and the full-length protein is usually co-located on the chromosome with a second open reading frame that was later characterized as the FRP. Often, biosynthetic genes for ketocarotenoid synthesis (e.g., CrtW) are nearby. These conserved functional linkages underscore the evolutionary importance of the OCP style of photoprotection for many cyanobacteria.
The first structure determination of the OCP coincided with the beginning of the genome sequencing era, and it was already apparent in 2003 that there is also a variety of evolutionarily related genes which encode proteins with only one of the two domains present in OCP. The N-terminal domain (NTD), "Carot_N", is found only in cyanobacteria, but exhibits a considerable amount of gene duplication. The C-terminal domain (CTD), however, is homologous with the widespread NTF2 superfamily, which shares a protein fold with its namesake, nuclear transport factor 2, as well as around 20 other subfamilies of proteins with functions as diverse as limonene-1,2-epoxide hydrolase, SnoaL polyketide cyclase, and delta-5-3-ketosteroid isomerase (KSI). Most, if not all, of the members of the NTF2 superfamily form oligomers, often using the surface of their beta sheet to interact with another monomer or other protein.
Bioinformatic analyses carried out over the past 15 years has resulted in the identification of new groups of carotenoid proteins: In addition to new families of the OCP, there are HCPs and CCPs that correspond to the NTD and CTD of the OCP, respectively. Based on the primary structure, the HCPs can be subdivided into at least nine evolutionarily distinct clades, each binds carotenoid. The CCPs resolve into 2 major groups, and these proteins also bind carotenoid. Given these data, and the ability to devolve OCP into its two component domains while retaining function has led to a reconstruction of the evolution of the OCP. | 5 | Photochemistry |
The specific study of the non-ferrous metals used in past. Gold, silver and copper were the first to be used by ancient humans. Gold and copper are both found in their native state in nature, and were thus the first to be exploited as they did not need to be smelted from their ores. They could be hammered into sheets or decorative shapes. The extraction of copper from its ores may have developed due to the attractive colouring and value of ores such as malachite. | 8 | Metallurgy |
In the aldol reaction, the diastereoselectivity of the product is often dictated by the geometry of the enolate. The Zimmerman–Traxler model predicts that the Z enolate will give syn products, and that E enolates will give anti products. Reactions catalyzed by tin-based CLAs allow products to deviate from this pattern.
The transition structures for reactions with both the R and S catalyst enantiomers are: | 4 | Stereochemistry |
Natural cloning is the production of clones without the involvement of genetic engineering techniques. It may occur accidentally in the case of identical twins, which are formed when a fertilized egg splits, creating two or more embryos that carry almost identical DNA. It may also be part of asexual reproduction, which is a process where a single parent organism produces genetically identical offspring by itself.
Cloning is a natural form of reproduction that has allowed life forms to spread for hundreds of millions of years. It is a reproduction method used by plants, fungi, and bacteria, and is also the way that clonal colonies reproduce themselves. Examples of these organisms include blueberry plants, Hazel trees, the Pando trees, the Kentucky coffeetree, Myrica, and the American sweetgum.
If artificial cloning and natural cloning both lead to the same result, which is the formation of a clone, that is, an organism with identical or nearly identical genes to another organism, then the plight of This creation is very different between the two creatures. The main difference between the two is that natural cloning does not involve any human intervention, whereas artificial cloning is a genetic engineering technique.
Natural cloning occurs through a variety of natural mechanisms, from single-celled organisms to complex multicellular organisms. Some of the mechanisms are explored and used into plants and animals as binary fission, Budding, Fragmentation, parthenogenesis. | 1 | Biochemistry |
Nutrient bioextraction is bioremediation involving cultured plants and animals. Nutrient bioextraction or bioharvesting is the practice of farming and harvesting shellfish and seaweed for the purpose of removing nitrogen and other nutrients from natural water bodies. | 2 | Environmental Chemistry |
At the appropriate Krafft temperature and critical micelle concentration these molecules will form individual tear-drop loops, where the hydrophobic ends are attracted to one another, to other molecules, and also to the similarly hydrophobic QDs. This forms a loaded micelle with a hydrophilic outer shell and a hydrophobic core.
When encapsulating hydrophobes in this way it is important to ensure the particle size is appropriate for the PEG backbone being utilized, as the number of PEG mer units (generally with a molecular weight of 6 kDa or 10 kDa) determines the maximum particle size that can be successfully contained at the core of the micelle.
To determine the average diameter, D, of the QDs, the following empirical equation is used:
Where
* is the diameter of the CdSe QD in nm
* is the wavelength of the first absorption peak in nm | 7 | Physical Chemistry |
In 1526 Kamiya Jutei, a wealthy merchant from Hakata, founded the Iwami Ginzan Silver Mine in Ōda. Seeking to increase silver production, In 1533 he introduced a Korean method of silver refining to the mine which became the Hai-Fuki-Ho method. The two technicians, Keiju (慶寿; Korean: 경수; Revised Romanization: Gyeongsu) and Sotan (宗丹; Korean: 종단; Revised Romanization: Jongdan), were invited to Japan to instruct their skills. Historians have compared the Hai-Fuki-Ho method to the Medieval European method of silver smelting.
Under the Hai-Fuki-Ho method, silver-containing copper ore would be cast-smelted with lead, then allowed to dry. The silver in the copper ore would bind to the lead, creating a single mixture. This mixture would then be heated so that the lead melted and separated out of the copper, taking the bonded silver with it. The silver-rich lead would then be treated with an oxidizing airflow to separate the silver. This was akin to a liquation method.
The high-purity silver produced by the Hai-Fuki-Ho method was highly desired by foreign merchants. In addition, the process allowed for greater amounts of the silver to be produced by Japanese mines, which had more efficient refining processes than their competitors. By the 16th century, Japanese mines were producing up to one third of the world's silver.
The Hai-Fuki-Ho method was eventually replaced by more modern methods of silver mining. | 8 | Metallurgy |
Inflammation is the bodys response to foreign objects, irritants, germs, and even pathogens. Although such a response is standard in some cases, if left untreated, chronic inflammation can lead to muscle degeneration, gastrointestinal disorders, and some types of cancers. While most treatments, such as anti-inflammatory drugs and steroid injections, can help relieve symptoms, they often fail to address the conditions underlying cause. Therefore, researchers have sought to explore new and innovative ways of inflammation treatment, such as chemotactic drug delivery.
One promising drug delivery system was based on engineered neutrophils that targeted inflammation sites through chemotaxis's unique properties. This approach took advantage of the concentration difference between iNOS and ROS for inflammatory disease sites and normal tissues. By doing so, this drug delivery system provides the possibility to target areas of inflammation, increase drug efficacy, and minimize damage to the surrounding tissue. Moreover, because this concentration gradient is ubiquitous in the microenvironment of inflammatory diseases, common drug-targeting limitations such as individual differences can be avoided. Another example of an innovative drug delivery system that uses the property of chemotaxis is leukocytes. Indeed, during inflammation, the molecules on a cell that allows for adhesion are overly produced. With this unique condition, researchers can modify leukocytes to quickly detect the cell, attach itself to the surface, and deliver a therapeutic payload. Overall, many promising therapies and drug delivery systems are being developed to target inflammation more effectively. Chemotactic drug delivery systems are just one of many promising avenues that seek to increase target sites specifically, decreasing the needed drug dosage, reducing toxicity, and increasing drug efficacy. | 1 | Biochemistry |
Glycomimetic is a term used to refer to molecules that have structures similar to carbohydrates, but with some variation. This will normally result in modified biological properties. | 1 | Biochemistry |
Including the original Keggin structure there are 5 isomers, designated by the prefixes α-, β-, γ-, δ- and ε-. The original Keggin structure is designated α. These isomers are sometimes termed Baker, Baker–Figgis or rotational isomers, These involve different rotational orientations of the units, which lowers the symmetry of the overall structure. | 7 | Physical Chemistry |
Alternative polyadenylation (APA) is a regulatory mechanism that forms multiple 3' end on mRNA.
APA isoforms from the same gene can encode different proteins and/or contain different 3' untranslated regions (UTRs). Deregulation of APA has been associated with a number of human diseases. Since longer UTRs have more binding sites for microRNAs and/or RNA-binding proteins in comparison to shorter UTRs, APA require different stability, translation efficiency, and/or intracellular localization.
Mammalian PASs have a number of key cis elements.
* A(A/U)AAA hexamer
* U/GU-rich downstream element (DSE)
* U-rich upstream auxiliary elements (USEs)
* Upstream sequences conforming to the consensus UGUA
PAS sequences are variable, and many PASs lack one or more cis elements. PAS recognition is accomplished by protein-RNA interactions.
CPSF synergistically binds to the AAUAAA hexamer and CstF synergistically binds to the downstream element (DSE). The CFI complex binds to the UGUA motifs. CPSF, CstF, and CFI bind directly to RNA. They also recruit other proteins such as CFII, symplekin, and the poly(A) polymerase (PAP) to assemble the mRNA 3' processing complex, also known as the cleavage and polyadenylation complex. The assembly of these factors are facilitated by the C-terminal domain (CTD) of the RNA polymerase II (RNAP II) large subunit. The CTD provides a landing pad for mRNA processing factors. | 1 | Biochemistry |
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Cleavage factors are two closely associated protein complexes involved in the cleavage of the 3' untranslated region of a newly synthesized pre-messenger RNA (mRNA) molecule in the process of gene transcription. The cleavage is the first step in adding a polyadenine tail to the pre-mRNA, which is one of the necessary post-transcriptional modifications necessary for producing a mature mRNA molecule.
In mammals, the two cleavage factors are known as CFIm and CFIIm. The proteins that constitute these complexes are recruited to the cleavage site by cleavage and polyadenylation specificity factor and cleavage stimulatory factor, and form a larger complex that also includes polyadenine polymerase, which performs the polyadenylation reaction. | 1 | Biochemistry |
After earning his doctoral degree, Kanu started a postdoctoral fellowship at Washington State University. He worked alongside Herbert H. Hill, Jr. on the development of ion mobility mass spectrometry. He proposed that this work could be used to reduce false positives in airport screening for explosives and drugs, and also showed that it was possible to separate drugs using the drift gas selectivity of ion-mobility spectrometry–mass spectrometry, and this work has since been cited over 1000 times. He has applied ion-mobility spectrometry–mass spectrometry to identify environmental pollutants in both indoor air and contaminated water. He has created a novel sampling system that incorporates a polydimethylsiloxane (PDMS) membrane and nanoparticles for one-step sampling, isolation, separation and desorption of environmental pollutants.
Alongside his academic research, Kanu works to improve the representation of minority students in science. He leads undergraduate research programmes and supports student chapters of the American Chemical Society and National Organization for the Professional Advancement of Black Chemists and Chemical Engineers. Kanu leads the annual Extreme Forensic Instrumentation Experience Lab at Winston-Salem State University, which sees high school seniors take part in a research project themed around a crime drama. He works with Chemists Without Borders to introduce young people in Sierra Leone to practical chemistry skills and help to rebuild the education system after the Civil War. As part of this work, Kanu created affordable green chemistry lab kits, which included materials and manuals. | 3 | Analytical Chemistry |
In any form of chromatography, the rate at which the solute moves down the column is a direct reflection of the percentage of time the solute spends in the mobile phase. To achieve separation in either elution or displacement chromatography, there must be appreciable differences in the affinity of the respective solutes for the stationary phase. Both methods rely on movement down the column to amplify the effect of small differences in distribution between the two phases. Distribution between the mobile and stationary phases is described by the binding isotherm, a plot of solute bound to (or partitioned into) the stationary phase as a function of concentration in the mobile phase. The isotherm is often linear, or approximately so, at low concentrations, but commonly curves (concave-downward) at higher concentrations as the stationary phase becomes saturated. | 3 | Analytical Chemistry |
Toshiko Mayeda was born in Tacoma, Washington. She grew up in Yokkaichi, Mie, and Osaka. When the United States entered World War II after the Japanese attack on Pearl Harbor, she and her father Matsusaburo Kuki were sent to the Tule Lake War Relocation Center. Whilst there she met her future husband, Harry Mayeda. After the war, she graduated with a bachelor's degree in chemistry from the University of Chicago in 1949. | 9 | Geochemistry |
NBQX (2,3-dioxo-6-nitro-7-sulfamoyl-benzo[f]quinoxaline) is an antagonist of the AMPA receptor.
NBQX blocks AMPA receptors in micromolar concentrations (~10–20 μM) and also blocks kainate receptors. In experiments, it is used to counter glutamate excitotoxicity. NBQX was found to have anticonvulsant activity in rodent seizure models.
As the disodium salt, NBQX is soluble in water at high concentrations (at least up to 100 mM). | 1 | Biochemistry |
After the DNA-gelatin mixture preparation, the mixture is pipetted onto a slide surface and the slide is placed in a covered petri dish. A desiccant is added to the dish to dry up the solution. Finally, cultured cells are poured into the dish for plasmid uptake. However, with the invention of different types of microarray printing systems, hundreds of transfection mixes (containing different DNA of interest) may be printed on the same slide for cell uptake of plasmids. There are two major types of microarray printing systems manufactured by different companies: contact and non-contact printing systems.
An example of a non-contact printing system is the Piezorray Flexible Non-contact Microarraying System. It uses pressure control and a piezoelectric collar to squeeze out consistent drops of approximately 333 pL in volume. The PiezoTip dispensers do not contact the surface to which the sample is dispensed; thus, contamination potential is reduced and the risk of disrupting the target surface is eliminated. An example of a contact printing system is the SpotArray 72 (Perkin Elmer Life Sciences) contact-spotting system. Its printhead can accommodate up to 48 pins, and creates compact arrays by selectively raising and lowering subsets of pins during printing. After printing, the pins are washed with a powerful pressure-jet pin washer and vacuum-dried, eliminating carryover. Another example of a contact printing system is the Qarray system (Genetix). It has three types of printing systems: QArray Mini, QArray 2 and QArray Max. After printing, the solution is allowed to dry up and the DNA-gelatin is stuck tightly in position on the array. | 1 | Biochemistry |
According to Planck, one may think of three main classes of thermodynamic process: natural, fictively reversible, and impossible or unnatural. | 7 | Physical Chemistry |
Cellular respiration is the process of which biological fuels are oxidised in the presence of an inorganic electron acceptor such as oxygen to produce large amounts of energy, to drive the bulk production of ATP.
Anaerobic respiration is used by microorganisms either bacteria or archaea in which neither oxygen (aerobic respiration) nor pyruvate derivatives (fermentation) is the final electron acceptor. Rather, an inorganic acceptor such as sulfate (SO), nitrate (NO), or sulfur (S) is used. Such organisms could be found in unusual places such as underwater caves or near hydrothermal vents at the bottom of the ocean., as well as in anoxic soils or sediment in wetland ecosystems.
In July 2019, a scientific study of Kidd Mine in Canada discovered sulfur-breathing organisms which live below the surface, and which breathe sulfur in order to survive. These organisms are also remarkable due to consuming minerals such as pyrite as their food source. | 1 | Biochemistry |
Surface energy comes into play in wetting phenomena. To examine this, consider a drop of liquid on a solid substrate. If the surface energy of the substrate changes upon the addition of the drop, the substrate is said to be wetting. The spreading parameter can be used to mathematically determine this:
where is the spreading parameter, the surface energy of the substrate, the surface energy of the liquid, and the interfacial energy between the substrate and the liquid.
If , the liquid partially wets the substrate. If , the liquid completely wets the substrate. | 7 | Physical Chemistry |
There are many other important measures of probability distance. Some of these are particularly connected with relative entropy. For example:
* The total-variation distance, . This is connected to the divergence through Pinskers inequality: Pinskers inequality is vacuous for any distributions where , since the total variation distance is at most . For such distributions, an alternative bound can be used, due to Bretagnolle and Huber (see, also, Tsybakov):
* The family of Rényi divergences generalize relative entropy. Depending on the value of a certain parameter, , various inequalities may be deduced.
Other notable measures of distance include the Hellinger distance, histogram intersection, Chi-squared statistic, quadratic form distance, match distance, Kolmogorov–Smirnov distance, and earth movers distance'. | 7 | Physical Chemistry |
Polyamorphism has also been observed in organic compounds, such as liquid triphenyl phosphite at temperatures between 210 K and 226 K and n-butanol at temperatures between 120 K and 140 K.
Polyamorphism is also an important area in pharmaceutical science. The amorphous form of a drug typically has much better aqueous solubility (compared to the analogous crystalline form) but the actual local structure in an amorphous pharmaceutical can be different, depending on the method used to form the amorphous phase.
Mannitol is the first pharmaceutical substance featuring polyamorphism. In addition to the regular amorphous phase, a second amorphous phase can be prepared at room temperature and pressure. This new phase has substantially lower energy, lower density and higher glass transition temperature. Since mannitol is widely used in pharmaceutical tablet formulations, mannitol polyamorphism offers a powerful tool to engineer the property and behavior of tablets. | 7 | Physical Chemistry |
The unicellular cyanobacterium Synechocystis sp. PCC6803 was the third prokaryote and first photosynthetic organism whose genome was completely sequenced. It continues to be an important model organism. Cyanothece ATCC 51142 is an important diazotrophic model organism. The smallest genomes have been found in Prochlorococcus spp. (1.7 Mb) and the largest in Nostoc punctiforme (9 Mb). Those of Calothrix spp. are estimated at 12–15 Mb, as large as yeast.
Recent research has suggested the potential application of cyanobacteria to the generation of renewable energy by directly converting sunlight into electricity. Internal photosynthetic pathways can be coupled to chemical mediators that transfer electrons to external electrodes. In the shorter term, efforts are underway to commercialize algae-based fuels such as diesel, gasoline, and jet fuel. Cyanobacteria have been also engineered to produce ethanol and experiments have shown that when one or two CBB genes are being over expressed, the yield can be even higher.
Cyanobacteria may possess the ability to produce substances that could one day serve as anti-inflammatory agents and combat bacterial infections in humans. Cyanobacteria's photosynthetic output of sugar and oxygen has been demonstrated to have therapeutic value in rats with heart attacks. While cyanobacteria can naturally produce various secondary metabolites, they can serve as advantageous hosts for plant-derived metabolites production owing to biotechnological advances in systems biology and synthetic biology.
Spirulina's extracted blue color is used as a natural food coloring.
Researchers from several space agencies argue that cyanobacteria could be used for producing goods for human consumption in future crewed outposts on Mars, by transforming materials available on this planet. | 5 | Photochemistry |
Other modifications have also been used, such as the one described in Bagriantsev et al., using traditional wet transfer and a TGB buffering system, and others using semi-dry transfer or capillary transfer.
DD-AGE, a further variation of the method that uses fully denaturing conditions - including reducing agents such as dithiothreitol (DTT) and heat denaturation at 95°C - is suitable for the analysis of heat-stable inclusion bodies of polyglutamine proteins. | 1 | Biochemistry |
After a 1996 PhD titled High-precision U-series dating of corals from Western Australia : implication for last interglacial sea-levels at the Australian National University, Stirling worked at University of Michigan and ETH Zürich before moving to the University of Otago in 2006, rising to full professor in 2018. [https://www.otago.ac.nz/geology/staff/academic/claudine-stirling.html Prof Stirling] is a member of the [https://www.otago.ac.nz/geology/index.html Department of Geology] with current research interests including: isotope geochemistry, biogeochemical cycles of trace metals, paleoceanography & paleoclimatology, and environmental geochemistry.
In 2024 Stirling was elected as a Fellow of the Royal Society Te Apārangi. | 9 | Geochemistry |
Phosphite esters are Lewis bases and hence can form coordination complexes with various metal ions. Representative phosphite ligands include trimethylphosphite ((MeO)P), triethylphosphite ((EtO)P), trimethylolpropane phosphite, and triphenylphosphite ((PhO)P). Phosphites exhibit a smaller ligand cone angles than the structurally related phosphine ligand family. Phosphite ligands are components of industrial catalysts for hydroformylation and hydrocyanation. | 0 | Organic Chemistry |
Radial spokes are T-shaped structures present inside the axoneme. Each spoke consists of a "head" and a "stalk," while each of these sub-structures is itself made up of many protein subunits. In all, the radial spoke is known to contain at least seventeen proteins, five in the head and twelve in the stalk. The spoke stalk binds to the A-tubule of each microtubule outer doublet, and the spoke head faces in towards the center of the axoneme (see illustration at right). | 1 | Biochemistry |
The European Molecular Spectroscopy Group, which was constituted informally after the Second World War to bring together spectroscopists from across Europe, met for the first time in Konstanz in 1947. Reinhard Mecke was at the time working in temporary accommodation at Wallhausen, a small village on the shores of Lake Constance, and the meeting (initiated by invitation of Professors Jean Lecomte and Alfred Kastler from Paris) was attended by French, German and Austrian spectroscopists.
However, the meeting which has since become regarded as the first of the EUCMOS series was organised under the auspices of Ernst Miescher in Basel in 1951, followed every two years by conferences in Paris (1953), Oxford (1955), Freiburg (1957), Bologna (1959), Amsterdam (1961), Budapest (1963), Copenhagen (1965), Madrid (1967) and Liége (1969). The next meeting was not held until 1973 when it was organized in Tallinn. The 1975 meeting in Strasbourg was devoted to the molecular spectroscopy of dense phases. The biennial meetings were perturbed for the second time in 1991 when EUCMOS XX, which was due to be held in Zagreb, had to be cancelled because of the Civil war in Yugoslavia. The following meeting, in Vienna, was brought forward by a year and the meetings have since been held in the even years. At EUCMOS XXII held in Essen (1994), William James Orville-Thomas retired as President of the International Committee and Austin Barnes was elected to this post. During his mandate, 11 conferences of the series were held, included the one organized in Coimbra in the Year 2000 (EUCMOS XXV). In EUCMOS XXXIII (2016, Szeged) Barnes retired as President of the International Committee and Rui Fausto (vice-President since EUCMOS XXVII, in Cracow, together with Henryk Ratajczak) was elected to this position. The new President had already been chosen as the organizer of the following EUCMOS meeting in Coimbra, 2018 (EUCMOS XXXIV). Sylvia Turrel and Michael Schmitt are the current vice-Presidents of the International Committee.
EUCMOS gathered over the years (present and future) Nobel prize winners from all areas of molecular physics as plenary speakers. This starts in 1953 with Alfred Kastler in Paris (Nobel prize 1966) followed by Gerhard Herzberg 1989 in Leipzig (Nobel prize 1971), Harold Kroto 2000 in Coimbra (Nobel prize 1996) and Theodor W. Hänsch 2010 in Florence (Nobel prize 2005). | 7 | Physical Chemistry |
The term magnetofection, currently trademarked by the company OZ Biosciences, combines the words magnetic and transfection. Magnetofection uses nucleic acids associated with magnetic nanoparticles. These molecular complexes are then concentrated and transported into cells using an applied magnetic field. | 1 | Biochemistry |
Like any other linear free-energy relationship established, the Swain–Lupton equation will too fail when special circumstances arise, i.e. change in the rate determining step of a mechanism or solvation structure. | 7 | Physical Chemistry |
is a potent greenhouse gas. A ton of HFC-23 in the atmosphere has the same effect as 11,700 tons of carbon dioxide. This equivalency, also called a 100-yr global warming potential, is slightly larger at 14,800 for HFC-23.
The atmospheric lifetime is 270 years.
HFC-23 was the most abundant HFC in the global atmosphere until around 2001, when the global mean concentration of HFC-134a (1,1,1,2-tetrafluoroethane), the chemical now used extensively in automobile air conditioners, surpassed those of HFC-23. Global emissions of HFC-23 have in the past been dominated by the inadvertent production and release during the manufacture of the refrigerant HCFC-22 (chlorodifluoromethane).
Substantial decreases in HFC-23 emissions by developed countries were reported from the 1990s to the 2000s: from 6-8 Gg/yr in the 1990s to 2.8 Gg/yr in 2007.
The UNFCCC Clean Development Mechanism provided funding and facilitated the destruction of HFC-23.
Developing countries have become the largest producers of HCFC-23 in recent years according to data compiled by the Ozone Secretariat of the World Meteorological Organization. Emissions of all HFCs are included in the UNFCCCs Kyoto Protocol. To mitigate its impact, can be destroyed with electric plasma arc technologies or by high temperature incineration. | 2 | Environmental Chemistry |
When a cell enters G1, Cyclin D- Cdk4/6 phosphorylates pRb at a single phosphorylation site. No progressive phosphorylation occurs because when HFF cells were exposed to sustained cyclin D- Cdk4/6 activity (and even deregulated activity) in early G1, only mono-phosphorylated pRb was detected. Furthermore, triple knockout, p16 addition, and Cdk 4/6 inhibitor addition experiments confirmed that Cyclin D- Cdk 4/6 is the sole phosphorylator of pRb.
Throughout early G1, mono-phosphorylated pRb exists as 14 different isoforms (the 15th phosphorylation site is not conserved in primates in which the experiments were performed). Together, these isoforms represent the “hypo-phosphorylated” active pRb state that was thought to exist. Each isoform has distinct preferences to associate with different exogenous expressed E2Fs.
A recent report showed that mono-phosphorylation controls pRb's association with other proteins and generates functional distinct forms of pRb. All different mono-phosphorylated pRb isoforms inhibit E2F transcriptional program and are able to arrest cells in G1-phase. Importantly, different mono-phosphorylated forms of pRb have distinct transcriptional outputs that are extended beyond E2F regulation. | 1 | Biochemistry |
Amines reacts with nitrous acid to give diazonium salts. The alkyl diazonium salts are of little importance because they are too unstable. The most important members are derivatives of aromatic amines such as aniline ("phenylamine") (A = aryl or naphthyl):
Anilines and naphthylamines form more stable diazonium salts, which can be isolated in the crystalline form. Diazonium salts undergo a variety of useful transformations involving replacement of the group with anions. For example, cuprous cyanide gives the corresponding nitriles:
Aryldiazoniums couple with electron-rich aromatic compounds such as a phenol to form azo compounds. Such reactions are widely applied to the production of dyes. | 0 | Organic Chemistry |
SOFIA is an apparatus and method for improved optical geometry for enhancement of spectroscopic detection of analytes in a sample. The invention has already demonstrated its proof-of-concept functionality as an apparatus and method for ultrasensitive detection of prions and other low-level analytes.
SOFIA combines the specificity inherent in monoclonal antibodies for antigen capture with the sensitivity of surround optical detection technology. To detect extremely low signal levels, a low-noise, photovoltaic diode is used as the detector for the system. SOFIA uses a laser to illuminate a microcapillary tube holding the sample. Then, the light collected from the sample is directed to transfer optics from optical fibers. Next, the light is optically filtered for detection, which is performed as a current measurement amplified against noise by a digital signal processing lock-in amplified. The results are displayed on a computer and software designed for data acquisition.
The advantages of such a detection array are numerous. Primarily, it permits the use of very small samples at low concentration to be optimally interrogated using the laser-induced fluorescence technique. This fiber-based detection system is adaptable to existing short-pulsed detection hardware that was originally developed for sequencing single DNA molecules. The geometry is also amenable to deployment for short-pulse laser, single-molecule detection schemes. The multiport geometry of the system allows efficient electronic processing of the signals from each arm of the device. Finally, and perhaps most importantly, fiberoptic cables are essentially 100% efficient in optical transmission, having an attenuation less than 10 dB/km. Thus, once deployed for use in a facility, the fluorescence information can be fiberoptically transmitted to a remote location, where data processing and analysis can be performed. | 1 | Biochemistry |
In the long term, sustainable use of the soil must be guaranteed in order to meet the needs of the world's population. The project brings together numerous universities, research institutions, companies and stakeholders with the aim of creating a web-based, free system to support practical agriculture and land users in making decisions about sustainable land use, environmental protection and agricultural use.
With the active participation of various and numerous stakeholders in and outside Europe, the consortium also aims at legislation at European level, based on scientific data that is processed and modeled in the system.
In the research framework program Horizon 2020, the project is organized under the direction of Fabio Terribile at the University of Naples Federico II. | 1 | Biochemistry |
Lichens have been shown to degrade polyester resins, as can be seen in archaeological sites in the Roman city of Baelo Claudia in Spain. Lichens can accumulate several environmental pollutants such as lead, copper, and radionuclides. Some species of lichen, such as Parmelia sulcata (called a hammered shield lichen, among other names) and Lobaria pulmonaria (lung lichen), and many in the Cladonia genus, have been shown to produce serine proteases capable of the degradation of pathogenic forms of prion protein (PrP), which may be useful in treating contaminated environmental reservoirs. | 2 | Environmental Chemistry |
*4.C.1 The Proposed Fatty Acid Transporter (FAT) Family
*4.C.2 The Carnitine O-Acyl Transferase (CrAT) Family
*4.C.3 The Acyl-CoA Thioesterase (AcoT) Family | 1 | Biochemistry |
Experiments in atomic physics are often done with a laser of a specific frequency (meaning the photons have a specific energy), so they only couple one set of states with a particular energy to another set of states with an energy . However, the atom can still decay spontaneously into a third state by emitting a photon of a different frequency. The new state with energy of the atom no longer interacts with the laser simply because no photons of the right frequency are present to induce a transition to a different level. In practice, the term dark state is often used for a state that is not accessible by the specific laser in use even though transitions from this state are in principle allowed. | 7 | Physical Chemistry |
Because of the double-stranded nature of DNA, essentially all of the nucleotides take the form of Watson–Crick base pairs between nucleotides on the two complementary strands of the double helix.
In contrast, both RNA and proteins are normally single-stranded. Therefore, they are not constrained by the regular geometry of the DNA double helix, and so fold into complex three-dimensional shapes dependent on their sequence. These different shapes are responsible for many of the common properties of RNA and proteins, including the formation of specific binding pockets, and the ability to catalyse biochemical reactions. | 7 | Physical Chemistry |
Advocates of the non-classical nature of the stable 2-norbornyl cation typically depict the species using either resonance structures or a single structure with partial bonds (see Figure 2). This hypovalent interaction can be imagined as the net effect of i) a partial sigma bond between carbons 1 and 6, ii) a partial sigma bond between carbons 2 and 6, and iii) a partial pi bond between carbons 1 and 2. Each partial bond is represented as a full bond in one of the three resonance structures or as a dashed partial bond if the cation is depicted through a single structure.
There has been some debate over how much the pi-bonded resonance structure actually contributes to the delocalized electronic structure. Through H and C NMR spectroscopy, it has been confirmed that significant positive charge lies on methylene carbon 6. This is surprising as primary carbocations are much less stable than secondary carbocations. However, the 2-norbornyl cation can be formed from derivatives of β-(Δ-cyclopentenyl)-ethane, indicating that the pi-bonded resonance structure is significant.
The 2-norbornyl cation was one of the first examples of a non-classical ion. Non-classical ions can be defined as organic cations in which electron density of a filled bonding orbital is shared over three or more centers and contains some sigma-bond character. The 2-norbornyl cation is seen as the prototype for non-classical ions. Other simple cations such as protonated acetylene (ethynium, ), protonated ethylene (ethenium, ), and protonated ethane (ethanium, ) have been shown to be best described as non-classical through infrared spectroscopy.
The most frequently proposed molecular orbital depiction of the 2-norbornyl cation is shown in Figure 3. Two p-type orbitals, one on each of carbons 1 and 2, interact with a sp-hybridized orbital on carbon 6 to form the hypovalent bond. Extended Hückel Theory calculations for the 2-norbornyl cation suggest that the orbital on carbon 6 could instead be sp-hybridized, though this only affects the geometry of the geminal hydrogens. | 7 | Physical Chemistry |
The hydroxyl radical, HO, is the neutral form of the hydroxide ion (HO). Hydroxyl radicals are highly reactive and consequently short-lived; however, they form an important part of radical chemistry. Most notably hydroxyl radicals are produced from the decomposition of hydroperoxides (ROOH) or, in atmospheric chemistry, by the reaction of excited atomic oxygen with water. It is also an important radical formed in radiation chemistry, since it leads to the formation of hydrogen peroxide and oxygen, which can enhance corrosion and SCC in coolant systems subjected to radioactive environments. Hydroxyl radicals are also produced during UV-light dissociation of HO (suggested in 1879) and likely in Fenton chemistry, where trace amounts of reduced transition metals catalyze peroxide-mediated oxidations of organic compounds.
In organic synthesis hydroxyl radicals are most commonly generated by photolysis of 1-Hydroxy-2(1H)-pyridinethione.
The hydroxyl radical is often referred to as the "detergent" of the troposphere because it reacts with many pollutants, often acting as the first step to their removal. It also has an important role in eliminating some greenhouse gases like methane and ozone. The rate of reaction with the hydroxyl radical often determines how long many pollutants last in the atmosphere, if they do not undergo photolysis or are rained out. For instance, methane, which reacts relatively slowly with hydroxyl radical, has an average lifetime of >5 years and many CFCs have lifetimes of 50+ years. Pollutants, such as larger hydrocarbons, can have very short average lifetimes of less than a few hours.
The first reaction with many volatile organic compounds (VOCs) is the removal of a hydrogen atom, forming water and an alkyl radical (R).
:HO + RH → HO + R
The alkyl radical will typically react rapidly with oxygen forming a peroxy radical.
:R + O → RO
The fate of this radical in the troposphere is dependent on factors such as the amount of sunlight, pollution in the atmosphere and the nature of the alkyl radical that formed it (See chapters 12 & 13 in External Links "University Lecture notes on Atmospheric chemistry) | 2 | Environmental Chemistry |
In surface vibrational spectroscopy, the surface selection rule is applied to identify the peaks observed in vibrational spectra. When a molecule is adsorbed on a substrate, the molecule induces opposite image charges in the substrate. The dipole moment of the molecule and the image charges perpendicular to the surface reinforce each other. In contrast, the dipole moments of the molecule and the image charges parallel to the surface cancel out. Therefore, only molecular vibrational peaks giving rise to a dynamic dipole moment perpendicular to the surface will be observed in the vibrational spectrum. | 7 | Physical Chemistry |
In bioinformatics, a sequence entropy, also known as sequence complexity or information profile, is a numerical sequence providing a quantitative measure of the local complexity of a DNA sequence, independently of the direction of processing. The manipulations of the information profiles enable the analysis of the sequences using alignment-free techniques, such as for example in motif and rearrangements detection. | 1 | Biochemistry |
The most common adverse effects of tramadol include nausea, dizziness, dry mouth, indigestion, abdominal pain, vertigo, vomiting, constipation, drowsiness, and headache. Other side effects may result from interactions with other medications. Tramadol has the same dose-dependent adverse effects as morphine including respiratory depression. | 4 | Stereochemistry |
* Award of the Ministry of Science and Higher Education (1985)
* Award of the Scientific Secretariat of the Polish Academy of Sciences (1980, 1989)
* Member of the Polish Chemical Society (1985) | 7 | Physical Chemistry |
In elementary arithmetic geometry, stereographic projection from the unit circle provides a means to describe all primitive Pythagorean triples. Specifically, stereographic projection from the north pole (0,1) onto the -axis gives a one-to-one correspondence between the rational number points on the unit circle (with ) and the rational points of the -axis. If is a rational point on the -axis, then its inverse stereographic projection is the point
which gives Euclid's formula for a Pythagorean triple. | 3 | Analytical Chemistry |
* [http://www.science.uottawa.ca/~eih/ch1/ch1.htm Environmental Isotopes] (University of Ottawa)
* [http://wwwrcamnl.wr.usgs.gov/isoig/isopubs/itchch2.html Fundamentals of Isotope Geochemistry] (C. Kendall & E.A. Caldwell, chap.2 in Isotope Tracers in Catchment Hydrology [edited by C. Kendall & J.J. McDonnell], 1998)
* [http://pubs.usgs.gov/info/seal2/ Stable Isotopes and Mineral Resource Investigations in the United States] (USGS) | 9 | Geochemistry |
The spatial resolution achievable in topographic images can be limited by one or several of three factors:
the resolution (grain or pixel size) of the detector, the experimental geometry, and intrinsic diffraction effects.
First, the spatial resolution of an image can obviously not be better than the grain size (in the case of film) or the pixel size (in the case of digital detectors) with which it was recorded. This is the reason why topography requires high-resolution X-ray films or CCD cameras with the smallest pixel sizes available today. Secondly, resolution can be additionally blurred by a geometric projection effect. If one point of the sample is a "hole" in an otherwise opaque mask, then the X-ray source, of finite lateral size S, is imaged through the hole onto a finite image domain given by the formula
where I is the spread of the image of one sample point in the image plane, D is the source-to-sample distance, and d is the sample-to-image distance. The ratio S/D corresponds to the angle (in radians) under which the source appears from the position of the sample (the angular source size, equivalent to the incident divergence at one sample point). The achievable resolution is thus best for small sources, large sample distances, and small detector distances. This is why the detector (film) needed to be placed very close to the sample in the early days of topography; only at synchrotrons, with their small S and (very) large D, could larger values of d finally be afforded, introducing much more flexibility into topography experiments.
Thirdly, even with perfect detectors and ideal geometric conditions, the visibility of special contrast features, such as the images of single dislocations, can be additionally limited by diffraction effects.
A dislocation in a perfect crystal matrix gives rise to contrast only in those regions where the local orientation of the crystal lattice differs from average orientation by more than about the Darwin width of the Bragg reflection used. A quantitative description is provided by the dynamical theory of X-ray diffraction. As a result, and somehow counter-intuitively, the widths of dislocation images become narrower when the associated rocking curves are large. Thus, strong reflections of low diffraction order are particularly appropriate for topographic imaging. They permit topographists to obtain narrow, well-resolved images of dislocations, and to separate single dislocations even when the dislocation density in a material is rather high. In more unfavourable cases (weak, high-order reflections, higher photon energies), dislocation images become broad, diffuse, and overlap for high and medium dislocation densities. Highly ordered, strongly diffracting materials – like minerals or semiconductors – are generally unproblematic, whereas e.g. protein crystals are particularly challenging for topographic imaging.
Apart from the Darwin width of the reflection, the width of single dislocation images may additionally depend on the Burgers vector of the dislocation, i.e. both its length and its orientation (relative to the scattering vector), and, in plane wave topography, on the angular departure from the exact Bragg angle. The latter dependence follows a reciprocity law, meaning that dislocations images become narrower inversely as the angular distance grows. So-called weak beam conditions are thus favourable in order to obtain narrow dislocation images. | 3 | Analytical Chemistry |
Lanthanide probes are a non-invasive analytical tool commonly used for biological and chemical applications. Lanthanides are metal ions which have their 4f energy level filled and generally refer to elements cerium to lutetium in the periodic table. The fluorescence of lanthanide salts is weak because the energy absorption of the metallic ion is low; hence chelated complexes of lanthanides are most commonly used. The term chelate derives from the Greek word for “claw,” and is applied to name ligands, which attach to a metal ion with two or more donor atoms through dative bonds. The fluorescence is most intense when the metal ion has the oxidation state of 3+. Not all lanthanide metals can be used and the most common are: Sm(III), Eu(III), Tb(III), and Dy(III). | 1 | Biochemistry |
Lactic acid fermentation is also used in the production of sauerkraut. The main type of bacteria used in the production of sauerkraut is of the genus Leuconostoc.
As in yogurt, when the acidity rises due to lactic acid-fermenting organisms, many other pathogenic microorganisms are killed. The bacteria produce lactic acid, as well as simple alcohols and other hydrocarbons. These may then combine to form esters, contributing to the unique flavor of sauerkraut. | 1 | Biochemistry |
The spectral intensity of a blackbody, was first determined by Max Planck. It is given by Plancks law per unit wavelength as:This formula mathematically follows from calculation of spectral distribution of energy in quantized electromagnetic field which is in complete thermal equilibrium with the radiating object. Plancks law shows that radiative energy increases with temperature, and explains why the peak of an emission spectrum shifts to shorter wavelengths at higher temperatures. It can also be found that energy emitted at shorter wavelengths increases more rapidly with temperature relative to longer wavelengths.
The equation is derived as an infinite sum over all possible frequencies in a semi-sphere region. The energy, , of each photon is multiplied by the number of states available at that frequency, and the probability that each of those states will be occupied. | 7 | Physical Chemistry |
When referring to a promoter some authors actually mean promoter + operator; i.e., the lac promoter is IPTG inducible, meaning that besides the lac promoter, the lac operon is also present. If the lac operator were not present the IPTG would not have an inducible effect.
Another example is the Tac-Promoter system (Ptac). Notice how tac is written as a tac promoter, while in fact tac is actually both a promoter and an operator. | 1 | Biochemistry |
There are two causes of charge carrier motion and separation in a solar cell:
#drift of carriers, driven by the electric field, with electrons being pushed one way and holes the other way
#diffusion of carriers from zones of higher carrier concentration to zones of lower carrier concentration (following a gradient of chemical potential).
These two "forces" may work one against the other at any given point in the cell. For instance, an electron moving through the junction from the p region to the n region (as in the diagram at the beginning of this article) is being pushed by the electric field against the concentration gradient. The same goes for a hole moving in the opposite direction.
It is easiest to understand how a current is generated when considering electron-hole pairs that are created in the depletion zone, which is where there is a strong electric field. The electron is pushed by this field toward the n side and the hole toward the p side. (This is opposite to the direction of current in a forward-biased diode, such as a light-emitting diode in operation.) When the pair is created outside the space charge zone, where the electric field is smaller, diffusion also acts to move the carriers, but the junction still plays a role by sweeping any electrons that reach it from the p side to the n side, and by sweeping any holes that reach it from the n side to the p side, thereby creating a concentration gradient outside the space charge zone.
In thick solar cells there is very little electric field in the active region outside the space charge zone, so the dominant mode of charge carrier separation is diffusion. In these cells the diffusion length of minority carriers (the length that photo-generated carriers can travel before they recombine) must be large compared to the cell thickness. In thin film cells (such as amorphous silicon), the diffusion length of minority carriers is usually very short due to the existence of defects, and the dominant charge separation is therefore drift, driven by the electrostatic field of the junction, which extends to the whole thickness of the cell.
Once the minority carrier enters the drift region, it is swept across the junction and, at the other side of the junction, becomes a majority carrier. This reverse current is a generation current, fed both thermally and (if present) by the absorption of light. On the other hand, majority carriers are driven into the drift region by diffusion (resulting from the concentration gradient), which leads to the forward current; only the majority carriers with the highest energies (in the so-called Boltzmann tail; cf. Maxwell–Boltzmann statistics) can fully cross the drift region. Therefore, the carrier distribution in the whole device is governed by a dynamic equilibrium between reverse current and forward current. | 7 | Physical Chemistry |
Apart from mass spectrometry and chromatography, other two validation techniques have been developed, namely
#Pre- and post-labelling techniques:
*Pre-labelling → involves the use of P: cells are grown in P containing medium, thus allowing the incorporation of [α-P]NTPs during transcription by T7 RNA polymerase. The modified RNA is then extracted, and each RNA species is isolated and subsequently digested by T2 RNase. Next, RNA is hydrolyzed into 5' nucleoside monophosphates, which are analyzed 2D-TLC (two-dimensional thin-layer chromatography). This method is able to detect and quantify every modification but will not contribute to the characterization of the sequence.
*Post-labelling → implicates the selective labelling of a specific position within the sequence: these techniques rely on the Stanley-Vassilenko approach principles, that has been adjusted to achieve a better validation quality. First, RNA is cleaved into free 5’-OH fragments either by RNase H or DNAzymes, by sequence specific hydrolysis. The polynucleotide kinase (PKN) then performs the 5’ radioactive post-labelling phosphorylation using [γ-P]ATP. At this point, the labelled fragments undergo a size fragmentation, that can be performed either by Nuclease P1 or according to the SCARLET method. In both cases, the final product is a group of 5’ nucleoside monophosphates (5’ NMPs) that will be analyzed by TLC.
**SCARLET: this recent approach exploits not just one, but two sequence selection steps, the last of which is obtained during the splinted ligation of the radioactive-labelled fragments with a long DNA oligonucleotide, at its 3’-end. After degradation, the labelled residue is purified together with the ligated DNA oligonucleotide and finally hydrolyzed and therefore released thanks to the activity of the Nuclease P1.
This method has proven to be very useful in the validation of modified residues in mRNAs and lncRNAs, such as m6A and Ψ
#Oligonucleotide-based techniques: this method includes several variants
*Splinted ligation of particular modified DNAs, that exploits the ligase sensitivity to 3’ and 5’ nucleotides (so far used for m6A, 2’-O-Me, Ψ)
*Microarray modification identification through a DNA-chip, that exploits the decrease in duplex stability of cDNA oligonucleotides, due to the impediment in conventional base-pairing caused by modifications (ex. m1A, m1G, m22G)
*RT primer extension at low dNTPs concentration, for mapping of RT arrest signals. | 1 | Biochemistry |
Receptors on the opposite side of the synaptic gap bind neurotransmitter molecules. Receptors can respond in either of two general ways. First, the receptors may directly open ligand-gated ion channels in the postsynaptic cell membrane, causing ions to enter or exit the cell and changing the local transmembrane potential. The resulting change in voltage is called a postsynaptic potential. In general, the result is excitatory in the case of depolarizing currents, and inhibitory in the case of hyperpolarizing currents. Whether a synapse is excitatory or inhibitory depends on what type(s) of ion channel conduct the postsynaptic current(s), which in turn is a function of the type of receptors and neurotransmitter employed at the synapse. The second way a receptor can affect membrane potential is by modulating the production of chemical messengers inside the postsynaptic neuron. These second messengers can then amplify the inhibitory or excitatory response to neurotransmitters. | 1 | Biochemistry |
NHCs are often strongly basic (the pKa value of the conjugate acid of an imidazol-2-ylidene was measured at ca. 24) and react with oxygen. Clearly these reactions are performed using air-free techniques, avoiding compounds of even moderate acidity. Although imidazolium salts are stable to nucleophilic addition, other non-aromatic salts are not (i.e. formamidinium salts).
In these cases, strong unhindered nucleophiles are avoided whether they are generated in situ or are present as an impurity in other reagents (such as LiOH in BuLi).
Several approaches have been developed in order to prepare stable carbenes, these are outlined below. | 0 | Organic Chemistry |
Kenneth B. Storey (born October 23, 1949) is a Canadian scientist whose work draws from a variety of fields including biochemistry and molecular biology. He is a Professor of Biology, Biochemistry and Chemistry at Carleton University in Ottawa, Canada. Storey has a world-wide reputation for his research on biochemical adaptation - the molecular mechanisms that allow animals to adapt to and endure severe environmental stresses such as deep cold, oxygen deprivation, and desiccation. | 1 | Biochemistry |
The cerium anomaly, in geochemistry, is the phenomenon whereby cerium (Ce) concentration is either depleted or enriched in a rock relative to the other rare-earth elements (REEs). A Ce anomaly is said to be "negative" if Ce is depleted relative to the other REEs and is said to be "positive" if Ce is enriched relative to the other REEs. | 9 | Geochemistry |
Delamanid, a drug used to treat multi-drug-resistant tuberculosis (MDRTB) in combination with other antituberculosis medications, is activated in the mycobacterium by deazaflavin-dependent nitroreductase (Ddn), an enzyme which uses dihydro-F (reduced form). The activated form of the drug is highly reactive and attacks cell wall synthesis enzymes such as DprE2. Pretomanid works in the same way. Clinical isolates resistant to these two drugs tend to have mutations in the biosynthetic pathway for F. | 1 | Biochemistry |
Some organisms can oxidize methane, functionally reversing the process of methanogenesis, also referred to as the anaerobic oxidation of methane (AOM). Organisms performing AOM have been found in multiple marine and freshwater environments including methane seeps, hydrothermal vents, coastal sediments and sulfate-methane transition zones. These organisms may accomplish reverse methanogenesis using a nickel-containing protein similar to methyl-coenzyme M reductase used by methanogenic archaea. Reverse methanogenesis occurs according to the reaction:
: + CH → + HS + HO | 1 | Biochemistry |
In cardiovascular physiology, the diagram is often applied to the left ventricle, and it can be mapped to specific events of the cardiac cycle. PV loop studies are widely used in basic research and preclinical testing, to characterize the intact heart's performance under various situations (effect of drugs, disease, characterization of mouse strains)
The sequence of events occurring in every heart cycle is as follows. The left figure shows a PV loop from a real experiment; letters refer to points.
* A is the end-diastolic point; this is the point where contraction begins. Pressure starts to increase, becomes rapidly higher than the atrial pressure, and the mitral valve closes. Since pressure is also lower than the aortic pressure, the aortic valve is closed as well.
* Segment AB is the contraction phase. Since both the mitral and aortic valves are closed, volume is constant. For this reason, this phase is called isovolumic contraction.
* At point B, pressure becomes higher than the aortic pressure and the aortic valve opens, initiating ejection.
* BC is the ejection phase, volume decreases. At the end of this phase, pressure lowers again and falls below aortic pressure. The aortic valve closes.
* Point C is the end-systolic point.
* Segment CD is the isovolumic relaxation. During this phase, pressure continues to fall. The mitral valve and aortic valve are both closed again so volume is constant.
* At point D pressure falls below the atrial pressure and the mitral valve opens, initiating ventricular filling.
* DA is the diastolic filling period. Blood flows from the left atrium to the left ventricle. Atrial contraction completes ventricular filling.
As it can be seen, the PV loop forms a roughly rectangular shape and each loop is formed in an anti-clockwise direction.
Very useful information can be derived by examination and analysis of individual loops or series of loops, for example:
* the horizontal distance between the top-left corner and the bottom-right corner of each loop is the stroke volume
* the line joining the top-left corner of several loops is the contractile or inotropic state.
See external links for a much more precise representation. | 7 | Physical Chemistry |
The total synthesis of moroidin has not yet been described. Partial syntheses including the Leu-Trp and Trp-His linkages have been achieved. In their total synthesis of celogentin C, Castle and coworkers first obtained the Leu-Trp cross-link. The formation of this bond involved an intermolecular Knoevenagel condensation followed by radical conjugate addition and nitro reduction. This gave a product mixture of diastereomers, with the major product having the desired configuration.
A second approach by Jia and coworkers employed an asymmetric Michael addition and bromination, a stereoselective reaction that gave a compound with the correct configuration and Leu-Trp linkage.
Chen and coworkers demonstrated another stereoselective approach, which coupled iodotryptophan to 8-aminoquinoline by palladium catalysis to give a single diastereomer with the desired Leu-Trp linkage and configuration.
The Trp-His cross-link is addressed by Castle and coworkers, who used oxidative coupling by NCS to form the C-N linkage. To prevent over-chlorination, NCS was incubated with Pro-OBn, which reacts with NCS so as to modulate its concentration. This method of cross-linking tryptophan and histidine was used in subsequent total synthesis efforts. | 0 | Organic Chemistry |
Fischer's lab team designed the material by building compounds made of individual copper and aluminum atoms. For this superatom, a mixture of aluminium atoms complexed with pentamethylcyclopentadiene (Cp*) and copper atoms complexed with mesitylene (Mes) were combined in an inert atmosphere.
:[AlCp*] + [CuMes] → [CuAl](Cp*)
After adding a solvent, the copper and aluminum atoms spontaneously separated from the organic compounds and formed the superatom cluster. The exergonic nature of the reaction demonstratesg that this specific arrangement of copper and aluminum atoms is stable. | 7 | Physical Chemistry |
Like many other energy generation technologies, the manufacture of solar cells, especially its rapid expansion, has many environmental and supply-chain implications. Global mining may adapt and potentially expand for sourcing the needed minerals which vary per type of solar cell. Recycling solar panels could be a source for materials that would otherwise need to be mined. | 7 | Physical Chemistry |
There are two main types of kineses, both resulting in aggregations. However, the stimulus does not act to attract or repel individuals.
Orthokinesis: in which the speed of movement of the individual is dependent upon the stimulus intensity. For example, the locomotion of the collembola, Orchesella cincta, in relation to water. With increased water saturation in the soil there is an increase in the direction of its movement towards the aimed place.
Klinokinesis: in which the frequency or rate of turning is proportional to stimulus intensity. For example, the behaviour of the flatworm (Dendrocoelum lacteum) which turns more frequently in response to increasing light thus ensuring that it spends more time in dark areas. | 1 | Biochemistry |
Variations in iron isotopes are caused by a number of chemical processes which result in the preferential incorporation of certain isotopes of iron into certain phases. Many of the chemical processes which fractionate iron are not well understood and are still being studied. The most well-documented chemical processes which fractionate iron isotopes relate to its redox chemistry, the evaporation and condensation of iron, and the diffusion of dissolved iron through systems. These processes are described in more detail below. | 9 | Geochemistry |
In aerobic cells with sufficient oxygen, as in most human cells, the pyruvate is further metabolized. It is irreversibly converted to acetyl-CoA, giving off one carbon atom as the waste product carbon dioxide, generating another reducing equivalent as NADH. The two molecules acetyl-CoA (from one molecule of glucose) then enter the citric acid cycle, producing two molecules of ATP, six more NADH molecules and two reduced (ubi)quinones (via FADH as enzyme-bound cofactor), and releasing the remaining carbon atoms as carbon dioxide. The produced NADH and quinol molecules then feed into the enzyme complexes of the respiratory chain, an electron transport system transferring the electrons ultimately to oxygen and conserving the released energy in the form of a proton gradient over a membrane (inner mitochondrial membrane in eukaryotes). Thus, oxygen is reduced to water and the original electron acceptors NAD and quinone are regenerated. This is why humans breathe in oxygen and breathe out carbon dioxide. The energy released from transferring the electrons from high-energy states in NADH and quinol is conserved first as proton gradient and converted to ATP via ATP synthase. This generates an additional 28 molecules of ATP (24 from the 8 NADH + 4 from the 2 quinols), totaling to 32 molecules of ATP conserved per degraded glucose (two from glycolysis + two from the citrate cycle). It is clear that using oxygen to completely oxidize glucose provides an organism with far more energy than any oxygen-independent metabolic feature, and this is thought to be the reason why complex life appeared only after Earth's atmosphere accumulated large amounts of oxygen. | 1 | Biochemistry |
Like Ohta, H.T.Odum also sought to order energy form conversions according to their quality, however his hierarchical scale for ranking was based on extending ecological system food chain concepts to thermodynamics rather than simply relative ease of transformation . For H.T.Odum energy quality rank is based on the amount of energy of one form required to generate a unit of another energy form. The ratio of one energy form input to a different energy form output was what H.T.Odum and colleagues called transformity: "the EMERGY per unit energy in units of emjoules per joule" (H.T.Odum 1988, p. 1135). | 7 | Physical Chemistry |
Inverted sugar syrup for fermented water is usually home-made by fully dissolving sugar in cold tap water. Yeast requires oxygen rich water that do not exceed 25 degrees Celsius.
A common manual way to dissolve refined sugar is to mix with water in a container which is half filled, and then sealed and shaken. However, a mixer or blender may be used to automatically dissolve the sugar, in turns, if necessary. | 1 | Biochemistry |
Aluminum has been found to compete with iron and magnesium and bind to DNA, membranes, or cell walls, leading to its toxic effect on microbes, such as cyanobacteria, soil bacteria and mycorrhizal fungi.
Aluminium triacetate (Burow's solution) is used as an astringent mild antiseptic. | 1 | Biochemistry |
Both TLR3 and TLR4 use the TRIF-dependent pathway, which is triggered by dsRNA and LPS, respectively. For TLR3, dsRNA leads to activation of the receptor, recruiting the adaptor TRIF. TRIF activates the kinases TBK1 and RIPK1, which creates a branch in the signaling pathway. The TRIF/TBK1 signaling complex phosphorylates IRF3 allowing its translocation into the nucleus and production of Interferon type I. Meanwhile, activation of RIPK1 causes the polyubiquitination and activation of TAK1 and NFκB transcription in the same manner as the MyD88-dependent pathway.
TLR signaling ultimately leads to the induction or suppression of genes that orchestrate the inflammatory response. In all, thousands of genes are activated by TLR signaling, and collectively, the TLRs constitute one of the most pleiotropic yet tightly regulated gateways for gene modulation.
TLR4 is the only TLR that uses all four adaptors. Complex consisting of TLR4, MD2 and LPS recruits TIR domain-containing adaptors TIRAP and MyD88 and thus initiates activation of NFκB (early phase) and MAPK. TLR4-MD2-LPS complex then undergoes endocytosis and in endosome it forms a signalling complex with TRAM and TRIF adaptors. This TRIF-dependent pathway again leads to IRF3 activation and production of type I interferons, but it also activates late-phase NFκB activation. Both late and early phase activation of NFκB is required for production of inflammatory cytokines. | 1 | Biochemistry |
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