|
Hatu
HATU (Hexafluorophosphate Azabenzotriazole Tetramethyl Uronium) is a reagent used in peptide coupling chemistry to generate an active ester from a carboxylic acid. HATU is used along with Hünig's base (''N,N''-diisopropylethylamine), or triethylamine to form amide bonds. Typically DMF is used as solvent, although other polar aprotic solvents can also be used. History HATU was first reported by Louis A. Carpino in 1993 as an efficient means of preparing active esters derived from 1-hydroxy-7-azabenzotriazole (HOAt). HATU is commonly prepared from HOAt and TCFH under basic conditions and can exist as either the uronium salt (''O-''form) or the less reactive iminium salt (''N''-form). HATU was initially reported as the O-form using the original preparation reported by Carpino; however, X-ray crystallographic and NMR studies revealed the true structure of HATU to be the less reactive guanidinium isomer. It is, however, possible to obtain the uronium isomer by preparing HATU usin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amide
In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a chemical compound, compound with the general formula , where R, R', and R″ represent any group, typically organyl functional group, groups or hydrogen atoms. The amide group is called a peptide bond when it is part of the Polymer backbone, main chain of a protein, and an isopeptide bond when it occurs in a side chain, as in asparagine and glutamine. It can be viewed as a Derivative (chemistry), derivative of a carboxylic acid () with the hydroxyl group () replaced by an amino group (); or, equivalently, an acyl group, acyl (alkanoyl) group () joined to an amino group. Common amides are formamide (), acetamide (), benzamide (), and dimethylformamide (). Some uncommon examples of amides are ''N''-chloroacetamide () and chloroformamide (). Amides are qualified as primary (chemistry), primary, secondary (chemistry), secondary, and tertiary (chemistry), tertiary according to the number of acyl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TCFH
TCFH (''N'',''N'',''N''’,''N''’-tetramethylchloroformamidinium hexafluorophosphate) is an electrophilic amidine reagent used to activate a number of functional groups for reaction with nucleophilies. TCFH is most commonly used to activate carboxylic acids for reaction with amines in the context of amide bond formation and peptide synthesis. __TOC__ Preparation TCFH is commercially available. It may be prepared from tetramethylurea using a chlorinating agent such as oxalyl chloride, thionyl chloride or phosphorus oxychloride followed by salt exchange. Uses TCFH itself is a common reagent used in the preparation of uronium and guanidinium salts used for amide bond formation and peptide synthesis, such as HATU. Amide bond formation with TCFH can be performed in a wide range of organic solvents, most commonly acetonitrile, but also water and in the solid state. Reactions typically require an added Brønsted base, and a wide range can be employed including ''N,N''-diisopro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetramethylurea
Tetramethylurea is the organic compound with the formula (Me2N)2CO. It is a substituted ureas, urea. This colorless liquid is used as an Protic solvent, aprotic-polar solvent, especially for aromatic compounds and is used e. g. for Grignard reagents. Tetramethylurea is a colorless liquid with mild aromatic odor. Unusual for an urea is the liquid state of tetramethylurea in a range of > 170 °C. Production It is obtained by the reaction of dimethylamine with phosgene in the presence of sodium hydroxide solution. A closely related method combines dimethylcarbamoyl chloride with excess dimethylamine. This reactions is highly exothermic. The removal of the resulting dimethylamine hydrochloride requires some effort. The reaction of diphenylcarbonate with dimethylamine in an autoclave is also effective. Tetramethylurea is formed upon the oxygenation of tetrakis(dimethylamino)ethylene (TDAE). Tetramethylurea is also a common by-product formed in Amide, amide bond fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peptide Coupling
In organic chemistry, peptide synthesis is the production of peptides, compounds where multiple amino acids are linked via amide bonds, also known as peptide bonds. Peptides are chemically synthesized by the condensation reaction of the carboxyl group of one amino acid to the amino group of another. Protecting group strategies are usually necessary to prevent undesirable side reactions with the various amino acid side chains. Chemical peptide synthesis most commonly starts at the carboxyl end of the peptide (C-terminus), and proceeds toward the amino-terminus (N-terminus). Protein biosynthesis (long peptides) in living organisms occurs in the opposite direction. The chemical synthesis of peptides can be carried out using classical solution-phase techniques, although these have been replaced in most research and development settings by solid-phase methods (see below). Solution-phase synthesis retains its usefulness in large-scale production of peptides for industrial purposes more ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reagent
In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a substance ''consumed'' in the course of a chemical reaction. ''Solvents'', though involved in the reaction mechanism, are usually not called reactants. Similarly, ''catalysts'' are not consumed by the reaction, so they are not reactants. In biochemistry, especially in connection with enzyme-catalyzed reactions, the reactants are commonly called substrates. Definitions Organic chemistry In organic chemistry, the term "reagent" denotes a chemical ingredient (a compound or mixture, typically of inorganic or small organic molecules) introduced to cause the desired transformation of an organic substance. Examples include the Collins reagent, Fenton's reagent, and Grignard reagents. Analytical chemistry In analytical chemistry, a reag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peptide Coupling Reagents
Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Da or more are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. Peptides fall under the broad chemical classes of biological polymers and oligomers, alongside nucleic acids, oligosaccharides, polysaccharides, and others. Proteins consist of one or more polypeptides arranged in a biologically functional way, often bound to ligands such as coenzymes and cofactors, to another protein or other macromolecule such as DNA or RNA, or to complex macromolecular assemblies. Amino acids that have been incorporated into peptides are termed residues. A water molecule is released during formation of each amide bond.. All peptides except cyclic peptides have an N-terminal (amine group) and C-terminal (carboxyl group) residu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Differential Scanning Calorimetry
Differential scanning calorimetry (DSC) is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature. Both the sample and reference are maintained at nearly the same temperature throughout the experiment. Generally, the temperature program for a DSC analysis is designed such that the sample holder temperature increases linearly as a function of time. The reference sample should have a well-defined heat capacity over the range of temperatures to be scanned. Additionally, the reference sample must be stable, of high purity, and must not experience much change across the temperature scan. Typically, reference standards have been metals such as indium, tin, bismuth, and lead, but other standards such as polyethylene and fatty acids have been proposed to study polymers and organic compounds, respectively. The technique was developed by E. S. Watson and M. J. O'Ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Globally Harmonized System Of Classification And Labelling Of Chemicals
The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is an internationally agreed-upon standard managed by the United Nations that was set up to replace the assortment of hazardous material classification and labelling schemes previously used around the world. Core elements of the GHS include standardized hazard testing criteria, universal warning pictograms, and safety data sheets which provide users of dangerous goods relevant information with consistent organization. The system acts as a complement to the UN numbered system of regulated hazardous material transport. Implementation is managed through the UN Secretariat. Although adoption has taken time, as of 2017, the system has been enacted to significant extents in most major countries of the world. This includes the European Union, which has implemented the United Nations' GHS into EU law as the CLP Regulation, and United States Occupational Safety and Health Administration standards. History B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LLNA
The murine local lymph node assay (LLNA) is an ''in vivo'' test for skin sensitisation. LLNA has largely superseded the guinea pig maximisation test and the Buehler test. It is considered more scientific and less cruel (lower number of animals; less suffering) and has found broad scientific and regulatory acceptance. The principle underlying the LLNA is that skin sensitizers induce growth of lymphocytes in the lymph nodes draining the site of application. Lymphocyte proliferation can be measured by radiolabeling (quantifying tritiaded thymidine), bioluminescence (quantifying ATP content in lymphocytes) or immunoassay (ELISA utilizing an antibody specific for BrdU). The test material is applied to the ears of mice. Optionally, a tracer substance such as 3H-Methyl-thymidine or BrdU is injected intraperitoneally for lymphocyte incorporation. The animals are euthanized and their lymph node cells are removed and analyzed. The ratio of tracer incorporation in lymph nodes from dosed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sensitization (immunology)
In immunology, the term sensitization is used for the following concepts:Anderson DM, ed. (2003). "Sensitization." ''Dorland's Illustrated Medical Dictionary'', 30th ed. Philadelphia: Saunders, p. 1680. .Brown MJ, ed. (1992). "Sensitization." ''Miller-Keane Encyclopedia & Dictionary of Medicine, Nursing, and Allied Health'', 5th ed. Philadelphia; London: Saunders, p. 1352. .Pugh MB, ed. (2000). "Sensitization." ''Stedman's Medical Dictionary'', 27th ed. Philadelphia: Lippincott Williams and Wilkins, p. 1619. .Tada T, Taniguchi M, Okumura Y, Miyasaka M, eds. (1993). "Sensitization." ''Dictionary of Terms in Immunology'', 3rd ed. Osaka: Saishin-Igakusha, Ltd., p. 510. C3547 (in Japanese). * Immunization by inducing an adaptive response in the immune system. In this sense, sensitization is the term more often in usage for induction of allergic responses.Janeway C, Travers P, Walport M, Shlomchik M, eds. (2001). ''Immunobiology 5: The Immune System in Health and Disease.'' New York: Ga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OECD
The Organisation for Economic Co-operation and Development (OECD; , OCDE) is an international organization, intergovernmental organization with 38 member countries, founded in 1961 to stimulate economic progress and international trade, world trade. It is a forum (legal), forum whose member countries describe themselves as committed to democracy and the market economy, providing a platform to compare policy experiences, seek answers to common problems, identify good practices, and coordinate domestic and international policies of its members. The majority of OECD members are generally regarded as developed country, developed countries, with High-income economy, high-income economies, and a very high Human Development Index. their collective population is 1.38 billion people with an average life expectancy of 80 years and a median age of 40, against a global average of 30. , OECD Member countries collectively comprised 62.2% of list of countries by GDP (nominal), global nom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
