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Beta-peptide
Beta-peptides (β-peptides) are peptides derived from β-amino acids, in which the amino group is attached to the β-carbon (i.e. the carbon two atoms away from the carboxylate group). The parent β-amino acid is β-alanine (H2NCH2CH2CO2H), a common natural substance, but most examples feature substituents in place of one or more C-H bonds. β-peptides usually do not occur in nature. β-Peptide-based antibiotics are being explored as ways of evading antibiotic resistance. Early studies in this field were published in 1996 by the group of Dieter Seebach and that of Samuel Gellman. Structure As there are two carbons available for substitution, β-amino acids have four sites (chirality included; as opposed to two in α-amino acids) for attaching the organic residue group. Accordingly, two main types β-amino acids exist differing by which carbon the residue is attached to: ones with the organic residue (R) next to the amine are called β3 and those with position next to the carbo ...
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Peptidomimetic
A peptidomimetic is a small protein-like chain designed to mimic a peptide. They typically arise either from modification of an existing peptide, or by designing similar systems that mimic peptides, such as peptoids and β-peptides. Irrespective of the approach, the altered chemical structure is designed to advantageously adjust the molecular properties such as stability or biological activity. This can have a role in the development of drug-like compounds from existing peptides. Peptidomimetics can be prepared by cyclization of linear peptides or coupling of stable unnatural amino acids. These modifications involve changes to the peptide that will not occur naturally (such as altered backbones and the incorporation of nonnatural amino acids). Unnatural amino acids can be generated from their native analogs via modifications such as amine alkylation, side chain substitution, structural bond extension cyclization, and isosteric replacements within the amino acid backbone. Based on ...
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Dieter Seebach
Dieter Seebach is a German chemist known for his synthesis of biopolymers and dendrimers, and for his contributions to stereochemistry. He was born on 31 October 1937 in Karlsruhe. He studied chemistry at the University of Karlsruhe (TH) under the supervision of Rudolf Criegee and at Harvard University with Elias Corey finishing in 1969. After his habilitation he became professor for organic chemistry at the University of Giessen. After six years he was appointed professor at the ETH Zurich where he worked until he retired in 2003. Work Seebach worked on dendrimer chemistry and on the synthesis of beta-peptides. The development of the umpolung, a polarity inversion of the carbonyl group, with 1,3-propanedithiol together with Corey had a big influence on organic synthesis, and subsequently the Corey-Seebach reaction was named after them. The Fráter–Seebach alkylation, a diastereoselective reaction of beta-hydroxy esters, is named after him. Awards *2000 Marcel Benoist P ...
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Peptide
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 g ...
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Gauche Conformation
In chemistry, rotamers are chemical species that differ from one another primarily due to rotations about one or more single bonds. Various arrangements of atoms in a molecule that differ by rotation about single bonds can also be referred to as conformations. Conformers/rotamers differ little in their energies, so they are almost never separable in a practical sense. Rotations about single bonds are subject to small energy barriers. When the time scale for interconversion is long enough for isolation of individual rotamers (usually arbitrarily defined as a half-life of interconversion of 1000 seconds or longer), the species are termed atropisomers (''see:'' atropisomerism). The ring-flip of substituted cyclohexanes constitutes a common form of conformers. The study of the energetics of bond rotation is referred to as conformational analysis. In some cases, conformational analysis can be used to predict and explain product selectivity, mechanisms, and rates of reactions. Conform ...
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Microcystin
Microcystins—or cyanoginosins—are a class of cyanotoxins, which are toxins produced by cyanobacteria, sometimes known as blue-green algae. Over 250 different microcystins have been discovered so far, of which microcystin-LR is the most common. Chemically they are cyclic heptapeptides produced through nonribosomal peptide synthases. Cyanobacteria can produce microcystins in large quantities during algal blooms which then pose a major threat to drinking and irrigation water supplies, and the environment at large. Characteristics Microcystins—or cyanoginosins—are a class of toxins produced by certain freshwater cyanobacteria; primarily ''Microcystis aeruginosa'' but also other '' Microcystis'', as well as members of the ''Planktothrix'', ''Anabaena'', ''Oscillatoria'' and ''Nostoc'' genera. Microcystin-LR (i.e. ''X'' = leucine, ''Z'' = arginine) is the most toxic form of over 80 known toxic variants, and is also the most studied by chemists, pharmacologists, biologists, ...
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Asparagine
Asparagine (symbol Asn or N) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a side chain carboxamide, classifying it as a polar (at physiological pH), aliphatic amino acid. It is non-essential in humans, meaning the body can synthesize it. It is encoded by the codons AAU and AAC. The one-letter symbol N for asparagine was assigned arbitrarily, with the proposed mnemonic asparagi''N''e; History Asparagine was first isolated in 1806 in a crystalline form by French chemists Louis Nicolas Vauquelin and Pierre Jean Robiquet (then a young assistant). It was isolated from asparagus juice, in which it is abundant, hence the chosen name. It was the first amino acid to be isolated. Three years later, in 1809, Pierre Jean Robiquet identified a substance from l ...
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Aspartic Acid
Aspartic acid (symbol Asp or D; the ionic form is known as aspartate), is an α-amino acid that is used in the biosynthesis of proteins. The L-isomer of aspartic acid is one of the 22 proteinogenic amino acids, i.e., the building blocks of proteins. D-aspartic acid is one of two D-amino acids commonly found in mammals. Apart from a few rare exceptions, D-aspartic acid is not used for protein synthesis but is incorporated into some peptides and plays a role as a neurotransmitter/ neuromodulator. Like all other amino acids, aspartic acid contains an amino group and a carboxylic acid. Its α-amino group is in the protonated –NH form under physiological conditions, while its α-carboxylic acid group is deprotonated −COO− under physiological conditions. Aspartic acid has an acidic side chain (CH2COOH) which reacts with other amino acids, enzymes and proteins in the body. Under physiological conditions (pH 7.4) in proteins the side chain usually occurs as the negatively charged a ...
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Pantothenic Acid
Pantothenic acid (vitamin B5) is a B vitamin and an essential nutrient. All animals need pantothenic acid in order to synthesize coenzyme A (CoA), which is essential for cellular energy production and for the synthesis and degradation of proteins, carbohydrates, and fats. Pantothenic acid is the combination of pantoic acid and beta-Alanine, β-alanine. Its name comes from the Greek language, Greek ''pantothen'', meaning "from everywhere", because pantothenic acid, at least in small amounts, is in almost all foods. Deficiency of pantothenic acid is very rare in humans. In dietary supplements and animal feed, the form commonly used is calcium pantothenate, because chemically it is more stable, and hence makes for longer product shelf-life, than sodium pantothenate and free pantothenic acid. Definition Pantothenic acid is a water-soluble vitamin, one of the B vitamins. It is synthesized from the amino acid β-alanine and pantoic acid (see #Biosynthesis, biosynthesis and structu ...
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Magainin
The magainins are a class of antimicrobial peptides found in the African clawed frog (''Xenopus laevis''). The peptides are cationic, generally lack a stable conformation in water but form amphipathic α-helix in membranes; their mechanism against micro-organisms is unclear but they disrupt the cell membranes of a broad spectrum of bacteria, protozoa, and fungi. They were independently discovered at around the same time by the labs of Michael Zasloff at the NIH and Dudley H. Williams at the University of Cambridge. They were named by Zasloff, after the Hebrew word for "shield," מגן māgēn (Ashkenazi pronunciation: magain). Zasloff helped found a company, Magainin Pharmaceuticals (subsequently called Genaera) to develop magainins into drugs. One candidate was an analog of magainin called pexiganan (MSI-78) that the company developed as a topical agent for infected diabetic foot ulcer Diabetic foot ulcer is a breakdown of the skin and sometimes deeper tissues of the foot ...
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In Vivo
Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, and plants, as opposed to a tissue extract or dead organism. Examples of investigations ''in vivo'' include: the pathogenesis of disease by comparing the effects of bacterial infection with the effects of purified bacterial toxins; the development of non-antibiotics, antiviral drugs, and new drugs generally; and new surgical procedures. Consequently, animal testing and clinical trials are major elements of ''in vivo'' research. ''In vivo'' testing is often employed over ''in vitro'' because it is better suited for observing the overall effects of an experiment on a living subject. In drug discovery, for example, verification of efficacy ''in vivo'' is crucial, because ''in vitro'' assays can sometimes yield misleading results with drug c ...
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