peptide

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peptide,

organic compound composed of amino acidsamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
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 linked together chemically by peptide bonds. The peptide bond always involves a single covalent link between the α-carboxyl (oxygen-bearing carbon) of one amino acid and the amino nitrogen of a second amino acid. In the formation of a peptide bond from two amino acids, a molecule of water is eliminated. Small peptides with fewer than about ten constituent amino acids are called oligopeptides, and peptides with more than ten amino acids are termed polypeptides. Compounds with molecular weights of more than 10,000 (50–100 amino acids) are usually termed proteins. Organisms commonly contain appreciable quantities of low-molecular-weight peptides some arising from proteins while others are synthesized directly. Certain of these molecules are unusual in that they incorporate amino acids not found in proteins such as amino acids of the d-configuration. Among the biological peptides are many with physiological or antibacterial activity, such as the peptide hormones oxytocinoxytocin
, hormone released from the posterior lobe of the pituitary gland that facilitates uterine contractions and the milk-ejection reflex. The structure of oxytocin, a cyclic peptide consisting of nine amino acids, was determined in 1953 and in the same year it was
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 and vasopressin; adrenocorticotropic hormoneadrenocorticotropic hormone
, polypeptide hormone secreted by the anterior pituitary gland. Its chief function is to stimulate the cortex of the adrenal gland to secrete adrenocortical steroids, chief among them cortisone.
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 (ACTH), secreted by the pituitary gland; and several cyclic peptides, in which the amino-acid sequence forms a ring structure rather than a straight chain, such as the antibiotics tyrocidin and gramicidingramicidin
, antibiotic obtained from the bacterial species Bacillus brevis, which is found in soil. Gramicidin is particularly effective against gram-positive bacteria (see Gram's stain).
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. Laboratory synthesis of peptides has risen to the level of a well-defined art in recent years. Synthetic peptides, composed of as many as a hundred amino acids in specified sequence, have been prepared in the laboratory with good purity and high yields.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/

Peptide

A compound that is made up of two or more amino acids joined by covalent bonds which are formed by the elimination of a molecule of H2O from the amino group of one amino acid and the carboxyl group of the next amino acid. Peptides larger than about 50 amino acid residues are usually classified as proteins. Glutathione is the most abundant peptide in mammalian tissue. Hormones such as oxytocin (8), vasopressin (8), glucagon (29), and adrenocorticotropic hormone (39) are peptides whose structures have been deduced; in parentheses are the numbers of amino acid residues for each peptide.

For each step in the biological synthesis of a peptide or protein there is a specific enzyme or enzyme complex that catalyzes each reaction in an ordered fashion along the biosynthetic route. However, it is noteworthy that, although the biological synthesis of proteins is directed by messenger RNA on cellular structures called ribosomes, the biological synthesis of peptides does not require either messenger RNA or ribosomes. See Amino acids, Protein, Ribonucleic acid (RNA), Ribosomes

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Peptide

 

an organic substance consisting of identical or different amino-acid residues joined by peptide bonds. Peptides are classified according to the number of component amino-acid residues as dipeptides, tripeptides, tetrapeptides, and so on, and as polypeptides.

Small quantities of low-molecular-weight peptides occur in nearly all living cells. For example, the tripeptide glutathione is widely distributed in plant and animal tissues, and the dipeptides anserine and carnosine are present in the muscle tissue of vertebrates. Many natural biologically active substances are classified as peptides, including certain hormones (insulin, adrenocortico-trophic hormone, glucagon, vasopressin, oxytocin), antibiotics (gramicidin, bacillin), and angiotensins and kinins, which are present in blood plasma.

The peptide molecule is a linear or branched chain. If the molecule is linear, it has two termini with one terminal amino group (—NH2) and one terminal carboxyl group (—COOH). Peptides with a closed-chain structure are called cyclopeptides, which include many bacterial toxins, hormones, and antibiotics. Many natural peptides contain amino acids that are not present in proteins, for example, D-amino acids. Peptides exhibit amphoteric properties, give biuret (beginning with tripeptides) and ninhydrin reactions, and dissolve readily in water, acids, and alkalies but are practically insoluble in organic solvents. They decompose upon heating to 200°-300°C.

In living cells, peptides are synthesized from amino acids or formed during the enzymatic breakdown of proteins. Chemical synthesis is used to obtain many biologically active natural peptides and their numerous analogues. Advancements in peptide chemistry have resolved many complex problems in modern biochemistry and molecular biology, such as the deciphering of the genetic code.

REFERENCE

Khimiia biologicheski aktivnykh prirodnykh soedinenii. Moscow, 1970.

N. N. CHERNOV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

peptide

[′pep‚tīd]
(biochemistry)
A compound of two or more amino acids joined by peptide bonds.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

peptide

any of a group of compounds consisting of two or more amino acids linked by chemical bonding between their respective carboxyl and amino groups
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
RP-HPLC-UV/MS peptide mapping was used to detect posttranslational modifications, such as deamidation, oxidation, and phosphorylation.
Protein surface topology-probing by selective chemical modification and mass spectrometric peptide mapping. Proceedings of the National Academy of Sciences 89:5630-5634.
Waters' new CSH130 particle technology columns offer selectivities for UPLC and HPLC peptide mapping and proteomics applications.
Tryptic and CNBr peptide mapping located the modification site to the C terminus and yielded a more precise value of 128 Da for the actual decrease in mass.
mAb 3D6 (in contrast to 6E10, 4G8, or WO2) selectively identified A[beta] peptides with a free amino group at [Asp.sup.1], which confirmed previously published data obtained by peptide mapping experiments (13) or 2-dimensional gel electrophoresis (8).
Synthetic peptide mapping studies have suggested that the binding sites for MAbs specific for free PSA reside in the regions 50-69 (19) and 80-91 (20).
ProFound: an expert system for protein identification using mass spectrometric peptide mapping information.
Peptide mapping. Synthetic 15-mer peptides with 10-residue overlaps covering the whole PSA sequence were used for the determination of specific binding sites of antibodies that recognize continuous epitopes.
Sequence information is especially important for the identification of proteins and may be obtained by MALDI MS analysis together with the use of enzymatic digestion followed by postsource decay of the resulting peptides or database-based peptide mapping (21-23).
Candidate reference methods for hemoglobin A1c based on peptide mapping. Clin Chem 1997;43:1944-51.
Peptide mapping of bovine T-cell epitope for the 38 kDa tuberculosis antigen.