Amino acids peptide bonds

Peptides are short chains of amino acids linked by peptide bonds. Most biologically active peptides contain two to ten amino acids. Peptide bonds are formed between the carboxyl carbon of one amino acid and the amino nitrogen of another. Since water is released, this is an example of dehydration synthesis. The bond forms as illustrated in Figure 16.7. 

Primary Structure The primary structure of the protein is the amino acid sequence of the protein. The primary structure results from the formation of covalent peptide bonds between amino acids. Peptide bonds are amide bonds formed between the a-carboxylate group of one amino acid and the a-amino group of another. 

See also Amino Acids, Peptide Bonds, Translation. Genetic Code, Polypeptides, Nucleic Acids, RNA, Translation Overview (from Chapter 27), The Genetic Code, Polyampholytes... 

By far the majority of carbohydrate material in nature occurs in the form of polysaccharides. By our definition, polysaccharides include not only those substances composed only of glycosidically linked sugar residues but also molecules that contain polymeric saccharide structures linked via covalent bonds to amino acids, peptides, proteins, lipids, and other structures. 

Dipeptidyl aminopeptidase IV hydrolyzes substrates with free a-amino groups. Peptide bonds involving the carboxy group of either Pro or Ala are cleaved by this enzyme to X-Pro or X-Ala, where X may be any amino acid. It has been shown that peptides with the X-Pro moiety are hydrolyzed more completely than those with X-Ala [79],... 

Yarovsky, L, Aguilar, M.I., and Hearn, M.T.W., High-performance liquid-chromatography of amino-acids, peptides and proteins. 125. Molecular-dynamics simulation of n-butyl chains chemically bonded to sihca-based reversed-phase high-performance liquid-chromatography sorbents, 7. Chromatogr. A, 660, 75, 1994. 

Phenolic compounds can be condensed forming aryl-aryl and aryl-oxygen-aryl (ether linkages) bonds to yield diaryl and diaryl ether polymers (59). These are in many ways similar to natural humic acids, confirming earlier research by others (60-62) that humic acids are formed from the copolymerization of phenolic compounds with amino acids, peptides, and amino sugars. 

A.F. Spatola, Peptide backbone modifications A structure-activity analysis of peptides containing amide bond surrogates, conformational constraints, and related backbone replacements, in B. Weinstein(Ed.), Chemistry and Biochemistry of Amino Acids, Peptides and Proteins, Marcel Dekker, New York, 1983, pp. 267-357. 

The amino and carboxyl ends of two amino acids unite to form a peptide bond. In the process, water is produced. Notice that the dipeptide form has an amino and a carboxyl group at its end allowing other amino acids to bond to the structure. 

A large number of 13C NMR studies on proline derivatives and proline peptides have appeared in the literature [815-830]. As the electron charge density of cis-proline carbons is different from that of franx-prolinc carbons, these isomers can be differentiated by nCNMR spectroscopy [826, 830]. On the basis of calculations Tonelli [831] predicted four conformations for the dipeptide Boc-Pro-Pro-OBzl, three of which could be detected by 13C NMR spectroscopy [826, 830], In proline-containing peptides the stereochemistry of the proline residue plays an important role for the conformation of these oligomers. The 13C chemical shift data of cis and trans proline derivatives, collected in Table 5.29, are useful to determine the stereochemistry of the amino acid-proline bond, e.g. in cyclo-(Pro-Gly)3, melanocyte-stimulating hormone release-inhibiting factor or thyrotropin-releasing hormone. 

At the start of the peptide synthesis, the C-terminal amino acid is bonded through its carboxyl group to the resin by a nucleophilic attack of the carboxy-late ion on the chloromethyl groups. The a-amino group must be suitably protected, as with ferf-butoxycarbonyl, before carrying out this step ... 

Commercial bonded-phase chelation columns have also been offered for sale. The interest in these separations has risen because the chelation with metals such as Ni and Zn is asymmetric and allows the selective separation of optical isomers, such as amino acids, peptides, proteins, and carbohydrates. 

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