Peptide Bond

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peptide bond

[′pep‚tīd ‚bänd]
(organic chemistry)
A bond in which the carboxyl group of one amino acid is condensed with the amino group of another to form a ‒CO·NH‒ linkage. Also known as peptide linkage.

Peptide Bond

 

(also peptide linkage), an amide bond that arises during the formation of proteins and peptides when the α-amino group (—NH2) of one amino acid interacts with the α-carboxyl group (—COOH) of another amino acid:

where R1 and R2 are molecular parts that differ from one amino acid to another. The —CO—NH— group in proteins exhibits a keto-enol tautomerism.

The presence of peptide bonds in proteins and peptides was first proposed by A. Ia. Danilevskii and E. Fischer and later confirmed by chemical and physical data. Owing to tautomerism, the peptide bond exhibits a partial (40-percent) similarity to the double (conjugate) bond, which is indicated by the shorter length (1.32 A) of the peptide bond than of the single —C—N— bond (1.47 Å). The partially conjugate nature of the —C—N— bond determines the flat configuration of the —CO—NH— group (all four atoms are coplanar) and the existence of the trans and cis forms:

The greater stability of the trans form has been proved experimentally.

The enzymatic formation of peptide bonds in living cells occurs during protein biosynthesis. Laboratory methods have been developed for the chemical and enzymatic synthesis and cleavage of peptide bonds, thereby making it possible to synthesize a number of biologically active peptides and to determine the amino-acid sequence for many proteins and peptides.

N. N. ZAITSEVA

References in periodicals archive ?
One of the H-bond is formed with the amide group of Leu75 in the Beta5 loop and the second H-bond is formed with the amide group of the residue immediately following the catalytic serine which is Gln164 (Kraut, 1977).
Note that this repeating unit also contains six carbons, five that are attached only to hydrogen while the sixth one is part of the amide group.
Reaction at 162[degrees]C appears to provide an example of a transannular reaction between two amide groups of cyclic ethylene glutaramide.
3] end group of p-xylene) ~1865, 1791, 1700 C=O stretching of anhydride group ~1737, 1702 C=O stretching of amide group ~1635 C=C stretching ~1390, 1435 CH, [CH.
Although the methylene unit is a flexible chain, the amide group is a rigid bond because the strong polarity and large amount of hydrogen bond.
Most recent work suggests that copper ions can complex with the amide group in nylon, and may also complex with hydroperoxides formed on the N-vicinal methylene group, assisting with their breakdown to non-radical, harmless, species.
The results may indicate that carbonyl groups of MMA unit forms interassociated hydrogen bonds with amide groups of MAAM.
It was concluded that the interaction of water with nylon took place at the amide group.
With the increase in AA contents, the voiding is obvious because the functional monomer (AA) was reacted with the end amide group of PA 6 (Fig.
1] is the molar mass of polyamide per amide group (PA66 has two amide groups per monomer).
However, in the case of the amide group, both the crystalline and amorphous peaks could be measured without problem.