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.


References in periodicals archive ?
Concentration of amide groups during nonreactive PP/PA6 blends and reactive processing of PP/PA6/PP-g-AA prepared in a HAAKE internal mixer.
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.
The results may indicate that carbonyl groups of MMA unit forms interassociated hydrogen bonds with amide groups of MAAM.
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 substitution of OH adjacent to the amide group at the end of a cleaved alkyl chain may be caused by the presence of oxygen during UV exposure.
17 because of the interfacial reaction between the carboxyl group of AA component and the amide group of PA 6 during melt extrusion.
The effect of water on polyamide properties, such as the glass transition and the mechanical behavior, is well documented (3-20); due to the presence of polar amide groups along polyamide chains, strong interactions between polyamide and polar solvents like water can be formed.
The crystallinity of the amide group in the polymers calculated by this method was found to be around 75-80% (Table 1).
1] represents the vC = O H-bond, which indicates the presence of hydrogen bonding between the urethane group of CPU coating and the amide group of the PA6 fiber (14), (15).
As shown, the amide group peak at 175 pm only appeared in samples with high content of NTBA, i.
Because of the small differences in the solubility parameters between the soft segments of TPU and PA1212, at relatively low PA1212 content (about 5 wt%), the amide groups of PA1212 prefer to interact with the ester groups of TPU and increase the number of TPU hydrogen bonds accordingly, resulting in the obvious increases of the apparent viscosity and the mechanic property of the blends.