Peptide Bond

(redirected from Amide group)
Also found in: Dictionary, Thesaurus, Medical.

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 ?
There are five main minima under zero point line (dash line) for (1) the free carbonyl of MMA units at 1730 [cm.sup.-1] (the adsorption of MMA units hydrogen-bonded to amide groups is shown as a shoulder at 1720 [cm.sup.-1]), (2) the free amide I groups of MAAM units at 1681 [cm.sup.-1], (3) the amide I groups of MAAM hydrogen bonding intermolecularly to the carbonyl groups of MMA (HB amide I in Fig.
Glass transition and [alpha] relaxation temperatures ([T.sub.g], [T.sub.[alpha]])of dry and solvent-saturated PA66 samples and mass intake [DELTA] m (referred to the total PA66 mass) and molar intake [DELTA] n (referred to the amount of amide groups in the amorphous phase) of the studied solvents at room temperature (20 [degrees] C).
On the other hand, [beta]-transition is attributed to the segmental motion that involves the amide groups in amorphous regions, which are not bonded by hydrogen bonds to other amides or a nearby chain.
Among other properties of resulted PEAs, the dielectric ones must take into consideration for investigation being known that the polar amide groups containing in the macromolecular chains and reorientation motions of corresponding dipoles are sensitive to the electric stimulus [3,20].
The hypothesis in this work was that since each urea molecule contains four hydrogens and can establish strong intermolecular interactions (H-bonding) with the amide groups in the PA, it can disrupt the intermolecular interactions (hydrogen bonding) among the polymer chains, therefore resulting in an easier dissolution.
Essentially the free radical attacks a double bond on a monomer and the electron moves on to another monomer, the process is continued until the end result is a chain of cyclic amide groups which is attached to the hydrophobic back bone [11].
The [sup.1]H NMR spectra showed one signal for the amide group hydrogen as a triplet or singlet between 10.60 and 8.53 ppm.
The [sup.13]C NMR spectrum of 7 contains peaks at 19.20 ppm for methyl group bound to steroid nucleus; at 26.70-48.94, 114.18-114.70, 124.70, 134.10, and 139.72-154.78 ppm for steroid moiety; at 110.80, 118.22120.90, and 134.78 ppm for indole group; at 115.22, 123.45, 125.60-132.50, and 163.80 ppm for benzoyl azide group; and at 171.52 ppm for amide group. Finally, the presence of compound 7 was further confirmed from mass spectrum which showed a molecular ion at m/z 488.20.
The addition of various lipophilic aliphatic and aromatic groups had little effect on increasing potency of clicked compounds, while exchanging the ester group for an amide group (compounds 16a-h), which had shown to have important influence on inhibition in previous studies [26], had very little effect on potency.
has been granted a patent for a powder coating composition, which contains a macromolecule compound (A) having amide group and/or imide group, an anti-oxidizing material (B) and a fluororesin (C), wherein the macro-molecule compound (A) has an average particle size of 45 [micro]m or less, wherein the macromolecule.
Keywords Anhydride group, Amide group, Cellulose, Cotton, Infrared spectroscopy, Soybean oil
This group is called an amide group (in most of the world nylons are called polyamides) and it is responsible for the relatively high melting point, strength, and affinity for moisture that nylons exhibit.