𝔖 Bobbio Scriptorium
✦   LIBER   ✦

The nonplanar peptide unit. IV. Geometry and nonplanar distortions of the cis-peptide unit

✍ Scribed by A. S. Kolaskar; K. P. Sarathy

Book ID
102765062
Publisher
Wiley (John Wiley & Sons)
Year
1980
Tongue
English
Weight
529 KB
Volume
19
Category
Article
ISSN
0006-3525

No coin nor oath required. For personal study only.

✦ Synopsis

Semiempirical quantum chemical calculations were carried out using the CND0/2 and the INDO methods on the model compound cis-N-methylacetamide in order to get an insight into the problem of possible nonplanar distortions of the cis-peptide unit. In addition, the crystal structure data of cyclic peptides containing cis-peptide units were analyzed. These studies have indicated that the dihedral angles 8~ and Aw are correlated approximately by the relation A w = -ON, whereas Oc is small and is uncorrelated with Aw, as was found in the case of the trans-peptide unit. Both theory and crystal data suggest that out-of-plane distortions at the nitrogen atom of the peptide unit were quite likely to occur and should be included in the conformational calculations. The average geometry for the planar cis-peptide unit has also been obtained from the observed examples.

πŸ“œ SIMILAR VOLUMES

Ab initio studies on the nonplanarity of
Ab initio studies on the nonplanarity of a peptide unit: Calculations on model compounds
✍ A. Sawaryn; J. S. Yadav πŸ“‚ Article πŸ“… 1982 πŸ› John Wiley and Sons 🌐 English βš– 521 KB

## Abstract The nonplanarity of a peptide unit has been studied by the __ab initio__ method (GAUSSIAN 76) considering both the pyramidal structure of nitrogen and the variation of the Ο‰ angle for the __N__‐methyl‐acetamide and __N__‐ethyl‐acetamide in their __cis__ and __trans__ conformations. Seve

The nonplanar peptide unit III. Quantum
The nonplanar peptide unit III. Quantum chemical calculations for related compounds and experimental X-ray diffraction data
✍ A. S. Kolaskar; A. V. Lakshminarayanan; K. P. Sarathy; V. Sasisekharan πŸ“‚ Article πŸ“… 1975 πŸ› Wiley (John Wiley & Sons) 🌐 English βš– 665 KB

## Abstract The possible nonplanar distortions of the amide group in formamide, acetamide, __N__‐methylacetamide, and __N__‐ethylacetamide have been examined using CNDO/2 and INDO methods. The predictions from these methods are compared with the results obtained from X‐ray and neutron diffraction s

Stereochemical criteria for polypeptides
Stereochemical criteria for polypeptides and proteins. IV. Standard dimensions for the cis-peptide unit and conformation of cis-polypeptides
✍ G. N. Ramachandran; C. M. Venkatachalam πŸ“‚ Article πŸ“… 1968 πŸ› Wiley (John Wiley & Sons) 🌐 English βš– 409 KB πŸ‘ 2 views

Using potential energy formulas for variation of bond angles and for w-distortion, the conformation of minimum energy for the cis form of the petide unit has been worked out. This agrees very well with the corresponding set of atoms in the crystal structure of Leu-Pro-Gly and the dimensions of a sta