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The nonplanar peptide unit III. Quantum chemical calculations for related compounds and experimental X-ray diffraction data

Kolaskar, AS and Lakshminarayanan, AV and Sarathy, KP and Sasisekharan, V (1975) The nonplanar peptide unit III. Quantum chemical calculations for related compounds and experimental X-ray diffraction data. In: Biopolymers, 14 (5). pp. 1081-1094.

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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 studies on crystals of small open peptides, cyclic peptides, and amides. It is shown that the INDO results are in good agreement with observations, and that the dihedral angles N and defining the nonplanarity of the amide unit are correlated approximately by the relation N = -2 , while C is small and uncorrelated with . The present study indicates that the nonplanar distortions at the nitrogen atom of the peptide unit may have to be taken into consideration, in addition to the variation in the dihedral angles ( , ), in working out polypeptide and protein structures.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to John Wiley & Sons, Inc.
Keywords: formamide;acetamide;methylacetamide;ethylacetamide;nonplanar
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 11 Jun 2004
Last Modified: 19 Sep 2010 04:12
URI: http://eprints.iisc.ernet.in/id/eprint/383

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