The Effect of Side-Chain Branching on the Theoretically Predicted

Jul 11, 1977 - (9) L. Reich and S. S. Stivala, “Elements of Polymer Degradation”,. (10) C. H. Bamford et al., ”The Kinetics of Vinyl Polymerizat...
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Effect of Side-Chain Branching on Amino Acid Residues

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(9) L. Reich and S. S. Stivala, “Elements of Polymer Degradation”, McGraw-Hill, New York, N.Y., 1971. (10) C. H. Bamford et al., ” T h e Kinetics of Vinyl Polymerization by Radical Mechanisms”, Butterworths, London, 1958. (11) G. Gee and H. W. Melville, Trans. Faraday Soc., 44,240 (1944). (12) C. C. U’amser e t al., J . Am. Chem. Soc., 92,6362 (1970). (13) V. D. McGinniss, ACS Symp. Ser. No.25, 135 (1976). (14) S. L. Murov, “Handbook of Photochemistry”, Marcel Dekker, New York, N.Y., 1973.

The Effect of Side-Chain Branching on the Theoretically Predicted Conformational Space Available to Amino Acid Residues Yvonne Paterson and Sydney J. Leach* Russell Grimwade School of Biochernistr-3, C‘niversity of Melbourne, Parhuille, Victoria, 3052, Australia. Received J u l y 11, 1977

ABSTRACT: This study uses the most recently refined conformational energy parameters to define the conformational space available to both the backbone and side chains of the N-acetyl-N’-methylamide derivatives of alanine, P-methylalanine, valine, and p-methylvaline. T h e conformational space is described in terms of both conformational energy values and statistical percentage probabilities for 10’ increments of $J and $ and for different rotameric states of the side-chain torsion angles. Of the various regions of the (6,$)map. the area surrounding the C;“q conformation is the most favored overall for alanine, d-methylalanine, and valine, whereas that containing the extended conformational energy minimum is the most probable for 3-methylvaline. For both the valine and a-methylalanine residues the trans rotameric state for the C