Effect of Side-Chain Branching on Amino Acid Residues
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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
