ENERGY‐CONFORMATION STUDIES OF FREQUENCY OF β‐TURNS IN TETRAPEPTIDE SEQUENCES

The optimized energies of seven β‐bends, repeating C5 and C7, and right‐ and left‐handed α‐helical conformations for each of eight tetrapeptides have been computed using empirical methods. Eight tetramers were selected: four helix‐forming sequences with hydrophobic residues such as Val, Leu, Ile and Trp, and four helix‐breaking sequences with hydrophilic residues such as Asp, Asn and Ser, as determined by their frequency of occurrence in beta turns in proteins. Analysis of the optimized conformations with energies ≤2.1 kcal/mol from the absolute minimum energy conformer for each tetramer reveals a correlation between low‐energy conformations and those predicted from observed protein structures. These results show that energy calculations on small peptide fragments may be useful in predicting protein structure.