The dependence of the Chou-Fasman parameters on amino acid side chain structure

The Chou-Fasman conformational parameters, P, for amino acid residues in proteins are shown to be a linear function of intermolecular force and steric parameters. For alpha- helix, coil and turn parameters, steric effects are predominant; whereas for beta-sheet parameters, intramolecular forces are predominant. Turn and coil parameters show little or no difference in their dependence which is different from that of alpha-helix and in some ways almost reciprocal. Factors which increase the probability of finding an amino acid residue in an alpha-helix usually decrease the probability of finding it in coil or turn. Values of P were calculated for several of the less common amino acids.