The use of a steric parameter (Y gamma) in QSAR calculations for peptide hormones

A steric parameter (Y gamma) has been derived for alpha-amino acids to characterize the steric hindrances near to the alpha-carbon atom. This easily computable variable is suitable for quantitative structure-activity relationship (QSAR) calculations for peptide hormones. Successful multivariate analyses were performed for oxytocin and angiotensin II analogs with the help of parameters describing the lipophilic and steric properties and the measure of dispersion forces. In the case of position 4 substituted oxytocin analogs, the steric, lipophilic and H-bridge forming properties equally account for the different biological activities of the derivatives. In the case of position 5 substituted angiotensin II analogs, primarily the steric parameters account for the biological activity of the series of derivatives.