CNDO/2 calculation of the relative stability of poly(γ-hydroxy-l-proline)

The CNDO/2 method using the tight-binding approximation for polymers was applied to poly(γ-hydroxy-l-prolines) (PHP). The calculations were carried out for PHPs which have the same backbone structure as those of poly(l-proline I) (Pro-I) and poly(l-proline II)(Pro-II). The results obtained show the preferred orientation of the OH group at the γ-position, which is in agreement with the experimental results. The calculations were also carried out for the B form (PHP-B). The conformational stability between the A form (PHP-A) and PHP-B was explained by using the calculated results in connection with the previous experimental and theoretical treatments. From the analysis of the total energy, the dominant stabilizing factors for the two forms are discussed.