[Refinement of the structure of the polypeptide (glycyl-imino acid-imino acid)n as a model of collagen by the technic of theoretical conformational analysis].

Comprehensive conformational analysis of collagen like triple complexes of (Gly-Pro-Pro)n and (Gly-Pro-Hyp)n have been fulfilled taking into account the flexibility of pyrrolidine rings. Optimization procedure operates with 14 independent variables (8 dihedral angles and 6 bond angles). The final structures (essentially the same for both polymers) are characterizing by helical parameters h = 0.285 nm, t = 52 degrees strongly supporting 7/2 symmetry as in X-ray patterns. Conformations of pyrrolidine rings are of B-type following Ramachandran's notations. For both polymer units the conformation of third residues pyrrolidine ring are the same, but for second residues it differs. The difference of diffraction patterns for 7/2 and 10/3 helices has been discussed.