Formation of the collagen‐like triple‐helical structure in oligopeptides during elongation of the molecular chain

Oligotripeptides Z-(Gly-Pro-Pro)n-OMe (n = 1,2,…,8), Z-Gly-Pro_Pro-Gly-Pro-Gly-OMe, Z-Gly-Pro-Pro-Gly-Pro-Gly-Gly-Pro-Pro-OMe, Z-Gly-Pro-Pro-(Gly-Pro-Gly)2-Gly-Pro-Pro-OMe, and Z-(Gly-Pro-Ala)n-OMe (n = 1,2,…,4) were synthesized step-by-step and then studied by means of x-ray diffraction, ir spectroscopy, the kinetics of hydrogen-deuterium exchange of peptide groups, and circular dichroism,. Different stages in the formation of a triple helix in Z-(Gly-Pro-Pro)n-OMe were revealed during the chain elongation. In the solid state, at the first stage a conformation of the polyproline II-type is formed in the tripeptide and in the second stage a triple helical complex appears in the hexapeptide. Interpeptide hydrogen bonds in this complex are still of low order. At further stages an ordered set of interpeptide hydrogen bonds is gradually formed. It is shown that the degree of order of interpeptide H bonds depends on the length of the molecular chain, the amino acid composition, and residue sequence in the triplets.