[Thermodynamic studies of triple-helical structures of the collagen type in oligotripeptides during study of molecular chain elongation].

The conformational transition collagen-like triple helix in equilibrium with chains of oligotripeptides Z-(Gly-Pro-Pro)n-OMe with n = 6, 7, 8 in water by variation of solution temperature and sample concentration has been studied using IR-, CD-spectroscopy and microcalorimetry methods. The straight line correlation between the obtained value of the transition enthalpy and entropy and the number of the triplets (3n - 2), involved in the interpeptide set of hydrogen bonds was revealed. Evidently the effect of terminal groups is really weak in this case, and the interpeptide bonds of the triple helix may be regarded as equivalent one another. The estimated cooperative block of nucleation corresponds in length to the one full turn of the superhelix. The state diagrams of the oligotripeptides with n = 6, 7, 8 in aqueous solution are presented.