Thermodynamic studies of the collagen-like triple-helical structure in oligotripeptides by stepwise elongation of molecular chain

The conformational transition collagen-like triple helixe <----> dissociated chains of ogotripeptides 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 enthropy and the number of the triplets (3n-2), envolved in the interpeptide set of hydrogen bonds was revealed. Evidently the effect of terminal groups is realy weak in this case, and the interpeptide bonds of the triple helix may be regarded as aquivalent 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.