Effect of chain length on the formation of the triple-helical collagen-like complex in solutions. The role of water in the formation of triple helix.

Effect of molecular chain length on the formation of the collagen-like triple helix In synthetic oligotripeptides Z-(Gly-Pro-Pro)(n)-OMe (n=1,2,3,..,8) in solutions has been studied, using IR- and CD-spectroscopy methods. The helix formation under different conditions Is investigated: in the presence of a relatively inert solvent (chloroform), in the presence of a hydrogen bond acceptor (dioxan), in the presence of a hydrogen bond acceptor and donor as well (ethanol). Special attention is paid to the role of water in the formation of a stable triple-helical structure. Successive stages in the formation of a stable triple-helical structure in solutions during elongation of the peptide chain is revealed, which may be correlated with the helix nucleation process. A minimum peptide length, when peptide chains are still able to associate in the collagen-like triple-helical complex, involves three triplets for oligomers in chloroform solution, four triplets for oligomers in dioxan and ethanol solutions, six triplets for oligomers in aqueous solution. The main features of the completed triple-helical structure in water are found already in the oligotripeptide with n=8, where the formation one full turn of the superhelix is finished.