The ir amide bands of the triple-helical polytripeptides and collagens upon hydration of films are investigated. On the basis of our assignment of the amide I components, the formation of hydrogen bonds between the peptide backbone and structural water is studied. The C1O1--HOH hydrogen bonds are found more ordered than the C3O3--HOH hydrogen bonds. The specific incorporation of water in the triple helix is followed by multistep conformational changes and by increasing of the interpeptide hydrogen-bond strength. The formation of the polypeptide hydrate structure depending on the amino acid composition and the chain length is examined.

Pro-Pro-OMe, and Z-(Gly-Pro-Ala),-OMe (n = 1,2, . , . ,4) were synthesized step-by-step and then studied by means of x-ray diffraction, ir spectroscopy, the kinetics of hydrogendeuterium exchange of peptide groups, and circular dichroism. Different stages in the formation of a triple helix in Z-(Gly-Pro-Pro),-OMe were revealed during the chain elongation. In the solid state, at the first stage a conformation of the polyproline 11-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.

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