Energies of peptide–peptide and peptide–water hydrogen bonds in collagen: Evidences from infrared spectroscopy, quartz piezogravimetry and differential scanning calorimetry

The aim of the present work is a quantitative estimation of energies of peptide–peptide N1H1⋯O2C2 and peptide–water hydrogen bonds in collagen type I and model collagen polypeptide poly(Gly-Pro-Pro). Being a challenging theoretical task this is also an issue that can clarify the physical basis of stability of collagen structures that play a very important structural role in connective tissue. The study was performed on the basis of a complex approach of a number of experimental techniques, namely infrared spectroscopy, quartz piezogravimetry and differential scanning calorimetry. Our results indicate that binding of 3–4 water molecules of the internal hydration shell to each -Gly-X-Y- unit of poly(Gly-Pro-Pro) and collagen leads to simultaneous conformational reorganization of the triple helix and strengthening of the peptide–peptide hydrogen bonds. Enthalpies of hydration of poly(Gly-Pro-Pro) and collagen constitute −10.9 and −12.2 kJ/mol, respectively. Enthalpies of peptide-peptide N1H1⋯O2C2 hydrogen bonds are −7.6 and −6.0 kJ/mol in poly(Gly-Pro-Pro) and collagen, correspondently. The results obtained can be used for evaluation of the impacts of energies of different types of interactions into the total energy of stabilization of native triple helical collagen and poly(Gly-Pro-Pro).