RAMAN SPECTRAL EVIDENCE FOR HYDRATION FORCES BETWEEN COLLAGEN TRIPLE HELICES

Hydration forces are thought to result from the energetic cost of wate r rearrangement near macromolecular surfaces, Raman spectra, collected on the same collagen samples on which these forces were measured, rev eal a continuous change in water hydrogen-bonding structure as a funct ion of separation between collagen triple helices. The varying spectra l parameters track the force-distance curve. The energetic cost of wat er ''restructuring,'' estimated from the spectra, Is consistent with t he measured energy of intermolecular interaction, These correlations s upport the idea that the change in water structure underlies the expon entially varying forces seen in this system at least over the 13-18-An gstrom range of interaxial separations.