Effect of Hydration on the Thermal Stability of the Collagen Triple Helical Structure

Abstract

4(R)-Hydroxyproline (Hyp^R) is often found in natural collagen in spite of being a rare amino acid in proteins overall. It has been known that Hyp^R residue contributes to the thermal stability of the collagen triple helical structure. Intensive studies to investigate the stabilizing mechanism of the collagen triple helical structure have been performed by using a series of polytripeptides (X-Y-Gly)₁₀ [X, Y: Pro, Hyp^R, or 4-fluoroproline (fPro)], The thermodynamic parameters determined by DSC analyses of these model peptides indicate that the enthalpy term contributes predominantly to the thermal stability of (Pro-Hyp^R-Gly)₁₀, whereas the entropy term is primarily responsible for the enhanced stabilities of (Pro-fPro^R-Gly)₁₀ and (fPro^S-Pro-Gly)₁₀. Based on the comparison of molecular volumes observed in solution with intrinsic ones from the crystal structure, the difference comes from the difference of hydration on these peptides.