Folding studies of pH-dependent collagen peptides.

Synthetic collagen model peptides containing carboxylate-modified hydroxyproline residues (P(E)) have been shown to form a collagen triple helix at low pH (1). Based on the fact that P(E)-containing peptides unfold on demand by altering the pH, we investigated the folding kinetics of a series of these collagen-based peptides. Refolding data indicated that the introduction of P(E) residues within a peptide affects the stability and refolding of the collagen peptides through electrostatic interactions and steric hindrance. Moreover, the specific placement of the P(E) residues within the collagen peptides allowed for selective testing for possible nucleation sites at the termini or the center of the peptides. Specifically, the data demonstrated that collagen peptides may nucleate from either terminally or internally located repeating sequences of Pro-Hyp-Gly. These studies indicate that the P(E) residue may play a useful role as a tool for studying the folding mechanism of synthetic collagen peptides.