Helix formation via conformation diffusion search

The helix-coil transition kinetics of an alpha-helical peptide were investigated by time-resolved infrared spectroscopy coupled with laser-induced temperature-jump initiation method. Specific isotope labeling of the amide carbonyl groups with C-13 at selected residues was used to obtain site-specific information. The relaxation kinetics following a temperature jump, obtained by probing the amide l'band of the peptide backbone, exhibit nonexponential behavior and are sensitive to both initial and final temperatures. These data are consistent with a conformation diffusion process on the folding energy landscape, in accord with a recent molecular dynamics simulation study.