Infrared Signature and Folding Dynamics of a Helical β-Peptide

Abstract

Synthetic foldamers consisting of β-amino acids offer excellent model systems for examining the effect of backbone flexibility on the dynamics of protein folding. Herein, we study the folding−unfolding kinetics of a β-peptide that folds into a 14-helical structure in water. We find that the T-jump induced relaxation kinetics of this peptide occur on the nanosecond time scale and are noticeably slower than those of alanine-based α-helical peptides, and additionally, the relaxation rates show a weaker dependence on temperature. These differences appear to indicate that the folding energy landscapes of these peptides are different. In addition, we find that the amide I′ band of this β-peptide exhibits a sharp feature at ∼1612 cm⁻¹, which we believe is a distinct infrared reporter of 14-helix.