title: Slow folding-unfolding kinetics of an octameric β-peptide bundle.
abstract: β-Peptide foldamers offer attractive frameworks for examining the effect of backbone flexibility on the dynamics of protein folding. Herein, we study the folding-unfolding kinetics of a β-peptide, Acid-1Y,1 which folds in aqueous solution into an octameric bundle of peptides in a conformation known as the 14-helix. Acid-1Y is comprised exclusively of β-amino acids, which differ from α-amino acids by the addition of a single methylene into the backbone. We aim to understand how the additional degree of freedom and increased backbone flexibility in the β-amino acid affect folding dynamics and to measure folding rates of this octameric β-peptide. Previously, we found that the T-jump induced relaxation kinetics of a monomeric β-peptide that forms a monomeric 14-helix occurred on the nanosecond time scale2 and were noticeably slower than a similar alanine-based α-helical peptide.3 Additionally, in comparison to similar α-helices, the relaxation rates showed a weaker dependence on temperature. Here, we find that the T-jump induced relaxation kinetics of the octameric β-peptide occurs on an even slower time scale (minutes) and the unfolding relaxation rates show a large dependence on temperature. These differences indicate that folding energy landscapes of β-peptide secondary and quaternary structure are markedly distinct from one another and also from their α-helical counterparts.
authors.affiliation: Department of Biochemistry & Biophysics, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
authors.forename: Geronda L
authors.initials: GL
authors.lastname: Montalvo
authors.forename: Feng
authors.initials: F
authors.lastname: Gai
authors.forename: Heinrich
authors.initials: H
authors.lastname: Roder
authors.forename: William F
authors.initials: WF
authors.lastname: DeGrado
mesh_terms: D007700:Kinetics; D009842:Oligopeptides / Q000737:chemistry*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013696:Temperature; D013816:Thermodynamics; D014443:Tyrosine
chemical_list: D009842:Oligopeptides; D014443:Tyrosine