期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2001
卷号：98
期号：5
页码：2188-2193
DOI：10.1073/pnas.041611998
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The effect of a solvation on the thermodynamics and kinetics of polyalanine (Ala12) is explored on the basis of its energy landscapes in vacuum and in an aqueous solution. Both energy landscapes are characterized by two basins, one associated with -helical structures and the other with coil and {beta}-structures of the peptide. In both environments, the basin that corresponds to the -helical structure is considerably narrower than the basin corresponding to the {beta}-state, reflecting their different contributions to the entropy of the peptide. In vacuum, the -helical state of Ala12 constitutes the native state, in agreement with common helical propensity scales, whereas in the aqueous medium, the -helical state is destabilized, and the {beta}-state becomes the native state. Thus solvation has a dramatic effect on the energy landscape of this peptide, resulting in an inverted stability of the two states. Different folding and unfolding time scales for Ala12 in hydrophilic and hydrophobic chemical environments are caused by the higher entropy of the native state in water relative to vacuum. The concept of a helical propensity has to be extended to incorporate environmental solvent effects.
