文章基本信息

标题：The α-helix folds on the millisecond time scale
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作者：David T. Clarke ; Andrew J. Doig ; Benjamin J. Stapley 等
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：1999
卷号：96
期号：13
页码：7232-7237
DOI：10.1073/pnas.96.13.7232
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：It has long been believed that nucleation of the -helix is a very fast reaction, occurring in around 10-7 s. We show here that helix nucleation, in fact, takes place on the millisecond time scale. The rate of -helix nucleation in two polyalanine-based peptides and in lysine and glutamic acid homopolymers was measured directly by stopped-flow deep UV CD with synchrotron radiation as the light source. Synchrotron radiation CD gives far superior signal to noise than a conventional instrument. The 16-aa AK peptide folds with first-order kinetics and a rate constant of 15 s-1 at 0{degrees}C. The rate-determining step is presumably the initiation of a new helix, which occurs at least 105 times slower than expected. Helix folding occurs in at least two steps on the millisecond time scale for the longer peptides, with a transient overshoot of helix content significantly greater than at equilibrium, similar to that seen in the folding of several proteins. We suggest that the overshoot is caused by the formation of a single long helix followed by its breakage into the two or more helices present at equilibrium.