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：1975
卷号：72
期号：6
页码：2002-2006
DOI：10.1073/pnas.72.6.2002
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Conformational potentials of sidechains in the bovine pancreatic trypsin inhibitor have been studied with an empirical energy function. Calculated minimumenergy positions are in excellent agreement with the x-ray structure for sidechains in the core or at the surface of the protein; as expected, angles for sidechains that are directed out into the solvent do not agree with the calculated values. The contributions to the potentials are analyzed and compared with the potentials for the free amino acid. Although there is a large restriction in the available conformational space due to nonbonded interactions, the minimum energy positions in the protein are close to those of the free amino acid; the significance of this result is discussed. To estimate the effective barriers for rotation of the aromatic rings (tyrosine and phenylalanine), calculations are done in which the protein is permitted to relax as a function of the ring orientation. Thr resulting barriers, which are much lowere than the rigid rotation barriers, are used to evaluate the rotation rates; comparison is made with the available nuclear magnetic resonance data.
