Gelin B R, Karplus M
Proc Natl Acad Sci U S A. 1975 Jun;72(6):2002-6. doi: 10.1073/pnas.72.6.2002.
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.
已使用经验能量函数研究了牛胰蛋白酶抑制剂中侧链的构象势能。计算得到的最低能量位置与蛋白质核心或表面侧链的X射线结构高度吻合；正如预期的那样，伸向溶剂中的侧链角度与计算值不一致。分析了对势能的贡献并与游离氨基酸的势能进行了比较。尽管由于非键相互作用，可用构象空间存在很大限制，但蛋白质中的最低能量位置与游离氨基酸的位置相近；讨论了该结果的意义。为了估计芳香环（酪氨酸和苯丙氨酸）旋转的有效势垒，进行了计算，其中允许蛋白质根据环的取向进行弛豫。得到的势垒比刚性旋转势垒低得多，用于评估旋转速率；并与现有的核磁共振数据进行了比较。
