Wollmer A, Fleischhauer J, Strassburger W, Thiele H
Biophys J. 1977 Nov;20(2):233-43. doi: 10.1016/S0006-3495(77)85546-X.
Previous calculations using crystal structure coordinates (Strickland and Mercola [1976], Biochemistry. 15: 3857) have predicted that about 40 percent of the calculated tyrosyl circular dichroism of hexameric insulin is due to one of the four tyrosine residues: viz. the A14-tyrosine interacting with the nearby B1-phenylalanine ring group. We have tested this prediction by measuring the tyrosyl circular dichroism of an isomorphous analogue of insulin, des-B1-phenylalanine-insulin. Contrary to expectation, the resulting circular dichroism was the same as that of insulin. It is concluded that the B1-phenylalanine residue does not in fact make a large contribution to the circular dichroism of A14-tyrosine. This result is probably due to the thermal motion of the B1 and A14 ring groups not taken into account by the calculations. An example of the effects of thermal motion on the calculated circular dichroism is given and improvements that do take into account thermal motion are discussed.
此前利用晶体结构坐标进行的计算（斯特里克兰和默科拉[1976]，《生物化学》。15: 3857）预测，六聚体胰岛素计算所得的酪氨酰圆二色性中，约40%归因于四个酪氨酸残基之一：即A14 - 酪氨酸与附近的B1 - 苯丙氨酸环基团相互作用。我们通过测量胰岛素的同晶型类似物——去B1 - 苯丙氨酸胰岛素的酪氨酰圆二色性，对这一预测进行了检验。与预期相反，所得圆二色性与胰岛素的相同。得出的结论是，B1 - 苯丙氨酸残基实际上对A14 - 酪氨酸的圆二色性贡献不大。这一结果可能是由于计算未考虑到B1和A14环基团的热运动。给出了热运动对计算所得圆二色性影响的一个例子，并讨论了考虑热运动的改进方法。
