Ramakrishnan C, Ramachandran G N
Biophys J. 1965 Nov;5(6):909-33. doi: 10.1016/S0006-3495(65)86759-5.
The conformation of a polypeptide or protein chain may be specified by stating the orientations of the two linked peptide residues at each alpha carbon atom in the chain, namely the two dihedral angles varphi, varphi' about the single bonds N-alphaC and alphaC-C' from a defined standard conformation. By using certain criteria of minimum contact distances between the various atoms, the allowed anges of (varphi, varphi') have been worked out for three values of the angle N-alphaC-C' (tau), namely 105, 110, and 115 degrees for non-glycyl, and 110 and 115 degrees for glycyl residues. The theory is compared with all the available crystallographic data (up to early 1965) on simple (di- and tri-) peptides, cyclic peptides, polypeptide and protein structures, and the observed data fully support the conclusions from theory. The effect of the gamma carbon atom, in its three possible positions, is also discussed, and is found to alter the outer limits of the allowed region of (varphi, varphi') only slightly. The paper contains exhaustive references to the published data on these structures, using x-ray diffraction.
多肽或蛋白质链的构象可以通过说明链中每个α碳原子上两个相连肽残基的取向来确定，即从定义的标准构象围绕单键N-αC和αC-C'的两个二面角φ、φ'。通过使用各种原子之间最小接触距离的某些标准，已经计算出了角N-αC-C'（τ）的三个值（即非甘氨酰残基为105、110和115度，甘氨酰残基为110和115度）下允许的（φ，φ'）角度。将该理论与关于简单（二肽和三肽）、环肽、多肽和蛋白质结构的所有现有晶体学数据（截至1965年初）进行了比较，观察到的数据充分支持了理论得出的结论。还讨论了γ碳原子在其三个可能位置的影响，发现其仅略微改变了（φ，φ'）允许区域的外部界限。本文包含了对这些结构的已发表X射线衍射数据的详尽参考文献。
