Hooft R W, Sander C, Vriend G
EMBL, Heidelberg, Germany.
Comput Appl Biosci. 1997 Aug;13(4):425-30. doi: 10.1093/bioinformatics/13.4.425.
Statistical methods that compare observed and expected distributions of experimental observables provide powerful tools for the quality control of protein structures. The distribution of backbone dihedral angles ('Ramachandran plot') has often been used for such quality control, but without a firm statistical foundation.
A new and-simple method is presented for judging the quality of a protein structure based on the distribution of backbone dihedral angles. Inputs to the method are 60 torsion angle distributions extracted from protein structures solved at high resolution; one for each combination of residue type and tri-state secondary structure. Output for a protein is a Ramachandran Z-score, expressing the quality of the Ramachandran plot relative to current state-of-the-art structures.
比较实验观测值的观测分布和预期分布的统计方法为蛋白质结构的质量控制提供了强大工具。主链二面角的分布（“拉氏图”）常被用于此类质量控制，但缺乏坚实的统计基础。
提出了一种基于主链二面角分布判断蛋白质结构质量的新的简单方法。该方法的输入是从高分辨率解析的蛋白质结构中提取的60个扭转角分布；每种残基类型和三态二级结构的组合各一个。蛋白质的输出是一个拉氏Z分数，表达了相对于当前最先进结构的拉氏图的质量。
