Murshudov G N, Vagin A A, Lebedev A, Wilson K S, Dodson E J
Chemistry Department, University of York, Heslington, York YO1 5DD, England and CLRC, Daresbury Laboratory, Daresbury, Warrington WA4 4AD,
Acta Crystallogr D Biol Crystallogr. 1999 Jan;55(Pt 1):247-55. doi: 10.1107/S090744499801405X. Epub 1999 Jan 1.
This paper gives the equations for the use of fast Fourier transformations in individual atomic anisotropic refinement. Restraints on bonded atoms, on the sphericity of each atom and between non-crystallographic symmetry related atoms are described. These have been implemented in the program REFMAC and its performance with several examples is analysed. All the tests show that anisotropic refinement not only reduces the R value and Rfree but also improves the fit to geometric targets, indicating that this parameterization is valuable for improving models derived from experimental data. The computer time taken is comparable to that for isotropic refinements.
本文给出了在单个原子各向异性精修中使用快速傅里叶变换的方程。描述了对成键原子、每个原子的球形度以及非晶体学对称相关原子之间的约束。这些已在REFMAC程序中实现，并分析了其在几个示例中的性能。所有测试表明，各向异性精修不仅降低了R值和Rfree值，还改善了与几何目标的拟合度，表明这种参数化对于改进从实验数据导出的模型很有价值。所花费的计算机时间与各向同性精修相当。
