Mukherjee M, Ghosh S, Woolfson M M
Department of Solid State Physics, Indian Association for the Cultivation of Science, Calcutta 70032, India.
Acta Crystallogr D Biol Crystallogr. 1999 Jan;55(Pt 1):168-72. doi: 10.1107/S0907444998006374. Epub 1999 Jan 1.
The direct-methods program MULTAN88 has been applied to a known protein, ribonuclease (RNAP1), containing 808 non-H atoms, including five S atoms, plus 83 ordered solvent water molecules. Phase sets with mean phase errors between 69 and 75 degrees were selected by modified figures of merit for trials with the full data at 1.17 A resolution and also with restricted data at 1.25 and 1.5 A resolution. These figures of merit had previously only been applied to protein structures containing heavy atoms, and this is the first demonstration of their usefulness with no heavy atom present. An initial set of 1091 phases from a 1.17 A trial was developed by an objective procedure to give the full structure with a residual of 0. 21, which agrees well with the published structure.
直接法程序MULTAN88已应用于一种已知蛋白质——核糖核酸酶（RNAP1），它含有808个非氢原子，包括5个硫原子，外加83个有序溶剂水分子。通过修正优值选择平均相位误差在69至75度之间的相位集，用于在1.17埃分辨率下使用完整数据以及在1.25和1.5埃分辨率下使用受限数据的试验。这些优值此前仅应用于含有重原子的蛋白质结构，这是首次证明在不存在重原子的情况下它们的实用性。通过一个客观程序从1.17埃分辨率的试验中得到了一组初始的1091个相位，以给出残余值为0.21的完整结构，这与已发表的结构吻合良好。
