IMPROVEMENT OF MACROMOLECULAR ELECTRON-DENSITY MAPS BY THE SIMULTANEOUS APPLICATION OF REAL AND RECIPROCAL SPACE CONSTRAINTS
IMPROVEMENT OF MACROMOLECULAR ELECTRON-DENSITY MAPS BY THE SIMULTANEOUS APPLICATION OF REAL AND RECIPROCAL SPACE CONSTRAINTS
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DOI：
10.1107/s0907444992007698
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发表时间：
1993-01-01
期刊：
影响因子：
--
通讯作者：
MAIN, P
中科院分区：
文献类型：
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作者：
COWTAN, KD;MAIN, P
本文提出了一种综合利用真实的和倒易空间的信息来改进电子密度图的一般方案。该方案中塞尔方程、溶剂平坦化和直方图匹配的使用已在前面描述[Main（1990）. Acta Cryst.A46，372-377]。现在增加了非晶体学对称平均、部分结构的使用和对单个结构因子的约束。一个计算机程序，SQUASH，描述了同时适用于所有这些约束。它的应用地图的几个结构已成功，特别是当非晶体对称性。无法解释的地图已经改进到可以识别大量结构的程度。同时应用这些约束比依次应用它们更强大。
A general scheme for the improvement ot electron-density maps is described which combines information from real and reciprocal space. The use of Sayre's equation, solvent flattening and histogram matching within this scheme has been described previously [Main (1990). Acta Cryst. A46, 372-377]. Non-crystallographic symmetry averaging, the use of a partial structure and constraints on individual structure factors have now been added. A computer program, SQUASH, is described which applies all these constraints simultaneously. Its application to the maps of several structures has been successful, particularly so when non-crystallographic symmetry is present. Uninterpretable maps have been improved to the point where a significant amount of the structure can be recognized. Applying the constraints simultaneously is more powerful than applying them all in series.