IMPROVED FOURIER COEFFICIENTS FOR MAPS USING PHASES FROM PARTIAL STRUCTURES WITH ERRORS
IMPROVED FOURIER COEFFICIENTS FOR MAPS USING PHASES FROM PARTIAL STRUCTURES WITH ERRORS
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DOI：
10.1107/s0108767386099622
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发表时间：
1986-05-01
期刊：
影响因子：
--
通讯作者：
READ, RJ
中科院分区：
文献类型：
--
作者：
READ, RJ
大分子的未精制或部分精制模型通常是不完整的，并且通常具有大的坐标误差。结果表明，相位概率方程适合于一个完美的部分结构，导致不准确的相位概率估计在这种情况下。因此，有必要使用已经导出的方程，该方程允许部分结构中的误差。给出了一种由观测和计算的结构因子幅值估计这些相位概率表达式中参数σA的方法。从σA随分辨率的变化，可以估计模型的平均坐标误差。使用部分结构相位计算的电子密度图偏向于部分结构。当存在坐标误差时，给出了非中心傅里叶系数[（2 m| FN|- D| FCP|）exp（iαcP）]来抑制该模型偏差。从电子密度图与正确结构图和部分结构图的相关系数来看，本文导出的傅里叶系数比目前使用的其它傅里叶系数好上级。
Unrefined or partially refined models of macromolecules are generally incomplete and typically have large coordinate errors. It is shown that phase probability equations appropriate for a perfect partial structure lead to inaccurate estimates of phase probabilities in such cases. Therefore, it is necessary to use equations that have been derived allowing for errors in the partial structure. A method is given to estimate the parameter σA in these phase probability expressions from the observed and calculated structure factor amplitudes. From the variation of σA with resolution, one can estimate the mean coordinate error for the model. Electron density maps calculated using partial structure phases are biased towards the partial structure. When there are coordinate errors, a new expression for the non-centric Fourier coefficients [(2m|FN| - D|FcP|) exp(iαcP)] is required to suppress this model bias. Judged by correlation coefficients comparing electron density maps with the correct and the partial structure maps, the Fourier coefficients derived here are superior to others currently in use.