Cowtan Kevin
Department of Chemistry, University of York, Heslington, York YO10 5DD, England.
Acta Crystallogr D Biol Crystallogr. 2010 Apr;66(Pt 4):470-8. doi: 10.1107/S090744490903947X. Epub 2010 Mar 24.
Classical density-modification techniques (as opposed to statistical approaches) offer a computationally cheap method for improving phase estimates in order to provide a good electron-density map for model building. The rise of statistical methods has lead to a shift in focus away from the classical approaches; as a result, some recent developments have not made their way into classical density-modification software. This paper describes the application of some recent techniques, including most importantly the use of prior phase information in the likelihood estimation of phase errors within a classical density-modification framework. The resulting software gives significantly better results than comparable classical methods, while remaining nearly two orders of magnitude faster than statistical methods.
经典的密度修正技术（与统计方法相对）提供了一种计算成本较低的方法，用于改进相位估计，以便为模型构建提供良好的电子密度图。统计方法的兴起导致研究重点从经典方法上转移；因此，一些最新进展尚未融入经典密度修正软件中。本文描述了一些最新技术的应用，其中最重要的是在经典密度修正框架内，将先验相位信息用于相位误差的似然估计。由此产生的软件比同类经典方法给出的结果要好得多，同时比统计方法快近两个数量级。
