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Abstract：
This paper describes various components of the macromolecular crystallographic refinement program REFMAC5, which is distributed as part of the CCP4 suite. REFMAC5 utilizes different likelihood functions depending on the diffraction data employed (amplitudes or intensities), the presence of twinning and the availability of SAD/SIRAS experimental diffraction data. To ensure chemical and structural integrity of the refined model, REFMAC5 offers several classes of restraints and choices of model parameterization. Reliable models at resolutions at least as low as 4 Å can be achieved thanks to low-resolution refinement tools such as secondary-structure restraints, restraints to known homologous structures, automatic global and local NCS restraints, `jelly-body\' restraints and the use of novel long-range restraints on atomic displacement parameters (ADPs) based on the Kullback-Leibler divergence. REFMAC5 additionally offers TLS parameterization and, when high-resolution data are available, fast refinement of anisotropic ADPs. Refinement in the presence of twinning is performed in a fully automated fashion. REFMAC5 is a flexible and highly optimized refinement package that is ideally suited for refinement across the entire resolution spectrum encountered in macromolecular crystallography.
摘要：
本文介绍了大分子晶体学细化程序REFMAC5的各种组件，该程序作为CCP4套件的一部分分发。REFMAC5根据所采用的衍射数据（振幅或强度）利用不同的似然函数，孪生的存在和SAD/SIRAS实验衍射数据的可用性。为了确保精制模型的化学和结构完整性，REFMAC5提供了几类约束和模型参数化的选择。借助诸如二级结构限制之类的低分辨率细化工具，可以实现分辨率至少低至4µ的可靠模型，对已知同源结构的限制，自动全局和局部NCS约束，“果冻体”约束和基于Kullback-Leibler散度对原子位移参数（ADP）的新型远程约束的使用。REFMAC5还提供TLS参数化，当高分辨率数据可用时，各向异性ADP的快速细化。在存在孪生的情况下以全自动方式进行细化。REFMAC5是一个灵活的和高度优化的细化包，非常适合在大分子晶体学中遇到的整个分辨率光谱的细化。
