Weak data do not make a free lunch, only a cheap meal
Weak data do not make a free lunch, only a cheap meal
复制标题
DOI：
10.1107/s1399004713026680
复制
发表时间：
2014-02-01
影响因子：
2.2
通讯作者：
Dauter, Zbigniew
中科院分区：
文献类型：
--
作者：
Luo, Zhipu;Rajashankar, Kanagalaghatta;Dauter, Zbigniew
四个数据集的处理分辨率明显超过传统上用于估计衍射数据分辨率极限的标准。对这些数据和相应模型质量指标的分析表明，过去广泛采用的分辨率限制标准可能有些保守。 R-merge和I/sigma(I)、光学分辨率以及相关系数CC1/2和CC*等各种参数可用于判断内部数据质量，而可靠性因子R和R-free以及最大似然目标值和实空间图相关系数可用于估计数据与细化模型之间的一致性。然而，这些标准都没有提供数据分辨率截止极限的可靠估计。分析表明，将最大分辨率扩展至当前采用的限制（即 I/sigma(I) 值降至 2.0）之外大约 0.2 埃不会降低精细结构模型的质量，但有时可能是有利的。这种延伸对于显着的各向异性衍射可能特别有利。就所需的工作而言，在数据收集和结构细化阶段扩展最大分辨率是便宜的，并且绝对比接受过于保守的分辨率截止更可取，不幸的是，这在蛋白质数据库中存放的晶体结构中非常常见。
Four data sets were processed at resolutions significantly exceeding the criteria traditionally used for estimating the diffraction data resolution limit. The analysis of these data and the corresponding model-quality indicators suggests that the criteria of resolution limits widely adopted in the past may be somewhat conservative. Various parameters, such as R-merge and I/sigma(I), optical resolution and the correlation coefficients CC1/2 and CC*, can be used for judging the internal data quality, whereas the reliability factors R and R-free as well as the maximum-likelihood target values and real-space map correlation coefficients can be used to estimate the agreement between the data and the refined model. However, none of these criteria provide a reliable estimate of the data resolution cutoff limit. The analysis suggests that extension of the maximum resolution by about 0.2 angstrom beyond the currently adopted limit where the I/sigma(I) value drops to 2.0 does not degrade the quality of the refined structural models, but may sometimes be advantageous. Such an extension may be particularly beneficial for significantly anisotropic diffraction. Extension of the maximum resolution at the stage of data collection and structure refinement is cheap in terms of the required effort and is definitely more advisable than accepting a too conservative resolution cutoff, which is unfortunately quite frequent among the crystal structures deposited in the Protein Data Bank.