Biocomputing Unit, National Center for Biotechnology (CSIC), Darwin 3, Campus Univ. Autónoma de Madrid, Cantoblanco, 28049, Madrid, Spain.
Univ. Autónoma de Madrid, Campus Univ. Autónoma de Madrid, Cantoblanco, 28049, Madrid, Spain.
Nat Commun. 2021 Jan 4;12(1):42. doi: 10.1038/s41467-020-20295-w.
In recent years, advances in cryoEM have dramatically increased the resolution of reconstructions and, with it, the number of solved atomic models. It is widely accepted that the quality of cryoEM maps varies locally; therefore, the evaluation of the maps-derived structural models must be done locally as well. In this article, a method for the local analysis of the map-to-model fit is presented. The algorithm uses a comparison of two local resolution maps. The first is the local FSC (Fourier shell correlation) between the full map and the model, while the second is calculated between the half maps normally used in typical single particle analysis workflows. We call the quality measure "FSC-Q", and it is a quantitative estimation of how much of the model is supported by the signal content of the map. Furthermore, we show that FSC-Q may be helpful to detect overfitting. It can be used to complement other methods, such as the Q-score method that estimates the resolvability of atoms.
近年来，冷冻电镜技术的进步极大地提高了重构的分辨率，相应地，解决原子模型的数量也有所增加。人们普遍认为，冷冻电镜图谱的质量在局部上存在差异；因此，对图谱衍生的结构模型的评估也必须在局部进行。本文提出了一种用于图谱与模型拟合的局部分析方法。该算法使用了两个局部分辨率图谱的比较。第一个是全图谱与模型之间的局部傅里叶壳相关（Fourier shell correlation，FSC），而第二个是在典型的单颗粒分析工作流程中通常使用的半图谱之间的计算。我们称之为“FSC-Q”的质量度量，它是对模型有多少部分由图谱的信号内容支持的定量估计。此外，我们还表明，FSC-Q 可能有助于检测过拟合。它可以用于补充其他方法，如估计原子分辨率的 Q 分数方法。
