Department of Biophysical Structural Chemistry, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands.
Ultramicroscopy. 2010 Mar;110(4):350-8. doi: 10.1016/j.ultramic.2010.01.011. Epub 2010 Feb 1.
The typical resolution of three-dimensional reconstruction by cryo-EM single particle analysis is now being pushed up to and beyond the nanometer scale. Correction of the contrast transfer function (CTF) of electron microscopic images is essential for achieving such a high resolution. Various correction methods exist and are employed in popular reconstruction software packages. Here, we present a novel approximation method that corrects the amplitude modulation introduced by the contrast transfer function by convoluting the images with a piecewise continuous function. Our new approach can easily be implemented and incorporated into other packages. The implemented method yielded higher resolution reconstructions with data sets from both highly symmetric and asymmetric structures. It is an efficient alternative correction method that allows quick convergence of the 3D reconstruction and has a high tolerance for noisy images, thus easing a bottleneck in practical reconstruction of macromolecules.
目前，冷冻电镜单颗粒分析的三维重构的典型分辨率正在被推向纳米级及以上。为了实现如此高的分辨率，必须校正电子显微镜图像的对比传递函数（CTF）。目前存在多种校正方法，并应用于流行的重构软件包中。在这里，我们提出了一种新的近似方法，通过用分段连续函数卷积图像来校正对比传递函数引入的幅度调制。我们的新方法易于实现，并可以集成到其他包中。该方法应用于来自高度对称和非对称结构的数据集，可实现更高分辨率的重构。它是一种有效的替代校正方法，可以快速收敛三维重构，并且对噪声图像具有高容忍度，从而缓解了大分子实际重构中的瓶颈问题。
