Fourier amplitude decay of electron cryomicroscopic images of single particles and effects on structure determination
Fourier amplitude decay of electron cryomicroscopic images of single particles and effects on structure determination
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DOI：
10.1006/jsbi.2001.4330
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发表时间：
2001-01-01
影响因子：
3
通讯作者：
Chiu, W
中科院分区：
文献类型：
--
作者：
Saad, A;Ludtke, SJ;Chiu, W
电子显微镜的空间和时间连贯性，标本运动，记录介质和扫描仪光学元件的几个因素有助于电子图像强度测得的傅立叶振幅的衰减。我们将这些因子的组合近似为单个高斯的包膜函数，其宽度由单个实验B因子描述，我们提出了一种改进的方法，可以通过结合X射线的使用来估算单个显微照片的B-因子。溶液散射和数值拟合粒子图像的平均功率谱。使用了200多个单纯疱疹病毒1型衣壳的统计估计来估计数据集的实验B因子中的扩散。实验表明，B因子取决于显微镜的客观镜头散焦设置。平均B因子，样品的X射线散射强度以及确定较低分辨率的结构所需的颗粒数，可用于估计延伸所需的颗粒数量的最小倍数增加单个粒子重建为指定的较高分辨率。我们得出的结论是，显微镜和成像改进以减少实验B因子对于获得原子分辨率结构至关重要。 （c）2001学术出版社。
Several factors, including spatial and temporal coherence of the electron microscope, specimen movement, recording medium, and scanner optics, contribute to the decay of the measured Fourier amplitude in electron image intensities. We approximate the combination of these factors as a single Gaussian envelope function, the width of which is described by a single experimental B-factor, We present an improved method for estimating this B-factor from individual micrographs by combining the use of X-ray solution scattering and numerical fitting to the average power spectrum of particle images. A statistical estimation from over 200 micrographs of herpes simplex virus type-1 capsids was used to estimate the spread in the experimental B-factor of the data set. The B-factor is experimentally shown to be dependent on the objective lens defocus setting of the microscope. The average B-factor, the X-ray scattering intensity of the specimen, and the number of particles required to determine the structure at a lower resolution can be used to estimate the minimum fold increase in the number of particles that would be required to extend a single particle reconstruction to a specified higher resolution. We conclude that microscope and imaging improvements to reduce the experimental B-factor will be critical for obtaining an atomic resolution structure. (C) 2001 Academic Press.