Defocus-dependent Thon-ring fading.
Defocus-dependent Thon-ring fading.
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DOI：
10.1016/j.ultramic.2021.113213
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发表时间：
2021-03
期刊：
影响因子：
2.2
通讯作者：
Russo CJ
中科院分区：
文献类型：
--
作者：
Glaeser RM;Hagen WJH;Han BG;Henderson R;McMullan G;Russo CJ
现代肖特基场发射枪的亮度可以产生具有非常高的空间相干性的电子束，特别是用于结构生物学中的单粒子电子冷冻显微镜的弱照明条件。即便如此，许多用户已经观察到散焦相关的Thon环衰落，这导致他们将他们的数据收集策略限制为具有相对小的散焦值的成像。在本文中，我们再现离焦相关的托恩环衰落的观察，并产生定量分析和明确的解释其原因。我们证明，一个主要的原因是离域的高分辨率傅立叶分量以外的领域的相机。我们还表明，正确表征的现象，重要的是要进行校正的线性放大各向异性。即使各向异性非常小，在对通村环进行圆形平均之前，它也会出现在所有散焦值处，在合并来自许多方向的粒子的数据之前也是如此。在本文中使用的条件下，这是典型的单粒子电子低温显微镜中使用的那些，由于源相干性的通村环的衰落是可以忽略不计的。主要结论是，可以使用比目前认为可能的更高的散焦值来记录图像，记住上述傅立叶分量的离域最终将成为限制。这种增加的理解应该给电子显微镜的信心，使用更高的散焦量，以允许，例如，更好的可见性，他们的粒子和埃瓦尔德球校正。
The brightness of modern Schottky field-emission guns can produce electron beams that have very high spatial coherence, especially for the weak-illumination conditions that are used for single-particle electron cryo-microscopy in structural biology. Even so, many users have observed defocus-dependent Thon-ring fading that has led them to restrict their data collection strategy to imaging with relatively small defocus values. In this paper, we reproduce the observation of defocus-dependent Thon-ring fading and produce a quantitative analysis and clear explanation of its causes. We demonstrate that a major cause is the delocalization of high-resolution Fourier components outside the field of view of the camera. We also show that, to correctly characterize the phenomenon, it is important to make a correction for linear magnification anisotropy. Even when the anisotropy is quite small, it is present at all defocus values before circular averaging of the Thon rings, as is also true before merging data from particles in many orientations. Under the conditions used in this paper, which are typical of those used in single-particle electron cryomicroscopy, fading of the Thon rings due to source coherence is negligible. The principal conclusion is that much higher values of defocus can be used to record images than is currently thought to be possible, keeping in mind that the above-mentioned delocalization of Fourier components will ultimately become a limitation. This increased understanding should give electron microscopists the confidence to use higher amounts of defocus to allow, for example, better visibility of their particles and Ewald sphere correction.
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影响因子：
3
作者：
Crowther, RA;Henderson, R;Smith, JM
通讯作者：
Smith, JM
使用冷冻电子叠层成像技术对生物样本进行低剂量相检索
影响因子：
16.6
作者：
Zhou, Liqi;Song, Jingdong;Wang, Peng
通讯作者：
Wang, Peng
影响因子：
3
作者：
Glaeser RM;Typke D;Tiemeijer PC;Pulokas J;Cheng A
通讯作者：
Cheng A
影响因子：
64.5
作者：
Cheng Y
通讯作者：
Cheng Y
影响因子：
2.2
作者：
Russo CJ;Henderson R
通讯作者：
Henderson R