A tilt-pair based method for assigning the projection directions of randomly oriented single-particle molecules
A tilt-pair based method for assigning the projection directions of randomly oriented single-particle molecules
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DOI：
10.1093/jmicro/dfv002
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发表时间：
2015-04-01
期刊：
影响因子：
1.8
通讯作者：
Kawasaki, Kazunori
中科院分区：
文献类型：
--
作者：
Ueno, Yutaka;Mine, Shouhei;Kawasaki, Kazunori
在本文中，我们描述了一种改进的方法，使用倾斜对图像来分配平均图像的投影角度，以便从随机定向的单粒子分子图像进行三维重建。我们的研究解决了单粒子重建中所谓的“初始体积问题”，其中涉及粒子图像投影角度的估计。将不同倾斜观察中颗粒的投影图像混合并平均以获得特征视图。在根据可靠倾斜角信息对这些组平均图像进行排序之后，根据构成倾斜对信息来分配图像之间的相互倾斜角。然后，制作并合并多个圆锥倾斜系列以构建粒子图像在投影角度方面的网络图，该网络图针对三维重建进行了优化。我们利用合成物体的图像开发了该方法，并将其应用于古细菌纯化脱乙酰酶的单粒子图像数据集。通过引入低角度倾斜观测来最大程度地减少由于倾斜而产生的不利成像条件，结果证明了合理的重建模型，而无需对结构强加对称性。该方法还指导用户区分分子不同构象状态的粒子图像。
In this article, we describe an improved method to assign the projection angle for averaged images using tilt-pair images for three-dimensional reconstructions from randomly oriented single-particle molecular images. Our study addressed the so-called 'initial volume problem' in the single-particle reconstruction, which involves estimation of projection angles of the particle images. The projected images of the particles in different tilt observations were mixed and averaged for the characteristic views. After the ranking of these group average images in terms of reliable tilt angle information, mutual tilt angles between images are assigned from the constituent tilt-pair information. Then, multiples of the conical tilt series are made and merged to construct a network graph of the particle images in terms of projection angles, which are optimized for the three-dimensional reconstruction. We developed the method with images of a synthetic object and applied it to a single-particle image data set of the purified deacetylase from archaea. With the introduction of low-angle tilt observations to minimize unfavorable imaging conditions due to tilting, the results demonstrated reasonable reconstruction models without imposing symmetry to the structure. This method also guides its users to discriminate particle images of different conformational state of the molecule.