Abstract：
Electron crystallography of two-dimensional (2D) crystals determines the structure of membrane proteins in the lipid bilayer by imaging with cryo-electron microscopy and image processing. Membrane proteins can be packed in regular 2D arrays by their reconstitution in the presence of lipids at low lipid to protein weight-to-weight ratio. The crystal quality depends on the protein purity and homogeneity, its stability, and on the crystallization conditions. A 2D crystal presents the membrane protein in a functional and fully lipidated state. Electron crystallography determines the 3D structure even of small membrane proteins up to atomic resolution, but 3D density maps have a better resolution in the membrane plane than in the vertical direction. This problem can be partly eliminated by applying an iterative algorithm that exploits additional known constraints about the 2D crystal. 2D electron crystallography is particularly attractive for the structural analysis of membrane proteins that are too small for single particle analyses and too unstable to form 3D crystals. With the recent introduction of direct electron detector cameras, the routine determination of the atomic 3D structure of membrane-embedded membrane proteins is in reach.
摘要：
二维（2D）晶体的电子晶体学通过低温电子显微镜和图像处理成像来确定脂质双层中膜蛋白的结构。膜蛋白可以通过在低脂质与蛋白质重量比的脂质存在下重建而被包装在规则的2D阵列中。晶体质量取决于蛋白质的纯度和均匀性，其稳定性,和结晶条件。2D晶体呈现功能和完全脂化状态的膜蛋白。电子晶体学甚至可以确定原子分辨率的小膜蛋白的3D结构，但是3D密度图在膜平面上比在垂直方向上具有更好的分辨率。通过应用利用关于2D晶体的附加已知约束的迭代算法,可以部分地消除该问题。2D电子晶体学对于膜蛋白的结构分析特别有吸引力，膜蛋白对于单颗粒分析而言太小，并且太不稳定而无法形成3D晶体。随着最近直接电子探测器相机的推出，可以实现对嵌入膜的膜蛋白的原子3D结构的常规测定。
