Yonekura K, Toyoshima C
Institute of Molecular and Cellular Biosciences, The University of Tokyo, Japan.
Ultramicroscopy. 2000 Jul;84(1-2):29-45. doi: 10.1016/s0304-3991(00)00008-5.
Solvent flattening is considered to be a principal means for improving the data quality in X-ray crystallography. It could be equally effective for tubular crystals of membrane proteins imaged by electron microscopy because of the large empty space inside the tubes. However, tubular crystals are difficult objects for solvent flattening due to lack of electron diffraction amplitudes. Therefore, solvent flattening was used to align images more accurately and to improve the completeness of the data by reducing contributions of noise in the solvent (+ lipid) region. The methods developed were tested with the tubular crystals of Ca2+-ATPase embedded in amorphous ice. The improvement of the data quality was remarkable when solvent flattening was applied to many individual images before averaging. In this way, noises contaminated in the protein region by contrast transfer function were removed effectively. Solvent flattening was far more powerful than simple averaging described in Part II of this series (K. Yonekura, C. Toyoshima, Ultramicroscopy 84 (2000) 15).
溶剂扁平化被认为是提高X射线晶体学数据质量的主要手段。由于管内存在较大的空隙，它对于通过电子显微镜成像的膜蛋白管状晶体同样有效。然而，由于缺乏电子衍射振幅，管状晶体对于溶剂扁平化来说是困难的对象。因此，溶剂扁平化被用于更精确地对齐图像，并通过减少溶剂（+脂质）区域中噪声的贡献来提高数据的完整性。所开发的方法用嵌入非晶冰中的Ca2+-ATP酶管状晶体进行了测试。在平均之前将溶剂扁平化应用于许多单独的图像时，数据质量有显著提高。通过这种方式，有效地去除了由对比度传递函数在蛋白质区域中污染的噪声。溶剂扁平化比本系列第二部分（K. Yonekura，C. Toyoshima，Ultramicroscopy 84 (2000) 15）中描述的简单平均要强大得多。
