Macromolecular Crystallography Research with Synchrotron Radiation

利用半胱氨酸和蛋氨酸残基的硫原子或核酸中固有存在的磷原子提供的非常小的异常衍射信号，可以成功地用于解决蛋白质的晶体结构。这种方法部分是由我们首创的，目前正越来越受欢迎，并成为大分子结晶学实践中的常规技术。用寡核苷酸和寡肽晶体的同步辐射测量了0.6-0.8埃范围内极高分辨率的衍射数据，改进后的模型揭示了所研究分子前所未有的结构细节，包括原子之间sigma键的电子密度。在这种结构中观察到的非常精细的特征将有助于改进用于较低分辨率的蛋白质晶体结构的常规精炼的立体化学库。我们参与了多个生物重要蛋白质的合作结构项目，如用作生物标志物的荧光蛋白、人线粒体螺旋酶、根瘤菌岩藻糖基转移酶和植物S-腺苷-同型半胱氨酸水解酶。我们对大分子晶体的X射线辐射损伤效应进行了准确的评估，并确定了可接受的吸收剂量限值为7mGy.

Utilization of a very small anomalous diffraction signal provided by sulfur atoms of the cysteine and methionine residues or by phosphorus atoms of nucleic acids, intrinsically present in all proteins or RNA/DNA can be successfully used to solve crystal structures of proteins. This approach, in part pioneered by us, is currently gaining increasing popularity and becomes a routine technique in the practice of macromolecular crystallography. The diffraction data to extremely high resolution in the range of 0.6-0.8 angstrom were measured using synchrotron radiation from crystals of oligonucleotides and oligopeptides, and the refined models revealeed the unprecedented structural details of the investigated molecules including electron densities at the sigma bonds between atoms. The observed very fine features in this structures will serve to improve the stereochemical libraries used for routine refinement of protein crystal structures at lower resolution. We participated in several collaborative structural projects on various biologically important proteins, such as fluorescenty proteins used as biomarkers, human mitochindrial helicase, rhizobium fucosyltransferase and plant S-adenosyl-homocysteine hydrolase. We performed the accurate evaluation of the effects of X-ray radiation damage incurred in macromolecular crystals and established the limit of acceptable absorption dose at 7 MGy.