Leiros H K, McSweeney S M, Smalås A O
Protein Crystallography Group, Department of Chemistry, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway.
Acta Crystallogr D Biol Crystallogr. 2001 Apr;57(Pt 4):488-97. doi: 10.1107/s0907444901000646.
Radiation damage is an inherent problem in protein X-ray crystallography and the process has recently been shown to be highly specific, exhibiting features such as cleavage of disulfide bonds, decarboxylation of acidic residues, increase in atomic B factors and increase in unit-cell volume. Reported here are two trypsin structures at atomic resolution (1.00 and 0.95 A), the data for which were collected at a third-generation synchrotron (ESRF) at two different beamlines. Both trypsin structures exhibit broken disulfide bonds; in particular, the bond from Cys191 to Cys220 is very sensitive to synchrotron radiation. The data set collected at the most intense beamline (ID14-EH4) shows increased structural radiation damage in terms of lower occupancies for cysteine residues, more breakage in the six disulfide bonds and more alternate conformations. It appears that high intensity and not only the total X-ray dose is most harmful to protein crystals.
辐射损伤是蛋白质X射线晶体学中一个固有的问题，最近的研究表明这个过程具有高度特异性，表现出诸如二硫键断裂、酸性残基脱羧、原子B因子增加以及晶胞体积增大等特征。本文报道了两个原子分辨率（1.00和0.95埃）的胰蛋白酶结构，其数据是在第三代同步加速器（欧洲同步辐射装置）的两条不同光束线上收集的。两个胰蛋白酶结构均显示出二硫键断裂；特别是，从半胱氨酸191到半胱氨酸220的键对同步辐射非常敏感。在最强光束线（ID14-EH4）收集的数据集显示，就半胱氨酸残基占有率降低、六个二硫键更多断裂以及更多交替构象而言，结构辐射损伤增加。看来高强度而非仅仅是总X射线剂量对蛋白质晶体最具危害性。
