Murray James W, Rudiño-Piñera Enrique, Owen Robin Leslie, Grininger Martin, Ravelli Raimond B G, Garman Elspeth F
Laboratory of Molecular Biophysics, Department of Biochemistry, Oxford University, Rex Richards Building, UK.
J Synchrotron Radiat. 2005 May;12(Pt 3):268-75. doi: 10.1107/S0909049505003262. Epub 2005 Apr 14.
The lifetime of a macromolecular crystal in an X-ray beam is assumed to be limited by the absorbed dose. This dose, expressed in Gray (Gy = J kg(-1)), is a function of a number of parameters: the absorption coefficients of the constituent atoms of the crystal, the number of molecules per asymmetric unit, the beam energy, flux, size and profile, the crystal size, and the total irradiation time. The effects of these variables on the predicted absorbed dose, calculated using the program RADDOSE, are discussed and are illustrated with reference to the irradiation of a selenomethionine protein crystal of unknown structure. The results of RADDOSE can and will in the future be used to inform the data collection procedure as it sets a theoretical upper limit on the total exposure time at a certain X-ray source. However, as illustrated with an example for which the experimental data are compared with prediction, the actual lifetime of a crystal could become shorter in those cases where specific damage breaks down crucial crystal contacts.
大分子晶体在X射线束中的寿命被认为受吸收剂量的限制。该剂量以格雷表示（Gy = J kg(-1)），是多个参数的函数：晶体组成原子的吸收系数、每个不对称单元中的分子数、束流能量、通量、尺寸和轮廓、晶体尺寸以及总照射时间。讨论了这些变量对使用RADDOSE程序计算的预测吸收剂量的影响，并以对结构未知的硒代蛋氨酸蛋白质晶体的照射为例进行说明。RADDOSE的结果现在以及将来都可用于指导数据收集过程，因为它设定了在特定X射线源下总曝光时间的理论上限。然而，正如通过将实验数据与预测进行比较的示例所示，在特定损伤破坏关键晶体接触的情况下，晶体的实际寿命可能会变短。
