The positions of hydrogen atoms significantly define protein functions. However, such information from protein crystals is easily disturbed by X-rays. The damage can not be prevented completely even in the data collection at cryogenic temperatures. Therefore, the influence of X-rays should be precisely estimated in order to derive meaningful information from the crystallographic results. Diffraction data from a single crystal of the high-potential iron-sulfur protein (HiPIP) from Thermochromatium tepidum were collected at an undulator beamline of a third generation synchrotron facility, and were merged into three data sets according to X-ray dose. A series of structures analyzed at 0.70A shows detailed views of the X-ray induced perturbation, such as the positional changes of hydrogen atoms of a water molecule. Based on the results, we successfully collected a low perturbation data set using attenuated X-rays. There was no influence on the crystallographic statistics, such as the relative B factors, during the course of data collection. The electron densities for hydrogen atoms were more clear despite the slightly lower resolution.
Detailed assessment of X-ray induced structural perturbation in a crystalline state protein.,Takeda K, Kusumoto K, Hirano Y, Miki K J Struct Biol. 2010 Feb;169(2):135-44. Epub 2009 Sep 24. PMID:19782139
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↑ Takeda K, Kusumoto K, Hirano Y, Miki K. Detailed assessment of X-ray induced structural perturbation in a crystalline state protein. J Struct Biol. 2010 Feb;169(2):135-44. Epub 2009 Sep 24. PMID:19782139 doi:10.1016/j.jsb.2009.09.012