title: Quantifying X-ray radiation damage in protein crystals at cryogenic temperatures.
abstract: The dependence of radiation damage to protein crystals at cryogenic temperatures upon the X-ray absorption cross-section of the crystal has been examined. Lysozyme crystals containing varying heavy-atom concentrations were irradiated and diffraction patterns were recorded as a function of the total number of incident photons. An experimental protocol and a coefficient of sensitivity to absorbed dose, proportional to the change in relative isotropic B factor, are defined that together yield a sensitive and robust measure of damage. Radiation damage per incident photon increases linearly with the absorption coefficient of the crystal, but damage per absorbed photon is the same for all heavy-atom concentrations. Similar damage per absorbed photon is observed for crystals of three proteins with different molecular sizes and solvent contents.
authors.affiliation: Physics Department, Cornell University, Ithaca, NY 14853, USA. kmetkoj@kenyon.edu
authors.forename: Jan
authors.initials: J
authors.lastname: Kmetko
authors.forename: Naji S
authors.initials: NS
authors.lastname: Husseini
authors.forename: Matthew
authors.initials: M
authors.lastname: Naides
authors.forename: Yevgeniy
authors.initials: Y
authors.lastname: Kalinin
authors.forename: Robert E
authors.initials: RE
authors.lastname: Thorne
mesh_terms: D000042:Absorption; D003080:Cold Temperature; D003460:Crystallization; D018360:Crystallography, X-Ray; D004307:Dose-Response Relationship, Radiation; D007454:Iodides / Q000737:chemistry; D015233:Models, Statistical; D009113:Muramidase / Q000737:chemistry; D017785:Photons; D011506:Proteins / Q000737:chemistry* / Q000528:radiation effects*; D012680:Sensitivity and Specificity; D012997:Solvents / Q000737:chemistry; D013696:Temperature; D014961:X-Ray Diffraction; D014965:X-Rays
chemical_list: D007454:Iodides; D011506:Proteins; D012997:Solvents; D009113:Muramidase