title: Investigation of possible free-radical scavengers and metrics for radiation damage in protein cryocrystallography.
abstract: The introduction of highly intense wiggler and undulator beamlines has reintroduced the problem of X-ray radiation damage in protein crystals even at cryogenic temperatures. Several metrics for monitoring radiation damage are considered and unit-cell volume expansion is systematically investigated using crystals of three different types, but it is found to be too variable to be a useful metric. Radical scavengers of secondary radiation damage are investigated as possible mitigating agents. Styrene is found to be ineffective. A method of spectroscopically measuring the radiation damage with a microspectrophotometer was used and, in conjunction with crystallographic data, provided tentative but suggestive evidence for the efficacy of ascorbate as a free-radical scavenging agent in cryocooled hen egg-white lysozyme crystals.
authors.affiliation: Laboratory of Molecular Biophysics, Department of Biochemistry, Oxford University, Rex Richards Building, South Parks Road, Oxford OX1 3QU, UK.
authors.forename: James
authors.initials: J
authors.lastname: Murray
authors.forename: Elspeth
authors.initials: E
authors.lastname: Garman
mesh_terms: D000818:Animals; D018360:Crystallography, X-Ray; D004527:Egg Proteins / Q000737:chemistry* / Q000528:radiation effects*; D016166:Free Radical Scavengers / Q000528:radiation effects*; D006801:Humans; D008795:Metronidazole / Q000737:chemistry* / Q000528:radiation effects*; D009113:Muramidase / Q000528:radiation effects; D011487:Protein Conformation / Q000528:radiation effects; D011832:Radiation Injuries / Q000209:etiology*; D014961:X-Ray Diffraction
chemical_list: D004527:Egg Proteins; D016166:Free Radical Scavengers; D008795:Metronidazole; D009113:Muramidase