title: Parameters affecting the X-ray dose absorbed by macromolecular crystals.
abstract: 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.
authors.affiliation: Laboratory of Molecular Biophysics, Department of Biochemistry, Oxford University, Rex Richards Building, UK.
authors.forename: James W
authors.initials: JW
authors.lastname: Murray
authors.forename: Enrique
authors.initials: E
authors.lastname: Rudiño-Piñera
authors.forename: Robin Leslie
authors.initials: RL
authors.lastname: Owen
authors.forename: Martin
authors.initials: M
authors.lastname: Grininger
authors.forename: Raimond B G
authors.initials: RB
authors.lastname: Ravelli
authors.forename: Elspeth F
authors.initials: EF
authors.lastname: Garman
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry / Q000528:radiation effects; D001426:Bacterial Proteins / Q000737:chemistry / Q000528:radiation effects; D002868:Chromosomal Proteins, Non-Histone; D003460:Crystallization; D005615:Freezing; D046911:Macromolecular Substances / Q000737:chemistry* / Q000528:radiation effects*; D011487:Protein Conformation / Q000528:radiation effects; D011506:Proteins / Q000737:chemistry* / Q000528:radiation effects*; D014157:Transcription Factors; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; D002868:Chromosomal Proteins, Non-Histone; D046911:Macromolecular Substances; D011506:Proteins; D014157:Transcription Factors