title: Protein crystallography with a micrometre-sized synchrotron-radiation beam.
abstract: For the first time, protein microcrystallography has been performed with a focused synchrotron-radiation beam of 1 microm using a goniometer with a sub-micrometre sphere of confusion. The crystal structure of xylanase II has been determined with a flux density of about 3 x 10(10) photons s(-1) microm(-2) at the sample. Two sets of diffraction images collected from different sized crystals were shown to comprise data of good quality, which allowed a 1.5 A resolution xylanase II structure to be obtained. The main conclusion of this experiment is that a high-resolution diffraction pattern can be obtained from 20 microm(3) crystal volume, corresponding to about 2 x 10(8) unit cells. Despite the high irradiation dose in this case, it was possible to obtain an excellent high-resolution map and it could be concluded from the individual atomic B-factor patterns that there was no evidence of significant radiation damage. The photoelectron escape from a narrow diffraction channel is a possible reason for reduced radiation damage as indicated by Monte Carlo simulations. These results open many new opportunities in scanning protein microcrystallography and make random data collection from microcrystals a real possibility, therefore enabling structures to be solved from much smaller crystals than previously anticipated as long as the crystallites are well ordered.
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, England.
authors.forename: Rouslan
authors.initials: R
authors.lastname: Moukhametzianov
authors.forename: Manfred
authors.initials: M
authors.lastname: Burghammer
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Edwards
authors.forename: Sebastien
authors.initials: S
authors.lastname: Petitdemange
authors.forename: Dimitri
authors.initials: D
authors.lastname: Popov
authors.forename: Maikel
authors.initials: M
authors.lastname: Fransen
authors.forename: Gregory
authors.initials: G
authors.lastname: McMullan
authors.forename: Gebhard F X
authors.initials: GF
authors.lastname: Schertler
authors.forename: Christian
authors.initials: C
authors.lastname: Riekel
mesh_terms: D018360:Crystallography, X-Ray / Q000295:instrumentation / Q000379:methods; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D017356:Synchrotrons; D014995:Xylosidases / Q000737:chemistry
chemical_list: D011506:Proteins; D014995:Xylosidases