title: X-ray diffraction in temporally and spatially resolved biomolecular science.
abstract: Time-resolved Laue protein crystallography at the European Synchrotron Radiation Facility (ESRF) opened up the field of sub-nanosecond protein crystal structure analyses. There are a limited number of such time-resolved studies in the literature. Why is this? The X-ray laser now gives us femtosecond (fs) duration pulses, typically 10 fs up to ∼50 fs. Their use is attractive for the fastest time-resolved protein crystallography studies. It has been proposed that single molecules could even be studied with the advantage of being able to measure X-ray diffraction from a 'crystal lattice free' single molecule, with or without temporal resolved structural changes. This is altogether very challenging R&D. So as to assist this effort we have undertaken studies of metal clusters that bind to proteins, both 'fresh' and after repeated X-ray irradiation to assess their X-ray-photo-dynamics, namely Ta6Br12, K2PtI6 and K2PtBr6 bound to a test protein, hen egg white lysozyme. These metal complexes have the major advantage of being very recognisable shapes (pseudo spherical or octahedral) and thereby offer a start to (probably very difficult) single molecule electron density map interpretations, both static and dynamic. A further approach is to investigate the X-ray laser beam diffraction strength of a well scattering nano-cluster; an example from nature being the iron containing ferritin. Electron crystallography and single particle electron microscopy imaging offers alternatives to X-ray structural studies; our structural studies of crustacyanin, a 320 kDa protein carotenoid complex, can be extended either by electron based techniques or with the X-ray laser representing a fascinating range of options. General outlook remarks concerning X-ray, electron and neutron macromolecular crystallography as well as 'NMR crystallography' conclude the article.
authors.affiliation: School of Chemistry, University of Manchester M13 9PL, UK. john.helliwell@manchester.ac.uk.
authors.forename: John R
authors.initials: JR
authors.lastname: Helliwell
authors.forename: Alice
authors.initials: A
authors.lastname: Brink
authors.forename: Surasak
authors.initials: S
authors.lastname: Kaenket
authors.forename: Victoria Laurina
authors.initials: VL
authors.lastname: Starkey
authors.forename: Simon W M
authors.initials: SW
authors.lastname: Tanley
mesh_terms: D001965:Bromides / Q000737:chemistry*; D002338:Carotenoids / Q000737:chemistry; D002352:Carrier Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004583:Electrons; D005293:Ferritins / Q000737:chemistry*; D054018:Lasers, Excimer; D008027:Light; D008854:Microscopy, Electron; D009113:Muramidase / Q000737:chemistry*; D017671:Platinum Compounds / Q000737:chemistry*; D017356:Synchrotrons; D013635:Tantalum / Q000737:chemistry*; D013997:Time Factors; D014961:X-Ray Diffraction
chemical_list: D001965:Bromides; D002352:Carrier Proteins; D017671:Platinum Compounds; C018494:crustacyanins; C107153:tantalum bromide; D002338:Carotenoids; D013635:Tantalum; D005293:Ferritins; C421864:hen egg lysozyme; D009113:Muramidase