Gwyndaf Evans is Principal Beamline Scientist for the Microfocus Macromolecular Crystallography beamline I24. The I24 beamline has been designed to address the challenging problems of membrane protein and multi-protein complex structure determination where crystals are typically very small and very weakly diffracting. His main interests are in the development of methods, instrumentation and software for the measurement and analysis of diffraction data. He previously worked within a crystallographic software development group in Cambridge, UK and prior to that, at the Advanced Photon Source in Chicago, USA. He is a visiting Fellow of the Department of Biochemistry at the University of Oxford.
Key Research Areas
Absorption corrections, microdiffraction, anomalous scattering
Current Research Interests
Integral to the measurement of precise diffraction data is a clear appreciation of all the sources of random and systematic errors contributing to measurement noise. My current research aims to identify significant sources of error and develop hardware or software solutions to reduce them.
Wes Armour, a Post Doctoral Research Assistant on I24, is carrying out one such development funded by CCP4 (Collaborative Computing Project number 4). The project aims to accurately determine and apply analytical absorption corrections to diffraction data from protein samples embedded in externally absorbing material such as protein crystal support loops.
We are developing new phosphor X-ray converters for CCD detectors which will have point spread functions (PSF) 10-20 times smaller than standard phosphor used in fibre-optic-coupled CCD detectors that typically have PSF's of ~150μm (FWHM). These converters will help in the measurement of diffraction data using X-ray microbeams and should significantly reduce the amount of unwanted background scatter measured together with the diffraction peak thereby reducing the measurement noise in the data.
The Diamond Membrane Protein Laboratory headed by So Iwata (Imperial College and Diamond) with support from Louise Johnson and Gwyndaf Evans has been funded by the Wellcome Trust as a facility for growing, crystallising and investigating membrane proteins. In addition the funds will support the development of technologies for improving the sample handling techniques for membrane proteins with a view to minimizing the accumulation of background scatter from the sample during a diffraction experiment. Also being developed is a system for in situ crystal screening by diffraction on I24. These developments will enhance the capabilities of the I24 microfocus beamline and bring the crystallization steps of membrane protein structure determination closer to the data measurement and analysis steps.
- K. J.V. Poole, M. Lorenz, G. Evans, G. Rosenbaum, A. Pirani, R. Craig, L. S. Tobacman, W. Lehman and K. C. Holmes (2006) A comparison of muscle thin filament models obtained from electron microscopy reconstructions and low-angle X-ray fibre diagrams from non-overlap muscle Journal of Structural Biology, Article accepted, in press and available on line.
- T. Izard, G. Evans, R. A. Borgon, C. L. Rush, G. Bricogne & P. R. J. Bois (2004) Vinculin activation by talin through helical bundle conversion Nature 427, 171-175.
- G. Evans and R. F. Pettifer (2001) CHOOCH: a program for deriving anomalous-scattering factors from X-ray fluorescence spectra. J. Appl. Cryst. 34, 82-86.
- R. W. Alkire, G. Rosenbaum and G. Evans (2000) Design of a vacuum-compatible high-precision monochromatic beam-position monitor for use with synchrotron radiation from 5 to 25 keV. J. Synchrotron. Rad. 7, 61-68.
- G. Evans and G. Bricogne (2003) Triiodide derivatization in protein crystallography. Acta Cryst. D59, 1923-1929.