National Synchrotron Light Source Seminar

"High-resolution solution X-ray scattering and its application to crystallographic phasing"

Presented by Xinguo Hong, MacChess, Cornell High Energy Synchrotron Source, Cornell University

Friday, January 9, 2009, 12:00 pm — Seminar Room, Bldg. 725

X-ray scattering from biological macromolecules in solution is an increasingly important technique that yields low-resolution structural information on the molecules, and can be used to monitor their shape and conformational changes, including molecular associations 1 ,2, 3. However, in contrast to numerous successful applications of small angle X-ray scattering (SAXS), e.g. ref. 4-6, practical use of wide-angle X-ray scattering (WAXS) data has been limited due to the weak protein scattering despite of the higher-resolution structural information of disordered and partially ordered systems.
Recently, we have succeeded in developing an effective method to overcome the long-standing issue of radiation damage in the field of solution scattering 7. Precise solution SAXS and WAXS data of X-ray sensitive protein solutions can be obtained with small stationary cell7. High resolution pair-distance distribution function, P(r), of protein molecules has been obtained in terms of the complete solution scattering curve by combining accurate SAXS and WAXS data out to crystallographic resolution. X-ray crystallographic data demonstrate that in terms of the complete solution scattering profile, some high resolution aspects of the structural hierarchy and function of a protein may be investigated in solution8.
In addition, we have applied the high resolution scattering curve to solve the phase problem, which remains central to crystallographic structure determination. The high-resolution solution models (envelope/bead) were constructed based on the complete SAXS/WAXS data up to 5 Å resolution, and a 6-dimensional search method of molecular replacement (FSEARCH) was used to locate a low-resolution molecular envelope determined from small angle X-ray scattering (SAXS) within the crystallographic unit cell. The inclusion of high resolution WAXS data is essential for correctly locating the molecular envelope in the crystal unit cell, as well as for locating heavy atom sites 9. The in

Hosted by: Lin Yang

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