Structural refinement of time-resolved wide-angle X-ray scattering data

BIOL 87

Sena Ahn, praise@kaist.ac.kr and Hyotcherl Ihee. Department of Chemistry, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong Yuseong-gu, Daejeon, South Korea
Time-resolved wide-angle X-ray scattering (WAXS) is an emerging technique that can be used to follow structural changes of protein in solution. To check if it is possible to obtain 3D structural information of transient protein intermediates from TR-WAXS data, we have applied the refinement technique of X-ray crystallography to the analysis of mock TR-WAXS data. Since the number of data points in TR-WAXS data is much smaller than that available for X-ray crystallography, the number of fitting parameters has to be reduced by using constraints and grouping atoms into alpha-helices and loops. A similar target function consisting of data term and chemical term was used in the refinement. The use of R and free R factors borrowed from X-ray crystallography allowed us to check the degree of over-fitting.