Difference Structures from Time-resolved SAXS/WAXS

Abstract

It has been thought that there is not enough information to recover a solution to the problem of inverting time-resolved Small Angle X-ray Scattering (SAXS) / Wide Angle X-ray Scattering (WAXS) difference data. In this context, this study presents a new idea by extending the concept of “difference Fourier method” which aims to overcome the above limitation in the idealized case of simulated data. If the structural changes in a typical time-resolved studies are generally confined to a relatively localized region, they can be found from difference SAXS/WAXS curves and knowledge of the atomic coordinates of one of the states. The method has some similarities to the difference Fourier method of crystallography, which may not be directly applicable to SAXS/WAXS analysis. This study demonstrates the identification of the displaced residues once this proposed idea/method is applied to structural changes involved in Photoactive Yellow Protein (PYP), which has been used as a test case in time-resolved studies.