Probing protein fine structures by wide angle solution X-ray scattering

In this report we have investigated the use of wide angle scattering data not only to resolve overall size and shape of protein molecules in solution, but also to resolve details of fine structure. Methods have been developed for calculating protein solution scattering profiles based on atomic coordinates over a wide range of q with high accuracy in order to compare protein atomic models to wide angle scattering data. Calculations based upon these procedures show that X-ray scattering profiles for X-ray crystal and NMR solution structures for cytochrome c are significantly different, and that these differences can be resolved by high-precision wide angle X-ray scattering measurements. It is also shown that wide angle X-ray scattering profiles are rather sensitive to atomic fluctuations (Debye-Waller temperature factors), suggesting that wide angle scattering data may provide an opportunity for evaluation of protein dynamics.