total X-ray scattering and atomic pair distribution function (PDF) analysis to determine the high-resolution structure of protein and polysaccharide in aqueous solutions*

Resolving structures and dynamics of biomacromolecules in aqueous solutions at high spatial resolution are experimentally nontrivial due to the high instrumental requirements and challenges in modeling. Small-angle x-ray/neutron scattering, using scattering data below ≈ 1 Å^-1, provides low-resolution structural information of biomacromolecules. While there have been reports of wide-angle scattering characterization (up to ≈ 3 Å^-1) of biomacromolecules, high-quality data suitable for high-resolution modeling providing detailed insights into the structure are unavailable. Here, for the first time, by taking advantage of high-energy wide-angle X-ray scattering (WAXS) at 11-ID-B at the Advanced Photon Source, Argonne National Laboratory, we reliably collected WAXS profiles of several types of biomacromolecules including protein and polysaccharide in aqueous solutions up to ≈ 20 Å^-1. Our atomic pair distribution function analyses shed new light on resolving the conformation states of these biomacromolecules.