Hydration Behavior around Proteins probed by Small- and Wide-Angle X-Ray Scattering

Orion Shih^1*, Yi-Qi Yeh¹, Kuei-Fen Liao¹, Je-Wei Chang¹, Bradley Mansel¹, Chun-Jen Su¹, Wei-Ru Wu¹, U-Ser Jeng^1,2

¹National Synchrotron Radiation Research Center, Hsinchu, Taiwan
²Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Orion Shih, email:shih.orion@nsrrc.org.tw

Small- and wide-angle X-ray scattering (SWAXS) data provides information about the shape and size of bio-macromolecules in solution. The newly developed BioSAXS endstation at the beamline 13A of the Taiwan Photon Source features an in-vacuum SWAXS detecting system comprising two area detectors (Eiger X 9M/1M) and an online size-exclusion chromatography system incorporated with several optical probes, including UV-vis absorption spectrometer and refractometer (Liu et al., 2021; Shih et al., 2022). The instrumentation allows simultaneous SAXS and WAXS data collection with a high signal-to-noise ratio, enhancing structural studies of biomolecules by accessing finer details of solution structures. Here we tested a model protein BSA with two common denaturants: urea and guanidinium chloride (GdmCl). The intradomain interaction loss is clear around the middle q region. The high q peak (~1.5 Å^-1) was previously assigned to the secondary structure but is still present when the protein is fully denatured. We showed how the solvation structure changes correlate with the high q peak change and discussed the different outcomes from urea and GdmCl, suggesting a totally different denaturation mechanism.

Keywords: SAXS, WAXS, protein denature, solvation