Molecular Insights into Protein Separations from Scattering Methods

Obtaining molecular-level insights into protein separations requires spatial resolution on the order of nanometers, which can be especially challenging for systems that include high concentrations, multiple phases and separation agents such as chromatographic media. Drawing on methods that are widely used in the soft matter community, we have used small-angle neutron scattering (SANS) and small-angle x-ray scattering (SAXS) to characterize the structure of systems arising in protein separations. Because both neutrons and x-rays have wavelengths on the order of Ångströms, these methods are able to access the size range of proteins, albeit results are obtained in reciprocal space and generally require model fitting to interpret. Examples that will be presented include protein precipitates and gels as well as ion-exchange adsorbents with and without adsorbed protein.