Extended q-Range X-Ray Scattering Reveals High-Resolution Structural Details of Biomacromolecules in Aqueous Solutions

We communicate a feasibility study for high-resolution structural characterization of biomacromolecules in aqueous solution from X-ray scattering experiments measured over a range of scattering vectors (q) that is approximately two orders of magnitude wider than used previously for such systems. Scattering data with such an extended q-range enables the recovery of the underlying real-space atomic pair distribution function, which facilitates structure determination. We demonstrate the potential of this method for biomacromolecules using several types of cyclodextrins (CD) as model systems. We successfully identified deviations of the tilting angles for the glycosidic units in CDs in aqueous solutions relative to their values in the crystalline forms of these molecules. Such level of structural detail is inaccessible from standard small angle scattering measurements. Our results call for further exploration of ultra-wide-angle X-ray scattering measurements for biomacromolecules.

Automated summary

We propose a method for high-resolution structural characterization of biomacromolecules in aqueous solution using X-ray scattering experiments with an extended range of scattering vectors (q). This method allows the recovery of the atomic pair distribution function and facilitates structure determination. We demonstrate the potential of this method by studying cyclodextrins (CD) as model systems and successfully identifying deviations in the tilting angles of glycosidic units. Our results highlight the need for further exploration of ultra-wide-angle X-ray scattering measurements for biomacromolecules.