Increasing Versatility of Small Angle X‐Ray Scattering

Abstract

Small Angle X‐ray Scattering (SAXS), a technique initially popular in the bio‐medical community largely due to the relative logistical ease compared to other structural biological techniques has in recent years emerged as a much more versatile biophysical tool that gives unprecedented access to a real time view of structural alterations occurring during critical processes such as protein and nucleic acid folding, enzyme‐substrate binding and other ligand induced conformational changes in biological macromolecules. Developmental efforts spanning the last decade at the Biophysics Collaborative Access Team (BioCAT) located at The Advanced Photon Source (APS), Chicago, have resulted in a time‐resolved SAXS instrument which combines a state‐of‐the‐art synchrotron beamline capable of delivering up to 1013 photons/s with microfluidic mixers that afford access to time regimes ranging from 10s of microseconds to 1.5 seconds. After being made available to the general SAXS user community the time‐resolved SAXS setup has been used to study several interesting systems of biomedical interest, which in turn have led to unprecedented insights. For instance, key aspects of protein‐folding were elucidated using the chaotic flow mixer which gives access to a time regime from ~80μs to ~95ms and mechanistic details of the Insulin Degrading Enzyme (IDE) were revealed using the laminar flow mixer which allows measurement of time‐points from ~5ms to 1.5s. Improved operational efficiency and minimal sample consumption have made these heretofore challenging experiments feasible for a wider user community.Furthermore, the equilibrium SAXS instrument, which already had an integrated liquid chromatography setup to ensure optimal sample quality, now also has in‐line MALS and DLS detectors making BioCAT a unique facility for comprehensive biophysical characterization of biological macromolecules. Software tools developed in‐house have ensured a high degree of user‐friendliness and we hope to introduce this powerful biophysical tool to a larger community of non‐expert users.Support or Funding InformationNIGMS ‐ P41 GM103622