A Realistic View of Proteins : Solution Scattering at the Life Sciences X‐ray Scattering Beamline (LIX)

Abstract

Small angle X‐ray scattering is an important tool that reveals the behavior of proteins in their native environment. The scattering pattern produced from a SAXS experiment represents an average of all conformations present in the solution. Since most proteins in our body function in a solution environment, SAXS data can reveal additional biologically relevant states of a molecule or molecular complex. Furthermore, SAXS provides data about the shape and size of the molecule of interest and is a complementary technique to other structural methods. Combining SAXS data with X‐ray crystallography, NMR or Cryo‐EM can lead to a more robust understanding of the species being studied. High quality SAXS data can be used to build ab initio low resolution bead models, which provide a 3D envelope of your molecule. Here at the life sciences X‐ray scattering beamline (LiX), we collect data by flowing sample through the X‐ray path in a 3 channel flow cell. As the sample enters the X‐ray path, the simultaneous collection of SAXS and wide angle X‐ray scattering (WAXS) is obtained via a 3 detector setup. The detector setup has a q‐range of 0.006Å−1 to 3.2 Å−1, primarily to obtain scattering data from the water peak to normalize buffer subtraction. Automated sample handling at LiX allows for collection of up to 360 samples, packaging of data and processing. One challenge in obtaining high quality SAXS data is preparation of pure, monodisperse samples. For these complicated samples that have multiple species, our in‐line HPLC system seamlessly integrates with our beamline for SEC‐SAXS (size‐exclusion chromatography‐SAXS), and increases the chances of obtaining a more pure, monodisperse sample immediately before data collection.Support or Funding InformationLiX beamline is part of the Life Science Biomedical Technology Research resource, co‐funded by the National Institute of General Medical Sciences (NIGMS) under grant P41 GM111244 and by the DOE Office of Biological and Environmental Research under grant KP1605010, with additional support from NIH under grant S10 OD012331. The operation of NSLS2 is supported by US Department of Energy, Office of Basic Energy Sciences, under contract No. DE‐SC0012704.