Solution X-Ray Scattering for Membrane Proteins.

While X-ray crystallography remains the most popular and productive technique for protein structure determination, it very often produces incomplete models, either due to truncations introduced by the scientists or locally weak experimental data. This problem is even more common for transmembrane proteins, owing to the difficulties inherent in their crystallization. By the virtue of operating in solution, SAXS bypasses the problems with crystallization and allows for easier work with full-length constructs and, thus, can potentially be used to fill the missing (and often crucial) details. Here, we describe a complete procedure to build a complete model of a transmembrane protein based on a truncated crystallographic model and experimental SEC-SAXS data using refractometry and UV absorption for internal validation of the measurements.