Minimizing Heterogeneity of Protein Samples for Metal Transporter Proteins Using SAXS and Metal Radioisotopes.

The scattering profiles at small angles, obtained after an X-ray beam is incident on biological samples (protein), are nowadays successfully used to obtain important structural information. Small angle X-ray scattering (SAXS) is now helpful in providing information about shape, conformation, and assembly state of molecules, besides macromolecular folding-unfolding, aggregation, and extended conformations. The article discusses here a protocol to identify those fractions of heterogeneous proteins that are rich in homogeneous samples, testified by proper conformation and protein activity. The protocol in reference to a class of proteins known as metal binding (transporter) proteins or ion channels is discussed using applications of SAXS and metal radioisotopes. With requisite modifications, the protocol can be adapted to other classes of proteins.