Peak Proteins Ltd. 1 article published in JoVE Biochemistry Rapid Assessment of Membrane Protein Quality by Fluorescent Size Exclusion Chromatography Ewa Rejnowicz1, Jack Wright1, Margaret Veldman-Jones1, Steven Harborne1 1Peak Proteins Ltd. The present protocol describes a procedure to perform fluorescent size exclusion chromatography (FSEC) on membrane proteins to assess their quality for downstream functional and structural analysis. Representative FSEC results collected for several G-protein coupled receptors (GPCRs) under detergent-solubilized and detergent-free conditions are presented.