Illustration showing the styrene maleic acid lipid particle (SMALP) method which can be used to extract membrane proteins. Traditionally, detergents are used for extracting membrane proteins for characterization. However, this usually causes surrounding lipids to be lost, which may cause unwanted structural and functional changes to the proteins. In this illustration, a GPCR protein (blue) is extracted. Styrene maleic acid (SMA) copolymers (depicted yellow) can solubilize the membrane protein together with its surrounding lipids (purple), forming a small disc of lipid bilayer which is lined with a ring of SMA copolymers.