Biophysical Studies of Styrene-maleic Acid Copolymer Stabilized Membrane Mimetics

Traditional methods of isolating membrane proteins involve the use of detergents that destabilize the membrane environment. Biophysical studies of membrane proteins are challenged by the requirement of a stable membrane platform. Lipodisq nanoparticles are novel membrane mimetics that consist of 3:1 styrene-maleic acid copolymer encircling phospholipids to form discoidal species on the order of 10 nm in diameter. Bacteriorhodopsin was previously incorporated into Lipodisq nano-particles from its native purple membrane without the addition of detergent. In this study, dynamic light scattering was used to investigate the stability of empty Lipodisq nano-particles over time. These data show that Lipodisq nano-particles are stable for up to 48 hours at both 20 and 30°C. At each temperature, Lipodisq nano-particles consist of greater than 95% of the total volume of the sample. Therefore, it is reasonable to investigate the properties of lipids and membrane proteins in Lipodisq nano-particles using experimental techniques that require up to 48 hours.