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