Characterizing the Structure of Lipodisq for Membrane Protein Spectroscopic Studies

Abstract

Membrane protein spectroscopic studies are challenging due to the difficulty introduced in preparing homogenous and functional protein incorporated lipid system. Traditional membrane mimetics such as micelles or vesicles are proved to be powerful. Though, they all possess their own drawbacks. The lack of lipid bilayers of micelles could result in the increasing dynamics of membrane proteins and obtaining homogenous vesicles are not easy in the real applications. Recently, a nano-sized particle lipodisq was utilized to serve as a better membrane mimetic, it provides a lipid bilayer environment and homogenous samples. Furthermore, unlike nanodisc, lipodisq won't interfere the absorbance property of membrane proteins. Though lipodisq shows a high potential to become a good membrane mimetic to enhance the biophysical studies of membrane proteins, there is still lack of structural characterization of lipodisq in different lipid compositions that close to native lipid environment of membrane proteins. In this study, the formation of lipodisq nanoparticles using different weight ratio of 3:1 SMA polymer to POPC/POPG lipid was characterized using dynamic light scattering (DLS) and solid state nuclear magnetic resonance (SSNMR) spectroscopy. We achieved a physiologically relevant size (10nm) of lipodisq nanoparticles complex at weight ratio of 2.25:1 (3:1 SMA polymer : POPC/POPG lipid) and the transition phase from vesicle to lipodisq was characterized. These data were also compared with the corresponding data obtained for bicelles and micelles. This study will provide a proper path for the researcher working on membrane protein system to obtain pertinent structure and dynamic information on physiologically relevant membrane mimetic environment.