Using EPR Spectroscopy to Characterize the Structure of Lipid Membrane-Polymer Nanoring Complexes

Abstract

Spectroscopic studies of membrane proteins are challenging due to difficulties introduced in preparing homogenous and functional lipid membrane systems into which membrane proteins are incorporated. While traditional membrane systems such as micelles or liposomes can be highly useful, there are evident limitations for their use in membrane protein studies. Micelle complexes do not form lipid bilayers, resulting in increased mobility of membrane proteins, and liposomes are difficult to produce homogenously in solution. Recently, a new nano-sized polymer ring was developed to serve as a better membrane mimetic comprised of a lipid bilayer environment capable of forming homogenous nano-sized particles. Although nano-rings present a promising membrane mimetic environment, they have not been structurally characterized, and the interactions between the lipid bilayer and the solubilized SMA polymer are not fully understood. In our study, EPR spectroscopy using different PC-based nitroxide spin labels will be used to detect the perturbation on the aceyl chain upon introduction of the SMA polymer. Additionally, the membrane protein KCNE1 will be incorporated into nano-rings to study changes in lipid dynamics. This study will verify the feasibility of the nano-rings as a protein-incorporated membrane mimetic and will provide useful information for researchers working on membrane protein systems by acquiring significant information on the structure and dynamics of a potentially physiologically relevant membrane mimetic system.