Comparative EPR studies on lipid bilayer properties in nanodiscs and liposomes

• Structure of POPC and DMPC bilayers in liposomes and nanodiscs is compared.
• Set of lipid spin labels is applied to probe different regions of bilayers.
• Cholesterol-like changes induced by scaffold proteins in nanodisc are observed.
• Bilayer structure of nanodiscs should be considered in membrane proteins studies.

Studies of the membrane proteins suggest their close interaction with the lipid surroundings. Membrane proteins and their activities are affected by the composition and structure of the lipid bilayer, therefore adequate surroundings for studied protein are crucial for the model membrane to ensure its biological relevance. In recent years nanodiscs which are small fragments of lipid bilayer stabilised by derivatives of apolipoprotein, called membrane scaffold protein (MSP), have been established as alternative tool in structural and functional studies of membrane proteins. In this study, the influence MSP of different length on structure and dynamics of DMPC and POPC bilayer was investigated and compared to bilayer present in liposomes. EPR spectroscopy technique using different PC-based spin probes was employed to show cholesterol-like organising effect of MSPs on lipid bilayer, thus giving a better insight into the nanodiscs model membrane structure, and its possible implications in the research of membrane protein applications.

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