Detergent-Free Incorporation of a Seven-Transmembrane Receptor Protein into Nanosized Bilayer Lipodisq Particles for Functional and Biophysical Studies

SMA-Lipodisq nanoparticles, with one bacteriorhodopsin (bR) per 12 nm particle on average (protein/lipid molar ratio, 1:172), were prepared without the use of detergents. Using pulsed and continuous wave nitroxide spin label electron paramagnetic resonance, the structural and dynamic integrity of bR was retained when compared with data for bR obtained in the native membrane and in detergents and then with crystal data. This indicates the potential of Lipodisq nanoparticles as a useful membrane mimetic.