Electron spin resonance in membrane research: protein-lipid interactions from challenging beginnings to state of the art.

摘要: Conventional electron paramagnetic resonance (EPR) spectra of lipids that are spin-labelled close to the terminal methyl end acyl chains able resolve directly contacting protein from those in fluid bilayer regions membrane. This allows determination both stoichiometry lipid–protein interaction (i.e., number lipid sites at perimeter) and selectivity for different species association constants relative background lipid). Spin-label EPR data summarised 20 or more transmembrane peptides proteins, 7 distinct lipids. Lineshape simulations two-component conventional spin-label allow estimation rate which protein-associated exchange with bulk For do not display a protein, intrinsic off-rates region 10 MHz: less than 10× slower rates diffusive membranes. Lipids an affinity lipid, have leaving correspondingly slower. Non-linear EPR, depends on saturation spectrum high radiation intensities, is optimally sensitive dynamics timescale spin-lattice relaxation, i.e., microsecond regime. Both progressive transfer experiments provide definitive evidence interface exchanging this timescale. The sensitivity non-linear low frequencies spin also location membrane residues lipids, double-labelling experiments.