Electron spin resonance in membrane research: Protein–lipid interactions

Different electron spin resonance (ESR) methods are described that allow determination of the stoichiometry and selectivity of interaction of spin-labelled lipids with integral transmembrane peptides or proteins, and also with peripheral surface-binding membrane proteins or peptides. In addition, ESR methods for determining the exchange rates of spin-labelled lipids at the protein–lipid interface are described, as well as methods to detect penetration of surface-binding peptides into the hydrophobic membrane core. Instrumental requirements are considered, and also sample handling, spin-labelling techniques and the synthesis of spin-labelled lipids.