High-field spin-label EPR of lipid membranes.

High-field EPR of spin-labelled lipid chains has proved to be an extremely productive means for biophysical investigations of phospholipid bilayer membranes. Results on the following three topics are reviewed: 1. Non-axial ordering of lipid chains in cholesterol-containing membranes; 2. Transmembrane polarity profiles and water penetration in lipid membranes; 3. Role of HF-EPR in multi-frequency spectral simulations to investigate lipid-chain dynamics in membranes. These results are obtained from phosphatidylcholine spin probes with the nitroxide systematically stepped down the sn-2 chain, in fully hydrated bilayer membranes of dimyristoyl phosphatidylcholine (DMPC)-containing cholesterol. Copyright 2005 John Wiley & Sons, Ltd