High-field electron spin resonance of spin labels in membranes

High-field electron spin resonance (ESR) spectroscopy is currently undergoing rapid development. This considerably increases the versatility of spin labelling which, at conventional field strengths, is already well established as a powerful physical technique in membrane biology. Among the unique advantages offered by high-field spectroscopy. particularly for spin-labelled lipids, are sensitivity to non-axial rotation and lateral ordering, a better orientational selection, an extended application to rotational dynamics, and an enhanced sensitivity to environmental polarity. These areas are treated in some depth, along with a detailed consideration of recent developments in the investigation of transmembrane polarity profiles. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.