ABSTRACT
One fundamental tool for studying structure-function relationships in biological membranes is electron spin resonance (ESR or EPR) using nitroxide spin labels or spin probes. Spin labeling is used to investigate both the dynamic structure of membranes and the dynamic relationships among membrane components. EPR studies of biological material have received much attention recently and have been reviewed extensively. 1 – 14 The purpose of this chapter is to introduce spin labeling and outline some of the methods by which spin labeling can answer questions concerning structure-function relationships in biological membranes. I have included examples of experiments which have been used to answer questions about membrane fluidity, order, and dynamics, as well as a section on new techniques, especially electron spin echo spectroscopy, and some cautionary notes.
