Spin echoes and the dynamic properties of membranes

Abstract

Abstract The discovery of spin echoes by Erwin Hahn in 1950 [ 19] has provided seminal ideas for many of the important concepts of modern NMR. For example, the observation of transient ‘free induction decay’ (FID) signals, following one or more short r.f. pulses applied at a frequency close to the average nuclear Larmor frequencyw0,led ultimately to Fourier transform NMR spectroscopy. Also, today it is impossible to conceive of preparing complex spin systems in well defined, ‘interesting’, non-equilibrium states without using pulse sequences of one sort or another. Biological and model membranes are two systems for which NMR, and especially deuterium (2H) NMR, has provided special insights in recent years. The2H NMR techniques that have proved to be fruitful up to now in elucidating the properties of membranes are very close to those described in Hahn’s original work, so that this is a particularly suitable place to discuss recent work in this area. We shall discuss several studies in our laboratory of membrane dynamics using2H NMR and shall try to place this within the perspective of current developments in membrane biophysics, which is a vibrant and dynamic field at the present time. Membrane biophysics is in the process of generating an enormous literature, so that our selection of background material is necessarily personal, being severely limited by space considerations to questions that we deem to be of potential interest to a general audience and, at the same time, amenable to study in our own laboratory.