Q-band electron spin resonance studies of slow motions in bilayers with high order

Abstract

Q-band electron spin resonance (ESR) experiments on macroscopically oriented multilayers of dimyristoyl lecithin/cholesterol (2:1 molar ratio)/cholestane spin label, order parameter S ≈ 1, have been carried out in the temperature range −32°C to +20°C. The spectra were simulated by a numerical soultion of the stochastic Liouville equation using Padé approximants. The simulations show that the rates of reorientation of the spin label molecules their long axes fall within the slow-motion regime. At low temperatures the molecular motion is best described in terms of a small step diffusion model, while at the higher temperatures a random jump model or an intermediate jump model provides a better description.