SLOW MOTION ELECTRON-SPIN-RESONANCE LINE-SHAPES OF SPIN-LABELED MOLECULES UNDERGOING RESTRICTED ROTATIONAL DIFFUSION IN A CONE - APPLICATIONS TO LYSOLECITHIN WATER-SYSTEMS

The restricted diffusion-in-a-cone (DC) model is formulated within the context of a slow-motional electron-spin resonance (ESR) line shape t o describe the local reorientation of amphiphile molecules in lipid bi layers. A special program is designed to reduce the computation amount , and the computational time for the DC model is comparable to that fo r the familiar Maier-Saupe (MS) potential model. Special emphasis is p laced on comparing the two potential models in ESR line shape calculat ions. Illustrative analyses of ESR spectra are presented for some sele cted bilayers. It is found that the DC model is particularly suitable for describing the local dynamic states of single chain systems. The s imulation results show that while the two models give similar values f or the reorientational rates, the DC model predicts lower local molecu lar orders.