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 to describe the local reorientation of amphiphile molecules in lipid bilayers. A special program is designed to reduce the computation amount, and the computational time for the DC model is comparable to that for the familiar Maier–Saupe (MS) potential model. Special emphasis is placed on comparing the two potential models in ESR line shape calculations. Illustrative analyses of ESR spectra are presented for some selected bilayers. It is found that the DC model is particularly suitable for describing the local dynamic states of single chain systems. The simulation results show that while the two models give similar values for the reorientational rates, the DC model predicts lower local molecular orders. [ABSTRACT FROM AUTHOR]