Lipid-gramicidin interactions using two-dimensional Fourier-transform electron spin resonance.

The application of two-dimensional Fourier-transform electron-spin-resonance (2D-FT-ESR) to the study of lipid/gramicidin A (GA) interactions is reported. It is shown that 2D-FT-ESR spectra provide substantially enhanced spectral resolution to changes in the dynamics and ordering of the bulk lipids (as compared with cw-ESR spectra), that result from addition of GA to membrane vesicles of dipalmitoylphosphatidylcholine (DPPC) in excess water containing 16-PC as the lipid spin label. The agreement between the theory of Lee, Budil, and Freed and experimental results is very good in the liquid crystalline phase.

Longitudinal relaxation and diffusion measurements using magnetic resonance signals from laser-hyperpolarized 129Xe nuclei.

Methods for T1 relaxation and diffusion measurements based on magnetic resonance signals from laser-hyperpolarized 129Xe nuclei are introduced. The methods involve optimum use of the perishable hyperpolarized magnetization of 129Xe. The necessary theoretical framework for the methods is developed, and then the methods are applied to measure the longitudinal relaxation constant, T1, and the self-diffusion constant, D, of hyperpolarized 129Xe.