An electron spin resonance study of interactions between gramicidin A' and phosphatidylcholine bilayers.

The model of microscopic order and macroscopic disorder was used to stimulate electron spin resonance spectra of spin-labeled lipids, 5-PC, 10-PC, and 16-PC in multilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC) containing gramicidin A' (GA) at temperatures above the gel-to-liquid crystal transition of DPPC. The simulations show that at a lower concentration of GA (i.e., molar ratios of DPPC/GA greater than 3), GA has only a slight effect on the acyl chain dynamics. The rotational diffusion rate around the axis parallel to the long hydrocarbon chain remains unchanged or increases s...

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