The effect of hydration of lecithin-water lamellar phases: a comparative study of solute diffusion and ESR spectroscopic measurements

An analysis of the paramagnetic resonance spectra of spin labels in the lipidic region of lecithin-water lamellar phases as a function of phase water content has been carried out. The observed variation of the local organization and mobility of the lipids is consonant with previous results obtained from solute diffusion measurements. The previously observed sudden changes of solute diffusion for hydration of 9 and 18 molecules water per lecithin molecule are compared with the concomitant sudden changes as seen by ESR spectroscopy. The results also indicate that there is a gradient of fluidity across the lipid leaflets which are therefore not homogeneous to diffusing molecules.