Mobility and location of anesthetics in lipid bilayer membranes by high-resolution, high-field-gradient NMR

Natural-abundance 13C and high-field-gradient NMR at 600 MHz were applied to shed light on the binding site and the mobility of anesthetics in lipid bilayer membranes. A high-power pulsed-field-gradient probe was specially designed for the reliable monitoring of molecular motions in a viscous membrane environment. A newly developed sensitive probe for the 10 mm diameter tube was also used for the natural abundance 13C NMR measurement. Large unilamellar vesicles, rather than micelles, were adopted as the most appropriate model for cell membranes in view of the dynamical structure. The binding of ethanol, chloroform, and sevoflurane in membranes was not deep but shallow at the membrane interface whose polarity is intermediate between water and the hydrophobic core. The anesthetics moved much faster than the lipid matrices in membrane. The movement was in sharp contrast to the slow motion of endocrine disruptors, the mobility comparable with the membrane lipid diffusion.