An infrared spectroscopic based method to measure membrane permeance in liposomes

A new method for studying membrane permeance in liposomes is described. The method uses liposomes fabricated to contain IR probe molecules with CN moieties in combination with attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. The liposomes are adsorbed on a TiO2 coated ATR crystal and remain intact to flowing aqueous solutions. A change in permeance is determined by monitoring the time dependent decrease in the intensity of a band due to CN groups. It is shown that the transport of the probe molecule depends on the size of the probe molecule and the structure of the liposome membrane. A much clearer molecular understanding of membrane permeance is obtained when the information derived from transport of the probe molecules is combined with the membrane packing arrangement determined from the infrared bands due to the lipids.