Effects of surface charges and cholesterol content on amino acid permeabilities of small unilamellar vesicles

The permeabilities of amino acids through bilayer lipid membranes were determined using small unilamellar vesicles (SUV). Alanine, lysine, arginine, and glutamate show permeabilities on the order of 10(-10)-10(-11) cm/s in the case of SUV prepared from dimyristoylphosphatidylcholine and dicetylphosphate. An increase in the amount of negative charges introduced by dicetylphosphate enhanced the permeability of the positively charged amino acid (i.e., lysine). The permeabilities of net charged amino acids decreased with an increase in cholesterol content, and became less than 10(-12) cm/s with the membrane which consists of equimolar amounts of dimyristoylphosphatidylcholine and cholesterol.