VOLTAGE-DEPENDENT PORE ACTIVITY OF THE PEPTIDE ALAMETHICIN CORRELATED WITH INCORPORATION IN THE MEMBRANE - SALT AND CHOLESTEROL EFFECTS

Strong aggregation of incorporated alamethicin in the bilayer of lipid vesicles has been observed spectroscopically at aqueous peptide concentrations above a critical value c* . On the other hand in conventional gating studies with planar lipid films, the onset of conducting pore formation can be characterized by a threshold voltage V.. We present experimental evidence of a direct correspondence between the effects on c* and V. when these parameters are modulated by adding NaCl (to the aqueous medium) or cholesterol (to the lipid moiety). A quantitative analysis supports the idea that the measured aggregation actually results in pore formation, the voltage-dependence being due to an electric field effect on the partition equilibrium of the peptide between the aqueous and lipid phases.