Representative current recordings which illustrate the alamethicin activity in lipid membranes under control conditions (no amphiphile added, panel b), and presence on the trans side of the membrane of either RH 421 [8 µM] (panel a), or phlorizin [500 µM] (panel c).

<p>The applied potential was −60 mV. The closed state of alamethicin oligomers is denoted by the dotted line, and downward spikes designate the electrical current mediated by alamethicin pores in their various conductive state. Beneath it is shown an over-simplified geometric view of changes ensued on the overall membrane potential profile, by the increase (panel a, dotted line) or decrease (panel c, dotted line) of the trans-monolayer dipole potential (Δψ_d) of the <i>trans</i> lipid monolayer only, as compared to control conditions (panels a, b, and c, solid line). When the dipolar electric field - initially similar for both the cis and trans monolayers (E_control) - is altered in the trans monolayer only, as a consequence of RH-421 (E_RH-421 > E_control) or phlorizin (E_phlorizin< E_control) adsorption, a corresponding change in the intramembrane potential across the hydrophobic region of the membrane will follow. As a result, the net potential difference sensed by the cis-side adsorbed alamethicin over the hydrophobic region while crossing the membrane, will equal that seen under control conditions at a given trans-applied potential, from which a given value must be subtracted (denoted by ΔU_RH-421; panel a, dashed line) or added to (denoted by ΔU_phlorizin; panel c, dashed line). Based on the presented simplified geometric and electric considerations, this value (ΔU) should match the change brought about by either amphiphile adsorption on the trans-monolayer dipole potential (Δψ_d). The solid arrows assigned to P_alamethicin indicate the orientation of alamethicin monomers dipole moment, while in the transmembrane orientation.