MIXED MONOLAYERS OF VALINOMYCIN AND DIPALMITOYLPHOSPHATIDIC ACID

The interactions of mixed monolayers of the hydrophobic peptide valino myciun and the negatively charged phospholipid dipalmitoylphosphatidic acid (DPPA) with alkali metal cations in the aqueous subphase were in vestigated. For this purpose, the isotherms of surface pressure, surfa ce potential and Brewster reflectivity versus molecular area were meas ured for the mixed monolayers (valinomycin-DPPA) in the absence and pr esence of Na+ and K+ ions, respectively, in the aqueous subphase. Comp lete miscibility of the components in the monolayers is deduced from B rewster angle microscopy. Two additional states of valinomycin-DPPA mo nolayers were observed when K+ ions were present instead of Na+ ions i n the aqueous subphase. This phenomenon correlates with the strong com plexation between the valinomycin and K+ ions in the bulk. The negativ ely charged phospholipid (DPPA) influences the ability of valinomycin to bind cations at the interface.