Effect of monovalent ion adsorption on the electric charge of phosphatidylcholine - decylamine liposomal membranes

We examined the effect of adsorbed monovalent ions on the surface charge of phosphatidylcholine (PC) – decylamine (DA) liposomal membranes. Surface charge density values were determined from electrophoretic mobility measurements of lipid vesicles performed at various pH levels. The interaction between solution ions and the PC-DA liposomal surface was described by a six component equilibrium model. The previously determined association constants of the -PO^(-) and –N⁽⁺⁾(CH₃)₃ groups of PC with H⁺, OH^-, Na⁺ and Cl^- ions (K _A1H, K _B1OH, K _A1Na, K _B1C1) were used to calculate K _B2OH, and K _B2C1, the association constants of the –N⁽⁺⁾H₃ group of DA with OH^- and Cl^- ions, providing an experimental verification for the proposed model.