[Interaction of monovalent cations with phospholipid liposomes]

Action of monovalent cations on phospholipid liposome surface properties was studied using hydrophobic spin labels. Addition of monovalent cations to liposome incubation media led to an increase of the partition coefficient of negatively charged I1,14 spin label in the membrane, but produced an opposite effect in the partition coefficient of positively charged CAT12 spin label. The effect increased with cation concentration in series of NH4+ greater than Li+ greater than Na+ greater than K+ greater than or equal to Rb+ greater than or equal to Cs+. The result is explained by the thermodynamics of cation hydration and quantum effects of cation interaction with specifically ordered ligands.