Monovalent cation-induced phospholipid vesicle aggregation: effect of ion binding

Abstract

Aggregation of acidic phospholipid vesicles induced by monovalent cations was studied for vesicles of small and large sizes. It was found that there were two phases in the aggregation of large acidic phospholipid vesicles. In the initial phase, observed in the range of 0.1-0.4 M monovalent salts, aggregation took place spontaneously after a change in salt concentration; in the second phase (greater than 0.4 M salt), aggregation progressed gradually with time. The order of capability for monovalent cations to induce the initial phase of aggregation of large phosphatidylserine vesicles (more than 1000 A in diameter) was Li+ greater than Na+ greater than K+ greater than TEA+. However, for the second phase of aggregation, the order was Na+ greater than Li+ greater than K+ greater than TEA+, which was the same as that to induce massive aggregation of small phosphatidylserine vesicles (250 A in diameter). A similar reversal in the order was observed in studies of the surface potential of the phosphatidylserine monolayer. In these studies, the order of the binding strength of monovalent cations was deduced from the change in surface potential produced by successive additions of MgCl2 to the subphase solution, which contained a certain level of monovalent salt initially. These measurements were carried out with monolayers that had a range of areas per molecule. The order was Na+ greater than Li+ greater than K+ for monolayers of large area (greater than 80 A2) per molecule and was Li+ greater than Na+ greater than K+ for those of small area (less than 80 A2) per molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged stochastic single ion channel recordings in S-layer protein stabilized lipid bilayer membranes

“…The vesicles were added to the Teflon bath (0.8 cm in diameter) and mixed with Ca-free buffer solution (MOPS/KCl 5/250 mM, pH 7.4) and S-layer protein (0.2 mg/ml). Then a monolayer was formed by spreading a chloroform solution (1.5 l of a 5 mg/ml lipid DPhPC:DPhPE 7:3 mol ratio) on the bath solution in order to allow vesicle fusion and the formation of a bilayer [36]. After 1 h, 0.4 l of a 1 M CaCl 2 solution was added to initiate the S-layer self-assembly process.…”

Influence of La3+ ions on the egg-yolk phosphatidylcholine and sodium taurocholate self-assemblies in aqueous suspension

“…In addition, metal ions are known to considerably affect the colloidal behavior of phospholipids and bile salts respectively [10][11][12][13]. Tanaka et al [11] found that very low concentration of La 3+ and Gd 3+ induced a shape change of giant unilamellar vesicles of phosphatidylcholine.…”

“…Tanaka et al [11] found that very low concentration of La 3+ and Gd 3+ induced a shape change of giant unilamellar vesicles of phosphatidylcholine. Ohki et al [12,13] reported the phenomena of monovalent and divalent cation-induced phospholipid vesicle aggregation. The complexation of metal ions by bile salts in aqueous solution also has been investigated [14][15][16][17][18][19][20][21].…”

Preparation and Properties of Liposomes Composed of Various Phospholipids with Different Hydrophobic Chains Using a Supercritical Reverse Phase Evaporation Method

“…With the aid of this new method, we have succeeded in preparing liposomes with a significantly high trapping efficiency for water-soluble drugs with ease and in one step without using toxic organic solvent [36][37][38][39] . Meanwhile, various kinds of phospholipids with different chemical structures are found in the natural world [40][41][42] and the effects are still unknown of the chemical structure of hydrophobic groups of these phospholipids on the formation and properties of liposomes prepared by the scCO 2 RPE method.…”