Alkali ion transport through lipid bilayer membranes mediated by enniatin A and B and beauvericin.

摘要: Stationary conductance measurements with lipid bilayer membranes in the presence of enniatin A and B beauvericin were performed. For comparison, some valinomycin systems investigated. It was found that case is caused by a carrier ion complex 1∶1 stoichiometry, whereas for beauvericin, 3∶1 has to be assumed explain dependence on concentration aqueous phase. The current-voltage curves measured dioleoyl phosphatidylcholine show superlinear behavior three carriers potassium. On other hand, supralinear observed from different monoglycerides, except beauvericin. results obtained are satisfactory agreement an earlier proposed model assuming complexation between at membrane water interface. discrimination potassium sodium ions much smaller enniatins than valinomycin. This selectivity as well fact cause highest may due size cyclic molecules, which contain 6 residues ringvs. 12 Charge-pulse relaxation studies performed B, monoolein only valinomycin, all relaxations predicted could resolved. In probably more fluid monolinolein (Δ9, 12-C18: 2) monolinolenin 12, 15-C18: 3) observed. association rate constantk R , dissociation D two translocation constantsk MS andk s complexed free carrier, respectively, calculated data. phase had no influence constants cases, strong saturation increasing enniatins. Because saturation,k did not exceed value 4×105 m −1 sec−1 1m salt irrespective ion, or membrane-forming lipid. similar but less pronounced also S carrier. independent enniatins, kind transported ion. series K+, Rb+ Cs+,k increases about threefold. turnover numbers range 104 105 do difference individual carriers. investigated here therefore mainly partition coefficients,