TABLE 3.
Ion selectivity of planar phospholipid bilayer membranes modified by sPB1-F2
| Bathing solutions and membrane compositiona | Reversal potential (mV)b | Selectivity |
|---|---|---|
| NaCl/NaCl (0.1 M/0.35 M) | 14 ± 3.6 | PNa/PCl = 2.9 |
| PC/PE/PS (50%/30%/20%) | ||
| KCl/KCl (0.1 M/0.25 M) | 6.5 ± 0.5c | PK/PCl = 1.8 |
| PC/PE/PS (50%/30%/20%) | ||
| KCl/KCl (0.1 M/0.25 M) | 9 ± 1c | PK/PCl = 2.4 |
| DPhC | ||
| KCl/NaCl (0.1 M/0.1 M) | 0 ± 3c | PK/PNa = 1 |
| DPhC | ||
| MgCl2/MgCl2 (5 mM/25 mM) | −24 ± 3.9 | PMg/PCl = 0.15 |
| DPhC |
Compositions and concentrations of the electrolytes separated by the membrane are given as trans/cis. Membrane composition is shown in italic type. PC, phosphocholine; PE, phosphatidylethanolamine; PS, phosphatidylserine.
A concentration or composition gradient of electrolytes was formed across a lipid bilayer in presence of 10 to 40 nM sPB1-F2. Under these conditions, ions diffuse across the bilayer according to the ion selectivity of pores. Gradients of permeant ions will create potentials. These potentials were determined here by measuring the current reversal potential, i.e., the external potential that had to be applied in order to make the current through the lipid bilayer zero. Reversal potentials were used to calculate the relative pore selectivity, defined as the ratios of the pore permeability for different ions. Unless indicated otherwise, data are mean ± standard deviation for three or four measurements.
Average of two measurements ± maximum deviation.