The Changes in the Conductance of Bilayer Lipid Membranes Caused by Pluronics L61 and F68: Similarities and Differences

The effect of pluronics L61 and F68 containing hydrophobic poly(propylene oxide) blocks of the same length and hydrophilic poly(ethylene oxide) blocks of different lengths on the conductance of planar bilayer lipid membranes made of azolectine is investigated. The conductance of these membranes increases as the concentration of both pluronics increases. For the same concentration of pluronics in solution, the conductance is higher for L61. Based on the literature data, the concentration of pluronics bound with the bilayer is calculated. For the close concentration of membrane-bound pluronics, the conductance of membranes is also close. It is concluded that in the first approximation, the appearance of the same hydrophobic parts of pluronics L61 and F68 in a membrane is accompanied by the same increase in its conductance. The conductance vs. concentration curves are superlinear for L61 and sublinear for F68. In the presence of either of these pluronics, the conduction spikes with the amplitude from 10 to 300 pSm and higher are observed for approximately 40% of membranes. These surges of conductance are associated with the appearance of conductive pores or defects in the membrane. The number of pores observed in the membrane is a random variable with a large scatter and does not correlate with the pluronic concentration. The difference between the average pore conductivities for membranes containing L61 and F68 is statistically insignificant.