CONICET | Buscador de Institutos y Recursos Humanos

The present work was aimed at achieving a global characterization of the temporal dynamics of the fluctuation pattern of ionic currents across planar bilayers lipid membranes (BLM) under the hypothesis that it encodes some aspects of the membrane structural dynamics. Electric conductance of BLM formed by 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) at a 7:3 molar ratio, in absence (BLM0) or presence of 30 (BLM30), 40 (BLM40) or 50 (BLM50) mole % of cholesterol, was studied using electrophysiological techniques. Electrical current intensities (I) were measured in voltage clamped conditions between 0 and ± 200mV. The autocorrelation parameter α, derived from detrended fluctuation analysis (DFA) on temporal fluctuation patterns of electrical currents, allowed discriminating between non-correlated (α=0.5, white noise) and long range correlated (0.5 < α < 1) behaviors. The rise in the holding potential (ΔV) and cholesterol content, increased the number of conductance states, as well as the magnitude of conductance level, the capacitance of the bilayers, and favored the development of long-range auto-correlated (fractal) processes (0.5 < α ≤ 1). Experiments were performed above the phase transition temperature of the lipid mixtures in conditions where the compositions of lipids used have been described to adopt a superlattice organization. This leads to the conclusion that structural defects, beyond the phase coexistence, may promote lipid pore formation under voltage clamped conditions. Furthermore, cholesterol concentration modulates the voltage threshold that allows the percolation of channel behavior, where isolated channels become an interconnected network.