Cholesterol favors the emergence of a long-range autocorrelated fluctuation pattern in voltage-induced ionic currents through lipid bilayers

NATALIA A. CORVALÁN; JACKELYN M. KEMBRO ; PEDRO D. CLOP; MARIA A. PERILLO

BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 p. 1754 - 1764

0005-2736

The present paper was aimed at evaluating the effect of cholesterol (CHO) on the voltage-induced lipid pore formation in bilayer membranes through a global characterization of the temporal dynamics of the fluctuation pattern of ion currents. The bilayer model used was black lipid membranes (BLMs) of palmitoyloleoylphosphatidylethanolamine and palmitoyloleoylphosphatidylcholine (POPE:POPC) at a 7:3 molar ratio in the absence (BLM0) or in the presence of 30 (BLM30), 40 (BLM40) or 50 (BLM50) mol% of cholesterol with respect to total phospholipids. Electrical current intensities (I) were measured in voltage (deltaV) clamped conditions at ΔV ranging between 0 and ±200 mV. The autocorrelation parameter α derived from detrended fluctuation analysis (DFA) on temporal fluctuation patterns of electrical currents allowed discriminating between non-correlated (alpha = 0.5, white noise) and long-range correlated (0.5 > alpha > 1) behaviors. The increase in |deltaV| as well as in cholesterol content increased the number of conductance states, the magnitude of conductance level, the capacitance of the bilayers and increased the tendency towards the development of long-range autocorrelated (fractal) processes (0.5 > alpha > 1) in lipid channel generation. Experimentswere performed above the phase transition temperature of the lipidmixtures, but compositions used predicted a superlattice-like organization. This leads to the conclusion that structural defects other than phase coexistence may promote lipid channel formation under voltage clamped conditions. Furthermore, cholesterol controls the voltage threshold that allows the percolation of channel behavior where isolated channels become an interconnected network.