Fluctuation analysis of ionic currents measured across black lipid membranes.

CORVALÁN, N.A.; KEMBRO, J.M.; PERILLO M.A.

Los Cocos, Córdoba

Congreso; XXXVIII Reunión Anual de la Sociedad Argentina de Biofísica; 2009

Sociedad Argentina de Biofísica

Some aspects of the membrane dynamics may be encoded in the temporal fluctuation of ionic currents. From this perspective, in the present work we studied the conductance of K+ and Cl- through black lipid membranes (BLM) formed from poPC/POPE 3:7 dissolved in n-decane (~25 mg/ml) on a 150 um of diameter hole, carved in a wall that separated two chambers filled with solutions of identical composition HEPES 10 mM, 150 mM KCl, pH 7.4). Electrical transmembrane potential  within +/- 200mV was applied using Ag/AgCl electrodes connected through a saline 200 mM KCl bridge. The electrical current intensity (I) was recorded for 10 s at 10 kHz. Within the range 0 to +/- 100 mV, a single conductance state(G=6.4 +/- 0.6 fS) was observed. The magnitude, dispersion and amount of conductance states (2-4)increased at an absolute electrical transmembrane potential  >100 mV. These results could be associated with the formation of transients pores induced by electrostriction of the membrane. Detrended fluctuation analysis (DFA) of the temporal pattern of electric current amplitude recorded between +/- 100 mV showed no autocorrelations (white noise). Beyond +/- 160 mV a transition to 1/f type noise was observed which is characteristic of critical states acquired by biological systems far from equilibrium. In our system this would correspond to the appearance of reversible pores that precede the electroporation of the bilayer. This behavior was modulated by the membrane order and composition as revealed by the enhanced or depressed sensitivity exhibited upon increasing in the BLM the cholesterol or the protein content, respectively.