ELECTROPORATION IN SYMMETRICAL AND ASYMMETRIC MEMBRANES

We present results of electrical measurements performed both on symmet ric and asymmetric membranes in current-clamp conditions. The current- voltage characteristic curve of the membranes shows a reversible condu ctance transition to a higher level above a critical potential V(c). T he experimental results are interpreted in the light of the electropor ation theory, which allows estimates of the line tension to be made. T hese estimates are compared to previous experimental findings or theor etical calculations. The behaviour of symmetric membranes of different chain lengths or consisting of mixtures of short and long chains indi cates a strong dependence of V(c) on the chain composition and on the presence of charges on the polar head. The electroporation process is also analyzed in asymmetric bilayers consisting of a charged and an un charged monolayer, a condition which mimics that of natural membranes. Therefore it is possible to analyze the electrical forces acting on t he uncharged monolayer due to the presence of charges on the other one , under several ionic-strength conditions. It is shown that the instab ility arises in the uncharged monolayer, while the coupling between th e two monolayers triggers the electroporation process.