  We report a new and facile method for measuring edge tensions of lipid
membranes. The approach is based on electroporation of giant unilamellar
vesicles and analysis of the pore closure dynamics. We applied this method to
evaluate the edge tension in membranes with four different compositions: egg
phosphatidylcholine (EggPC), dioleoylphosphatidylcholine (DOPC), and mixtures
of the latter with cholesterol and dioleoylphosphatidylethanolamine (DOPE). Our
data confirm previous results for EggPC and DOPC. The addition of 17 mol %
cholesterol to the DOPC membrane causes an increase in the membrane edge
tension. On the contrary, when the same fraction of DOPE is added to the
membrane, a decrease in the edge tension is observed, which is an unexpected
result considering the inverted-cone shape geometry of the molecule.
Presumably, interlipid hydrogen bonding lies in the origin of this behavior.
Furthermore, cholesterol was found to lower the lysis tension of DOPC bilayers.
This behavior differs from that observed on bilayers made of
stearoyloleoylphosphatidylcholine, suggesting that cholesterol influences the
membrane mechanical stability in a lipid-specific manner.
