Determination of pore edge tension from the kinetics of rupture of giant unilamellar vesicles using the Arrhenius equation: effects of sugar concentration, surface charge and cholesterol.

Abstract

The pore edge tension (Γ) of a membrane closely intertwines with membrane stability and plays a vital role in the mechanisms that facilitate membrane resealing following pore formation caused by electrical and mechanical tensions. We have explored a straightforward procedure to determine Γ by fitting the inverse of the tension-dependent logarithm of the rate constant of rupture of giant unilamellar vesicles (GUVs) using the Arrhenius equation. The GUVs were prepared using a combination of 1,2-dioleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DOPG) and 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) in a physiological environment. The effects of sugar concentration, membrane surface charge density, and membrane cholesterol concentration on Γ have been investigated. The values of Γ increase with sugar concentration in the physiological buffer, measuring 9.6 ± 0.3, 10.4 ± 0.1, and 16.2 ± 0.1 pN for 40, 100, and 300 mM, respectively. A higher concentration of anionic lipids (70 mol% of DOPG) significantly reduces Γ. An increasing trend of Γ with cholesterol content was observed; specifically, the values of Γ were 11.9 ± 0.9, 13.9 ± 0.7, and 16.2 ± 0.4 pN for 15, 29, and 40 mol% cholesterol, respectively. Thus, the presence of higher anionic lipids in the bilayer led to a decrease in membrane stability. In contrast, the presence of higher sugar concentrations in the buffer and increased cholesterol concentration in the membranes enhanced membrane stability.