Bioelectrochemisry and Bioenergetics. 34 ( 1994) 101 - 107

# Deformation of a lipid vesicle in an electric field: a theoretical study

## A. Sokirko ^{1},
V. Pastushenko^{2},
S. Svetina^{3} and
Ž i e kš ^{3}

^{1}
Department of Chemistry, Trent University, Peterborough K9J 7BR Ontario (Canada)

^{2}
Institute of Biophysics, J. Kepler University of Linz, Altenbergerstr. 69, A-4040 Linz-Auhof (Austria)

^{3}
Institute of Biophysics, Medical Faculty and J. Stefan Institute, University of Ljubljana,
Lipičeta, 61105 Ljubljana (Slovenia)

### Abstract

The deformation of a lipid vesicle in an external electric field is analyzed assuming constant membrane
area and variable vesicle volume doe to water transport through the membrane. The shape of the vesicle is
approximated by a rotational ellipsoid. The equilibrium ratio of the semi-axes varies monotonically with field
strength *E*_{0}. This ratio is useful for experimental determination of the bending elasticity
modulus. The kinetics of vesicle deformation is described by the characteristic relaxation time *t*.
This time increases drastically with vesicle size. A non-monotonic dependence of *t* on *E*_{0}
is shown numerically and analytically. For weak and strong fields *t*is proportional to
*E*_{0}^{4} and *E*_{0}^{-8/3}_{ }respectively.