  We investigate the effect of an applied electric potential on the mechanics
of a coarse grained POPC bilayer under tension. The size and duration of our
simulations allow for a detailed and accurate study of the fluctuations.
Effects on the fluctuation spectrum, tension, bending rigidity, and bilayer
thickness are investigated in detail. In particular, the least square fitting
technique is used to calculate the fluctuation spectra. The simulations confirm
a recently proposed theory that the effect of an applied electric potential on
the membrane will be moderated by the elastic properties of the membrane. In
agreement with the theory, we find that the larger the initial tension the
larger the effect of the electric potential. Application of the electric
potential increases the amplitude of the long wavelength part of the spectrum
and the bending rigidity is deduced from the short wavelength fluctuations. The
effect of the applied electric potential on the bending rigidity is
non-existent within error bars. However, when the membrane is stretched there
is a point where the bending rigidity is lowered due to a decrease of the
thickness of the membrane. All these effects should prove important for
mechanosensitive channels and biomembrane mechanics in general.
