We have performed electrical measurements on bilayer lipid membranes (
BLMs) in the presence of nisin. The membranes were formed in 0.1 M KCI
solution following the technique of Montal-Mueller as well as that of
Rudin-Mueller. Nisin was dissolved in water and introduced in small a
mount into one side (cis-side) of the solution bathing the membrane to
final concentrations of 10(-7)-10(-5) M. By applying external voltage
s of different polarity, membrane conductance increases were observed.
In Montal-Mueller membranes, channels with elementary conductance of
about 145 pS were detected both for trans-negative and trans-positive
potentials (50 mV). Channels with elementary conductance around 400 pS
were observed only for trans-negative potentials. The log-log plot of
macroscopic conductance versus nisin concentration was linear with a
slope of (1.0 +/- 0.1), showing that one nisin molecule is involved in
channel formation.