We have measured the effect of tension on dimerization kinetics of the
channel-forming peptide gramicidin A. By aspirating large unilamellar
vesicles into a micropipette electrode, we are able to simultaneously
monitor membrane tension and electrical activity. We find that the di
mer formation rate increases by a factor of 5 as tension ranges from 0
to 4 dyn/cm. The dimer lifetime also increases with tension. This beh
avior is well described by a phenomenological model of membrane elasti
city in which tension modulates the mismatch in thickness between the
gramicidin dimer and membrane.