Dynamical membrane curvature instability controlled by intermonolayer friction

Abstract

We study a dynamical curvature instability caused by a local chemical modification of aphospholipid membrane. In our experiments, a basic solution is microinjected close to agiant unilamellar vesicle, which induces a local chemical modification of somelipids in the external monolayer of the membrane. This modification causes alocal deformation of the vesicle, which then relaxes. We present a theoreticaldescription of this instability, taking into account both the change of the equilibriumlipid density and the change of the spontaneous membrane curvature inducedby the chemical modification. We show that these two types of changes of themembrane properties yield different dynamics. In contrast, it is impossible todistinguish them when studying the equilibrium shape of a vesicle subjected to aglobal modification. In our model, the longest relaxation timescale is related to theintermonolayer friction, which plays an important part when there is a change in theequilibrium density in one monolayer. We compare our experimental results to thepredictions of our model by fitting the measured time evolution of the deformationheight to the solution of our dynamical equations. We obtain good agreementbetween theory and experiments. Our fits enable us to estimate the intermonolayerfriction coefficient, yielding values that are consistent with previous measurements.