Electric field-induced reorganization of a two-component lipid monolayer. An experimental and theoretical approach

NATALIA WILKE, LUIS REINAUDI, SERGIO A. DASSIE, BRUNO MAGGIO, EZEQUIEL P. M. LEIVA

Montevideo

Conferencia; 6th International Conference of Biological Physics; 2007

Intrinsic electrostatic features of lipid and protein molecules anisotropically oriented at hydrocarbon-aqueous interface can act as sensitive local and long-range sensors of the electric properties along and across a biomembrane interface. The resultant dipole moment densities, in conjunction with line tension forces, are major factors responsible for the individual morphology of coexisting phase domains as well as their lattice organization along the surface. Electrostatic field applied to lipid monolayers have been shown to induce in-plane migration of domains or phase separation in a homogeneous system.We have investigated the effect of externally applied electrostatic fields on the distribution of the domains formed in different inmiscible binary lipid monolayers. A positive potential applied above the monolayer induced domain migration away from under the electrode until a steady state is reached in which a circular constant-size exclusion zone of domains is achieved. We proposed a model that explains the properties of the achieved steady state in terms of the forces acting on domains present on the border of the exclusion zone, which are the electric field force and the dipolar repulsive force generated by the surrounding domains.In this work, we investigate the process through which the steady state is achieved. The kinetic of this process depends on the forces involved in the steady state and on the drag force experimented by the moving domains. Besides, the electrical permittivity of the monolayer influences this process although it does not influence the steady state. The distribution of the domains at different experimental times is compared with the results predicted by the system motion equations.On the other hand, the experimental system can be simulated by Brownian dynamics assuming the domains are point dipoles. In this way, a simulated experiment was performed and their behavior was compared with the experimental behavior.