WILKE NATALIA
Congresos y reuniones científicas
Título:
Effect of externally applied electric field on lipid monolayers at the air-water interfase
Autor/es:
N. WILKE, BRUNO MAGGIO1, SERGIO A. DASSIE, EZEQUIEL P. M. LEIVA
Lugar:
La Cumbre
Reunión:
Taller; Primera Escuela Argentina de Matemática y Biología; 2005
Institución organizadora:
BioMat
Resumen:
Lipid and protein molecules anisotropically oriented at a hydrocarbon-aqueous interface configure a dynamic array of selforganized
molecular dipoles. Electrostatic fields applied to lipid monolayers have been shown to induce in-plane migration of
domains or phase separation in a homogeneous system. In this work, we have investigated the effect of externally applied electrostatic
fields on the distribution of the condensed ceramide-enriched domains in mixed monolayers with sphingomyelin. In
these monolayers, the lipid segregates in different phases at all pressures. This allows analyzing by epifluorescence microscopy
the effect of the electrostatic field at all lateral pressures since dark domains are always present. Our observations indicate that
a positive potential applied to an electrode placed over the monolayer induces lateral displacements of the dark-condensed
domains from the electrode perturbed region. The effect is rather insensitive to the film composition, depends inversely on the
lateral pressure and exhibits threshold dependence on the in-plane elasticity. The experimental results were modeled considering
the repulsive force created by the electrostatic field on the dipole clusters and an opposing force generated by the dipolar
repulsion between the domains. The electric force was calculated assuming a cylindrical rode homogeneously charged (electrode)
at a given distance of the ground (electrolyte solution). Once a steady state of displacement is reached, the electrode and
the dipolar forces are compensated for two exclusion zone sizes values.
molecular dipoles. Electrostatic fields applied to lipid monolayers have been shown to induce in-plane migration of
domains or phase separation in a homogeneous system. In this work, we have investigated the effect of externally applied electrostatic
fields on the distribution of the condensed ceramide-enriched domains in mixed monolayers with sphingomyelin. In
these monolayers, the lipid segregates in different phases at all pressures. This allows analyzing by epifluorescence microscopy
the effect of the electrostatic field at all lateral pressures since dark domains are always present. Our observations indicate that
a positive potential applied to an electrode placed over the monolayer induces lateral displacements of the dark-condensed
domains from the electrode perturbed region. The effect is rather insensitive to the film composition, depends inversely on the
lateral pressure and exhibits threshold dependence on the in-plane elasticity. The experimental results were modeled considering
the repulsive force created by the electrostatic field on the dipole clusters and an opposing force generated by the dipolar
repulsion between the domains. The electric force was calculated assuming a cylindrical rode homogeneously charged (electrode)
at a given distance of the ground (electrolyte solution). Once a steady state of displacement is reached, the electrode and
the dipolar forces are compensated for two exclusion zone sizes values.
