Non-homogeneous rheological and electrostatic properties in biointerfaces: effect on the dynamics

WILKE NATALIA

Salta

Congreso; XIV Reunion de la Sociedad Argentina de Biofísica, conjunta con Latin American Protein Society; 2010

Sociedad Argentina de Biofísica y Latin American Protein Society

Contrary to the Singer and Nicolson fluid mosaic model, most natural membranes show phase coexistence, normally characterized by segregated domains in a more fluid environment. It is expected (and has already been demonstrated in several systems) that the presence of the domains influences not only the local but also the macroscopic rheological properties of the membrane. In turn, the rheological properties of the membrane influence important biological phenomena, such as the fusion of vesicles, the breakdown of foams and emulsions, the opening of transitory pores, and the lateral diffusion of the components in membranes, which is a factor that determines, among others, the velocity of biochemical reaction-diffusion processes8 and thus the function of cells. The understanding of factors that define the mechanical properties of membranes, being complex two-dimensional fluids, is an active research area that has not yet been completely deciphered. The domains, which can reach to tens of micrometers, provide an inhomogeneous scenario, not only related to rheological properties but also to electrostatics. The electrostatic field generated by the domains can attract or repel the diffusing components thus influencing its lateral motion. In the present work, I recount the influence of the presence of domains on the mechanical and electrostatic properties of Langmuir lipid monolayers. The shear properties are determined analyzing the Brownian motion of domains and/or microscopically sized beads inserted at the interface. The compressibility properties are obtained trough experiments with oscillatory variations of the trough area.