Electrostatic inter-domain interactions in charged lipid monolayers

BENJAMÍN CARUSO; LUIS REINAUDI; BRUNO MAGGIO; NATALIA WILKE

San Javier (Tucumán)

Congreso; XLI Reunión Anual de la Sociedad Argentina de Biofísica; 2012

Sociedad Argentina de Biofísica

In this work we evaluated the effect of a net charge on the lipids formingdomains on the topography of Langmuir monolayers. This study wasperformed by the determination of two parameters that depend on thedomain-domain interaction in different systems and their comparison withneutral systems [1,2]. We studied domain diffusion and domainarrangement in the plane of the monolayer. In the diffusion analysis, thedomain size should be considered. We compared the change in the diffusioncoefficient with the percent of liquid-condensed area for charged domainswith the change found for neutral domains [2]. For fractions of condensedarea higher than 20%, the diffusion coefficient decreased as the condensedarea increases, and this depended on the NaCl concentration in thesubphase. In comparison, the neutral domains are affected by the presenceof other domains for 30% of condensed areas [2]. On the other hand, thedistribution of the domains is different for charged domains in neutralenvironment compared with charged domains in charged environment anddoes not depend on the NaCl concentration. The debye length in the studiedcases is in the order of nm and the domain-domain distances are in the orderof the μm. Therefore the electrostatic domain-domain interactions in allcases should be related with the repulsion of the dipoles formed between thecharge in the polar headgroup of the lipids and the cations at the doublelayer. Since this depends on the ionic strength, the result is unexpected,therefore we are still working on this.