Inter-domain interactions in charged lipid monolayers

BENJAMÍN CARUSO; LUIS REINAUDI; BRUNO MAGGIO; NATALIA WILKE

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 forming domains on the topography of Langmuir monolayers. This study was performed by the determination of two parameters that depend on the domain-domain interaction in different systems and their comparison with neutral systems [1,2]. We studied domain diffusion and domain arrangement in the plane of the monolayer. In the diffusion analysis, the domain size should be considered. We compared the change in the diffusion coefficient with the percent of liquid-condensed area for charged domains with the change found for neutral domains [2]. For fractions of condensed area higher than 20%, the diffusion coefficient decreased as the condensed area increases, and this depended on the NaCl concentration in the subphase. In comparison, the neutral domains are affected by the presence of other domains for 30% of condensed areas [2]. On the other hand, the distribution of the domains is different for charged domains in neutral environment compared with charged domains in charged environment and does not depend on the NaCl concentration. The debye length in the studied cases is in the order of nm and the domain-domain distances are in the order of the µm. Therefore the electrostatic domain-domain interactions in all cases should be related with the repulsion of the dipoles formed between the charge in the polar headgroup of the lipids and the cations at the double layer. Since this depends on the ionic strength, the result is unexpected, therefore we are still working on this. References: 1.Wilke, N; Maggio, B (2009) Journal of Physical Chemistry B. 113 12844?12851 2.Wilke, N; Vega Mercado F; Maggio, B (2010) Langmuir 26(13), 11050?11059 3.Egorova, EM. (1998) Colloids and Surfaces A. 131 7-18 4.F. Vega Mercado, B. Maggio ; N. Wilke. Chemistry and Physics of Lipids 164, 386-392 5.I.F. Sbalzarini, P. Koumoutsakos (2005) Journal of Structural Biology 151 182?195