Inter-Domain Interactions in Charged Lipid Monolayers

BENJAMÍN CARUSO; MARCOS VILLARREAL; LUIS REINAUDI; NATALIA WILKE

JOURNAL OF PHYSICAL CHEMISTRY B - (Print)

AMER CHEMICAL SOC

Lugar: Washington; Año: 2014 vol. 118 p. 19 - 529

1520-6106

Phase coexistence is common in model bio-membranes with the presence of domains formed by lipids in a dense phase state modulating lateral diffusion of species through hydrodynamic and electrostatic interactions. In this study, inter-domain interactions in monolayers of charged surfactants were analyzed and compared with neutral systems. Interactions were investigated at different inter-domain distances and by varying the ionic strength (I) of the subphase. At low percentages of condensed area (%Ac), i.e. high inter-domain distances, domains were approximated as point charges or dipoles, and a comparison between the simulated and experimental results was made. At high %Ac, domains were arranged in a distorted hexagonal lattice, and the energy of a domain around its equilibrium position in the lattice was modeled using a harmonic potential and the spring constant determined.On subphases of high I, charged domains interacted in a manner similar to neutral domains with domain motion being precluded at high percentages of condensed area. At low I, a higher inter-domain repulsion was observed along with a lower domain motion and, therefore, a higher apparent viscosity at comparable %Ac. Interestingly, this effect was observed at conditions where the Debye-Hückel length was still two orders lower than the inter-domain distances.