Mechanical properties of monolayers composed of dmpc:dspc mixtures

F. VEGA MERCADO, B. MAGGIO, N. WILKE

Congreso; VII Iberoamerican Congreso of Biophysics; 2009

Many biologically relevant monolayers show coexistence of discrete domains of a long-range ordered condensedphase dispersed in a continuous, disordered, liquid-expanded phase. In this work, we determined the viscous and elasticcomponents of the compressibility modulus and the shear viscosity of monolayers exhibiting phase coexistence with theaim at elucidating the contribution of each phase to the observed monolayer mechanical properties. To this purpose,mixed monolayers with different proportions of distearoylphosphatidylcholine (DSPC) and dimyristoylphosphatidylcholine(DMPC) were prepared and their rheological properties were analyzed. The relationship between the phasediagram of the mixture at 10 mN m-1 and the rheological properties was studied. We found that the monolayer shearviscosity is highly dependent on the presence of domains and on the domain density. In turn, the monolayercompressibility is only influenced by the presence of domains for high domain densities. For monolayers that lookhomogeneous on the micrometer scale (DSPC amount lower that 23 mol %), all the analyzed rheological propertiesremain similar to those observed for pure DMPC monolayers, indicating that in this proportion range the DSPCmolecules contribute as DMPC to the surface rheology in spite of having hydrocarbon chains four carbons longer