COSURFACTANTS LOWER SURFACE-TENSION OF THE DIGLYCERIDE WATER INTERFACE - A MOLECULAR-DYNAMICS STUDY/

We performed molecular dynamics (MD) simulations of bulk 1,2-dilauroyl -sn-glycerol (DLG) systems in contact with a water layer. In the DLG o il phase cosurfactants were placed with increasing concentration: 1-mo nolauroyl-sn-glycerol (1MG), 2-monolauroylglycerol (2MG), and dodecano ic acid (FA, fatty acid). These cosurfactants are hydrolysis products of lipase activity that take place on the DLG interface. We performed four simulations at 340 K of 2.5 ns each: two with different concentra tion of monoglycerides and fatty acids (uncharged or nondissociated) a nd two simulations with comparable concentrations, but which contained charged fatty acids and Na+-counterions. The latter system is a more realistic model and we were interested if the charges were of influenc e on the results. We describe the behavior of the DLG and cosurfactant molecules and the effect of the latter molecules on the interfacial p roperties. The main effects are that these cosurfactants apparently lo wer the surface tension and increase the total order of all molecules at the interface. Another observation is that the cosurfactants do not show a clustering behavior (e.g. hydrophilic patches at the interface ), but do not form a disperse pattern either. Introducing charges in t hese systems does not produce significant differences.