Molecular dynamics simulation of DPPC bilayer in DMSO.

We performed molecular dynamics simulations on dipalmitoylphosphatidylcholine (DPPC)/dimethylsulfoxide (DMSO) system that has the same lipid:solvent weight ratio as in our previous simulation done on DPPC/water. We did not observe a large change in the size of DPPC membrane when the solvent was changed from water to DMSO. Also, we did not observe that a large number of DMSO molecules is permeating into the membrane, as it was suggested to explain the observed change in the bilayer repeat period. We found that the surface potential reverses its sign when water is replaced by DMSO. Based on the results from our simulations, we propose that the repulsion force acting between membranes is reduced when DMSO is added to solvent water and therefore membrane surfaces approach closer to each other and the extra solvent is removed into excess solution.