aDepartament de Fisica, Universitat Autonoma de Barcelona, Bellaterra, Spain
bDepartment of Physics and Astronomy and Ames Laboratory, Iowa State University, Ames, Iowa 50011, United States
Abstract:
In this paper, we argue that many of the fascinating electrostatic effects that take place in amphiphilic systems are strongly related to the particular organization of the oxygen atoms within each individual molecule. In particular, we focus on two effects: charge inversion and dielectric overscreening. For that purpose, we present molecular dynamics simulations of phosphatidic acid (DMPA2?) in the presence of divalent counterions. Our results show that the many oxygens present in DMPA2? cooperatively create strong binding sites for counterions, which in some cases lead to charge inversion. We also present an analysis of the role of interfacial water and relate our analysis to the phenomenon of dielectric overscreening. Several experimental implications are discussed in the conclusions.