title: Atomistic simulations of pH-dependent self-assembly of micelle and bilayer from fatty acids.
abstract: Detailed knowledge of the self-assembly and phase behavior of pH-sensitive surfactants has implications in areas such as targeted drug delivery. Here we present a study of the formation of micelle and bilayer from lauric acids using a state-of-the-art simulation technique, continuous constant pH molecular dynamics (CpHMD) with conformational sampling in explicit solvent and the pH-based replica-exchange protocol. We find that at high pH conditions a spherical micelle is formed, while at low pH conditions a bilayer is formed with a considerable degree of interdigitation. The mid-point of the phase transition is in good agreement with experiment. Preliminary investigation also reveals that the effect of counterions and salt screening shifts the transition mid-point and does not change the structure of the surfactant assembly. Based on these data we suggest that CpHMD simulations may be applied to computational design of surfactant-based nano devices in the future.
authors.affiliation: Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland 21201, USA.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Morrow
authors.forename: Peter H
authors.initials: PH
authors.lastname: Koenig
authors.forename: Jana K
authors.initials: JK
authors.lastname: Shen
mesh_terms: D003198:Computer Simulation; D005227:Fatty Acids / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000737:chemistry*; D008823:Micelles; D008956:Models, Chemical; D008958:Models, Molecular; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D005227:Fatty Acids; D008051:Lipid Bilayers; D008823:Micelles; D013501:Surface-Active Agents