Itraconazole Perturbs Behavior of Fluorescent Probes in Lipid Bilayer

Abstract

1,6-diphenyl-1,3,5-hexatriene (DPH) is a frequently used fluorescence probe to study the ordering and mobility of the lipids bilayer. Here we present our studies combining molecular dynamics (MD) simulations and fluorescence anisotropy measurements in the lipid bilayer with antifungal drug Itraconazole (ITZ) added. ITZ is long, rigid, amphipathic molecule locating in the lipid bilayer below the water-membrane interface and adopting orientation parallel to the membrane surface [1]. MD simulations showed that ITZ increases the order of the hydrocarbon chains in their upper part and slightly decrease order of the lower part of the chain while steady-state fluorescence anisotropy measurement indicated substantial disordering effect of the ITZ. MD simulations of the bilayer with both ITZ and DPH showed that DPH behavior in this bilayer is determined by ITZ and not by lipids chains as assumed in traditional interpretation - DPH locates below ITZ thus its position is shifted towards bilayer center and adopt orientation parallel to the membrane surface which likely results from interactions with ITZ. These results show the limitation of the DPH in studies of lipid bilayers as DPH might report the behavior of, e.g. ITZ like molecules instead of lipids hydrocarbon chains.