Preparation and properties of DNA–lipid complexes carrying pyrene and anthracene moieties

Novel DNA–lipid complexes carrying pyrene and anthracene were prepared by substituting sodium counter cations with cationic amphiphilic lipids, namely lipid(PY) and lipid(Anth), in which the actual mole ratios of phosphate to lipid were 1:1.11 and 1:1.03, respectively. DNA–lipid(PY) and DNA–lipid(Anth) complexes were soluble in common organic solvents including CHCl3, CH2Cl2, methanol and ethanol, while insoluble in THF, toluene, and aqueous solutions. CD spectroscopy revealed that DNA–lipid(PY) and DNA–lipid(Anth) complexes took a predominantly double helical structure in methanol and that the helical structure was fairly stable against heating. The solution of DNA–lipid(PY) complex emitted fluorescence in 27.8% quantum yield, which were higher than that of the corresponding lipid(PY) (16.8%), while the fluorescence quantum yields of the solution of DNA–lipid(Anth) (45.4%) was lower than that of the lipid(Anth) (53.0%). The onset temperatures of weight loss of DNA–lipid(PY) and DNA–lipid(Anth) were both 220 °C according to TGA in air.