DNA-lipid complexes carrying azobenzene moieties: Preparation, characterization, and photoisomerization

- Novel DNA-lipid complexes carrying azobenzene were prepared by substituting sodium counter cations with cationic amphiphilic lipid(AZO) and lipid(diAZO); the actual molar ratios of phosphate to lipid in the products were 1:1.05 and 1:1.02. CD spectroscopic studies revealed that DNA-lipid(AZO) and DNA-lipid(diAZO) took predominantly double helical structure in methanol, and the helical structure was very stable against heating. The trans-azobenzene of the DNA-lipid complexes in the side chain isomerized into cis upon UV irradiation, and reisomerized into trans upon visible-light irradiation, but they did not recover completely the original geometry of azobenzene moieties in the side chain. Both DNA-lipid(AZO) and DNA-lipid(diAZO) exhibited lyotropic liquid crystalline properties.