A DNA-lipid complex in organic media and formation of an aligned cast film

A novel DNA−lipid complex is prepared by replacing sodium counter cations by cationic amphiphilic lipids (1). The DNA−lipid complex is insoluble in aqueous solutions, but is soluble in most organic media such as benzene, ethanol, and chloroform. The DNA−lipid complex was confirmed to form double helical strands even in organic media, and the internal conformation of DNA strands could be reversibly changed from B-form to C-form in the organic solution (CHCl3/EtOH = 4:1) by changing the water content. A self-standing, water-insoluble DNA−lipid (1) film was prepared by casting from the organic solution and could be stretched to produce oriented DNA strands with their axes aligned along the stretching direction. The film can be impregnated with the drug ethidium bromide in the aqueous solution. The linear dichroism characteristics of the drug−DNA film show that the DNA strands are well oriented and the ethidium molecules are intercalated, as they are in normal aqueous solutions.