ABSTRACT
Deoxyribonucleic acid (DNA) carries the genetic information of all living things and is well known to form a double-helical structure in which layers of four nucleic acids, namely, adenine, thymine, guanine, and cytosine, are stacked. DNA has a huge molecular weight of over billions and can form a clear —lm, while DNA is water soluble with sodium counterions that are not appropriate for applying DNA to material sciences such as electronic devices. However, DNA molecules become insoluble in water, yet become soluble in polar organic solvents such as ethanol, when sodium cations are replaced with quaternary ammonium salts, lipids that contain long alkyl chains to form DNA-lipid complexes, and clear and tough —lms are easily obtained by solvent casting of ethanol solutions (Wang et al. 2001).
