Preparation of DNA-cationic amphiphile multilayer films by alternate adsorption and a study of their structure

DNA-hexadecylamine and DNA-hexadecyltrimethylammonium bromide multilayer fi lms were produced by alternate adsorption of DNA and a cationic amphiphile on a solid support. The growth of the film was studied by UV spectroscopy T he interlayer distances, DNA conformational states, and hydration and stabi lity of the films in aqueous and aqueous-salt solutions were determined by small-angle X-ray scattering and IR and UV spectroscopies. The structures o f the films were proposed. It was shown that the DNA double helix is unwoun d during the formation of the hexadecylamine multilayer film. In the case o f hexadecyltrimethylammonium, the DNA double helix retains the B-form, but its lability diminishes; no transition into the A-form occurs with decreasi ng humidity. As for hexadecylamine, the influence of the polar head of the amphiphile molecule on the DNA conformational state occurs because of the s ubstitution of base-base intramolecular hydrogen bonds by base-hexadecylami ne intermolecular hydrogen bonds. Multilayer films containing the same comp onents but prepared under different conditions (Langmuir process or alterna te adsorption of the components on the support) were found to differ in str ucture.