Conformations of DNA in multilayer films with cationic amphiphiles

Multilayer films containing complexes of DNA with dodecylamine and dodecyltrimethylammonium bromide and a multilayer DNA-sphingosine film were prepared by alternating adsorption of the components on a solid support, and by the Langmuir-Blodgett technique, respectively. The conformational state of the DNA in the films was studied by IR spectroscopy. It was shown that the conformation of the DNA in the films depends on the molecular structure of the amphiphile ionic fragment. When such a fragment is the -NH + 3 group, DNA is uncoiled in the film. When the hydrogen atoms in the -NH + 3 fragment are replaced by methyl groups, DNA retains its double-helix B-form during the formation of a multilayer film with the cationic amphiphile. In a multilayer film of DNA with sphingosine, whose ionic fragment contains both amino and hydroxyl groups, DNA exists in a new double-helix conformation different from the known B-, A-, and Z-forms. Based on the molecular structure of the cationic amphiphile, a strategy of using multilayer DNA-cat-ionic amphiphile films as sensors for determining DNA-tropic substances was suggested.