Cation-Assisted Surfactant Templating of DNA at the Air-Water Interface: New Insights into Nucleic Acid Surface...

DNA, a highly negatively charged polyelectrolyte biomolecule, shows negligible propensity for the air-water interface, as DNA prefers to remain fully hydrated in aqueous solutions. Previous studies have shown that cationic surfactants can complex with DNA at the air-water interface through electrostatic interactions and drive DNA to the interface. Here we show a new mechanism, involving DNA complexes to palmitic acid monolayers in the presence of divalent cations Mg²⁺ and Ca²⁺, suggesting that the interaction occurs through a divalent cation bridge that stabilizes DNA at the air-water interface. Interestingly, we find that the surface propensity of DNA depends on the base sequence due to differential nucleotide affinities for interfacial complexation. Oligomers with higher AT content were the most surface-active. Overall, this study provides new insights into DNA at the air-water interface under environmentally and biologically relevant conditions.