Molecular recognition at the air-water interface and Langmuir-Blodgett films

The novel amphiphile 9-octadecyladenine (AdC18), which has an adenine headgroup and a long hydrocarbon chain, was synthesized. Its monolayer behavior and its interactions with three guest molecules were investigated at the air-water interface by means of surface pressure-area isotherms. The structures of multilayer Langmuir-Blodgett (LB) films of AdC18 were characterized by Fourier transform IR spectroscopy. When the monolayer was transferred from a uridine aqueous solution to a solid substrate, the IR spectra varied significantly from the spectrum of the film transferred from the pure water subphase. Shifts of band positions and particularly the appearance of a broadened band demonstrated that guest molecules were transferred to the solid substrate along with the AdC18 monolayer and that hydrogen bonds were formed between complementary nucleobases within the LB films.