Proton-induced conformation changes and sensoric properties of polycytidilic acid immobilized in Langmuir and polyelectrolyte multilayer films

Two different types of film incorporating poly(C) were prepared: a multilayer Langmuir-Blodgett (LB) film containing dioctadecyldimethylammonium (DODA) and polyelectrolyte self-assembled (SA) films. Poly(C), which exists in a double-stranded and base-paired conformation at acidic pH (pH 5.6 in solution) was shown to undergo a transition into the single-stranded non-base-paired form on SA film preparation. In contrast, single-stranded non-protonated poly(C) (pH 7.2) transforms into the partially protonated and apparently partially double-stranded form under conditions of LB-film formation. The proton-induced conformation transition of poly(C) from single- to double-stranded form was found to take place at lower pH in the SA-film and at higher pH in the LB-film as compared with the aqueous solution. Both SA- and LB-films were able to bind nucleic acid monomers complementary to cytosine: guanosine and 2′–3′ cyclic GMP (G > p), whereas non-complementary 2′–3′ cyclic AMP was only poorely bound. A marked difference in guanosine and G > p binding was found in the films studied as well.