446 -- Electrochemical examination of nucleoside interaction : Adenosine--guanosine and cytidine--guanosine

Abstract

The adsorption at the solution/mercury electrode interface of guanosine, adenosine and cytidine alone and in guanosine--adenosine and guanosine--cytidine mixtures was examined for pH 4.0 and 7.2 solutions at 25 and 40[deg]C; the principal index used was the a.c. polarographic quadrature current component. All of the nucleosides are adsorbed at the 1.0 mM and lower concentrations examined. There is evidence at 25[deg]C for: 1. (a) the self-association of uncharged adsorbed guanosine;2. (b) formation at pH 4 of a 2 : 1 guanosine--adenosine complex, which is at least partially positively charged, is more stable than the self-associated guanosine and associates in the adsorbed state;3. (c) formation at pH 7.2 of a similar 2 : 1 but uncharged guanosine--adenosine complex;4. (d) formation of a probably positively charged 1 : 1 guanosine--cytidine complex, which adsorbs and associates at pH 4 and of a similar neutral complex at pH 7.2.Association of the adsorbed species is not seen at 40[deg]C. The controlling factor in determining the differential capacitance at the interface is generally the presence of the most surface-active species, guanosine.