COMPARATIVE-STUDIES OF THE INTERFACIAL BEHAVIOR OF SOME NUCLEIC-ACID BASES WITH AND WITHOUT THIO GROUP

A comparative study on the adsorption and association of nucleic acid bases with and without thio group such as guanine (Gua) guanosine (Guo), 6-thioguanine (6SGua), 6-thioguanosine (6SGuo) and 8-thioguanosine (8SGuo) was conducted using phase sensitive ac voltammetry. The reduction of the adsorbed species at the charged interface was studied using cyclic voltammetry and controlled potential coulometry. The influence of the tho group on the stacking interaction between vertically oriented molecules is discussed. The limiting value of the surface concentration Gamma(m) and the average area S-m per adsorbed molecule indicates the rather more compact interfacial structure for thioguanine and thioguanosine than for guanine and guanosine. The extent of intermolecular and intramolecular association is most pronounced for the nucleic acid bases containing this group.