Reactions of bases of nucleic acids with mercury electrode. anodic pulse-polarographic currents of pyrimidine bases and their derivatives

Abstract

Anodic currents of pyrimidine bases were studied by using differential and normal pulse polarography, cyclic voltammetry, and classical polarography in alkaline medium. All pyrimidine bases occurring usually in nucleic acids (cytosine, uracil, thymine, 5-methylcytosine, and hydroxymethylcytosine) gave anodic DPP peaks, NPP and d.c. polarographic waves at potentials close to 0 V due to the formation of sparingly soluble salts with mercury. Nucleosides and nucleotides derived from cytosine, uracil, and thymine were inactive. The mentioned bases and other pyrimidine derivatives (isocytosine, uracil-5-carboxylic acid, uracil-6-carboxylic acid (orotic acid), 2-amino-4,6-dioxypyrimidine, 2-amino-4,6-dioxy-5-methylpyrimidine, 4-amino-2,6-dioxy-pyrimidine, and 5-amino-2,4-dioxypyrimidine) gave anodic peaks and cathodic stripping peaks during reversal of the potential sweep on a hanging drop electrode, whereas 2-aminopyrimidine and 2-hydroxypyrimidine were inactive; the concentrations used were 5 . 10-6 - 5 . 10-5M. The bahaviour of cytosine, uracil, and thymine in DPP and NPP was studied at various concentrations of the bases, pH values, pulse amplitudes, etc. Differences between the behaviour of uracil and thymine were large at higher concentrations at which the electrode surface was fully covered, and they were explained on the assumption of a different adsorption behaviour of these compounds and a large tendency of uracil to form a film on the electrode.