Electrochemical properties of 4-thiouracil derivatives

Abstract

A study has been made of the polarographic behaviour of 4-thiouracil and its N-methylated derivatives, and of 4-thiouridine. Similar electrochemical properties are exhibited by all the compounds with a 2-keto-4-thione structure. In acid medium they give a typical catalytic hydrogen discharge wave, which disappears completely at pH values above 6. At pH values above 4.2 a second catalytic wave appears. Maximal catalytic activity is exhibited at pH 7.1, and decreases with increasing pH. Both catalytic waves possess pronounced surface characteristics, most likely due to adsorption of the molecules with differing orientations on the electrode surface. The second catalytic wave overlaps the reduction wave, which is placed in evidence under conditions where the catalytic effect is absent. The reduction wave is a 4 e −/4H + process involving reduction of the 4-thiouracil ring to 5,6-dihydropyrimidone-2. The same product is formed by a 2 e −/2H + reduction of 5,6-dihydro-4-thiouracil. The potential applications of the electrochemical properties of 4-thiouracil to studies on tRNA structure are discussed.