Acceleration of DNA Cleavage by Benzidine Derivatives under Weakly Acidic Conditions

Benzidine derivatives, especially 2, 7-diaminofluorene and benzidine, accelerated the cleavage of a plasmid DNA (form I) under weakly acidic conditions at 37°C. The acceleration was not inhibited by EDTA, superoxide dismutase, catalase, or hydroxyl radical scavengers. The rate of the cleavage was influenced by the pH value of the reaction buffer. The decrease in form I DNA in this reaction obeyed first-order kinetics. It was confirmed that the cleavage was enhanced by the amines themselves, and not by their oxidized derivatives. 2, 7-Diaminofluorene also cleaved a 3'-end-labeled 40-mer DNA with A and G base specificity. These results indicate that the acceleration is caused by depurination followed by breakage of the DNA sugar backbone.