Chemical reclosure of opened imidazole ring of guanine.

Imidazole ring opened adenine and guanine residues similar to those generated by gamma-irradiation of nucleosides of DNA, were chemically synthesised. Reaction conditions that promote the chemical reclosure of opened imidazole rings of guanine have been identified. The optimal conditions for the reclosure of such rings was found to be 0.2 M HCl at 37 degrees C. These conditions did not promote a reclosure of opened imidazole rings of adenine. The reclosure of opened imidazole rings of guanine was found to follow first order kinetics. The very low pH for this chemical ring reclosure precludes the likelihood that this reaction occurs intracellularly.