Is O-1(2) alone sufficient for DNA cleavage? Possible involvement of paramagnetic intermediates

It is proposed that singlet dioxygen reacting with guanosine or deoxyguanos ine part of nucleotides does not, by itself, cause DNA cleavage. The strand break originates at the endoperoxide stage whenever this link evolves into a O-centered radical. The O-centered radical is then in a good spatial pos ition to abstract an hydrogen intramolecularly from the ribose or desoxyrib ose part of the nucleotide. The carbon centered radical thus formed on the sugar part may lead to strand break either by a p-scission mechanism or by an homolytically induced solvolysis. High pH could also induce cleavage aft er the endoperoxide stage via a base catalyzed ring chain protomerism.