Strand breakage in DNA by silicic acid.

The alkaline unwinding assay has been used to demonstrate the formation of single-strand breaks in DNA on treatment with silicic acid. Double-stranded DNA, containing no single-strand breaks, when incubated with increasing concentrations of silicic acid, showed the formation of an increasing number of strand breaks per molecule. Experiments on reduction of silicic acid-treated DNA with NaBH4 suggested the possibility of creation of apurinic or apyrimidinic sites. The significance of silicic acid interaction with cellular DNA during asbestos exposure is discussed.