DNA-binding and DNA-photocleavaging properties of 12a,14a-diazoniapentaphene

The association of 12a,14a-diazoniapentaphene dibromide (5) with DNA and its ability to photoinduce DNA damage was studied. Spectrophotometric and fluorimetric titrations show that the title compound (5) binds to DNA (K ≈ 5·10 5 M -1 ) with the highest affinity towards GC-rich regions. The highest affinity was observed for GC base pairs. Compound 5 binds to DNA primarily by intercalation as shown by LD spectroscopy and energy-transfer experiments. Moreover, efficient DNA damage was observed on UVA irradiation in the presence of 5. Preliminary experiments suggest that singlet oxygen may be involved in the photoinduced DNA damage.