Département de chimie moléculaire

The damaging efficacy towards OligoDeoxyriboNucleotides (ODNs) of two photoreactive polyazaarom. rutheniumII complexes, Ru(T) and Ru(D), has been evaluated. Both compds. correspond to the known [Ru(TAP)2(dppz)]2+ complex, but they are anchored differently to a guanine-contg. single strand ODN (probe strand). This has allowed us to investigate the influence of the interactions existing between the tethered complexes and the single or double strand, on the photo-ligation processes. From melting temp. measurements of the duplex formed between these Ru-ODNs and their complementary sequence (target strand), it has been found that Ru(T) anchored via the TAP ligand interacts with the duplex by means of the intercalating dppz ligand (head on geometry), while Ru(D) anchored via the dppz ligand likely adopts a side on geometry without intercalation. Both single stranded Ru conjugates self-inhibit in the absence of their target ODN by forming exclusively a cyclic "seppuku" photo-adduct (intra-mol. photoreaction). In contrast, this intra-mol. photo-product is precluded in presence of the target strand, and the Ru-ODN sequence photo-crosslinks with the latter (inter-mol. photoreaction). Both intra- and inter-mol. processes with both complexes are efficient (80{%} yields) and lead to stable photo-adducts. Interestingly, detailed studies have revealed that the similar photo-damaging efficacy of crosslinking by Ru(T) and Ru(D) is a consequence of a cascade of events with compensatory effects, originating from the different geometry of interaction of the tethered complexes. Notably, antagonistic effects are present when the complex is intercalated, the guanine oxidn. step being highly favored and the recombination of the quenching products being hindered. [on SciFinder(R)]