Département de chimie moléculaire

Oxidizing polyazaarom. RuII complexes contg. two TAP ligands (TAP = 1,4,5,8-tetraazaphenanthrene) are able under illumination to crosslink irreversibly the two strands of an oligonucleotide (ODN) duplex by covalent bond formation. The crosslinking proceeds by two successive absorptions of a photon. An adduct of the metallic complex on a guanine (G) base of one ODN strand is first photoproduced, followed by a second photoaddn. of the same Ru species to a G base of the complementary strand, provided that the two G moieties are sepd. by 0 or 1 base pair. These two processes lead to the crosslinking of the two strands. Such a photocrosslinking is easily detected with [Ru(TAP)2(phen)]2+ (1; phen = 1,10-phenanthroline) and [Ru(HAT)2(phen)]2+ (2; HAT = 1,4,5,8,9,12-hexaazatriphenylene), whereas it is not obsd. with [Ru(TAP)2TPAC]2+ (3; TPAC = tetrapyridoacridine) at the same level of loading of the duplex by 3. With a concn. of 3 similar to that of 1 and 2, when the loading of the duplex by 3 is much more important than with 1 and 2, the photo-crosslinking with 3 can thus also be obsd. As 3 intercalates its TPAC ligand into the base pairs stack, its mobility is restricted in the duplex. In contrast, 1 and 2 can adopt different geometries of interaction, which probably facilitate the photocrosslinking. [on SciFinder(R)]