Photoreaction of [Ru(hat)₂phen]²⁺ with Guanosine‐5′‐Monophosphate and DNA: Formation of New Types of Photoadducts

Abstract

[Ru(hat)2phen]2+ (HAT=1,4,5,8,9,12-hexaazatriphenylene, phen=1,10-phenanthroline) interacts with a good affinity with polynucleotides and DNA by intercalation, despite the presence of a second voluminous ancillary HAT ligand. It photoreacts with guanosine-5'-monophosphate (GMP). From HPLC, ESMS and NMR analyses, it can be concluded that this complex forms photoadducts with GMP. In contrast to the photoadducts isolated with Ru-TAP complexes (TAP=1,4,5,8-tetraazaphenanthrene), the photoadducts with [Ru(hat)2phen]2+ contain a covalent link between the oxygen atom of the guanine unit and a HAT ligand. Formation of oxidised photoadducts and compounds resulting from the addition of two GMP entities to the complex are also detected as side products. In the presence of oligo- and polynucleotides, [Ru(hat)2phen]2+ yields photoadducts when guanine bases are present.

Ru–TAP complexes and DNA: from photo-induced electron transfer to gene photo-silencing in living cells

“…Viscosity measurements with CT-DNA indicate that [Ru(HAT) 2 phen] 2+ induces an increase in viscosity that is slightly lower than that with ethidium bromide [34], and its retention of emission polarization anisotropy in the presence of DNA is significantly lower than that for a classical metallo-intercalator [35]. presence of 100 mM NaCl and 100 mM KCl), which is mainly attributed to important electrostatic interactions between the negatively charged phosphate backbone and the 4+ charge of the complex.…”

“…However, the high-pressure liquid chromatography and mass analyses of an illuminated solution of [Ru(HAT) 2 phen] 2+ in the presence of GMP revealed, in addition to mono-adduct production, the occurrence of a bi-adduct. In electrospray mass spectrometry, the mono-adduct is characterized by a mass representing the sum of the mass of the complex plus that of GMP minus two H atoms [33,34]. Thus, quite logically, the mass of a bi-adduct should be characterized by a total mass comprising: the mass of the complex, plus two GMP molecules and minus four H atoms.…”

“…Thus, quite logically, the mass of a bi-adduct should be characterized by a total mass comprising: the mass of the complex, plus two GMP molecules and minus four H atoms. This mass was, indeed, detected with the HAT complex [34], but no further structural information could be obtained owing to the difficulty of isolating the bi-adduct in sufficient amounts. On the basis of these results, bi-adducts should also be formed with the Ru-TAP complexes discussed earlier.…”

Photoadducts of Metallic Compounds with Nucleic Acids − Role Played by the Photoelectron Transfer Process and by the TAP and HAT Ligands in the RuII Complexes

“…[35] ESMS analyses of the isolated photoproduct with GMP confirms the addition of one GMP to the Ru complex, without loss of the polyazaaromatic ligands. Furthermore, photoadduct formation with [Ru(HAT) 2 -(phen)] 2ϩ appears only with guanine-containing synthetic oligonucleotides, [35] as shown by gel electrophoresis experiments.…”

“…[41] Therefore, this excited [Ru(HAT) 2 (TAP)] 2ϩ ȇ Ϫ ȇ [39] [Ru(TAP) 2 (HAT)] 2ϩ ȇ ȇ Ȇ [39] [Ru(HAT) 2 (phen)] 2ϩ ȇ Ϫ Ȇ [35] [Ru(TAP) 2 (phen)] 2ϩ ȇ ȇ Ȇ [55] [Ru(HAT)(TAP)(bpy)] 2ϩ ȇ Ϫ Ȇ [39] [Ru(HAT) 2 species can abstract one electron from a guanine unit of DNA or GMP. The oxidising power can be estimated from the reduction potentials of the ground state and the energy of the emission maximum (∆E λ max ) ( Table 2):…”