Ru(II) complexes and light: molecular tools for biomolecules

Abstract

Ruthenium(II) (Ru(II)) complexes are the focus of numerous research works with various applications mainly due to their attractive photophysical and photochemical properties. In biological research areas, in particular, they are developed as efficient photoprobes or photosensors of biological molecules. More interestingly specific Ru(II) complexes bearing p-deficient ligands such as TAP ¼ 1,4,5,8-tetraazaphenanthrene, bpz ¼ 2,2(-bipyrazyl or HAT ¼ 1,4,5,8,9,12-hexaazatriphenylene exhibit interesting photoreactivity with biomolecules (DNA, polypeptides). The photoreactions are initiated by a photo-electron transfer from the biomolecule to the excited metal complex. A back electron transfer (BET) succeeds this primary process. However in competition with this BET, a DNA photocleavage and/or formation of adducts of the complex with guanine units of DNA or with tryptophan (Trp) residues of polypeptides can take place. In this review we highlight the studies of these photo-adducts carried out by our laboratories, and connected to some applications.

A Rigid Dinuclear Ruthenium(II) Complex as an Efficient Photoactive Agent for Bridging Two Guanine Bases of a Duplex or Quadruplex Oligonucleotide

“…These two steps give rise to the bridging of the two ODN strands. [3] With the aim of exploring novel targets for these photocrosslinkings and also improving these photoinduced double anchoring processes, we studied an a priori more appropriate Ru complex, namely the dinuclear [(tap) 2 RuA C H T U N G T R E N N U N G (tpac)Ru-A C H T U N G T R E N N U N G (tap) 2 ] 4 + complex (1, TPAC= tetrapyridoacridine). The photophysical and electrochemical properties of this compound suggest that it should act as an efficient photocrosslinking agent for the following reasons.…”

“…[1,2] Moreover, these Ru compounds are capable of crosslinking covalently two complementary oligodeoxyribonucleotide (ODN) strands, provided that each strand contains at least one G base, separated from each other by no or one base pair. However, the yield of this photoreaction is rather low because the crosslinking requires two successive absorptions of a photon by the same Ru species.…”

“…On the basis of results of gel electrophoresis, mass spectrometry, and molecular modelling, it is suggested that such photocrosslinking can also occur intramolecularly in the human telome-A C H T U N G T R E N N U N G ric quadruplex dA C H T U N G T R E N N U N G (T 2 AG 3 ) 4 . Keywords: DNA · N ligands · oligonucleotides · photochemistry · ruthenium [RuA C H T U N G T R E N N U N G (tap) 2 …”

“…The rigid dinuclear [(tap) 2 RuA C H T U N G T R E N N U N G (tpac)RuA C H T U N G T R E N N U N G (tap) 2 ] 4 + complex (1) (T AP= 1,4,5,8-tetraazaphenanthrene, TPAC = tetrapyridoacridine) is shown to be much more efficient than the mononuclear bis-TAP complexes at photodamaging oligodeoxyribonucleotides (ODNs) containing guanine (G). This is particularly striking with the Grich telomeric sequence dA C H T U N G T R E N N U N G (T 2 AG 3 ) 4 .…”

Excited state behaviour of substituted dipyridophenazine Cr(iii) complexes in the presence of nucleic acids

“…[7][8][9] d6 complexes such as those of ruthenium( II) or rhenium(I) have been extensively investigated as an advantage of these compounds is that their photochemical and photophysical properties can be readily tuned. For instance it is often possible to select a complex with an excited state having an appropriate redox potential or one which shows exquisite sensitivity to its environment.…”