The rigid dinuclear [(tap)(2)Ru(tpac)Ru(tap)(2)](4+) complex (1) (TAP=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 G-rich telomeric sequence d(T(2)AG(3))(4). Complex 1, which interacts strongly with the ODNs as determined by surface plasmon resonance (SPR) and emission anisotropy experiments, gives rise under illumination to the formation of covalent adducts with the G units of the ODNs. The yield of photocrosslinking of the two strands of duplexes by 1 is the highest when the G bases of each strand are separated by three to four base pairs. This corresponds with each Ru(tap)(2) moiety of complex 1 forming an adduct with the G base. This separation distance of the G units of a duplex could be determined thanks to the rigidity of complex 1. 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 telomeric quadruplex d(T(2)AG(3))(4).

Amphiphilic molecules-molecules that have both hydrophobic and hydrophilic properties-can self-assemble in water to form diverse structures such as micelles, vesicles and tubes, and these nanostructures can be used for delivering drugs, stabilizing membrane proteins or as nanoreactors. We have previously shown that lipids can self-organize on the surface of single-walled carbon nanotubes into regular ring-shaped assemblies. Here we show that these lipid assemblies can be polymerized and isolated from the nanotube template by application of an electric field. We also demonstrate that these assemblies are monodispersed, water-soluble, and can dissolve various hydrophobic rylene dyes, fullerenes and membrane proteins. The stability of these constructs and their diverse applications will be useful in the fields of cosmetics, medicine and material sciences.

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Oxidizing polyazaaromatic Ru(II) complexes containing two TAP ligands (TAP = 1,4,5,8-tetraazaphenanthrene) are able under illumination to cross-link irreversibly the two strands of an oligonucleotide (ODN) duplex by covalent bond formation. The cross-linking 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 photoaddition of the same Ru species to a G base of the complementary strand, provided that the two G moieties are separated by 0 or 1 base pair. These two processes lead to the cross-linking of the two strands. Such a photo-cross-linking 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 observed with [Ru(TAP)(2)TPAC](2+) (3; TPAC = tetrapyridoacridine) at the same level of loading of the duplex by 3. With a concentration 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-cross-linking with 3 can thus also be observed. 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 photo-cross-linking.

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