Understanding the factors controlling the photo-oxidation of natural DNA by enantiomerically pure intercalating ruthenium polypyridyl complexes through TA/TRIR studies with polydeoxynucleotides and mixed sequence oligodeoxynucleotides.

Ruthenium polypyridyl complexes which can sensitise the photo-oxidation of nucleic acids and other biological molecules show potential for photo-therapeutic applications. In this article a combination of transient visible absorption (TrA) and time-resolved infra-red (TRIR) spectroscopy are used to compare the photo-oxidation of guanine by the enantiomers of [Ru(TAP)(dppz)] in both polymeric {poly(dG-dC), poly(dA-dT) and natural DNA} and small mixed-sequence duplex-forming oligodeoxynucleotides. The products of electron transfer are readily monitored by the appearance of a characteristic TRIR band centred at 1700 cm for the guanine radical cation and a band centered at 515 nm in the TrA for the reduced ruthenium complex.

Controlled dehydration of a ruthenium complex-DNA crystal induces reversible DNA kinking.

Hydration-dependent DNA deformation has been known since Rosalind Franklin recognized that the relative humidity of the sample had to be maintained to observe a single conformation in DNA fiber diffraction. We now report for the first time the crystal structure, at the atomic level, of a dehydrated form of a DNA duplex and demonstrate the reversible interconversion to the hydrated form at room temperature. This system, containing d(TCGGCGCCGA) in the presence of Λ-[Ru(TAP)2(dppz)](2+) (TAP = 1,4,5,8-tetraazaphenanthrene, dppz = dipyrido[3,2-a:2',3'-c]phenazine), undergoes a partial transition from an A/B hybrid to the A-DNA conformation, at 84-79% relative humidity.

Crystal structures of Λ-[Ru(phen)₂dppz]²⁺ with oligonucleotides containing TA/TA and AT/AT steps show two intercalation modes.

The ruthenium complex [Ru(phen)(2)(dppz)](2+) (where phen is phenanthroline and dppz dipyridophenazine is known as a 'light switch' complex because its luminescence in solution is significantly enhanced in the presence of DNA. This property is poised to serve in diagnostic and therapeutic applications, but its binding mode with DNA needs to be elucidated further. Here, we describe the crystal structures of the Λ enantiomer bound to two oligonucleotide duplexes.

Structure determination of an intercalating ruthenium dipyridophenazine complex which kinks DNA by semiintercalation of a tetraazaphenanthrene ligand.

We describe a crystal structure, at atomic resolution (1.1 Å, 100 K), of a ruthenium polypyridyl complex bound to duplex DNA, in which one ligand acts as a wedge in the minor groove, resulting in the 51° kinking of the double helix. The complex cation Λ-[Ru(1,4,5,8-tetraazaphenanthrene)(2)(dipyridophenazine)](2+) crystallizes in a 11 ratio with the oligonucleotide d(TCGGCGCCGA) in the presence of barium ions.