On the interaction of [Ru(phen)₂dppz]²⁺ (dppz = dipyrido[3,2-a:2',3' c]phenazine) with different oligonucleotides

Luminescent titrations have been performed on a 'molecular light switch for DNA', [Ru(phen)₂dppz]²⁺ (dppz= dipyrido[3,2-a:2',3'-c]phenazine), with several different 16-bp oligonucleotides having sequence-directed shape ('straight', 'bent' and 'kinked'). Binding constants and binding site sizes are consistent with metal complex intercalation for all oligonucleotides. The emission maxima and relative intensities upon saturation are consistent with trends found for long DNAs based on relative GC content. [Ru(phen)₂dppz]²⁺ has a significantly higher binding constant and larger site size for the 'kinked' oligonucleotide than for the 'straight' and 'bent', suggesting that local DNA deformation plays a role in the interaction of metallointercalators with DNA.