Unique Optical Oxygen-Sensing Performance of [Ru(IP)2(HNAIP)](2+) during the Groove-Binding-Induced B-to-Z DNA Conformational Transition.

Abstract

The oxygen-sensing performance of [Ru(IP)2(HNAIP)](2+) (Ru1, IP = imidazo[4,5-f][1,10]phenanthroline and HNAIP = 2-(2-hydroxy-1-naphthyl)imidazo [4,5-f][1,10]phenanthroline) in the presence of DNA conformational transition has been investigated by means of absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopies, and circular dichroism spectroscopy. Ru1 shows a good linear response toward oxygen between pure nitrogen and pure oxygen with an on-off emission intensity ratio (I0/I100) of up to 9.3 via a dynamic quenching mechanism. Compared with [Ru(IP)2(DHPIP)](2+) (Ru2, DHPIP = 2-(2,4-dihydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline, I0/I100 = 5.8), the HNAIP ligand endows Ru1 with favorable oxygen binding sites to achieve larger energy and electron transfer rates. Simultaneously, Ru1 can induce the B-to-Z DNA conformational transition via a groove interaction with an intrinsic binding constant (K(b)) of 7.9 × 10(4) M(-1), whereas there is no same phenomenon for Ru2 intercalated into DNA (Kb = 3.3 × 10(5) M(-1)). Furthermore, the B-to-Z DNA conformational transition is interestingly found to decrease the Ru1-based oxygen-sensing rate by about 33%.