Label-free luminescence switch-on detection of hepatitis C virus NS3 helicase activity using a G-quadruplex-selective probeElectronic supplementary information (ESI) available: Compound characterisation and supplementary data. See DOI: 10.1039/c4sc03319a

A series of luminescent Ir( iii ) complexes were synthesised and evaluated for their ability to act as luminescent G-quadruplex-selective probes. The Ir( iii ) complex 9 , [Ir(phq) 2 (phen)]PF 6 (where phq = 2-phenylquinoline; phen = 1,10-phenanthroline), exhibited high luminescence in the presence of G-quadruplex DNA compared to dsDNA and ssDNA, and was employed to construct a label-free G-quadruplex-based assay for hepatitis C virus NS3 helicase activity in aqueous solution. Moreover, the application of the assay for screening potential helicase inhibitors was demonstrated. To our knowledge, this is the first G-quadruplex-based assay for helicase activity. A novel luminescent G-quadruplex-selective iridium( iii ) complex was employed in a label-free G-quadruplex-based detection assay for hepatitis C virus NS3 helicase activity.