Fluorogenic probes were synthesized on fluorophore-linkerbased CPG supports (Scheme 1) using standard 3 0 -DNAphosphoramidites. An Eclipse Dark Quencher was introduced at the 5 0 end using the corresponding phosphoramidite (www. glenresearch.com). Probes were purified by reverse-phase high-performance liquid chromatography (HPLC), dried and re-dissolved in 1· TE buffer. A nearest-neighbor model was applied to calculate extinction coefficient (e 260 ) of oligonucleotides (17) . A 260 measurements were made in PBS (pH 7.2) at ambient temperature and assumed to be a random coil DNA structure in solution. For each Eclipse Quencher, fluorophore 1 (FL1), fluorophore 2 (FL2) or fluorophore 3 (FL3) substitution an e 260 correction of +6600, +18 500, or +25 100 or 28 600 M À1 cm À1 was used, respectively.