Figure 2.

The presence of the quencher on one terminus of a short, single-stranded oligonucleotide (here T11) reduces the excited-state lifetime of a ruthenium complex on the opposite terminus, with the magnitude of the reduction reflecting the end-to-end collision rate. A construct lacking any quencher exhibits a biexponential decay (top residuals) with lifetimes of 461 ± 4 and 18 ± 2 ns. The slower of these two decays is accelerated significantly in the presence of either methyl viologen (249 ± 30 ns) or DABSYL (132 ns) on the opposite terminus. In contrast, the more rapid of these two lifetimes is unaffected by the presence of the quenchers (21 ± 10 ns and 19 ± 1 ns for methyl viologen and DABSYL, respectively).