Amine-Reactive Forms of a Luminescent ...

130 Bioconjugate Chem., Vol. 8, No. 2, 1997 Li and SelvinFigure 2. Lifetime of Tb 3+ and Eu 3+ bound to 2 attached tothe 5′ amine group of synthetic DNA. The Tb data are for DNAhybridized to an unlabeled complement. Solution conditions arethe same as in Table 1. Data were acquired every 2 µs, digitallybinned every 10 µs, and curve fit to a single exponential whichshowed no residual structure and r 2 > 0.99.Table 1. Lanthanide Excited State Lifetime Attached toDNA asample H 2O; RT (ms) D 2O; RT (ms) D 2O; 5 °C (ms)Tb-anhydride 1.5 (1.25) 2.38 (2.0) 2.98 (2.1-2.5)Tb-ITC 1.43 (1.35) 2.50 (2.19) 3.06Eu-anhydride 0.63 (0.63) (2.38) 2.41 (2.46)Eu-ITC (0.60) 2.39 2.45aThe table shows the excited state lifetime of terbium oreuropium attached to DNA either via 2 or via the anhydridereaction. The numbers in parentheses correspond to unhybridizedDNA, those not in parentheses to lanthanide-labeled DNA hybridizedto an unlabeled complement. Data were taken at 10 mM Tris,pH 8.0, 10 mM MgCl 2, 150 mM NaCl. In some cases, particularlythe single-stranded DNA, there was a minor component (