Terbium chelate as donor label in time-resolved fluorescence energy transfer study of DNA hybridization

A terbium chelate formed with diethylenetriaminepentaacetic acid and p-aminosalicylic acid (Tb–DTPA–pAS) was labeled on a 23-mer DNA strand and used as donor in the fluorescence resonance energy transfer (FRET) study of DNA hybridization. The change in donor fluorescence lifetime with and without DNA-bind acceptor carboxytetramethylrhodamine (TAMRA) showed high energy transfer efficiency (87%). The distance between the two ends of the 23-mer double-stranded DNA was estimated. This study provides a possibility of using the Tb-chelate as a probe in the studies of the geometry-dependent interaction between DNA strands or proteins.