Detection of higher-ordered DNA sequence by using terbium(III) luminescence

The detection of higher-ordered sequences of DNA such as the dyad symmetrical sequence was investigated using Tb(III) luminescence, based on energy transfer from excited bases in a single stranded DNA probe. An oligonucleotide carrying an iminodiacetic acid function as metal chelating moiety was used as the probe. The Tb(III) complex with this probe gave luminescence characteristic of Tb(III). The intensity of this luminescence was considerably suppressed when bound to the targeted double stranded DNA to form a triple helix. This behavior was especially pronounced when the probe forms a 2:1 (probe strand: Tb(III)) complex on the target double strand carrying a dyad symmetrical base sequence. When the analyte DNA strand does not contain a complementary sequence to the probe, the intensity of the luminescence was scarcely influenced. This characteristic luminescence change will be useful for detecting target genes having a higher-ordered sequence.