Dual molecular beacon

Fig. 14. Examples of homogeneous hybridization assay methods (F luminophore, Q quencher, D donor, A acceptor). Thick lines represent DNA strands. Open circles on DNA strands indicate a SNP/mutation site for Molecular Beacon and insertion/deletion sites for dual FRET probe and dual FRET Molecular Beacon when these methods are applied to SNP/mutation typing or deletion/insertion detection. The solid circle on die strand indicates the complementary site.

Tsourkas et al. (2003) reported dual FRET molecular beacon assays, where the donor probe was labeled with either Eu3+ or Tb3+ complex of DTPA-csl24-ethylenediamine (and no quenchers attached). For the Eu3+ complex, the acceptor probe was Cy5-labeled (and no quenchers attached) and for the Tb complex, the acceptor probe was labeled with Cy3 or ROX as a fluorophore and with dabcyl as a quencher. They demonstrated that these pairs of probes detected DNA targets ( 50-mer) with high S/N. 

Santangelo, P. J. Nix, B. Tsomkas, A. Bao, G. Dual FRET molecular beacons for mRNA detection in living cells. Nucleic Acids Res. 2004, 32, e57. 

Tsourkas, A. Behlke, M. A. Xu, Y. Bao, G. Spectroscopic features of dual fluorescence/luminescence resonance energy-transfer molecular beacons. Anal. Chem. 2003, 75, 3697-3703. 

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