Synthesis and Properties of Oligonucleotides Containing Novel Fluorescent Biaryl Units

Fine Tuning of Pyrene Excimer Fluorescence in Molecular Beacons by Alteration of the Monomer Structure

Oligonucleotide probes labeled with pyrene pairs that form excimers have a number of applications in hybridization analysis of nucleic acids. A long excited state lifetime, large Stokes shift, and chemical stability make pyrene excimer an attractive fluorescent label. Here we report synthesis of chiral phosphoramidite building blocks based on (R)-4-amino-2,2-dimethylbutane-1,3-diol, easily available from an inexpensive d-(-)-pantolactone. 1-Pyreneacetamide, 1-pyrenecarboxamide, and DABCYL derivatives have been used in preparation of molecular beacon (MB) probes labeled with one or two pyrenes/quenchers. We observed significant difference in the excimer emission maxima (475-510 nm; Stokes shifts 125-160 nm or 7520-8960 cm^-1) and excimer/monomer ratio (from 0.5 to 5.9) in fluorescence spectra depending on the structure and position of monomers in the pyrene pair. The pyrene excimer formed by two rigid 1-pyrenecarboxamide residues showed the brightest emission. This is consistent with molecular dynamics data on excimer stability. Increase of the excimer fluorescence for MBs after hybridization with DNA was up to 24-fold.

Photoinduced Electron-Transfer-Based Hybridization Probes for Detection of DNA and RNA

Here, we report the synthesis of a hybridization probe for detection of RNA and DNA based on photoinduced electron transfer (PeT). We designed and synthesized an oligonucleotide containing an adenosine analogue with a 9-(N,N-dimethylaminomethyl)anthracenyl moiety at its 6-position via an ethynylene linker as the hybridization probe. When the probe was hybridized with a complementary RNA or DNA, the fluorescence intensity increased 3-fold or 4.5-fold, respectively, compared to the single-stranded state.