5'-Dabsyl-dT-CE Phosphoramidite

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QUAL probes1 consist of two oligonucleotides, the first containing a nucleophilic group at the 3'-terminus, while the second has an electrophilic group at the 5'-terminus. When the probe pair finds the target, the oligos line up with the 3'-terminus of the first directly adjacent to the 5'-terminus of the second. An autoligation reaction then takes place to combine the two oligos into a single probe. As usual, the 3' nucleophilic group is the 3-thiophosphate, easily prepared using 3'-phosphate CPG with a sulfurizing step in the first cycle. In this case, the electrophilic group is a 5'-dabsyl group, which is an excellent leaving group as well as a fine quencher of fluorescence. The second oligo, therefore, contains a fluorophore which is quenched by the dabsyl group. A popular choice for fluorophore is fluorescein-dT but it is easy to imagine that a variety of fluorophores could be attached to any of the commercially available amino-modified nucleoside phosphoramidites.



  • Coupling: Monomers that allow for UltraMILD deprotection must be used. (dA: 10-1601-xx, dC: 10-1015-xx, dG: 10-1621-xx, dT: 10-1030-xx ). To avoid any exchange of the iPr-Pac group on the dG|with acetyl, use the UltraMild Cap Mix A (40-4210-xx/ 40-4212-xx).
  • Deprotection: UltraMILD deprotection: 0.05M Potassium Carbonate in Methanol, 4 hours at Room Temperature.
Diluent Anhydrous Acetonitrile
Storage Freezer storage, -10 to -30°C, dry
Stability 1-2days

Dilution/Coupling Data

The table below show pack size data and, for solutions, dilution and approximate coupling based on normal priming procedures.

ABI 392/394

Catalog # Pack Size Grams/Pack 0.1M Dil. (mL) Approximate Number of Additions
LV40 LV200 40nm 0.2μm 1μm 10μm
10-1532-02 0.25 g .25grams 3.43 101 60.6 37.88 27.55 20.2 5.05
10-1532-90 100 µmol .073grams 1 20 12 7.5 5.45 4 1


Catalog # Pack Size Grams/Pack Dilution (mL) Approximate Number of Additions
Molarity 50nm 0.2μm 1μm 15μm
10-1532-02 0.25 g .25grams 5.11 0.07 95.8 59.88 43.55 5.99
10-1532-90 100 µmol .073grams 1.5 0.07 23.6 14.75 10.73 1.48


1 S. Sando and E.T. Kool, J Amer Chem Soc, 2002, 124, 2096-2097.