Product Specifications

361.34(dithioate)Protected Nucleoside
CAS Number:
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Replacing two non-bridging oxygen atoms with sulfur atoms in a DNA phosphodiester linkage creates a phosphorodithioate (PS2) linkage.<sup>1</sup> Like natural DNA, the phosphorodithioate linkage is achiral at phosphorus. This analog is completely resistant to nuclease degradation and forms complexes with DNA and RNA with somewhat reduced stabilities.<sup>2</sup> Moreover, it has been found that PS2-ODNs bind proteins with a higher affinity than their phosphodiester analogues<sup>2-6</sup> suggesting that PS2-ODNs may have additional utility in the form of sulfur-modified phosphate ester aptamers (thioaptamers)<sup>3,6-8</sup> for therapeutic and diagnostic applications. Thiophosphoramidites are now commercially available after recent work at AM Biotechnologies (www.thioaptamer.com).

  1. Thiophosphoramidites (ThioPAs) are not soluble in anhydrous acetonitrile diluent. Rather, 10% DCM (v/v) in acetonitrile is an ideal diluent for all four of the thioPAs for a final amidite concentration of 0.15 M.
  2. ThioPAs are somewhat less stable than normal DNA phosphoramidites in anhydrous acetonitrile containing 10% DCM; however, the coupling efficiency of all four thioPAs is not reduced after two days in solution at room temperature.
  3. After synthesis, the thioPA bottle on the synthesizer should be replaced with one containing acetonitrile diluent and the synthesizer line flushed with acetonitrile.

A typical cycle for the solid-phase synthesis of a PS2 linkage is different from a standard cycle for the synthesis of normal phosphate linkages. After coupling, the resulting thiophosphite triester is then sulfurized with DDTT. Capping is carried out AFTER sulfurization. Upon completion of the automated synthesis, deprotection is carried out using a concentrated ammonia:ethanol (3:1, v:v) mix containing 20 mM DTT at 55°C for 15-16 h.



Diluent 10% (v/v) Anhydrous Dichloromethane in Anhydrous Acetonitrile
Storage Freezer storage, -10 to -30°C, dry
Stability Use Immediately

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
10-1720-02 0.25 g .25grams 1.78 46 27.6 17.25 12.55 9.2 2.3
10-1720-90 100 µmol .094grams 0.67 9 5.4 3.38 2.45 1.8 0.45


Catalog # Pack Size Grams/Pack Dilution (mL) Approximate Number of Additions
Molarity 50nm 0.2μm 1μm 15μm
10-1720-02 0.25 g .25grams 2.65 0.1 46.6 29.13 21.18 2.91
10-1720-90 100 µmol .094grams 1 0.1 13.6 8.5 6.18 0.85


1 J. Nielsen, W.K.D. Brill, and M.H. Caruthers, Tetrahedron Letters, 1988, 29, 2911-2914.
2 L. Cummins, D. Graff, G. Beaton, W.S. Marshall, and M.H. Caruthers, Biochemistry, 1996, 35, 8734-41.
3 X. Yang, and D.G. Gorenstein, Curr Drug Targets, 2004, 5, 705-15.
4 W .S. Marshall, and M.H. Caruthers, Science, 1993, 259, 1564-70.
5 J.L. Tonkinson, et al., Antisense Research and Development, 1994, 4, 269-278.
6 X. Yang, et al., Bioorg Med Chem Lett, 1999, 9, 3357-62.
7 X. Yang, et al., Ann N Y Acad Sci, 2006, 1082, 116-9.
8 X. Yang, et al., Nucleic Acids Res, 2002, 30, e132.