The simplest approach to the design of high affinity primers and probes is to substitute A sites with 2-amino-A, since the 2-amino-A-T base pair is equivalent in strength to the G-T base pair. 2-Amino-A also destabilizes A-G wobble mismatches, thus increasing specificity. In 1998, we introduced a 2-amino-dA monomer which exhibits fast and effective deprotection in ammonium hydroxide and it is stabilized to depurination during synthesis. We now recommend the use of 0.5 M CSO in anhydrous acetonitrile (40-4632-xx) for best results with multiple additions of 2-amino-dA. This is because the bis formamidine protected 2-amino-dA leads to significant strand scission when standard iodine oxidation is used during synthesis. For this reason, we have also added Pac-2-Amino-dA, a monomer with optimized protection to meet the following criteria: stable during oligonucleotide synthesis, oxidation, and detritylation; labile towards common deprotection conditions (NH3, AMA, MeNH2); and the nucleobase protecting groups are cleaved under fairly mild conditions.
Coupling: No changes needed from standard method recommended by synthesizer manufacturer.
Deprotection: 30% Ammonium Hydroxide for 4 hours at 65 °C or 8-17 hours at 55 °C. Compatible with 30% Ammonium Hydroxide/40% Methylamine 1:1 (AMA) for 20 minutes at 65 °C.