Oligos are made using a DNA synthesizer, which is a computer-controlled reagent delivery system. DNA is synthesized in the 3’→5’direction, and each base addition is accomplished through a series of chemical reactions. Since no chemical reaction is 100% efficient, during DNA synthesis, the maximum coupling efficiency obtainable is normally around 99%. This means that every time a base is added, approximately 1% of available bases fail to react with the newly added base. The failure sequences inherent to the oligo synthesis process can compete with the full-length product in some applications and may therefore need removing through purification before the oligo can be used successfully.

Purification options

Purification (for >20 bases)

Synthesis scale Desalted (OD) Cartridge (OD) HPLC (OD) PAGE (OD)
25 nmol 2 n/a n/a n/a
50 nmol 4 2 1 0.5
200 nmol 16 10 3 1
1 μmol 50 25 5 5
10 μmol 500 n/a 15 50