Molecular Weight and Extinction Coefficient of Oligonucleotides

The formula to calculate the molecular weight of DNA oligonucleotides is:

MW (g/mol) = (nA × 249,08619) + (nG × 265,0811) + (nC × 225,07496) + (nT × 240,07462)

To calculate ε (epsilon, the extinction coefficient) of an oligo, the formula is:

ε (in l/mmol) = amount of As x 15.4 + amount of Cs x 7.3 + amount of Gs x 11.4 + amount of Ts x 8.8

ε is needed to calculate the concentration of an oligonucleotide solution based on the optical density (OD) at 260nm. The formula is:

c (in mmol/l) = OD(260nm) / ε