Oligo & Primer Resuspension Calculator
Molecular weight, ε260 extinction and exact nuclease-free water volumes for resuspending lyophilised primers.
How it works
Oligonucleotide molecular weight is summed from nucleotide residue masses, and the ε260 extinction coefficient is summed from single-nucleotide values (dA 15,200, dC 7,050, dG 12,010, dT 8,400 M⁻¹cm⁻¹). The sum ignores base stacking, so it overestimates ε by roughly 5–10% and slightly underestimates the amount of oligo. Together these convert a synthesis yield in nanomoles or OD units into the exact volume of buffer needed to reach a target stock concentration.
Frequently asked questions
How do I resuspend a lyophilised primer to 100 µM?
Divide the delivered amount in nanomoles by 100 to get the volume in microlitres. A tube containing 25 nmol needs 250 µL of nuclease-free water or TE to give a 100 µM stock. Spin the tube briefly before opening — lyophilised pellets are easily lost — and let it dissolve for a few minutes with occasional vortexing before use.
Should I resuspend primers in water or TE buffer?
TE buffer is preferable for long-term storage because its slight alkalinity and EDTA content protect against acid hydrolysis and metal-catalysed degradation. Nuclease-free water is fine for short-term use and avoids introducing EDTA into downstream reactions, which matters for some enzymatic steps. Either way, store stocks frozen and work from dilute aliquots to avoid repeated freeze-thaw.