Useful Information and Calculations

1 ODU (A260) = 33 ug of single-stranded oligonucleotide in 1 mL

Determination of Exact Molecular Weight of an Oligo:

((#A's x 313.2) + (#G's x 329.2) + (#C's x 289.2) + (#T's x 304.2)) - 61 = MW

Note: If the oligo has a 5' phosphate group, do not subtract 61. This value is for dephosphorylated oligos only.

Approximation of Oligo Concentration (for an OD260 taken in a 1 cm3 cuvette):

nmol/ml = uMolar = (OD260 units x 90)/(length of oligo)

Molar extinction coefficients at 260 nm:

A = 15,200
G = 12,010
C = 7,050
T = 8,400

Storage Conditions for Oligonucleotides:

Oligonucleotides may be refrigerated as solutions (pH range 3-12) of concentrated ammonia, water, dilute buffer, or salt. It is important to refrigerate them to minimize degradation and bacterial growth. Oligonucleotides may also be stored in pellet form. When stored under refrigeration in 11% acetonitrile (the eluent used in HPLC) the oligonucleotides are stable for more than a year. When stored as a lyophilized pellet, the oligos are stable for years at -20.


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