How to Calculate Oligo MW?

Nigel Brown N.L.Brown at
Sun Nov 6 05:51:48 EST 1994

In Article <1994Nov3.140526.1 at>,
books at wrote:
>We are looking for a formula to calculate the exact MW for oligonucleotides.
>The oligo will have a 5'-hydroxy group. We can estimate oligonucleotide MW
>if we use 330 as the average MW for each base but we need a exact number. 
>Thanks DPSMITH smith_dennis_p at

GOOD GRIEF!  I have no objection to helping people with technical and other
problems of a specialist nature, but are there really people doing science
who cannot calculate a molecular weight?  No wonder
bionet.molbio.methds-reagnts is becoming overloaded.

Sorry to post rather than reply to the individual, but there is the general
point that bionet seems to be becoming the ONLY data source for some people.
What's wrong with books (remember them?) or asking in the lab for help?

Look in any biochemistry text for the formula of the deoxyribonucleoside
monophosphates and calculate out the individual molecular weights.  You can
even avoid this step by looking up the dNMP molecular weights in e.g. the
Sigma catalogue, Data for Biochemical Research or similar, but you may need
to substitute counterion atomic/molecular weights.   Then add-up the
molecular weights according to number of bases.  For most purposes real
precision is unnecessary, but subtract 79 for your 5' hydroxyl (HPO4 less OH
- ignoring counterions) and subtract 18 for each phosphodiester bond formed.

--- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ---
Nigel L. Brown                                    (N.L.Brown at
School of Biological Sciences, Univ. Birmingham, Birmingham, B15 2TT, UK
              Tel: +44-21-414-6556                  Fax: +44-21-414-6557

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