http://www.pitt.edu/~rsup/mgbresupfac11.html
The next step, capping, terminates any chains which did not undergo addition. Since
the unreacted chains have a free 5'-OH, they can be terminated or capped by acetylation.
These unreacted chains are also called "failure products" . Capping is
done with acetic anhydride and 1-methylimidazole. Since the chains which reacted
with the phosphoramidite in the previous step are still blocked with the DMT group,
they are not affected by this step. Although capping is not required for DNA synthesis,
it is highly recommended because it minimizes the length of the impurities and thus
facilitates product identification and purification.
NEXT STEP
Back to DNA synthesis Page