When I make amino-modified oligos for post-labelling I get very little yield and see a oligo mass + 53 in the mass spec. What is this and how can I stop this from happening?

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Amino modified oligos often react with the acrylonitrile produced by removing the cyanoethyl protection from the phosphate backbone to give oligo + 53Da. This can easily be prevented by treating the resin with 20% DEA in acetonitrile (or other suitable base that will not cleave the oligo from the support; piperidine, dibutylamine etc) followed by washing with acetonitrile. This removes the cyanoethyl protection prior to deprotection therefore the acrylonitrile is no longer present to react with the free amine.

Applicable to: 2123, 2124, 2182, 2193, 2133, 2350, 2371, 2365, 2369, 2367, 2532 and 2534.

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