A Comparative Study of the Phosphotriester Versus the Phosphoramidite Approach to Nitroxide Labeled Oligo dT

Abstract
Deoxyuridine labeled in C-5 with a one-atom-tehered 6-memberedring mitroxide (DUTA) was incorporated into the oligomer d(T)7(DUTA)d(T)7 by either the phosphotriester or phosphoramidite method. While the EPR specific activity (AEPR) of the phosphotriester product concurs with EPR data of nucleic acids spin labeled enzymatically, a lower AEPR is observed with the phosphoramidite product. The effects of the chemically harsher phosphoramidite conditions the DUTA label are held accountable for these results.