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 (A_EPR) of the phosphotriester product concurs with EPR data of nucleic acids spin labeled enzymatically, a lower A_EPR is observed with the phosphoramidite product. The effects of the chemically harsher phosphoramidite conditions the DUTA label are held accountable for these results.