Preparation of spin-labeled 2-amino-dA, dA, dC and 5-methyl-dC phosphoramidites for the automatic synthesis of EPR active oligonucleotides

2,2,6,6-Tetramethyl-1-piperidinyloxy free radical (TEMPO) labeled phosphoramidites of 2-amino-dA, dA, dC and 5-methyl-dC were synthesized and used for the automatic synthesis of mono-labeled oligodeoxyribonucleotides, which proved active to EPR. It is now possible to insert a paramagnetic probe into nucleic acids in a site- and type-specific manner. The combination of this synthetic approach with EPR spectroscopy can be exploited for performing studies on dynamics and local structural modifications in nucleic acids