Postsynthetic Modification of Oligonucleotides with Imidazophenazine Dye and its Effect on Duplex Stability

Carboxyalkyl derivative of the intercalating agent imidazo[4,5-b]phenazine was used for the postsynthetic oligonucleotide modification. Model pentadecathymidylate-imidazophenazine conjugate was prepared from 5′-aminoalkyl-modified (dT)₁₅ by using phosphonium coupling reagent BOP in the presence of 1-hydroxybenzotriazole. Spectral-fluorescent properties of the conjugate were studied. The attachment of the dye was found to increase the thermal stability of (dT)₁₅ duplex with poly(dA) by more than 4°C, probably by the intercalation mechanism.