4-Cyanoindole-2′-deoxyribonucleoside (4CIN): A Universal Fluorescent Nucleoside Analogue

The synthesis and characterization of a universal and fluorescent nucleoside, 4-cyanoindole-2ʹ-deoxyribonucleoside (4CIN), and its incorporation into DNA is described. 4CIN is a highly efficient fluorophore with quantum yields >0.90 in water. When incorporated into duplex DNA, 4CIN pairs equivalently with native nucleobases and has uniquely high quantum yields ranging from 0.15–0.31 depending on sequence and hybridization contexts, and surpassing that of 2-aminopurine, the prototypical nucleoside fluorophore. 4CIN constitutes a new isomorphic nucleoside for diverse applications.