Fluorescent ribonucleoside analogues as probes for investigating RNA structure and function*

Numerous biophysical tools based on fluorescence have been developed to advance the understanding of RNA–nucleic acid, RNA–protein, and RNA–small molecule inter actions. In this regard, fluorescent ribonucleoside analogues that are sensitive to their local environment provide sensitive probes for investigating RNA structure, dynamics, and recognition. Most of these analogues closely resemble the native ribonucleosides with respect to their overall dimension and have the ability to form canonical Watson–Crick (WC) base pairs. Therefore, it is possible to place these probes near the point of interaction in a target nucleic acid with minimum structural perturbations and gain insight into the intricacies of conformational changes taking place in and around the interaction site. Here, we provide a concise background on the development and recent advances in the applications of basemodified fluorescent ribonucleoside analogue probes. We first present various base-modified fluorescent ribonucleoside analogues, their photophysical properties, and methods to incorporate these analogues into oligoribonucleotides. We then discuss the established spectroscopic techniques, which make use of the fluorescence properties of these emissive ribo nucleoside analogues. Finally, we present the applications of base-modified fluorescent ribonucleoside analogues used as probes incorporated into oligoribonucleotides in investigating RNA structures and functions.