Photoresponsive molecular devices targeting nucleic acid secondary structures

Non B-DNA structures are non-canonical nucleic acid conformations adopted by single strands fulfilling specific sequence requirements. Numerous experimental evidences support their roles as regulators of biological processes, involving genetic information transfer. However, direct visualization of the folding and unfolding of such structures in live cells still remains elusive, as well as a detailed understanding of their mechanisms of action and functions. Fluorescent light-up probes are excellent tools to address these pending questions. This review aims at classifying the multitude of dyes available to date in terms of operating mechanism (conformational restriction, TICT, aggregation related phenomena, conjugation, etc.) and targeted structures. The most promising results are presented for each conformational class, contextually highlighting the main criticalities and the remaining gaps.