Reversible photocycloaddition of 8-pyrenylvinylguanine for photoreactive serinol nucleic acid (SNA).

Photoresponsive nanomachines are attractive components of functional nanodevices and nanosystems. To develop new photoresponsive nucleic acid-based nanomachines, we conjugated 8-pyrenylvinylguanine (^PVG) to a serinol linker and incorporated it into an acyclic xeno nucleic acid, serinol nucleic acid (SNA). The two ^PVG residues incorporated into SNA underwent interstrand photocycloaddition upon 447 nm light irradiation in the duplex state, whereas previously reported 8-pyrenylvinyladenine (^PVA) formed both intrastrand and interstrand photodimers. The ^PVG photodimer was converted to monomers by irradiation with 350 nm light. This photoreaction enabled reversible photoregulation of the formation and dissociation of the SNA/RNA duplex, although some byproducts were generated due to the slower photoreaction of ^PVGs than that of ^PVAs. In contrast, when a single ^PVG was incorporated into SNA, the interstrand photocycloaddition and cycloreversion were remarkably fast and effective in the single-stranded state. We utilized this to demonstrate a photocaging system that achieves one-way photoswitching of hybridization ability. The powerful photocycloaddition properties of ^PVG-SNA are expected to find applications in new photoresponsive nanodevices and nanosystems.