Synthesis and Characterizationof a Novel PhotocleavableFluorescent Dye Dyad for Diffusion Imaging

We report the synthesis and characterization of a photocleavable fluorescent dye dyad. The two constituting dyes show a large spectral overlap and are in close proximity to each other, leading to efficient Förster Resonance Energy Transfer (FRET). Photocleavage of the dyad and the subsequent independent diffusion of both fluorophores qualifies the system to be used for high accuracy diffusion measurements. In contrast to previous work, the dyad reported here can be applied in polar solvents and cleaved by UV-A light. Beneficially, the photolabile linker provides two orthogonal labeling sites for various commercially available fluorescent labels. In this work, we chose the cationic organic dyes ATTO565 and ATTO647N. We outline the synthesis and spectral characterization of the system with UV–Vis and fluorescence spectroscopy as well as fluorescence lifetime and fluorescence quantum yield measurements. Furthermore, we performed proof-of-principle microscopy experiments to demonstrate its capability in polyvinyl acetate films.