Small-molecular fluorophores are brighter than fluorescent protein, and occupy an important position in modern microscopy studies. To be useful in live-cell intracellular applications, these fluorophores should meet several requirements: i) excellent cell permeability, ii) rapid labeling kinetics, iii) optimal brightness and photostability, and iv) long-wavelength absorption and emission. While classic fluorophores like rhodamine, fluorescein, and coumarin possess the former two characteristics, we attempted to develop fluorophores with improved photophysical properties and red-shifted excitation and emission profiles through minimal structural changes. In our previous work, we synthesized a series of phosphinate-based rhodamines, and discovered that replacing the bridging oxygen atom in the xanthane ring with a phosphinate functionality would maintain the HOMO energy and lower the LUMO energy of the molecular, thus red-shifting the absorption and emission wavelength to the near-infrared (NIR) window. These rhodamines have excellent photostability and brightness and were termed Nebraska Red (NR) fluorophores. Herein, we sought to further apply this structural modification strategy to construct phosphinate-based rhodol and fluorescein derivatives to expand the diversity of the NR family. Our lab is currently pursuing the application of these new fluorescent probes as sensors for biological important enzymatic activities as well as imaging agents.

Phosphinate-based rhodol/fluorescein derivatives and their biological application

2019 Fall National Meeting

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