Lee, Y. et al. JACS https://doi.org/10.1021/jacs.7b10433 (2017).

Bioorthogonal probes are ideal for fluorescence imaging in living cells via click chemistry. These probes are fluorescent conjugates, in which tetrazine (Tz) often serves as both the bioorthogonal reactive group and the fluorescence quencher. These probes can be 'clicked' to target compounds harboring a trans-cyclooctene group. However, the fluorophore component as well as the linker can influence the reactivity of the probes, which is problematic for multiplexed imaging. Lee et al. generate a series of Tz conjugates based on Seoul-Fluor that cover a broad range of emission wavelengths and still have similar reactivity. The emission wavelength of Seoul-Fluor can simply be tuned by adding side groups to the fluorophore. The authors demonstrate the application of their probes by imaging microtubules in fixed cells and mitochondria in live cells.