XFD430, manufactured by AAT Bioquest, is a green-fluorescent dye that is structurally similar to Alexa Fluor™ 430 (Thermo Fisher). With excitation and emission maxima at 432 nm and 540 nm, respectively, it is optimally excited by a 405 nm violet laser. Its large Stokes shift reduces spectral overlap with blue-emitting fluorophores, providing a superior signal-to-noise ratio in multiplexed fluorescence assays. The dye incorporates a PEG4 linker, significantly enhancing its aqueous solubility, while maintaining pH stability across a wide range (pH 4–10). These properties make XFD430 particularly well-suited for applications requiring robust and reproducible fluorescence signals, such as fluorescence microscopy and flow cytometry.

The DBCO derivative of XFD430 is a highly reactive cycloalkyne optimized for copper-free click chemistry (SPAAC, strain-promoted azide-alkyne cycloaddition). This derivative exhibits a significantly higher reaction rate with azides compared to other cyclooctynes and copper-catalyzed click reactions (CuAAC). Uniquely, DBCO does not react with tetrazines, allowing for its use in bioorthogonal reactions alongside trans-cyclooctenes and tetrazines. For applications where the presence of copper is problematic, XFD430 DBCO serves as an effective alternative to copper-dependent fluorescent alkynes.