XFD350, manufactured by AAT Bioquest, is structurally similar to Alexa Fluor® 350 (Thermo Fisher). This blue-fluorescent dye exhibits strong absorption and moderate photostability, with consistent fluorescence across a broad pH range (pH 4–11). XFD350 is effectively excited by the 350 nm line of a UV laser, and its moderate brightness and stability make it particularly advantageous for direct imaging of high-abundance targets in both microscopy and flow cytometry applications.

The azide derivative of XFD350 is widely used for labeling terminal alkynes on peptides, antibodies, and other biomolecules via click chemistry. It participates in copper-catalyzed azide-alkyne cycloaddition (CuAAC) with alkyne-containing molecules and strain-promoted alkyne-azide cycloaddition (SPAAC) with DBCO- or BCN-containing molecules.