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 C5 maleimide derivative of  XFD350 is widely used for labeling biomolecules with free thiol (SH) groups, including antibodies, proteins, thiol-modified oligonucleotides, and low molecular weight ligands. Maleimides react readily with sulfhydryl groups, forming stable thio-ether bonds between the dye and the biomolecule, facilitating robust and reliable labeling for diverse experimental applications.