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 N-hydroxysuccinimidyl (NHS) ester of  XFD350 is a widely used reagent for the conjugation of this dye to proteins or antibodies. NHS esters react selectively and efficiently with primary amines (such as the side chains of lysine residues or aminosilane-coated surfaces) at pH 7–9, forming stable covalent amide bonds. This property makes  XFD350 NHS ester an excellent choice for labeling proteins, amine-modified oligonucleotides, and other amine-containing molecules.