XFD350 PEG4 DBCO

• Ex/Em: 343/441 nm
• Extinction coefficient: 19,000 cm^-1M^-1
• Reactive Group: DBCO
• Copper-Free Bioorthogonal Labeling: Enables rapid and efficient azide conjugation via copper-free SPAAC
• Moderate Brightness & pH Stability: Ideal for high-abundance targets and maintains consistent fluorescence across a broad pH range (4–11)
• Advanced PEG4 Spacer: Enhances solubility and minimizes steric hindrance for improved biocompatibility

XFD350, manufactured by AAT Bioquest, is a blue-fluorescent dye that is structurally identical to Alexa Fluor® 350 (ThermoFisher). The incorporation of a PEG4 spacer enhances its aqueous solubility, while the dye maintains strong absorption and stable fluorescence across a broad pH range (pH 4-11). XFD350 is optimally excited by the 350 nm line of a UV laser, and its moderate brightness and stability make it particularly well-suited for direct imaging of high-abundance targets in both microscopy and flow cytometry applications.

The DBCO derivative of XFD350 is a highly reactive cycloalkyne optimized for copper-free click chemistry (SPAAC, strain-promoted azide-alkyne cycloaddition). This derivative exhibits a higher reaction rate with azides compared to other cyclooctynes and traditional copper-catalyzed azide-alkyne cycloaddition (CuAAC). Importantly, DBCO does not react with tetrazines, making it compatible with bioorthogonal reactions involving trans-cyclooctenes and tetrazines. This feature allows XFD350 PEG4 DBCO to serve as an effective alternative to copper-dependent fluorescent alkynes in environments where copper ions may interfere with biological processes.