ATTO 655 PEG4 DBCO

• Ex/Em: 661/679 nm
• Extinction coefficient: 125,000 cm^-1M^-1
• Reactive group: DBCO
• Copper-Free Bioorthogonal Labeling: Efficient azide conjugation via SPAAC without copper, ideal for sensitive systems
• High Quantum Yield & Stability: Provides bright fluorescence with high photostability and thermal resilience
• Ozone-Resistant: Superior resistance to atmospheric ozone ensures reliable performance, ideal for microarray applications
• Hydrophilic PEG4 Spacer: Enhances solubility and minimizes steric hindrance for enhanced biocompatibility

ATTO 655 PEG4 DBCO is manufactured by AAT Bioquest for research and development use. ATTO 655 is a far-red fluorescent dye characterized by its strong absorption, high photo and thermal stability, and excellent ozone resistance. The dye exhibits enhanced aqueous solubility due to the incorporation of a PEG4 spacer and is optimally excited within the 640-660 nm wavelength range, which aligns with the 647 nm line of Krypton-Ion lasers and the 650 nm line of diode lasers. As a zwitterionic compound, ATTO 655 remains electrically neutral when conjugated to biomolecules or other substrates. Its strong electron-accepting properties result in efficient fluorescence quenching by electron donors such as guanine and tryptophan. These properties render ATTO 655 highly suitable for precise applications including single-molecule detection and super-resolution microscopy techniques like PALM, dSTORM, and STED. Furthermore, ATTO 655 is compatible with flow cytometry (FACS), fluorescence in situ hybridization (FISH), and a variety of other biological assays, making it a versatile tool in advanced fluorescence-based research.

The PEG4-DBCO derivative of ATTO 655 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, ATTO 655 PEG4 DBCO serves as an effective alternative to copper-dependent fluorescent alkynes.