ATTO 647N PEG4 DBCO

• Ex/Em: 645/663 nm
• Extinction coefficient: 150,000 cm^-1M^-1
• Reactive group: DBCO
• Copper-Free Bioorthogonal Labeling: Enables efficient azide conjugation via SPAAC without copper, ideal for sensitive systems
• High Quantum Yield & Stability: Provides bright fluorescence with high photostability, thermal resilience, and pH insensitivity across 2–11
• Ozone-Resistant: Enhanced resistance to atmospheric ozone degradation compared to cyanine dyes
• Hydrophilic PEG4 Spacer: Enhances solubility and minimizes steric hindrance for enhanced biocompatibility

ATTO 647N is a rhodamine-derived fluorescent dye specifically optimized for applications in the red spectral region. It exhibits spectral properties comparable to Cy5, with improved aqueous solubility conferred by a PEG4 spacer. The dye is characterized by a high molar absorptivity, robust fluorescence quantum yield, and superior thermal and photostability, making it a reliable choice for demanding experimental conditions. ATTO 647N is moderately hydrophilic and has an excitation maximum within the 625-660 nm range, which is well-suited for use with the 647 nm line of Krypton-Ion lasers and the 650 nm line of diode lasers. The dye retains consistent fluorescence across a wide pH spectrum (pH 2-11), ensuring its applicability in diverse biochemical and biophysical assays. Upon conjugation, ATTO 647N becomes cationic with a net positive charge of +1. Notably, this dye exhibits enhanced resistance to atmospheric ozone degradation compared to cyanine dyes, increasing its stability and reliability in microarray and other long-term applications. ATTO 647N is particularly suitable for high-precision techniques, including single-molecule detection, super-resolution microscopy (e.g., SIM, STED), flow cytometry (FACS), fluorescence in situ hybridization (FISH), and various other advanced biological and analytical methodologies.

The PEG4-DBCO derivative of ATTO 647N 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 647N DBCO serves as an effective alternative to copper-dependent fluorescent alkynes.