2026-02-02 Posted by TideChem view:51
DBCO labeling is based on a spontaneous reaction between a DBCO-functionalized probe and an azide-modified DNA strand. No catalyst is required.
Copper-Free Reaction – Avoids copper-induced DNA damage and cytotoxicity.
High Specificity – Efficient at physiological pH (7.0–8.5) with minimal off-target reactivity.
Improved Solubility – PEGylated variants (e.g., DBCO-PEG4) reduce aggregation and improve reaction efficiency.
Broad Compatibility – Applicable to ssDNA, dsDNA, LNA-modified oligos, and other chemically modified nucleic acids.
Because SPAAC proceeds under mild conditions, it is especially suitable for sensitive biological systems and in-cell labeling experiments.
The following example describes conjugation of DBCO-PEG4-FAM to 5’-azide single-stranded DNA. The same workflow can be adapted for Cy5, biotin, nanoparticles, or other DBCO-functionalized molecules.
| Component | Specification |
| Azide-modified DNA | 5’-azide-ssDNA, HPLC purified, ≥95% purity |
| DBCO reagent | DBCO-PEG4-FAM (1 mg/mL in anhydrous DMSO) |
| Reaction buffer | 1× PBS, pH 7.4 (amine-free preferred) |
| Purification tools | 3 kDa MWCO spin columns or 20% denaturing PAGE |
Note: Although SPAAC tolerates many buffers, avoid excess primary amines (e.g., Tris, glycine) if downstream chemistry is planned.
Dilute 5’-azide-ssDNA to 20 μM in PBS. Mix gently to avoid mechanical shearing.
Dilute DBCO-PEG4-FAM to 100 μM in PBS.
Tip: Always pre-dilute the DBCO reagent in buffer before adding it to DNA to minimize local aggregation.
Combine DNA and DBCO at a 1:1.2–1:1.5 molar ratio.
Example reaction:
50 μL DNA (20 μM)
12 μL DBCO (100 μM)
38 μL PBS
Incubate for 1–2 hours at room temperature, protected from light.
For bulky conjugates (e.g., proteins or nanoparticles) or lower concentrations, extend incubation to 4 hours.
Standard purification: Use a 3 kDa MWCO spin column (12,000 rpm, 5 min). Labeled DNA remains in the retentate.
High-stringency purification (e.g., for FISH): Perform 20% denaturing PAGE (7 M urea) to remove unreacted dye and partially modified species.
Use High-Purity DNA – HPLC purification is strongly recommended. Residual synthesis byproducts can reduce labeling efficiency.
Spacer Selection Matters – For large biomolecules, DBCO-PEG12 often improves accessibility and may increase coupling efficiency by up to ~40%.
Control DMSO Content – Keep final DMSO concentration below 1% to prevent DNA aggregation.
Storage Conditions – Store labeled DNA at −20 °C. Avoid more than three freeze–thaw cycles. Under proper storage, stability is typically at least 3 months.
| Issue | Possible Cause | Recommended Action |
| Low conversion (<70%) | Degraded reagents | Use fresh DNA and DBCO; verify pH 7.4–7.8 |
| High fluorescence background | Residual free dye | Repeat spin purification or perform PAGE |
| DNA aggregation | Excess DMSO | Reduce DMSO to <1% |
| Reduced fluorescence intensity | Dye positioned near triazole junction | Use longer PEG linker (PEG12) |
Yes. DBCO-PEG derivatives are cell-permeable and copper-free, making them suitable for live-cell imaging and intracellular labeling.
No significant impact is typically observed. The triazole linkage formed during SPAAC is compact and generally does not interfere with base pairing or enzymatic processes such as qPCR.
PEG4 – Suitable for small fluorophores or compact labels.
PEG12 – Recommended for large molecules (e.g., HRP enzymes, nanoparticles) to reduce steric hindrance and improve coupling efficiency.
High-purity DBCO-PEG reagents and custom azide-modified DNA are available for SPAAC-based labeling workflows. Technical assistance can be provided for assay optimization and scale-up.