CAS 206265-96-5

Cu(I) ions in aqueous solution rapidly react with dissolved oxygen to produce Cu(II) and reactive oxygen species (ROS), which oxidatively damage proteins, DNA, and lipids. Triazole ligands like THPTA and BTTAA tightly chelate Cu(I), shielding it from oxygen while maintaining its catalytic activity. This reduces biomolecular damage by >90% compared to ligand-free CuAAC.

For THPTA, a 2:1 or 3:1 ligand:Cu ratio is standard (e.g., 1.8 mM THPTA with 0.9 mM CuSO₄). For BTTAA, a 3:1 ratio is recommended. Excess ligand ensures complete Cu(I) coordination but very high concentrations may inhibit the reaction by over-stabilizing Cu(I) and reducing its reactivity with the azide.

THPTA is suitable for cell-surface labeling and extracellular applications but has limited cell permeability. For intracellular CuAAC, BTTAA offers better biocompatibility, though copper-free methods (SPAAC, IEDDA) are generally preferred for live-cell applications. THPTA has been successfully used for zebrafish embryo labeling at low Cu concentrations.

Stock solutions of THPTA or BTTAA (10–100 mM in DMSO or water) can be stored at −20 °C for several months. Avoid repeated freeze-thaw cycles. Working solutions (1–10 mM) should be prepared fresh or stored at 4 °C for up to one week. The ligands are stable at room temperature as solids.