The CuAAC Biomolecule Reaction Buffer Kit (BTTAA based) is suitable to perform Copper (Cu(I))-catalyzed Azide-Alkyne Click chem-istry reactions (CuAAC) with Azide-or Alkyne-modified biomolecules. 1 Kit provides sufficient amounts to perform 25 CuAAC experi-ments 200 l using 2 mM CuSO 4(copper source), 10 mM BTTAA (Cu(I)-stabilizing ligand) and 100 mM Na-Ascorbate (reduction reagent) in 100 mM Na-Phosphate reaction buffer.