We recommend that coupling reactions between BC-NH2 and NHS esters take place in anhydrous N,N-dimethylformamide (DMF) using triethylamine as a base.
Coupling reactions typically use an excess of the BC-NH2 (1.5 equivalents) relative to the desired NHS label (1 equivalent) at 5-20 mM final concentration. Add a 1.5-fold molar excess of triethylamine in DMF. The reaction in generally performed at 30°C overnight.
The purification strategy will depend on the label used. Good results have been obtained with both HPLC and silica gel chromatography.