We recommend that coupling reactions between BG-PEG-NH2 and NHS estes or activated carboxylic acids take place in anhydrous N,N-dimethyl formamide (DMF) using triethylamine as a base.
Typical reactions use approximately equimolar quantities of the BG-PEG-NH2 and the desired NHS-label at 5-20 mM final concentration in the presence of a 1.5 fold molar excess of triethylamine in DMF. The reaction is generally performed at 30°C overnight.
The purification strategy will depend on the label used and the reaction scale. Good results have been obtained with both HPLC and silica get chromatography.