Labeling reaction using BG-Alexa Fluor® 647 in Solution


Removal of non-reacted substrate
After the labeling reaction you may wish to separate the non-reacted substrate from the labeled SNAP-Tag fusion protein. You can use gel filtration as well as dialysis. Please refer to the vendor’s instructions for the separation tools you are using.


  1. Prepare a protein solution containing up to 20 μM SNAP-Tag fusion protein to be labeled in an appropriate buffer containing at least 1 mM DTT. We recommend labeling at least 100 µl of protein solution per experiment.
  2. Add SNAP-Tag substrate solution to a total volume of 1% of the volume of the protein solution. Carefully pipette the material up and down to mix, and vortex briefly.
  3. Incubate for 1 hour at 25°C in the dark. Alternatively incubate overnight at 4°C in the dark.