View source for Centrifugal Protein Concentration and Buffer Exchange

Centrifugal Protein Concentration/Buffer Exchange

# Obtain a centrifugal filter (Amicon or Centricon) with a molecular weight cutoff at least half of your protein’s weight.
# If the filter is new, run ~5 mL of nanopure water through before adding your protein mixture. 
## Make sure to balance the centrifuge with another centrifugal filter. I typically use an old one. Regular falcon tubes will unbalance the centrifuge even though they are the same weight.
# Add your protein mixture up to the recommended line.
# Spin at 4,000 rpm for ~40 minutes.
# Pour out the filtrate. The supernatant contains your protein.
# Add the rest of your protein mixture or add in the new buffer.
# Continue to add and spin down the new buffer until it is sufficiently exchanged and the protein is concentrated.
## ~50 mL works well
## Be sure not to over concentrate and aggregate your protein. 
# Keep the filter wet with 20% ethanol when it is stored.

[[category:Protein_Preparation]]