Wittrup: Protein concentration by ultrafiltration
Concentration of protein solution using centrifugal filter units
Select appropriate centrifugal filter based on sample volume and molecular weight of the protein. In general, the nominal molecular weight cutoff of the filter unit should be half to one-third the molecular weight of the protein in order to minimize loss.
Common centrifugal devices are:
Centricon Plus-20 Centrifugal Filter Units (< 20 mL)
Centriplus Centrifugal Filter Units (< 15 mL)
Centriprep® Centrifugal Filter Units (< 15 mL)
Microcon® Centrifugal Filter Units (< 0.5 mL)
Amicon Ultra-15 Centrifugal Filter Units (< 15 mL)
Centricon® Centrifugal Filter Units (< 2 mL)
General operating procedures
1. Fill the sample reservoir (of the centrifugal filter) with deionized water and place the filter into a centrifuge rotor. Counterbalance with a similar device.
2. Spin until half the rinse passes into the filtrate.
3. Remove the remaining rinse.
4. Add protein solution to sample reservoir. Do not touch the membrane pipette tip.
5. Spin the device until desired concentration is reached. Do not exceed the centrifugation limits. If the volume of protein solution is larger than the loading volume of the device, remove filtrate, repeat step (4) and (5).
6. Remove centrifugal filter assembly from the centrifuge.
7. Recover retentate.
The readers should consult the user guide that accompany the filter device for detailed information on centrifugation limit, procedures for recovery of retentate, chemical compatibility, spin times, and other information.