1. Add acetone to the final concentration of 80%.

2. Precipiate at -20 °C overnight or in dry ice for 2-3 hours.

3. Centrifuge for 10 minutes at 4°C and carefully remove supernatant.

4. Wash pellet gently with cold 100% acetone (-20 °C) twice.

5. Dry sample briefly under vacuum and store sealed at -20 °C.