ETHANOL PRECIPITATION:

Useful method to concentrate proteins and removal of Guanidine Hydrochloride before PAGE-SDS

1) Add to 1 volume of protein solution 9 volumes of cold Ethanol 100%. Mix and keep at least 60min.at ?20ºC. (Suggestion: leave ON).
2) Spin 15min 4ºC in microcentrifuge at maximum speed (15000g). Carefully discharge supernatant and retain the pellet: dry tube by inversion on tissue paper (pellet may be difficult to see).
3) Wash pellet  with 90% cold ethanol (keep at ?20ºC). Vortex and repellet samples 5min at full speed.
4) Dry samples under vaccum (speed vac) or dry air to eliminate any ethanol residue (smell tubes). For PAGE-SDS, resuspend samples in a minimal volume of sample buffer.