TCA precipitation of proteins

Trichloro acetic acid can be used to concentrate protein before SDS-PAGE.

Solution:
Basic Procedure:
  1. Add an equal volume of 20% TCA to protein solution.
  2. Incubate on ice for at least 15 minutes. For high protein concentrations the protein will precipitate immediately. For low concentrations, leave reaction on ice for a longer time.
  3. Centrifuge at maximum speed for 15 minutes at 4 degree C.
  4. Remove all supernatant to get rid of as much TCA as possible.
  5. Wash pellet twice with 500ul cold acetone to remove all TCA. Allow the pellet to air dry. Avoid complete desiccation of the protein pellet as this will make re-solubilization much harder
  6. Resuspend pellet in 2X sample buffer. Residual amount of TCA can turn the sample buffer green or yellow. In that case, sample can be neutralized by increasing concentration of the sample buffer eg. 4x sample buffer.
  7. Boil samples and load onto SDS-PAGE.