Precipitation of proteins is done by all of these except:
(A) Adding trichloroacetic acid. (B) Adding acetyl alcohol and acetone. (C) Adjusting pH to other than the isoelectric point. (D) Salts of heavy metals.
(C) Ans: C. Adjusting pH to other than the isoelectric pointProtein precipitation is widely used to concentrate proteins and purify them from various contaminants.Protein precipitation occurs at the isoelectric point of the protein and not at any other pH.Selective precipitation exploits differences in relative solubility of individual proteins as a function of pH (isoelectric precipitation), polarity (precipitation with ethanol or acetone), or salt concentration (salting out with ammonium sulfate).