TCA precipitation chemistry question

Peter pxpst2 at
Wed Nov 5 11:27:11 EST 1997

In article <Pine.SGI.3.95.971031133423.27085A-100000 at>, the
kid's alright <zhowar1 at> wrote:

> Can anybody explain to me the chemical mechanism of TCA precipitation of
> proteins? Just a brief headstart would be fine, I can't seem to find this
> in any chemistry book.

TCA is used because it is capable of mantaining a very acid pH in dilute
aqueous form(<7%).  It is also NOT a strong Acid so it will not hydrolyze
pepetide bonds.  The exception to this is the making of a TCA stock
greater than 30 percent.  TCA may breakdown and HCl will form, which will
hydrolyze peptide bonds.

How does it work?  Acid precip. works by altering the hydration spheres. 
It "squeezes" water out of the protein.  One may say it dehydrates the
protein similar to the way alchohol works.  The problem with this method
is that not all proteins precipitate equally and small proteins sometimes
not at all.
Unless you are working with high protein content(>1mg/ml), TCA is not a
good method of protein recovery.  Extraction is much better


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