TCA precipitation of proteins

Peter pxpst2 at unixs.cis.pitt.edu
Thu Dec 17 09:20:16 EST 1998


In article <nfVd2.54$os.363 at nnrp2.clara.net>, "Andrew Pridmore"
<ampridmore at clara.co.uk> wrote:
> When precipitating proteins with TCA, what does the TCA actually do to the
> protein structure? In particular I need to know:
> 
> 1 - The effect on conformation / folding

Well TCA is a potent dehydrator.  In other words it removes water that is
normally found in the protein.  The net effect is to cause hydrophobic
regions to ball up.  This is also why it is difficult to resolubilize
proteins after TCA precipitation.
> 
> 2 - The effect on bonds within the polypeptides

Ih the TCA is fresh and has not been exposed to light for prolong time, it
should do nothing to the peptide bonds.  But if the TCA was not stored
properly then HCl could have been generated, in which case acid hydrolysis
of peptide bonds may occur
> 
> 3 - The effect on electrical charge.

It is safe to say that the net carge of the protein will be positive.  I
say this because all the -COOH will be neutral and all the -NH3 groupds
will be prtonated yeilding -NH4+



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