TCA Precipitation

Peter pxpst2 at vms.cis.pitt.delet.edu
Wed Oct 15 08:48:04 EST 1997


In article <344412D3.429EB6F9 at rascal.med.harvard.edu>,
yip at rascal.med.harvard.edu wrote:

.> Does anyone know the lower limit for molecular size peptides which may
.> be precipitated by method of TCA precipitation?
.> 
.> That is, what's the smallest peptides which may be precipitated by TCA?
.> 
About 20 KD.  But the amt. of glycosylation matters and the aa
composition.  TCA precipitation is different for each protein/peptide.  My
protein HGF does not precipitate well at low concentrations (<1ug/ml)
while BSA precipitates well at half that.  Personally, I find TCA
precipitation to be unreliable and not good for precipitating proteins at
low concentrations and/or small molecular weight.  The best procedure that
I have found for the recovery of ng  quantities of protein(of any size) is
Phenol/ether extraction.  I have successfully recovered 15 ng from 1 ml. 
TCA cannot do this.

Peter

-- 
"Don't you eat that yellow snow
    WAtch out where the Huskies go"

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