klenchin at facstaff.REMOVE_TO_REPLY.wisc.edu
Fri Jan 14 16:04:53 EST 2000
:Nick Theodorakis wrote:
:> In article <387DF82A.BD3060FD at cajal.mbb.ki.se>, jonas at cajal.mbb.ki.se
:> (Jonas Anders) wrote:
:> > Hi all,
:> > is there a straightforward technique to remove BSA as main
:> > contaminant
:> > from the desired target protein (computed pI = 9)
:> > Any suggestions highly appreciated
Considering the very different pI of protein of interest and contaminant,
there is no doubt that chromatofocusing will resolve them quite nicely.
BSA does not bind to cation-exchanger at neutral pH but a protein with
pI 9 should. Thus, CM or S sepharose will also separate them. Then
there is hydroxylapatite which has very different binding properties
for acidic and alkaline proteins.
:> I seem to recall that in the old days people used to use Blue-Sepharose
:> (Cibaron Blue?) to remove albumin from serum, since the albumin bound
:> very tightly to it but the IgG did not.
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:Cibachron/m Blue is NOT specific for albumin. It also binds
:nucleotide-binding proteins, including heatshock proteins.
In fact, Blue Sepharose is a _very_ non-specific sorbent and at low salt
will bind ~ 50% of almost any given protein mixture.
But in cases where a given protein clearly does not bind (like IgG), it
becomes very useful.
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