Andy's point is indeed valid (although Corrado's requirement was actually
for purification of recombinant proteins rather than synthetic peptides)
and we have had circumstances where a high resolution material, including
some of Poly LC's fine products, was necessary to achieve the required
level of purity.
My interpretation of the original question however was a requirement for
cation exchangers for use in early stage separation of recombinant
proteins. The point I was trying to make was that a simpler, low cost
alternative MAY indeed be appropriate for the required resolution.
One thing that I often come across, dealing with people with little
chromatography experience, is the desire to reach for the catalog and order
the highest resolution column available without due consideration to the
chromatographic problem at hand. "I want my protein as pure as possible so
I'll order the $4000 column because that will give me the best result"
seems to be the mind set.
The potential solution I offered could be tested quickly and, probably, at
no cost. Find an empty column around the lab, call the BioRad rep and ask
for a sample of the packing and run a small aliquot of the sample in
question. If it does work, there are big bucks to be saved. If it doesn't,
"nothing ventured, nothing gained."
Regards...Ken
>This is in response to Ken Mitchelhill's advice to Corrado Guarnaccia to use
>medium pressure materials for cation-exchange of synthetic peptides. That
>combination would be fine if you only wanted to get rid of deprotection
>fragments and to perform a preliminary fraction of the product of an
>inefficient synthesis prior to reversed-phase HPLC. There will be cases where
>reversed-phase HPLC (RPC) won't have the necessary selectivity - e.g., a
>failure sequence minus a ser- residue or some such. In such cases, you'll
>need all the efficiency you can get at the cation-exchange step, and an
>expensive SCX column becomes unavoidable. If it's any consolation, they have
>four times the loading capacity of a RPC column of the same dimension.
>
>Andy Alpert
>PolyLC Inc.
>Columbia, MD USA
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Ken I. Mitchelhill
The John Holt Protein Structure Laboratory
St. Vincent's Institute of Medical Research
41 Victoria Parade
Fitzroy 3065 Victoria
AUSTRALIA
Telephone: 61-3-9288 2480
Facsimile: 61-3-9416 2676
Email: k.mitchelhill@medicine.unimelb.edu.au
Laboratory: http://www.medstv.unimelb.edu.au/WWWDOCS/SVIMRdocs/JHPSL.html
ABRF: http://www.abrf.org
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