Ionic interactions on Sephadex G-10

Angela c. Murphy acmurphy at
Fri Jan 27 16:41:07 EST 1995

Why not use 1% acetic acid in water as your eluent?  You can lyophilize 
your column peaks without any further treatment, and if your peptides are
that basic, they'll be too busy associating with the acetate carboxyls
(1% is *200*mM) to bother with any dextran carboxyls.  I've just used 1%
as an arbitrary concentration - you can use a lower one if you wish.  In
fact, many peptide chemists desalt synthetic peptides using 5% acetic acid
as eluent.  Hope this helps.
               Angela C. Murphy

On 17 Jan 1995, John Marcus wrote:

> According to Phamacia, ionic interactions on Sephadex G-10
> are due to the fact that the cross-linked dextran chains contain
> a few terminal carboxyl groups; the gel will therefore act as a 
> weak cation exchanger with very low capacity.
> To remove these effects, it is suggested to use an ionic strength
> of 50mM in the eluent buffer.
> I want to desalt low molecular weigth peptides (1000-5000Da) using
> G-10 Sephadex.  My problem is that I don't want any buffer at all 
> in the eluent.  The proteins I am desalting are quite basic so I fear
> that some might interact with the column packing if I were to totally
> do away with buffer.  Ideally, I would like to use straight deionized
> water to elute the proteins from the column.
> Can anyone suggest a way of capping the carboxyl groups so as to 
> remove any potential interactions between peptide samples and the
> column matrix?  Alternatively, are there better size exclusion gels
> available that don't have interfering carboxyl groups?  I have
> thought of dialysis and centricon devices but these methods have
> their own set of drawbacks.
> Thanks in advance for any assistance with this problem.
> Sincerely,
> John Marcus

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