Ionic interactions on Sephadex G-10

John Marcus J.Marcus at
Mon Jan 16 23:39:56 EST 1995

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.

John Marcus

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