Aggregation of His-tagged proteins

Matt Parker at332 at FreeNet.Carleton.CA
Fri May 3 16:40:04 EST 1996

N-terminal, to allow purification via a nickel-binding affinity column. We
are having difficulty in concentrating this protein after purification; it
tends to aggregate above 2 or 3 mg/mL.

	Since we are doing the concentrating at pH 7.6, I suspect that the
histidines (which should be mostly uncharged at this pH) are forming a
hydrophobic surface which promotes aggregation. I plan to try
concentrating it at a lower pH (say 5.5 or so) to try to get some
repulsion going. Has anybody had a similar problem, and can anyone offer


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