imidazole in protein purification - (Nov/11/2005 )

why does the 1st buffer in his-tagged protein purification contain a little bit of imidazole? please help me !!

To wash off contaminants which may bind non-specifically to the column. Ideally your his tagged protein will have a much higher affinity to the resin then non his tagged proteins, so it will remain bound in the presense of low imidazole while others get washed off.

according to Qiagen, imidizole also increases the solubility of your rProtein, but I'm not sure why that is the case...if I remember correctly, imidizole reduces proteins; perhaps this helps to break up aggregates, which will often form when you've got tons of rProtein hanging around in the cell...is this right? anyone? anyone?