lot of contaminating bands, what should i do - (May/27/2005 )

hello all
i have purified his tagged protein by ni nta resin in denaturing conditions using 1% sarcosyl. after elution with 1m imidazole , i see lot of contaminating bands in the elute.imidazole conc in my wash buffer is 20 mM. can i rebind the elute diluted to 20mM with fresh beads to remove these bands.

His taq- Ni sepharose is not as effeceint as described by the catalogues. The problem is that there are metal binding proteins which too append to the column and elute lateron. Try gel filtration after the first column. Thats what we do for one of the his tag clone in our lab.