Problem with MF protein on DEAE

[USF]

We are having problems getting our Membrane fraction enzyme off a DEAE 
column. We get a large peak of protein but no enzyme activity.  We do 
not have problems with the protein on a gel filtration column. We use a 
gradient of .1 to .5 M salt, should we be going higher?  Is there 
something in the column that could denature our enzyme? We do this 
procedure with the  cytosolic form of the same enzyme and no problem. I 
know Membrane proteins can be difficult, but I could use some good 
suggestions now.


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