His-tagged proteins

[Michael Yamauchi]

	Vadim-
			I have re-nickelated Ni-NTA-agarose resins with varying success.  I 
believe Qiagen provides a protocol for doing this.  If I remember 
correctly, it involves stripping the resin with EDTA and then passing 
nickel sulfate over the column.  
		Alternatively, I have also used Ni-NTA columns many more than 5 times 
and have had pretty good resolution.  Since these resins are available for 
about $5/ml, I would suggest using the resin as long as you still get good 
resolution and then either replace it (if it is a relatively small 
volume), or attempting to regenerate it if it is a large volume.