Copper-staining of proteins

[Craig Marshall]

I have tried the copper staining method posted here recently. The
protocol suggested that a 0.3M CuCl2 solution would stain proteins at
about 5X the sensitivity of coomassie. I tried this and it didn't
work. The problem seemed to be that the solution was very acid (pH 2
or so) and I was staining minigels which would not have had much
buffering capacity. Increasing the pH of the CuCl2 solution with NaOH
leads to the formation of insoluble Cu(OH)2 which is not much use.

So, does anybody have experience with this method. Does the Cu salt
matter, could I use a neutral solution of CuSO4.5H20? Could I
neutralize the CuCl2 with ammonia to keep the copper in solution.
Should I just use a much smaller amount of the stain?


Many thanks in advance,

--
        Craig Marshall          	craigm at sanger.otago.ac.nz or
        Biochemistry Department 	bioc07 at otago.ac.nz
        University of Otago     	Phone 64 3 479 7849   	
        P.O. Box 56             	Fax   64 3 479 7866   	
        Dunedin, New Zealand