whence Coomassie?

Basavaraju Shankarappa bsh at MED.PITT.EDU
Wed Oct 7 12:49:36 EST 1992


> I have a question that follows from the Coomassie one.
> At the moment I am running protein gels on Pharmacia's PhastGel
> system. It seems that high sensitivity silver stainning works
> better if the gel is Coomassie dyed first. 
> 
> Does anyone know why this is so? The Pharmacia reps didn't have a
> clue.

I second this observation.  I had seen it with both the Phastgel and 
the regular 1.5 mm polyacrylamide gels.  
I could be wrong but the line of reasoning I consoled myself was that
since there is a directt correlation between the length of fixing
and the quality of silver staining, the staining and destaining bby
coomassie does take out a lot of junk.  So it had always been better
silver after coomassie.
Another reason is that specially for some proteins it is next to impossible
to destain the gels completely to remove the stain.  So I think the coomassie
blue reacts with the silver stain reagent and intensifies the signal.
Is there a better explanation?  I will be interested.
Raj Shankarappa
Univ of Pittsburgh.




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