SDS-PAGE for purity

Frank Fürst ffrank at rz.uni-potsdam.de
Thu Jul 18 03:30:08 EST 2002


ballal_sv at hotmail.com (S.Ballal) schrieb:

> You will need a scanner/ densitometer for "percent area
> determination:. This is something which should not be done with
> "eyeing".

I agree, however:

> In case you know the minimum quantity of contaminant you want to
> detect( say 0.1%), then you can load the same amount of the same
> protein in another lane (say 0.1% of the loaded protein) and ensure
> that same is visible during staining and destaining. This you you can
> always prove that you have not understained your silver and
> overdestained your CBB stains.

That only assures that you don't have more than 0.1% of one particular
contaminant. However, you can still have 30 proteins, each with just
below 0.1%, and you won't get 99.9% purity, but rather 97.x%

In fact it is questionable how relevant such a contamination is - but
then it is equally questionable how sensible a statement is that a
protein "is 99% pure by SDS-PAGE".

Bye, Frank
-- 
Und die Glockenform von "Goethe" erinnert mich doch sehr an den Witz
mit dem Amerikaner vor dem Goethedenkmal: "Ah, Schiller, die kleine
Nachtmusik.  Ta ta ta taaaaah".							 [David Kastrup in dctt]



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