SDS-PAGE for purity
ballal_sv at hotmail.com
Mon Jul 22 01:15:33 EST 2002
You are absolutely right Frank, 99% by SDS does not mean anything much
untill the limits of assay and limits and method of detection are
This is true for any assay, for example HPLC where 99% pure by HPLC
will not mean much untill all the parameters for detection and
criteria for integration etc. are completely defined.
ffrank at rz.uni-potsdam.de (Frank Fürst wrote in message news:<87k7nttp4f.fsf at pc201-37.biochem.uni-potsdam.de>...
> 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
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