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His-tagged protein and SDS-PAGE migration

James Bassuk bassuk at u.washington.edu
Thu Mar 26 01:10:44 EST 1998

wrong.  one His residue has a MW of about 100 daltons.
	six times 100 = 600 or 0.6 kDa

Jim Bassuk
U Washington

On Wed, 11 Mar 1998 ct133 at columbia.edu wrote:

> >I don't know the system, but if it is a 6-His system, then it can run
> >a bit higher on SDS-PAGE. My 10 and 14 kDa proteins (low histidine
> >content) ran at 16 and 20 kDa, respectively. However, there are
> >exceptions to the rule, as a third protein I expressed (high histidine
> >content) ran at the expected MW.
> >
> >So summarizing: yes, up to 6 kDa higher (consult the QiaExpress manual
> >from Qiagen).
> The tag should be about 6 kD. My protein is 64 kD so I'm expecting a
> 70 kD protein. But what I saw on the gel runs at ~90 kD. This is a bit
> too much to be explained by the tag, isn't it?
> C. Tunyaplin

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