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His-tagged protein and SDS-PAGE migration

ct133 at columbia.edu ct133 at columbia.edu
Tue Mar 10 20:18:06 EST 1998

>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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