William Bains william at
Fri Oct 16 10:14:22 EST 1998

In article <3626717A.FFF1302F at>, Dave O'Neill
<doneill2 at> wrote:

> HI,
> Due to technical problems (received in sample buffer)  I was unable to
> quantify the total protein content of my cultured P19 (embryonic stem
> cells) cells.  I ran equal volumes on a mini-gel and then stained them
> with commassie blue.  I quantified the entire lane and tried to estimate
> relative protein loads.  Realizing this is a less desirable method, I
> wanted to standardize my protein loads.  I was told I could immunoblot
> with beta-actin.  I'm only concerned about equaling the loads in each
> lane rather than the absolute protein content.
> Is Beta Actin always proportion to total cellular protein?  Do you know
> a I might find a basic review on Beta Actin?  Often textbooks fail to
> mention its relative expression to total protein, or its induction??.
> Any thoughts are appreciated.
> Kind regards,
> Dave O'Neill

The proportion of total cellular protein that is beta actin varies, so
this is not a gold standard reference. However, for cells in similar
metabolic and growth states it is a good surrogate. So if you are
comparing p19s to stationary hepatocytes or differentiated muscle cells,
not so good, but if you are comparing them at different times or to other
stem cells of similar lineage, it is a good approximation.

William Bains

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