Total cellular protein vs cell number

Warren Gallin gal-1 at bones
Tue Mar 7 09:14:45 EST 1995



On Mon, 6 Mar 1995, Jeff Rawlings wrote:

> In article <sg-0503952030370001 at pc030.surgery.nwu.edu>, sg at nwu.edu
> (Stephen Gately) wrote:
> 
> > I am trying to quantitate a cell-associated protein, and want to
> > standardize it.  Does anyone have any suggestions on whether I should
> > standardize to cell number or to total cellular protein?
> > 
> I would standardize based on total protein. The reason: I think that
> percent of total protein should vary less than amount of protein per cell.
> Cells come in many ages, shapes, sizes, and are sometimes unhealthy, etc.
> All of that can introduce variation in amount of protein per cell.
> 
> When I did a similar experiment, I used a Western, with I-125 labeled
> secondary antibody, to quantitate. (I also used a phosphorimager, which
> makes quantitation much simpler).

It really depends on what point you are trying to get at.  If the issue 
is whether there is an absolute increase in protein synthesized, then 
normalization on a per cell basis would be more appropriate, to avoid 
losing the signal in changes in synthesis of other proteins.  Onthe other 
hand, normalizing to total protein would tell you something about the 
relative differences.  If you are comparing different cell types, the per 
cell protein content may differ, which couuld confuse the results.
   I think that the short answer is, you have to choose your 
normalization based on what the point of the experiment is, not on some 
global principle nor on ease of doing the normalization.
   If you tell us the point of the experiment you might get more useful 
advice.

Regards, Warren Gallin



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