Christian Moews Christian.Moews at
Thu Mar 14 17:53:55 EST 1996

ar229 at FreeNet.Carleton.CA (Allison Haggarty) wrote:

>I have been recently comparing transfections with Cos1 and Cos7.  I have
>decided to use the latter because they grow slightly faster and so it's
>easier to get enough cells to transfect.  Also I found that for my
>experiments (where I want to do immunofluorescence to localize the
>transfected protein) that electroporation works better than DEAE

>"David L. Haviland, Ph.D." (haviland at KIDS.WUSTL.EDU) writes:
>> Greetings:
>> Does anyone have any direct experience with protein expression (cDNA 
>> constructs) in the COS cells?  The Harvard manual states that COS-7's are 
>> best for this purpose however, as most know, the description of COS-1 and 
>> COS-7 cells are virtually identical in the ATCC catalog.  My only test 
>> thus far has been a beta-gal vector that serves as a control for 
>> transfection (DEAE).  Using this vector, transfection and expression are 
>> effectively the same as far as I can tell. 
>> Many thanks in advance.
>> Any thoughts?
>> David
I was doing a couple of transfections in COS-7 cells in order to
express a protein of desire.
Given that You are using a replicating vector for transfection (which
I strongly suppose, otherwise there would be no need of using
COS-cells at all), the succes of Your experiments is critically
depending on the content of the large T-antigen in Your cells.

I found that the content of large T-antigen is going down with
increasing passage numbers and hence the amount of protein expressed.
As a rule of thumb: The better Your cells look (by visual inspection)
the worse the expression of the wanted protein will be.
I hope this will help somehow.


Christian.Moews at

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