my experience with Biorad posphoimager GS250

Brain Foley brianf at
Wed Oct 6 17:23:13 EST 1993

We have had a Bio_Rad GS-250 in use for about 3 weeks now and are quite
happy with it.  The Mac software is a bit flaky (does not adhere to user
interface guidelines 100%) but does the job.

We find the sensitivity to be about 20-fold better than autoradiography
with an intensifying screen.  And the response is linear over a far
greater range than autoradiograms.

One drawback is that the results are not directly convertible to CPM
because the machine cannot tell how long you exposed the cassette.  You
can convert to CPM by dotting a known amount of radioactivity onto a blot
and using this as a standard.

It works well for 35-S, 32-P and 125-I.  I have not yet tried it with
14-C, but it is supposed to handle that as well.

If you are not getting a good exposure in 1 hour for a blot that gave good
results on film overnight, something is wrong with your GS-250.  

*  Brian Foley               *     If we knew what we were doing   *
*  Molecular Genetics Dept.  *     it wouldn't be called research  *
*  University of Vermont     *                                     *

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