Intensifying Screens

Karen Browning kbrowning at MAIL.UTEXAS.EDU
Mon Feb 20 15:41:13 EST 1995


Dr. Michael Cooley asks:

>Hi, I have a couple of questions regarding the use of intensifying screens.
>
>1) I can see no sensible reason to use two screens in autoradiography. 
>The screen furthest from the film must be obscurred by the blot and hence 
>is unneccesary. Yet others claim it is important (cause that's the way 
>they learned it).

Long ago, when screens were first being used (mid-70s) I did a study of 
them.  I found that only one was necessary for autoradiography.  The best 
screen was the Quanta III by Dupont.  Exposing at -70 was necessary for 
enhancement of 32P and 125I.  These are the only two isotopes that emit a 
particle strong enough to excite the fluor on the screen to emit a photon.  
If you are using a screen for 35S, 14C or 3H you are wasting your time.  You 
must use an imbedded fluor for those.  Hope this helps!


>
>2) I was told by one person that exposing the screen to light (especially 
>light with a lot of UV) destroys the screen. Any thoughts on that? 

The are particularly easily destroyed by water and vapors from dried gels 
with acetic acid.  I do not think that exposing them to light would do much 
other than possibly excite the fluor to emit photons and give a hazy 
background on the film.


Karen S. Browning, Ph.D.
Department of Chemistry and Biochemistry
University of Texas
Austin, TX  78712

512-471-4562
512-471-8696 FAX
kbrowning at mail.utexas.edu




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