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
kbrowning at mail.utexas.edu
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