Tracy Aquilla aquilla at
Mon Feb 27 11:12:20 EST 1995

>Tracy, We have made extensive comparisons of BioRad and MD.  MD is by far
>the more sensitive instrument for detecting low levels of 32P.
>Dave Gilbert
>Department of Biochemistry and Molecular Biology
>SUNY Health Science Center
>750 E. Adams St.
>Syracuse, N.Y. 13210
>Tel:(315) 464-8723
>FAX:(315) 464-8750

    I tried to email you directly, but the message kept bouncing back.
Thanks for the input. I was under the impression that the chemistry of the
Bio-Rad screens is quite different from that of Fuji and MD. I think
Bio-Rad's screens are Strontium Sulfide and MD's are Barium Fluoro Bromide.
It is my understanding that the Barium chemistry has a relativley short
signal retention time, due to high spontaneous discharge rates, which can
prevent imaging of very weak signals over long exposure times. The Bio-Rad
Strontium screen keeps charging and stores the charge without this signal
loss, thus allowing for more sensitivity when doing long exposures. Even
after exposure, the Bio-Rad screens can be stored for up to 24 hours before
    If you would be so kind as to explain your interpretation of the
differences you have noted, I would be very appreciative. Also, I would like
to know the conditions under which you made your comparisons (i.e. exposure
times, amounts of radioactivity assayed, detection limits of the screens,
etc.). I am not trying to start a flame-war, I just want the facts. I do not
have access to the MD imager, so I can't do the comparison for myself.
Seeing as how you have already done this, perhaps you could send me your
results or post them to the group. Thanks very much for your help.

Thomas T. Aquilla, Ph.D.         .***.   .***.           .***.   .***.
Molecular Physiology and Biophysics    * | | | *       * | | | * | | | *
University of Vermont Medical College*   * | | | *   * | | | *   * | | | *   
Burlington, VT 05482-0068          *       * | | | * | | | *       * | | | *
aquilla at    '***'           '***'   '***'           '***'   

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