Fluorography problems - was Making own gel dryer

Sean Patterson seanpat at fmed2.uncu.edu.ar
Mon Sep 25 08:14:02 EST 2000


>seanpat at fmed2.uncu.edu.ar (Sean Patterson) wrote:
>
>>	What is the inconsistency between fluorography and cellophane
>>sheets? Since the fluorophore converts the low energy beta into light I
>>assumed that there would be no problem. On the other hand, I am also
>>getting very weak signals now...
>
>Dear Sean,
>
>the problem is that 3H beta radiation is so low energy that cellophane
>is enough to shield it from the fluorophores.


	I'm not sure that this applies, since I permeate the gel with PPO
(using the APEX system)  so the beta doesn't have to pass through the
cellophane. Dima pointed out that the cellophane isn't 100% transparent (of
course, silly me) and thus will increase exposure time. I thought that
there might also be a "sensitizing" effect from surface emission of the low
energy beta on the apposed film, but I have no idea how much that would
contribute quantitatively.

	I switched to the cellophane so I could do two sided fluorography -
develop one film to give me an idea of what the optimal exposure period
would be for the second without having lost the time of the first exposure,
since the first exposure is usually a week to a month.

	Related to this, does anyone have experience with the storage-type
devices applied to tritium autoradiography or fluorography? When I ask the
reps I get a lot of hand waving but no quantitative comparison of how much
time could be saved.

>TEACHING MODE ON:
>That's what makes 3H so insidious - you usually just don't "see" it
>and start to forget that ingested it is quite strong enough to cause
>mutations.
>TEACHING MODE OFF ;-)

	I remember asking in my first radiation safety course (wayyyy back)
why tritium wasn't considered dangerous if 3H-thymidine would be rapidly
and efficiently incorporated into the DNA of dividing cells where the
relative energy of the emitted radiation was moot. The teacher muttered
something about not being a biologist and went on to the next question.

Sean



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