Phosphorimager Questions

Mark W. Trumbore Trumborm at
Fri Mar 3 10:24:34 EST 1995

In article <D.J.Glover.34.000F3D3E at>, D.J.Glover at
(David Glover) wrote:

>                       I am using a Molecular Dynamics Phosphorimager to 
> obtain quantitative data from northern blots. I have a couple of questions 
> that other users around me have been unable to answer to my satisfaction.
>                      One of the advantages of a phosphorimager over 
> autoradiography and densitometry is that the response of a phosphor screen is 
> linear over a much greater range than an autorad. film. Nevertheless, there 
> is a limit to the linearity of a phosphor screen.Therefore, should we always 
> calibrate our screen to check our signal is within the linear range of the 
> screen. I don't know anyone here who does. My 32P signals are often
quite weak 
> so I am not worried about saturation but rather the lineararity of the screen 
> at low range signals. 
>                       My second question regards the production of a 
> publication quality hardcopy of the image. I vaguely remember some discussion 
> on this newsgroup about this a long time ago.If I remember rightly the best 
> solution anybody offered was to expose the blot to an autorad. after exposure 
> to the phosphor screen and photograph it. This has also been suggested to me 
> by others here. I find this very disappointing for such an expensive piece of 
> equipment. I do a lot of these so if I had to expose to an autorad for
> days after quantitation on the phosphorimager I'd never get to finish my PhD! 
> At the moment I expose to the phosphor screen for 3-4 days so that I get a 
> good contrast between the signal and background and then print it out on
an HP 
> laserjet at 600 dpi. I'm not totally satisfied with this but I guess
I'll have 
> to make do unless anyone else has any suggestions.
>                        BTW, thanks to all those who take part in the 
> phosphorimager discussions. I find them most informative.
> Thanks in advance,
> David Glover
> School of Biochemistry,
> University of Birmingham, UK.

If you export the image as a tiff format file you can then read that file
into the graphics program of your choice and print it on a dye-sublimation
printer.  This should allow you to get near photographic quality output. 
Now you just need to find someone with a printer they will let you use.

Mark Trumbore

Mark W. Trumbore
National Institutes of Health
National Cancer Institute
Building 37, Room B109
Bethesda, MD 20892
Phone: (301)496-6682
Fax:   (301)402-0213
Email: Trumborm at

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