Phosphorimager Questions

neale at neale at
Tue Mar 7 01:00:29 EST 1995

In article <phef-0203951311200001 at>, phef at (Peter Heifetz) writes:
> 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.
> [snip]
>>                       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. 
> [snip]
> Try this:
>    - scan cassette at the highest resolution (88 microns)
>    - bring the image into your favorite TIFF-friendly draw program,
> annotate,etc.
>    - print on 600 dpi laserprinter (we use HP 4M+) using glossy HP plotter paper
>    - (it is still better to do an autorad and scan at 300 dpi, though. 
> These come out even better than the "Phosporimages" using the
> glossy-paper-trick. At first glance you can't tell it from a photo print.)
>    [I can't take credit for this, it was suggested by the Molecular
> Dynamics tech rep who came to demo a Fluorimager we didn't buy]
> -- 
> Peter Heifetz
> Duke University
> Developmental, Cell, and Molecular Biology Group

When we received training on our PhosphoImager by Molecular Dynamics we were
told that scanning at 88 microns was *not* desirable. The rep said that at that
resolution there is "bleed through" to the next 88 micron slice by the laser
which causes a *reduction* in sensitivity when that slice is detected in the
next pass of the laser.

So when you have a weak signal the best resolution to scan is 176 microns. (At
least that was what we were told!)

On a somewhat tangential note, have other users found that when you have a
really weak 32-P signal (ie requires 3 days or more to see faint bands on
autorads) that there does not seem to be much gain in sensitivity by using the

Geoff Neale

Dept. of Virology and Molecular Biology        E-mail: neale at
St. Jude Children's Research Hospital           Phone: (901) 522-0400
Memphis, TN                                       Fax: (901) 523-2622

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