Phosphoimagers vs Instantimager

Tracy Aquilla aquilla at
Tue Oct 4 18:35:25 EST 1994

In Article <36s05i$fd3 at>,
rsaldanh at (Roland J Saldanha) wrote:
>In talking to sales reps for the various machines it is my understanding that 
>Phosphorimagers are unparalled for resolution e.g. they could easily handle 
>nucleotide resolution (footprints, sequence etc) but the quantitation is 
>actually semi illusionary - several technical problems make the actual 
>quantitation poor some of which include, non-linear respose of the screen, 
>variability within and between screens, time-dependant decay of the image on 
>the screen and several artifacts due to the laser scanning.
>The instantimager appears to be far superior in the quantitation but the 
>resolution is poor relative to the phosphorimager and of course cannot be used 
>for chemiluminescence.

These are some significant disadvantages, I would say. How is it superior?

>Our own application would involve quantitative footprinting sorts of 
>experiments and thus both instruments have weak areas with respect to our 
>ultimate needs.  I would be grateful if some users could comment on these two 
>1) Accuracy of Quantitation
>2) Resolution of the phosphorimager
>Thank you.
>Roland Saldanha

Very interesting. Where did you get this information (do you trust sales
reps)? It is my understanding that phosphorimagers are relatively accurate
for quantitation; at the very least, it's much better than time-tested X-ray
film autoradiography (see BioTechniques 16(2); 290-294; Carcinogenesis
13(8): 1475-1479; Electrophoresis 11: 355-360). The dynamic linear range of
the instrument I have used is reported to be approximately 65,000:1
(compared to X-ray film, which is about 300:1). I have checked the screens I
use for a linear response, and find them to be at least as good as film
(within the range that can be used for comparison), and several-fold more
sensitive. I don't know anything about the Instaimager. Care to elaborate on
this technology?

Tracy Aquilla, Ph.D.
Molecular Physiology and Biophysics
University of Vermont
aquilla at

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