Real-time chemiluminescence- why?
Bernard P. Murray, PhD
bpmurray*STUFFER* at socrates.ucsf.edu
Fri Feb 12 22:18:13 EST 1999
In article <126.96.36.19990212091739.006d5404 at imm2.imm.uth.tmc.edu>,
dhavilan at IMM2.IMM.UTH.TMC.EDU ("David L. Haviland, Ph.D.") wrote:
> While conducting the search for an imaging system for our institute, I had
> numerous sales reps tell me the "wonders" of their particular machines and
> always made the point about being able to perform "real time
> chemiluminescence" imaging. Basically, performing the actual development
> of the blot while at the same time obtaining the image. I was "slathered"
> with all the gory details about the chips used in the CCD camera and why
> company X's was better than company Y's in performing long duration imaging.
> More importantly, when I asked those in our institute about "real time
> measurement" that perform chemiluminescent assays, I was greeting with
> bizzare looks, and the ever present question of "Why would I want to do it
> that way?"... They prefered just to use film and get a computer image of
> that instead. To some extent this is all moot, since with the system we
> did buy, we can now use a chemiluminescent imaging screen.
> But I'm still curious, why do real time imgaging? From what I've been
> told, it takes an enormous time (tens of minutes or more) to perform, ties
> up the machine, and makes little sense at the moment.
> Anyone care to enlighten me?
I have used Amersham's ECL+ and either film or a
Molecular Dynamics Storm/FluorImager. I use film
for convenience (the dark room is next door)
and qualitative results. I use the FluorImager
when I want quantification. The claimed sensitivity
of the FluorImager covers 5 orders of magnitude
whereas film is typically <2 (and you should really
pre-flash to get that). This means that with the
FluorImager you don't have to bracket the exposure as
you do with film when you want all the bands visible.
Also, if you quantify signals on a film using a
scanner you are still limited by the latitude of
the film (even if the scanner thinks it can do 16
million levels of grey).
With ECL+ the lifetime of the signal is long
enough to check the signal on film and then head
for the Imager for some hard numbers (or vice versa).
My only complaint/bias is that decent photo-quality
printers are not cheap so a 300 dpi printout from
the Imager always looks messy compared to a cheapo
piece of film.
I can't comment on CCD-based devices.
[No affiliation with Amersham or Molecular Dynamics
- and, if the truth be told, I prefer Pierce's "Super
Signal" when I am doing luminescence-only blots as
ECL+ is considerably more expensive]
Bernard P. Murray, PhD
Dept. Cell. Mol. Pharmacol., UCSF, San Francisco, USA
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