Gel documentation

Dean.Sequera at am.apbiotech.com Dean.Sequera at am.apbiotech.com
Tue Mar 10 11:53:59 EST 1998


In article <350480F4.7CB9 at whale.st.usm.edu>,
  sywang at whale.st.usm.edu wrote:
>
> Has anyone tried to put together a gel documentations system using a CCD
> camera, image capture card, gel analysis software and printer? Any
> suggestions as to where to look for such info? A colleague has a Kodak
> system. He likes the software but would like to improve the sensitivity
> of the system by going to a CCD camera. All of the components are
> relatively inexpensive. We were wondering how difficult it would be to
> put a system together. Could someone with experience tell us whether
> it's worth the trouble? Alpha Innotech, Bio-Rad, etc., make very nice
> systems but all cost over $10,000. The Kodak system is around $4,000,
> how does it compare to something like Alpha Innotech? Thanks for your
> attention.
>
> --
> Shiao Y. Wang
> University of Southern Mississippi
>

It depends on your use of the system. The Kodak system will be able to see
about 2 ng/band in an ethidium bromide stained gel. Most of the CCD based
camera systems will achieve 0.1 ng/band. Those system that integrate the
signal on the CCD chip itself (like the Amersham Pharmacia Biotech VDS
system) can reach this sensitivity in less than two seconds. Those that do
not take over a minute.

Most researchers only need digital storage (and analysis) for one out of ten
gels. For the rest, the hard copy record is needed. There are a couple of
considerations for this hard copy record. With the Kodak system, it takes
about three minutes to transfer the image over to the PC through a terribly
slow RS-232 serial port. If the sensitivity is wrong (and you can't really
judge that until the image gets there) then you have to do it again. Then it
takes over 4 1/2 minutes to print it out. The cost is over $0.50 apiece. With
the VDS, the cost is about $0.10 and it takes 20 seconds. Because it uses a
unique polymer film with a heat sensitive emulsion, the record looks like a
Polaroid photo. The heat sensitive paper systems do not show the same
resolution and quality. They also fade like fax paper.

The Kodak system must be tethered to a PC. That is quite inconvenient when
most of the time you just need a hard copy. The VDS stands alone and gives a
hard copy. If you want to transfer the digital image to a PC, it takes a half
second.

Even though the Kodak system has greater data point density (1024 X 768) this
does not produce greater band resolution for the digital. This has to do with
the blooming effect of fluorescence and background noise. By integrating on
the chip, the background can be removed and only the signal identified. That
maximizes band resolution. The file size is 2 1/2 times less than on the
Kodak system. That doesn't seem like a lot at first until you start saving
your experiment records.

The Kodak software is quite basic. If your gels are perfect and you don't
need to correct for abnormalities, accurate quantitation or molecular weight
calculation, analysis reports, GLP, documentation of the experiment, etc.,
then it will be adequate. Most researchers eventually find the software
lacking and yearn for more sophisticated features.

So, the bottom line is: you get what you pay for. More expensive systems
offer speed, quality, low cost per hard copy, convenience, features, etc. If
you have a high throughput lab (greater than ten results per day) then the
higher priced systems will pay for themselves within a few years based on the
cost per output alone.

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