Gel documentation systems

Ross Whetten rosswhet at unity.ncsu.edu
Mon Jan 17 10:04:57 EST 1994


In article <2h3t17$2ku at mserv1.dl.ac.uk>, "George Thomas" <gt at biotech.ssf.ernet.in> writes:

|>Hi Folks,
|>We are seriously considering buying a gel documentation system from UVP or
|>some other source since Polaroid costs are prohibitive (what with high cost
|>of importing the films and relatively short shelf life) for a country like 
|>India.  Any of you who have experience with both may be able to help me.
|>Can a ccd based camera and a thermal printer do as good a job as the 
|>polaroid in terms of clarity and resolution of the pictures?

Our multi-investigator group purchased a Stratagene Eagle Eye system (before 
the recent introduction of their Windows-based software) with a large format
(about 15cm x 20cm image size) printer. The people at the lab bench unanimously
agree that it is superior to Polaroid film for documenting gels, because of
the larger image size and ease of adjusting the exposure before making the
final print. It is possible, on close examination, to see pixels in the thermal
prints, so the resolution probably is not quite as good as with Polaroid film,
but with gel photos the resolution on the gel is usually the limiting factor.

|>Assuming that the answer to the above question is yes,
|>can anyone help me with recommendations on the available systems in the 
|>market?  We are considering UVP(UK), Vilber-Louermat (France) and 
|>Tracktel (Vision Systems, Australia).  Any suggestions or comments on these
|>systems or any other system worth considering will be highly appreciated.

At the time (about 2 years ago) we bought our system, none of the others we
tried (including UVP, but not the other two you mentioned) could match the
Stratagene system for sensitivity. If you can, try to get a demonstration from
someone who has one, so that you get a feel for how faint a band the CCD camera
will pick up. Ethidium-stained bands are a real challenge for CCD cameras,and
some image intensification or amplification is usually necessary to get decent
sensitivity. Our system will detect bands that are not visible to the (properly
shielded) eye, and my feeling is that it is about 5x more sensitive than film.
 
|>There is also a densitometry function.  How useful is it for sequence
|>reading?  The suppliers claim it works great; I'd like to hear from actual
|>users.  I know that a laser based densitometer is probably the best, but I
|>am trying to get documentation(of UV pictures) and densitometry in one.

Densitometry for quantitative analysis relies on having a good light box (no
bright spots) and a good CCD (linear response over a wide dynamic range) as 
well as the software. The software will give you numbers in any case, but they
won't necessarily be accurate unless you are very careful about the entire
process of image acquisition. As far as reading sequence, I would not think
the image acquisition would be as critical, but I haven't actually done that.

|>Thanks in advance.
|>-- 
|>George Thomas
|>gt at biotech.ssf.ernet.in



Ross Whetten 
Research Assistant Professor 
Forest Biotechnology Group
North Carolina State University
Raleigh, North Carolina 27695-8008  USA
telephone or fax (919)515-7801
e-mail rosswhet at unity.ncsu.edu
-- 


Ross Whetten 
Research Assistant Professor 



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