View a complete listing of gel documentation system suppliers here.
Illustration: Andrew Meehan
A typical low-cost gel-documentation system using a portable hood and digital camera is shown at right. At left is a typical high-end system based on a light-tight cabinet and a CCD.
Researcher Willy Walter of the University of Wisconsin, Madison, has fairly typical gel-documentation needs: "We take pictures of ethidium bromide-stained agarose gels using a UV transilluminator and of yeast colonies under white light." If, like Walter, recording simple digital images of gels is your goal, a low-end system will provide the necessary functionality for under $5,000, and many are flexible enough for other imaging tasks, given correct lighting and filters. Those with more sophisticated applications like chemiluminescence in mind, will need a more powerful system. But even these can be had for under $20,000.
High, Mid and Low-Range Suppliers
In the tables on the next few pages, we compare 28 selected systems in three price classes for several key features, including imaging hardware, darkroom type (portable hood or cabinet), and lighting options. More extensive tables are available here. (German manufacturer Biometra is not listed, as the company's instruments are priced through local distributors.)
There are other components to consider, too. Computers are usually optional, and purchasers may install software and/or hardware onto existing systems. Likewise, specific filters, overhead and Epi-lighting hardware, and printers may be offered as either optional or standard. Transilluminators, whether integrated, included, or optional, come in different sizes, have different lighting intensities, and may output at different wavelengths.
One of the biggest differences, and the hardest to quantify, is software quality, which dramatically affects analysis options as well as compliance with GLP and similar data tracking and verification requirements. As with any major purchase, it's wise to request an in-lab, hands-on demonstration, or at least a demo copy of the software, to establish that your application is easily handled.
Making Your Own
If you looked at our tables and thought "but I just need something simple and cheap to replace my instant film camera," you might want to consider building your own system.
James Burnette of Carnegie Mellon University in Pittsburgh, Pa., has posted detailed directions for doing just that on his Web site,
Adjustable exposure, quality optics, a macro option or zoom lens, and good low-light performance, are strongly preferable. The correct filter is also crucial. Narrow band filters (590 nm) for ethidium bromide-stained gels work better than simple red filters with some cameras because, says Gary Garnett, sales manager at Beloit, Wis.-based Peca Products, "most digital cameras can see infrared very well." Without a narrow band filter you may get a picture of the transilluminator bulbs, he says, which will interfere with seeing the bands in the gel.
Garnett says the Olympus 7070 ($410,
For more-elaborate systems, components can be mixed and matched. Says Mark Molenda, president of Oconomowoc, Wis.-based Scientific Digital Imaging: "We start customers with a camera and frame grabber. They like to pick and choose all the other components."
For image analysis, several free options exist, including ImageJ
Finally, consider current and future requirements carefully: Is a cabinet necessary? Does the lab have the space? How large will your gels get? And, will you ever need chemiluminescence? Answer these questions wisely and your homemade solution will provide flexibility and value for years to come.