Caitlin Smith has a B.A. in biology from Reed College, a Ph.D. in neuroscience from Yale University, and completed postdoctoral work at the Vollum Institute.
The ability to document DNA gels has come a long way from the early days of taping a Polaroid into your lab notebook. Researchers still rely on images of gels, but digital photography, software analysis and fluorescent dyes have changed gel documentation systems for the better. Here’s a look at important points to consider when choosing DNA gel documentation system today.
Ease and reliability
Ease of use and reliability are the biggest considerations in choosing a gel documentation system. “People want gel doc systems that are really easy to use but also robust enough to withstand a lot of use, for example, from multiple labs across a department,” says Raymond Miller, product manager in the protein quantitation division at Bio-Rad Laboratories. A feature that Bio-Rad incorporates into its GelDoc and ChemiDoc systems is the use of different trays for different types of gels (and blots for the ChemiDoc models). “The systems automatically recognize and use the correct settings for the application, such as for SYBR dye or UV, based on the type of tray,” says Miller. In addition to ease of use, Miller says vendor support is valuable—so you get a response quickly if you encounter problems.
Ease of use takes many forms, including compact size. Analytik Jena recently introduced stand-alone systems (i.e., they’re not connected to an external computer) with integrated tablets. The touch-screen tablet interface and software, says Stefanie Navabi, senior product manager in life science at Analytik Jena, make operations fast and self-explanatory. Tablet integration is available for a range of models, from the UVsolo touch (the company’s simplest gel documentation system) to the GelStudio SA22 (a more advanced gel documentation system) and the ChemStudioSA2 (for both gel documentation and chemiluminescence of Western blots).
Known for its compact, portable, hood-mount gel documentation systems, Fotodyne focuses on affordable, quality gel documentation systems that are easy to use. “Although we offer larger workstations with dedicated benchtop darkrooms, our small systems continue to be the most popular,” says Fotodyne marketing director Brian Walsh, “especially when combined with our FOTO/Phoresis transilluminators designed specifically for mini gels.”
Fotodyne’s most basic gel documentation option is the Discovery/Doc system, for which researchers use the camera on their own phone or tablet. “This started as a product designed for teaching labs, but we’ve seen increased interest among research labs,” says Walsh. “Capturing gel images on a smartphone makes it even easier to share them and get them into apps and software for downstream processing and analysis.” The company also offers a Discover/Doc conversion package that lets researchers take advantage of old, unused Polaroid hoods “and keep them out of the landfill,” Walsh says.
Gel Company also offers compact, tablet-based models. “Customers always ask for smaller, cheaper, faster,” says president Greg Richardson. Cost is one reason Gel Company offers five models of its gel documentation systems at different price points—but it’s wise to think ahead. “It is important to buy what you currently need, but with the option of upgrade paths in the future,” he says. Software is another powerful tool for boosting ease of use. Gel Company, Richardson says, “has been developing a SMART Capture software for autofocusing on samples of different thicknesses and light environments to make it easier for our customers.”
Syngene, a division of the Synoptics Group, recently introduced the tablet-based T:Genius for imaging DNA gels and protein blots. Jayne Arthur, marketing communications manager at Synoptics, says the latest improvements in Syngene’s systems include “application-driven image-capture software and enhanced CCD sensors in cameras, making them very sensitive.” According to Arthur, sensitivity, resolution, ease of use and cost are the most important considerations when looking for a gel documentation system. Luckily, you aren’t necessarily locked into a particular system’s features if you go the modular route. For example, Syngene’s “G:BOX range of imaging systems are all modular and can therefore be upgraded easily if applications change,” she says.
UV alternatives
Traditionally researchers visualized DNA gels using UV light, which causes ethidium bromide-stained nucleic acids to fluoresce. But increasingly, researchers are choosing to use safer fluorescent dyes instead of toxic ethidium bromide and to reduce the risk of UV exposure by using alternative light sources for excitation, such as blue light. “But this doesn’t work with all of the available dyes—mainly green and yellow fluorescent dyes,” says Analytik Jena’s Navabi. “Under UV excitation, these dyes require emission filters with adequate transmission range.”
To use blue light, look for systems that include either a blue-light transilluminator or a converter plate for UV-to-blue light, as well as an amber emission filter. In addition to many other vendors, Syngene is responding to the increased demand for UV alternatives. The T:Genius gel doc system includes a UV transilluminator but also incorporates blue lights for use with fluorescent dyes.
Analytik Jena’s UVsolo touch gel doc system offers a special configuration for UV protection. “The darkroom features two unique side-access doors for cutting out of gels while the main door is closed,” says Navabi. “A unique gel-viewing window in the front door allows a view of the fluorescent gel.” The computer-controlled BioDocAnalyze system integrates a UV-protection shield, the angle of which can be adjusted by the user.
Another example of alternatives for gel documentation is Azure Biosystems’ compact Azure c200 Gel Imaging Workstation. It includes a UV transilluminator for ethidium bromide-stained gels, as well as blue light for fluorescent dyes and white light for silver or Coomassie Blue stains. The system is also expandable to allow for future growth or change. “As the customer’s research expands, the c200 can be upgraded to a Western blot-imaging system for these new applications,” says Lisa Isailovic, director of marketing at Azure Biosystems. “I anticipate that even more light sources and more automation will be incorporated into these machines.”
Integrating chemiluminescence
Although it is still possible to buy a system whose only function is to document a DNA gel, instruments that combine capabilities for imaging both DNA gels and proteins (via Western blotting using chemiluminescent signals) are increasingly available. Because these machines are often used by many people (and multiple labs), the chances are good that both functions will receive a great deal of use. One example is Syngene’s tablet-based T:Genius system.
Another example is Bio-Rad’s newest system, the ChemiDoc Touch, a touch-screen system for documenting both protein blots and DNA gels. Miller says that while most customers use it for Western blots, “almost all of our customers use the system for some level of gel documentation.” It’s another reason to consider a gel doc system that also has chemiluminescent capabilities to analyze Western blots, “even if today you’re doing all DNA work and cloning experiments,” says Miller. “Maybe in the future you’ll want to do some immunoblotting so you can see how much of your protein of interest has been expressed.”
No matter how many bells and whistles a gel documentation system has, it must be easy to use. The ability to get on and off the system as fast as possible, with a minimum of fuss, is paramount. “Even the most basic systems will provide publication-quality images, but if you can't acquire a typical gel image in less than a minute or two, the system is probably too complicated,” says Walsh. So after you’ve decided what types of imaging capabilities you want—UV, fluorescent dyes and possibly chemiluminescence—zero in on models that assist you in using them for as little time as possible.