Gel Documentation Systems: Measuring More Than You Might Expect

“One of the biggest challenges with CCD-based systems is their categorization and customer perception as gel documentation systems,” agrees Sia Ghazvini, vice president of marketing and business development at Alpha Innotech. “Most systems available on the market today offer the flexibility of doing fluorescent gels, as well as advanced applications like chemiluminescent Westerns, among other applications.” Indeed, the technological advances of these versatile systems surprise some who think that film technology still allows the most sensitive assay. Ghazvini says that Alpha Innotech finds it a challenge to educate customers “as to the power of these systems to replace their use of dark rooms and x-ray film for Western blots. Today’s CCD-based systems are as sensitive as film for chemiluminescent Western blots with similar exposure times, while eliminating the need to have dark rooms, and managing developers, and chemicals that may be harmful for the environment.”

Technically, it is possible to concoct a gel documentation system yourself with a scientific grade digital camera and some experimentation. On the other hand, people without programming experience might prefer to invest in a commercial system to save time writing the software and troubleshooting the system as a whole. Even if you love writing software, the options available today may offer features that you might find indispensable but hadn’t thought of before—or at the very least, better sensitivity or reliability. Below are some of the recent systems sporting the latest in technological advances.

Automation is also featured in the new KODAK Image Station 4000MM Pro, from Carestream Health Molecular Imaging Systems (formerly Kodak Molecular Imaging Systems). According to White, this system is “the most versatile digital imaging system available for imaging chemiluminescent, selectable multi-wavelength fluorescent, and chromogenic applications (e.g. gels, blots, plates, [and] extracted tissue samples).” The latest release of this system offers a precision automated lens system that “records the precise F-stop, 10X zoom and focal plane parameters at each session, enabling reproducibility and traceability without time-consuming manual steps,” says White. She adds that the precision filter systems, in combination with other automated features, serve to minimize setup time and maximize productivity: “The system is equipped with a proprietary design including a selectable wavelength xenon epi-illumination light source, 10 automated excitation filters ranging from 380-780 nm, and four automated wide-angle emission filters ranging from 440-830 nm.”

UVP’s new BioSpectrum® Imaging System series is available with a fully motorized lift, and “four fully motorized, different F-mount lenses that enable full functionality and capability of the larger CCDs used in the new cameras,” says UVP’s Marketing Services Manager, Kathy Buckman. UVP also offers six types of scientific grade CCD cameras in their range of options that allow you to address your own needs. “The fully-motorized BioSpectrum provides unparalleled sensitivity with an F1.2-50mm fixed F-mount lens for low-light applications including chemiluminescence, bioluminescence, and fluorescence,” says Buckman. She adds that the combination of motorized darkroom, motorized lens, and motorized matched filter sets allow researchers “to create and use application templates to make image capture fast, foolproof, and reproducible. Also, the semi-automated analysis in VisionWorks® software allows for automatic lane and band identification and analysis, automatic report generation, and reproducible results in QC laboratories.”

When it comes to software for documentation imaging systems, Marc Winrow, the UK and international sales manager at UVItec, believes that automation features should be used only sparingly. “Software has now been designed to reduce user input to pressing go. Then the results come out,” says Winrow. “This software often digitally manipulates the information from the CCD [camera] and thus the image.” He cites automatic background subtraction as an example. “On first glance this looks good; however, the software is removing data from the image without the user’s consent. The same goes for any digital manipulations. How can you trust the data you have [are] accurate for quantification?” He cautions that researchers should keep in mind a caveat of automatic background subtraction—that very faint bands may be considered noise and removed, leaving the user with no idea that they existed.

Winrow explains that researchers who need accurate quantification should look for a camera with both a large pixel size and high resolution. “Pixel size is a major determining factor of a CCD's sensitivity,” he says. “Lots of pixels are great, but if the size is small they will have what is termed a small ‘full well capacity’ and won’t be able to collect much light.” And collected light, he notes, is data. UVItec’s New Alliance 4.7 system features a 4.2 Mega Pixel CCD sensor with a powerful cooling system to give the lowest read noise possible. “The system also has a short focal distance, helping with the sensitivity and allowing longer exposure times with less distortion of the image,” Winrow adds.

Winrow also notes that researchers should be aware of the dynamic range that they need in a system: “As CCD technology gets more powerful, both pixel size and bit number increase. Bit number determines the grey scales used to calculate the data—the dynamic range. A larger dynamic range gives more data to analyze. For a customer to get this right they need to correctly set the exposure and the aperture of the camera in order to collect the maximum amount of light.” He says that the software controlling most gel documentation systems often does not indicate the dynamic range used during data acquisition, so researchers may not be aware that they need to adjust their settings to collect better data.

Another choice is DNR’s new MF-ChemiBIS system, which supports fluorescence, colorimetric, and chemiluminescence applications. It features a robotic camera controlled by the software that allows vertical movement. This new technology allows the MF-ChemiBIS to outperform the standard zoom lens by a wider field of view, easier and faster operation, and better sensitivity, which all have a direct impact on the results, especially in faint samples, says Oron.

Gel documentation systems contain multiple, distinct components that must evolve together to function successfully, especially considering the recent advances in dyes. According to Oatey, “current challenges include being able to image to greater sensitivity as fluorescent dyes being developed become more sensitive, detecting lower amounts of protein concentrations. Additionally, new fluorescent dyes may have a larger dynamic range, so imaging systems need to be able to image such dyes.”