Featured Article
Monday May 01, 2006
Companies are now offering gel documentation systems that do far more than just take pretty pictures. The latest group of instruments can perform the number crunching and mind-numbing analyses to bring you one step closer to discovery. With enthusiasm for proteomics remaining strong, investing in a good unit could very well reap exponential returns.
Gel documentation systems depend on charge-coupled devices (CCD), whose humble beginnings date back to 1969. It was then that scientists at Bell Laboratories used silicon to create a chip that turns light into electrical signals. Over the following decades, funding from NASA helped to increase pixel density and decrease pixel size and noise readout. By 1990, the technology was sophisticated enough for the Hubble Space Telescope to use as part of its video equipment. The addition of cooling capabilities to CCDs has allowed them to provide the type of sensitivity and signal-to-noise ratio required to detect low abundance proteins that cause disease, or those that bear key responsibilities in maintaining normal cell function.
Cooled below ambient temperatures, the chip receives fewer photons that are not generated by the pertinent bands on the gel. Such photons hit one of about a million photodiodes on the CCD. Upon absorbing the photon, an electron converts the energy into an electric current, which is digitized into visual information. The collection of this information generates the digital image. Saved in a common file format, such as tiff or jpg, the image can easily undergo interpretation and preparation for publication. But that’s not the only advantage of digital images over traditional film photos. By using a gel documentation system, you will also contend with less variation and benefit from greater sensitivity.
You’ll find that the degree of sensitivity and other parameters will vary among the different brands and models. Typically, lower-end models come with limited options, while higher-end instruments offer more features. Most models, however, are designed for flexibility, with accessories and functionalities that you can add on as needed. You can purchase different filters to detect the light of various fluorescent probes. Although some models can be used with fluorescent, chemiluminescent, and colorimetric probes, you’ll have to purchase an extra module to capture chemiluminescence with instruments designed for either compactness or price (or both).
Another approach to maximizing your dollar is to purchase a system that can image blots, film, membranes, microplates, and colony plate assays, in addition to gels. You can set the instrument for one of multiple capture modes. This means you’re free to do anything else while the imager automatically performs time-lapse or progressive exposures. The scenario gets even better if the instrument is designed as part of a larger system. Then, you can integrate the imager with an automated spot picker that digests the gel to extract the protein, which can then be immediately fed into a connected mass spectrometry module.
Sound good? Take a look at the list below. You’ll soon find yourself looking into the universe of proteins.