The Gel Doc XR System provides a very useful tool for obtaining and saving gel images. Laboratories that use gel imaging extensively could definitely benefit from this system. The system is comprised of a 1.4 million pixel resolution camera on top of a darkroom enclosure; the system also includes the software for acquiring and analyzing the images.
I have used the Gel Doc XR system for documenting ethidium or SYBR® Green - stained nucleic acid gels; the system has excellent utility in this regard. It is also suitable for colony counting and for images of Coomassie blue stained protein gels.
For a user who is not experienced in working with focalization and diaphragm apertures, the automatic image acquisition is a big advantage. Moreover, the image is optimized without the need for consumables, other than the UV bulb. One does not need to worry about consuming film in order to obtain the optimal image of a gel (and this could be significant savings for laboratories performing large scale molecular cloning). In addition to the easier image acquisition (as compared to the instant Polaroid cameras), the Gel Doc XR System saves not only film, but also time, as the image can be saved directly to the computer and scanning is not required.
The darkroom of the unit also protects against accidental exposure to UV. Cutting out DNA fragments separated on gels can still be performed as the unit is equipped with a special design screen.
The software is user friendly. Besides helping in image acquisition, it also allows image processing (resizing, rotation and annotation) as well as band intensity quantification.
An apparent disadvantage is the large size of the system. On the other hand, there are no other pieces of equipment (e.g. film and prisms required for exposure of different gel sizes) to be stored. The Gel Doc XR System can also be upgraded to the Chemidoc XRS System which also allows chemiluminescent images to be obtained. However, as most labs already have access to a darkroom with film developing equipment, it is their decision whether to use the money spent on solutions and film to purchase this upgrade.
In conclusion, Bio-Rad’s Gel Doc XR System is a valuable piece of equipment, especially for labs dedicated to extensive molecular cloning, saving not only consumables but also precious work time.