Nucleic acid and protein gels are a fundamental part of lab life. Gel documentation is a method used to record and measure labeled nucleic acid and protein in various types of media, like acrylamide, agarose, or cellulose. DNA or RNA is usually stained by ethidium bromide, which intercalates into the nucleic acids and can be visualized with UV light.
These dyes are some examples of dyes that can imaged with blue light: SYBR® Safe, SYBR® Gold, SYBR® Green. They are safer dyes for staining DNA are also growing in popularity.
A gel documentation system (also nicknamed gel doc, gel image system or gel imager), is a piece of capital equipment used in molecular biology for the documentation and imaging of nucleic acid and proteins to gather more information on the genetic information stored in DNA.
A gel doc is used to image and document the genetic information from nucleic acids and proteins suspended within polyacrylamide or agarose gels. We outline the advantages of using a gel doc system compared to using film in Table 1.
Table 1. Benefits of using a gel documentation system
|Benefits of using a protein gel documentation system
|Saves time and can reduce overhead cost
|Less exposure to harmful chemicals
|Gives quantitative data
|Supports fluorescent detection for multiplexing
|Produces higher-resolution images
|Ability to access more applications (such as visible gel imaging, Western blotting, total protein normalization)
|Able to image more stains
|Advanced software makes it convenient to save and share data
Protein purification procedures often rely on verifying purity by SDS-PAGE and subsequent gel staining (Coomassie blue or silver stain) to check for contaminating protein bands. Gel documentation system are able to record and measure labeled protein and nucleic acid present across different media, such as cellulose or agarose.
Many stains, including TotalStain Q, AzureRed, Coomassie Fluor™, Deep Purple™, SYPRO® Ruby, SYPRO® Red, SYPRO® Tangerine, and more can be imaged using advanced digital imagers, such as chemiSOLO, or select Azure Imaging Systems.
The newer generation of imaging systems often contain sophisticated cameras that exhibit a broader dynamic range than film, thus avoiding the signal saturation problems that limit the dynamic range of film.
You should know the main features of a gel doc before making sure it’s the right one for your lab. Table 2 below gives a general outline of the features you should be aware of, and compares them with the characteristics of the Azure 600 Imaging System. We believe Azure Imagers are the perfect solution for high-performance gel documentation and analysis of gels.
For example, the Azure 200 has the imaging capabilities for many applications. With a dual-wavelength 302 nm and 365 nm UV transilluminator, ethidium bromide-stained DNA gels can be imaged in a fraction of a second. For excising bands from a gel, the UV transilluminator platform can be pulled out.
|Choose a gel doc based on
|The Azure 600 Imager has
|Two channel, laser-based IR and chemiluminescent detection, with the speed and sensitivity of film
|Wider Dynamic range
|Higher pixel well cap for higher dynamic range (4.8 OD dynamic range)
|Supported detection types
|Laser technology with two IR detection channels enabling you to image more than one protein in an assay. It provides accurate and fast chemiluminescent detection, as well as the sensitivity, dynamic range, and linearity needed for quantitative blot analysis.
|Gel doc size
|A small footprint of 42 x 56 x 33 cm. This small size translates into saving you more room on your bench.
|Software with preset protocols that also allows you to generate your own custom protocols combining any excitation source, emission filter, image overlay, lens aperture, exposure time, focus, distance to the camera, and resolution
Table 2. Features of a gel documentation system that you should be aware of when purchasing
The Azure 400 and Azure 600 imagers, as well as the Azure Sapphire FL Biomolecular Imager, open up the ability to document protein gels stained with a wide variety of fluorescent protein stains that fluoresce in the visible spectrum.
Finally, fluorescent dyes are relatively stable; blots can be archived and imaged months after the initial experiment as long as precautions are taken to avoid photo-bleaching of the fluorophores.
Azure imaging systems offer:
Multiplex fluorescence capabilities
Speed and sensitivity of X-ray film
Learn more about the Azure Imaging Systems, including full product specifications, user manuals and resources.
Gel docs usually contain UV transillumination that excites dyes from beneath the area the sample is placed. The light travels through an emission filter to a high-resolution camera where an image of the sample is collected. Gel documentation systems are essentially enclosed darkrooms that block external light from entering the inside in order to image gels, Western blots, tissues, arrays, and more.
Azure Imaging Systems use CCD cameras with fast lens options, auto detection, and 4.8 OD dynamic range to capture images. Learn more
Polyacrylamide gels form a crosslinked, mesh-like matrix through which proteins migrate with the application of current. The matrix functions like a sieve, allowing smaller, low molecular weight proteins to migrate quickly through the gel, while large, high molecular weight proteins tend to progress more slowly. When the electrophoresis is finished, proteins in each lane will be separated into a continuum, with the highest molecular weight proteins remaining near the loading site and the lowest molecular weight proteins reaching the opposite end of the gel. Read 6 tips on troubleshooting band separation
Proteins travel effectively through the gel matrix based exclusively on size.
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Chemiluminescent detection (Figure 1) depends on an enzymatic reaction so timing and the amount of both enzyme and substrate used have important effects on data quality.