Gel Documentation System: Introduction, Principle, Components, and Uses

Introduction

A Gel Documentation System (GDS) is a laboratory instrument used to visualize and document DNA, RNA, and protein samples that have been separated by gel electrophoresis. Gel electrophoresis is a common technique used in molecular biology for separating and analyzing biological molecules based on their size and charge.

The gel is placed on a UV transilluminator, and the GDS uses UV light to illuminate the gel and detect the presence of the samples. The GDS also typically includes a camera to capture digital images of the gel, which can be used for analysis and documentation.

GDSs are used in a wide range of applications, including molecular biology research, genetic analysis, and forensic science. They are available in a variety of sizes and configurations, ranging from small, portable units to large, fully automated systems capable of processing large volumes of samples.

Principle of Gel Documentation System

The principle of a GDS is to use UV light or visible light to excite fluorescent or chromogenic molecules in the gel, which then emit light that is captured by a camera and recorded as an image.

The basic components of a gel documentation system include a light source, a filter system to select the appropriate wavelength of light, a camera, and software for image capture and analysis. The gel is placed on a transilluminator, which emits UV light or visible light that excites the fluorescent or chromogenic molecules in the gel. The emitted light is then filtered and captured by a camera, which is connected to a computer that displays and stores the image.

The GDS can be used to visualize DNA fragments, RNA transcripts, or protein bands separated on a gel. This is useful for a variety of applications, such as verifying the success of a PCR reaction, analyzing gene expression, or determining the presence and quantity of a protein of interest.

Components

The basic components of a gel documentation system are:

1. Light source: The light source illuminates the gel with UV or visible light. UV light is commonly used for DNA and RNA samples, while visible light is used for protein samples.
2. Transilluminator: The transilluminator is a platform on which the gel is placed. It emits UV or visible light and is usually made of glass or plastic.
3. Filters: The filters are used to select the appropriate wavelength of light to excite the fluorescent or chromogenic molecules in the gel. The filters are placed between the transilluminator and the gel.
4. Camera: The camera captures the emitted light from the gel and converts it into an image. The camera can be either a CCD or a CMOS camera.
5. Lens: The lens focuses the light from the gel onto the camera sensor.
6. Software: The software is used to control the camera, capture images, and perform image analysis. The software allows the user to adjust exposure times, image resolution, and other settings to optimize the image quality.
7. Computer: The computer is used to store and display the images captured by the camera.

Additional components may include a darkroom, which reduces ambient light and improves image quality, and a printer or other output device to print or export the images.

Handling Procedure

The following is a general procedure for handling a GDS:

1. Prepare the gel: Run the DNA, RNA, or protein samples on an agarose or polyacrylamide gel according to the standard protocol for electrophoresis.
2. Stain the gel: Stain the gel with an appropriate DNA, RNA, or protein stain. Ethidium bromide or SYBR green is commonly used for DNA staining, while Coomassie blue is commonly used for protein staining.
3. Place the gel on the tray: Place the stained gel on the tray of the gel documentation system.
4. Turn on the UV light: Turn on the UV light of the gel documentation system to illuminate the gel.
5. Adjust the camera settings: Adjust the camera settings to optimize the image capture, including exposure time, aperture, and sensitivity.
6. Capture the image: Capture the image of the gel using the gel documentation system. Save the image to a file or print it out for documentation purposes.
7. Analyze the image: Analyze the image using appropriate software to quantify the amount of DNA, RNA, or protein in each band or to determine the molecular weight of the samples.
8. Clean the system: After use, turn off the UV light and clean the gel documentation system according to the manufacturer’s instructions to prevent contamination and prolong the lifespan of the equipment.

Uses of GDS

The Gel Documentation System is a versatile laboratory equipment that is commonly used in molecular biology, biochemistry, and biotechnology research. Its main use is to visualize and capture images of DNA, RNA, and protein samples separated by gel electrophoresis. Some of the specific uses of a GDS include:

1. DNA/RNA analysis: The gel documentation system is used to analyze DNA and RNA samples that have been separated by electrophoresis, allowing scientists to visualize and quantify the amount of DNA or RNA in a particular band or fragment.
2. Protein analysis: The gel documentation system is also used to analyze proteins that have been separated by electrophoresis, allowing scientists to visualize and quantify the amount of protein in a particular band or fragment.
3. DNA sequencing: The gel documentation system is used to capture images of DNA sequencing gels, allowing scientists to analyze the sequence of DNA fragments.
4. Western blotting: The gel documentation system is used to capture images of Western blots, allowing scientists to analyze the expression levels of specific proteins.
5. Colony counting: The gel documentation system can be used to count bacterial or yeast colonies on an agar plate, providing a quick and accurate method for quantifying bacterial or yeast growth.
6. Documentation: The gel documentation system is used to capture images of gels or blots for documentation purposes, allowing scientists to keep a record of their experimental results.

Keynotes

• It is important to note that the specific handling procedure may vary depending on the manufacturer’s instructions and the type of gel documentation system being used. Always follow the manufacturer’s instructions and wear appropriate personal protective equipment (PPE) when using the gel documentation system.
• Overall, the gel documentation system is an essential piece of laboratory equipment for visualizing and quantifying biological samples separated by electrophoresis, and it has many applications in molecular biology, biochemistry, and biotechnology research.

Further Readings

1. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, 5th Edition
2. Principles and Techniques of Biochemistry and Molecular Biology, Wilson and Walker 7th Edition
3. Short protocols in molecular biology, 4th edition
4. Pulsed-field gel electrophoresis( A Practical Guide ) by Bruce Birren
5. Molecular Biology. Editor: David Freifelder, 2nd ed, Publisher Jones and Bartlett Inc.