Gel Documentation System

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A Gel Documentation System is a type of imaging system which is widely and regularly used in molecular biology experiments. It is used mainly for the imaging or recording and measuring the labelled nucleic acid or proteins in a media such as Agarose gel or Acrylamide Gel. Nucleic acids and proteins are usually stained with ethidium bromide or fluorophores such as SYBR Green. 

Generally, a gel doc system includes a hood, ultra violet transilluminator, and a CCD Camera to capture the image. 

For Example: A nucleic acid is stained with ethidium bromide dye and run on the Agarose Gel. After electrophoresis is completed, this gel is then kept inside the gel doc system in the hood and covered. When UV light is illuminated on this gel, the nucleic acid plasmid stained with ethidium bromide will emit light. The emitted light will be in the form of bands. Each band in the gel represents the size of the nucleic acid base pairs. This is captured with the help of camera installed on top of the hood. Hood should be covered so that user won't get exposed to the harmful UV Light. 

Ethidium Bromide Stained, Agarose Gel Electrophoresis

Principle: 

    "The nucleic acids and/or proteins are stained with the fluorescent dyes in a media. The amount of fluorescent dye bonding depends on the molecular weight. These are then illuminated or excited by the ultra violet light which will emit the fluorescence of the fluorescent molecule stained. This emitted light is captured with the help of a camera. The image formed will be in the form of bands which represent the molecular weight." 

"Greater the amount of nucleic acid, brighter the bands".

Components of a typical Gel Doc System: 

        

Quantum ST5 - Lab.TV

Camera: To capture the fluorescence emitted and form the image. Ultra Violet Camera. 

Lenses: They are useful for the focusing of the gel. Most of the lenses are controlled by the computer software. They move upward or downwards to focus the gel to be  imaged. 

Filters: Some doc system have multiple emission filters for special applications. Commonly used is 1 or 2 emission filters. 

Illuminator:  This will illuminate the light required. there will be white light, ultra violet light and LED. First white light is used, so that user can keep check whether the gel is placed on the stage properly or not. Then white light is turned off and Ultra Violet light is illuminated on the gel. 

Adjustable Stage: which helps in adjusting the gels which can be moved closer to camera depending on the resolution and focus. 

Dark Room: suitable for the chemiluminescence, fluorescence, and other visible light applciations. 

Transilluminator: which has a variable intensity settings and it has a safety cut-off. 



Types of Gel Doc Systems: 

1)  CCD or Digital Doc System: which are usually used for imaging the staining of ethidium bromide. chemiluminescence, and densometric and visible light applications. 

2) Chemiluminescence System: These are primarly used for the western blotting to detect the separation of the protein bands depending on their molecular weight. Due to its high sensitivity and imaging system, it makes them best suitable for the western blotting applications. 

3) Auto Radiography: These are used for the radioisotopes. 

4) Phosphoimagers: these systems have enhanced sensitivity  for the applications such as radioisotopes and multiplex fluorescence. This type of doc systems also have the flexibility in the choice of emission filters.

There are also some other types of gel documentation system are available depending on the applications to be used or run. 

Applications: 

* Gel and Blot Imaging
* Counting of colonies
* Immunological Assays
* Monoclonal antibody binding affinities detection
* Multiplex Protein Detection
* 2D Electrophoresis and Protein Quantification
* Polyclonal Antibody binding affinities detection
* Characterization of Post Translational Modifications.