Difference Between Capillary Electrophoresis and Gel Electrophoresis

Key Difference – Capillary Electrophoresis vs Gel Electrophoresis
 

Electrophoresis is a technique that is used to separate biomolecules based on the particle charge, particle size, and the particle shape. The migration of the molecule, known as electrophoretic mobility, depends on the type of polymer/gel used, its pore size, the voltage provided, running time and the surface to volume ratio. There are different types of electrophoresis techniques based on the type of biomolecule used. The first type of electrophoresis invented was paper electrophoresis where a nitrocellulose paper was used as the medium for separation of biomolecules. The principle of gel electrophoresis where different pore sized gels were used to separate biomolecules, was invented later. Gel electrophoresis technique was further modified to improve the accuracy of the technique, and one such modification is capillary electrophoresis. The key difference between capillary electrophoresis and gel electrophoresis is that gel electrophoresis is performed in a vertical or horizontal plane using a polymer gel of standard pore size whereas capillary electrophoresis is performed in a capillary tube with a polymer liquid or a gel.

CONTENTS

1. Overview and Key Difference
2. What is Gel Electrophoresis
3. What is Capillary Electrophoresis
4. Similarities Between Capillary Electrophoresis and Gel Electrophoresis
5. Side by Side Comparison – Capillary Electrophoresis vs Gel Electrophoresis in Tabular Form
6. Summary

What is Gel Electrophoresis?

Gel electrophoresis is a technique used to separate mainly nucleic acids, proteins or amino acids based on its charge, size, and shape. This technique uses a physical gel, which is a polymer substance, as the separation medium. Most commonly utilized gels are Agarose (for nucleic acid separation) and Polyacrylamide (for protein separation). The gel electrophoretic apparatus contains the gel casting tray to prepare the gel, casting combs to prepare the wells, buffer tank, electrodes – positive (anode) and negative (cathode) and the voltage supply unit. Molecules like DNA or RNA, which are negatively charged, move from the cathode to the anode and molecules which are positively charged move vice versa. Gel preparation is done according to the requirement. If a high resolution or separation of molecules is required, a high concentration gel with a lesser pore size should be prepared. The molecules separated on the gel matrix are observed after a staining technique. The separated molecules appear as bands on the gel matrix.

Gel electrophoresis is used in molecular diagnostics such as DNA fingerprinting to determine the presence of a particular DNA/RNA fragment or a protein. Gel electrophoresis also determines the purity of the extracted biomolecule sample. Gel electrophoresis is performed as a preliminary step for in and hybridization and as a confirmatory analysis after sequencing.

What is Capillary Electrophoresis?

Capillary electrophoresis is a modification of gel electrophoresis which uses the same principle of separation based on charge, size of the molecule, but is performed in a capillary tube with either a gel substance or a liquid polymer. Capillaries are prepared of fused silica, and each capillary tube has an internal diameter of 50-100μm and is 25-100cm in length. Samples are injected into the capillary tube containing the polymer material and are separated much rapidly than the conventional gel electrophoresis. The capillary system is well protected inside an insulator jacket which protects the sample from any contamination. Capillaries can be filled with liquid polymers such as hydroxyethyl cellulose or high-resolution gels such as polyacrylamide. Capillary electrophoresis provides greater resolution; hence separation is more accurate. Capillary electrophoresis uses an automated detector system via spectrophotometric analysis. This is due to the higher surface area to volume ratio.

Capillary electrophoresis is used in situations such as in forensics where higher accuracy is required and is not commonly used as it is costly technique.

What are the Similarities Between Capillary Electrophoresis and Gel Electrophoresis?

• Separation of molecules in both techniques is based on the charge and size of the molecule.
• Both techniques can be used to separate both nucleic acids and proteins.
• The sample volume of the both techniques is the same.
• Both techniques use a buffer to facilitate separation.

What is the Difference Between Capillary Electrophoresis and Gel Electrophoresis?

Summary – Capillary Electrophoresis vs Gel Electrophoresis

Molecular diagnostics plays a major role in the scientific world. Identification and purification of DNA, RNA, and Proteins are critical steps in the diagnostic procedures. Electrophoresis is a technique which separates and identifies biomolecules in both gel electrophoresis and the much advanced capillary gel electrophoresis. Gel electrophoresis is performed in a vertical or horizontal plane using a polymer gel of standard pore size whereas capillary electrophoresis is performed in a capillary tube with a polymer liquid or a gel. This is the difference between capillary electrophoresis and gel electrophoresis. Upon completion of the electrophoresis technique, the biomolecules are further processed to obtain higher level information via hybridization or through techniques such as fingerprinting.

Download PDF Version of Capillary Electrophoresis vs Gel Electrophoresis

You can download PDF version of this article and use it for offline purposes as per citation note. Please download PDF version here Difference Between Gel Electrophoresis and Capillary Electrophoresis.

References:

1. Durney, Brandon C., et al. “Capillary electrophoresis applied to DNA: determining and harnessing sequence and structure to advance bioanalyses (2009–2014).” Analytical and Bioanalytical Chemistry, Springer Berlin Heidelberg, 2015, Available here. Accessed 28 Aug. 2017.
2. “Electrophoresis.” University of Leicester, 8 Jan. 2009, Available here. Accessed 28 Aug. 2017.
3. “Gel electrophoresis.” Khan Academy, Available here. Accessed 28 Aug. 2017.

Image Courtesy:

1. “DNA Agarose gel electrophoresis” By School of Natural Resources from Ann Arbor – DNA lab (CC BY 2.0) via Commons Wikimedia
2. “Capillary Gel Electrophoresis Instrument Schematic” By Chem4066sp13 – Own work (CC BY-SA 3.0) via Commons Wikimedia