Agarose

Agarose is a linear polymer composed of repeating units of agarobiose, a disaccharide of D-galactose and 3,6-anhydro-L-galactose. The polymer chains form a double helix that aggregates into a porous gel network upon cooling. The gel's pore size is controlled by the agarose concentration, allowing separation of molecules of different sizes. Agarose is neutral, lacks charged groups, and has low electroendosmosis, making it ideal for electrophoresis. It is also biocompatible and resistant to enzymatic degradation, which supports its use in microbiology and biotechnology.

Agarose gel electrophoresis is a standard method for separating DNA fragments by size, typically using concentrations of 0.5% to 3%. Nucleic acids are visualized with fluorescent dyes such as ethidium bromide or SYBR Green. Agarose is also used in Southern and Northern blotting, and in pulsed-field gel electrophoresis for large DNA molecules. In chromatography, agarose beads (e.g., Sepharose) are used for size-exclusion and affinity purification of proteins. Additionally, agarose is used in microfluidic devices and as a matrix for cell culture and tissue engineering.

Agarose was first isolated in the 1930s by Japanese researchers, but its widespread use began in the 1960s with the development of molecular biology techniques. The term 'agarose' was coined to distinguish the neutral gelling fraction from agaropectin, a sulfated polysaccharide. Today, agarose is produced from various species of red algae, including Gelidium and Gracilaria. It is used in food, pharmaceuticals, and cosmetics, and as a culture medium for bacteria and fungi. The global agarose market is driven by the demand for biotechnology research and diagnostics.

Agarose gels can be made with low melting point variants (e.g., SeaPlaque) that melt at 65°C, allowing recovery of DNA for cloning. Agarose is also used in the preparation of agarose beads for affinity chromatography, and in the production of microcarriers for cell culture. In forensic science, agarose gels are used for DNA fingerprinting. A niche application is the use of agarose in the study of protein crystallization, where it provides a stable matrix. Additionally, agarose has been used in the creation of artificial skin and in drug delivery systems. The gel's transparency and low autofluorescence make it suitable for optical imaging.

Agarobiose

The repeating disaccharide unit of agarose, composed of D-galactose and 3,6-anhydro-L-galactose.

Electroendosmosis

The movement of liquid through a gel under an electric field, which can affect separation.

Pulsed-field gel electrophoresis

A technique that alternates electric fields to separate very large DNA molecules.