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Agarose
An agarose is a polysaccharide polymer material, generally extracted from seaweed. Agarose is a linear polymer made up of the repeating unit of agarobiose, which is a disaccharide made up of D-galactose and 3,6-anhydro-L-galactopyranose.〔(Agar ) at lsbu.ac.uk Water Structure and Science〕 Agarose is one of the two principal components of agar, and is purified from agar by removing agar's other component, agaropectin.〔(【引用サイトリンク】title=Agar )〕 Agarose is frequently used in molecular biology for the separation of large molecules, especially DNA, by electrophoresis. Slabs of agarose gels (usually 0.7 - 2%) for electrophoresis are readily prepared by pouring the warm, liquid solution into a mold. A wide range of different agaroses, of varying molecular weights and properties are commercially available for this purpose. ==Structure==
Agarose is a linear polymer with a molecular weight of about 120,000, consisting of alternating D-galactose and 3,6-anhydro-L-galactopyranose linked by α-(1→3) and β-(1→4) glycosidic bonds. The 3,6-anhydro-L-galactopyranose is an L-galactose with an anhydro bridge between the 3 and 6 positions, although some L-galactose unit in the polymer may not contain the bridge. Some D-galactose and L-galactose units can be methylated, and pyruvate and sulfate are also found in small quantities.〔(【引用サイトリンク】title= Chapter 1 - Production, Properties and Uses of Agar )〕 Each agarose chain contains ~800 molecules of galactose, and the agarose polymer chains form helical fibres that aggregate into supercoiled structure with a radius of 20-30 nm. The fibers are quasi-rigid, and have a wide range of length depending on the agarose concentration. When solidified, the fibres form a three-dimensional mesh of channels of diameter ranging from 50 nm to >200 nm depending on the concentration of agarose used - higher concentrations yield lower average pore diameters. The 3-D structure is held together with hydrogen bonds and can therefore be disrupted by heating back to a liquid state.
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