Dextran blue for biochemistry Dextran blue is a soluble polymer compound consisting of dextran from Leucnostoc spp , which is covalently linked to the dye cibacron blue (F3G-A). Due to its high molecular weight, dextran blue is suitable as a molecular mass indicator in chromatography, or as a coprecipitant in DNA isolation. In scientific studies, dextran blue has also been used as a model compound in permeability assays. Furthermore, it has been shown that dextran blue has an antimicrobial effect against some microorganisms, such as Lactobacillus acidophilus . Since dextran blue has an oxidative effect, it can also be used to produce hydroquinone in the presence of other chemicals. Application examples: Calibration of gel filtration columns (empty volume indicator) Co-precipitance in DNA extraction/staining of DNA pellets Preparation of hydroquinone Model compound for permeability assays Directions for use When used as a coprecipitant in DNA isolation: Stock solution: 20 µg/µl dextran blue dissolved in water Working concentration: 1 µl stock solution to 750 µl precipitation reaction (or 20 µg dextran to 1 ng DNA before precipitation) Washing the pellet: With 70 % ethanol Even at higher concentrations used, dextran blue does not interfere with subsequent applications such as restriction digestion, ligation, gel electrophoresis or transformations. Before PCR however, a concentration of 125 g/ml should not be exceeded.