Description_x000D_ General description_x000D_ Dextran is a polymer of anhydroglucose. It is composed of approximately 95% alpha-D-(166) linkages. The remaining (163) linkages account for the branching of dextran. Conflicting data on the branch lengths implies that the average branch length is less than three glucose units. However, other methods indicate branches of greater than 50 glucose units exist. Native dextran has been found to have a molecular weight (MW) in the range of 9 million to 500 million. Lower MW dextrans will exhibit slightly less branching and have a more narrow range of MW distribution. Dextrans with MW greater than 10,000 behave as if they are highly branched. As the MW increases, dextran molecules attain greater symmetry. Dextrans with MW of 2,000 to 10,000, exhibit the properties of an expandable coil. At MW below 2,000, dextran is more rod-like. The MW of dextran is measured by one or more of the following methods: low angle laser light scattering, size exclusion chromatography, copper-complexation and anthrone reagent colorometric reducing-end sugar determination and viscosity._x000D_ Application_x000D_ Dextran labeled with fluorescein isothiocyanate for possible use in perfusion studies in animals._x000D_ FITC-dextran is used extensively in microcirculation and cell permeability research utilizing microfluorimetry. FITC-dextran has been used to study plant cell wall porosity and capillary permeability. Plasma proteins have been shown not to bind to FITC-dextran._x000D_ FITC-dextran is used in cardiovascular, microcirculation, perfusion, cell monolayer and cell membrane permeability research as fluorescent flux tracer compound that supports the measurement of processes such as blood flow, membrane damage, vascular drainage and renal elimination. Small FITC-dextrans are also used to measure processes such as endocytosis and cell junction permeability. FITC-dextran 70kDa (FD-70) may be used as a model compound for development of methods to deliver molecules into protoplasts and to study drug release from structures such as hydrogels and liposomes. It may be used in microvascular and cell monolayer permeability studies._x000D_ Packaging_x000D_ Bottomless glass bottle. Contents are inside inserted fused cone._x000D_ Preparation Note_x000D_ Sigma typically tests the solubility of FITC dextrans in water at concentrations at or above 25 mg/ml. Solutions should be protected from light. In vivo, FITC-dextran is stable for more than 24 hours.