Sephadex is a trademark for cross-linked dextran gel used for gel filtration. It was launched by Pharmacia in 1959, after development work by Jerker Porath and Per Flodin. The name is derived from separation Pharmacia dextran. It is normally manufactured in a bead form and most commonly used for gel filtration columns. By varying the degree of cross-linking, the fractionation properties of the gel can be altered.
These highly specialized gel filtration and chromatographic media are composed of macroscopic beads synthetically derived from the polysaccharide, dextran. The organic chains are cross-linked to give a three-dimensional network having functional ionic groups attached by ether linkages to glucose units of the polysaccharide chains.
Available forms include anion and cation exchangers, as well as gel filtration resins, with varying degrees of porosity; bead sizes fall in discrete ranges between 20 and 300 µm.
Sephadex is used to separate low and high molecular weight molecules. Sephadex is a faster alternative to dialysis (de-salting), requiring a low dilution factor (as little as 1.4:1), with high activity recoveries. Sephadex is also used for buffer exchange and the removal of small molecules during the preparation of large biomolecules, such as ampholytes, detergents, radioactive or fluorescent labels, and phenol (during DNA purification).
Fractionation Range of Globular Proteins (Da)
|Gel Type||Fractionation Range|
- chemeurope.com: From Sephadex to GE Healthcare, accessed on June 17, 2009
- Gel filtration: a method for desalting and group separation, Nature, vol. 183 (1959), s. 1657-1659