Dextran gels protein separations

Dextran Gels Proteins and nucleotides can be separated by using cross-linked dextran gels available in various types and particle sizes. The molecular weight of dextran-gels vary considerably depending upon the extent of cross-linked nature. 

Proteins are mostly separated by CZE. Strong interactions between the analyte molecules and the capillary wall that are predominately electrostatic in nature have a strong influence on separation efficiency. By the use of buffer additives like amines or the use of dynamically or permanently coated capillaries, highly efficient separation of proteins in CZE is achievable. Here, the native proteins with their tertiary structure are separated. Denatured proteins as SDS complexes can be separated in gels. Advantageous are polysaccharide-based polymers, because they permit UV detection at low wavelength (214 nm), impossible with acrylamide-based gels. A separation of SDS-denatured protein standards in a dextran gel is shown in Fig. 7. 

Sephadex is a commercial product of dextran. The polymer in Cu(II) form was employed for group separation of amino acids and proteins. Carboxymethylated dextran gel was found useful as a sorbent for LEC of enzymes. 

Plant estrogens and metabolites of these compounds that have been excreted by animals have been fractionated on dextran gel columns (Nilsson, 1962). Gel filtration has been used in an investigation of polyphenols from brewery wort (Woof, 1962). The catecholamines adrenalin and noradrenalin can be separated from plasma proteins on Sephadex (Marshall, 1963). Various constituents of Staphylococcus aureus have been separated on Sephadex, namely, teichoic acid, D-alanine, N-acetylglucos-amine, and N-acetylglucosaminylribitol (Sanderson et al., 1962). 

Aqueous SEC was first reported in 1959 by Porath and Flodin [1]. They separated proteins and salts according to molecular size by using cross-linked dextran gels. Since then it has been widely employed, especially in the field of biochemistry, for various purposes such as purification of proteins and nucleic acids, estimation of molecular masses of proteins and determination of molecular mass distributions of polysaccharides. In addition, it has been a powerful tool for the determination of molecular mass distributions of water-soluble synthetic polymers since high-performance aqueous SEC was realized in 1978 by the development of semirigid microparticulate macroporous supports based on hydrophilic synthetic polymers [2-4]. 

TSK gel SW molecular weight separation range In kllodaltons native globular dextrans polyethylene proteins glycols ... 

Using a method applicable to other biological systems, the binding constants of dextrans and isomaltose oligosaccharides to dextran-specific myeloma proteins have been determined by affinity electrophoresis. The retardation of electrophoretic mobility of myeloma proteins on addition of dextran to the separating gel may be reversed on addition of suitable oligosaccharides to the gel. 

An immunochemical technique similar to Immunoelectrophoresis, the difference being that instead of separating the proteins in the patients sample by electrophoresis, they are separated on a plate of dextran gel (e.g. Sephadex) which resolves the molecules on the basis of-their molecular size. Addition of antiserum parallel and adjacent to the direction of filtration results in the formation of a series of precipitin lines. The technique can be used to investigate for example monomer and pentamer IgM in macroglobulinaemia. 

Radioiodide has also been separated from iodine-labeled proteins (human serum albumin and Bovine IgG) by thin-layer gel filtration on Sephadex G-200 and G-75 superfine layers (163). (Sephadex is a modified dextran.) The protein solutions were applied in amounts of 5-10 vJL to the Sephadex layers and the angle of slope of the layers was 15°. Elution was carried out with 0.2 M Tris buffer (Tris = tris (hydroxymethyl) aminomethane) at pH 8.0. The buffer contained Tween 80. Separations took 45-60 min on Sephadex G-75 and 3-4 h on Sephadex G-200 and were particularly good on the latter. 

Size exclusion was first noted in the late fifties when separations of proteins on columns packed with swollen maize starch were observed (Lindqvist and Storgards, 1955 Lathe and Ruthven, 1956). The run time was typically 48 hr. With the advent of a commercial material for size separation of molecules, a gel of cross-linked dextran, researchers were given a purposely made material for size exclusion, or gel filtration, of solutes as described in the classical work by Porath and Flodin (1959). The material, named Sephadex, was made available commercially by Pharmacia in 1959. This promoted a rapid development of the technique and it was soon applied to the separation of proteins and aqueous polymers. The work by Porath and Flodin promoted Moore (1964) to apply the technique to size separation, gel permeation chromatography of organic molecules on gels of lightly cross-linked polystyrene (i.e., Styragel). 

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