Sephadex


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Sephadex

 

any of the synthetic derivatives of the polysaccharide dextran in which there is cross-linking to form a three-dimensional network with pores of a given size, that is, a molecular sieve. Sephadexes are produced in the form of granulated powder with particle sizes ranging from 20 to 300 micrometers and are classified according to pore size. Upon swelling in water or in salt solutions, sephadexes form gels, a two-phase system of the solvent within the granules and in the free volume. In chromatography, when columns are filled with sephadexes, large molecules are filtered more rapidly, being unaffected by the pores of the swollen gel; smaller molecules, however, become stuck in the pores and emerge only later. This filtering action accounts for the wide use of sephadexes in chemistry and biochemistry for the separation (fractionation) of mixtures of substances with molecular weights between 102 and 2 × 105. Sephadexes are also used in determining the molecular weight of globular proteins and enzymes and in desalting and concentrating high-molecular-weight molecules. The inclusion of ion-exchange groups in sephadexes produces ion exchangers with a high fractionating capacity, which are used in the purification of biopolymers. Sephadexes are used in industry in the production of vitamins and antibiotics.

N. N. CHERNOV

References in periodicals archive ?
Subfraction W-4.1 was subjected to a silica gel CC ([PHI]20 mm, L 800 mm with a solvent mixture of C[H.sub.2][Cl.sub.2]-MeOH, 9: 1) and passed over a Sephadex LH-20 column ([PHI]15 mm, L 950 mm) and then through an open YMC RP-C18 silica gel column ([PHI]15 mm, L 800 mm, 65 [right arrow] 100%, [H.sub.2]O-MeOH) to afford wednenol (2, colorless oil, 12.5 mg), cleroindicin E (3, colorless oil, 15.2 mg), and rengyol (4, white solid, 46.6 mg).
Column chromatography (CC) was performed with silica gel (300-400 mesh), polyamide (60-100 mesh), Sephadex LH-20, D101 macroporous, and ODS (50 [micro]m).
To obtain the peptides with higher antioxidant activity, CSPH was purified by gel filtration chromatography on Sephadex G-25 column, and four fractions (F1, F2, F3 and F4) were eluted (Figure 3).
Fractions containing 92% of the total BAEE hydrolase activity were applied to a DEAE Sephadex A-50 ion exchange column (2.6 X 81 cm) equilibrated with Tris buffer (50 mM Tris-HCl, 20 mM KCl, pH 7.2 at 0-4[degrees]C).
alternata crude extract by gel-filtration on Sephadex G-100 led to the discovery that A.alternata produced, in addition to the major allergen protein mixture (94, 77, 66 and 59 Kda MW by immunoblotting) a related cross-reacting protein (16 and 18 Kda MW), antigenic and immunogenic for the production of IgG antibodies but with little or no allergenic activity (hypoallergen).
The substrate L-asparagine, DEAE-cellulose and Sephadex G-100 were procured from Sigma (Sigma-Aldrich, USA).
Sephadex LH-20 was also used to clean the separated compounds or fractions.
Silica gel (70-230 mesh, F254 pre-coated plates) (Merck, Germany), reverse phase silica gel 90 (RP-18C; Fluka, Switzerland) and Sephadex LH-20 (Fluka, Switzerland) were used for isolation of compounds.
The dialyzed sample (200 mg protein) was applied to pre-equilibrated DEAE Sephadex A-50 ion exchange column (12cm X 3cm).
Sephadex (SP) LH-20 (SP LH-20) (General Electrics Healthcare) was used for gel permeation chromatography.
Column chromatography (CC) was performed on silica gel (200-300 mesh; Qingdao Marine Chemical Factory) and Sephadex LH-20 (40-70 um, Amersham Pharmacia Biotech AB, Uppsala, Sweden).
Sephadex G-100 (Sigma) was packed in a glass column (2.5 cm x 45.0 cm) and equilibrated with 400 ml of 0.02 M phosphate buffer at pH 8.0.