Gels, Sephadex

Recovery and Purification. The dalbaheptides are present in both the fermentation broth and the mycelial mass, from which they can be extracted with acetone or methanol, or by raising the pH of the harvested material, eg, to a pH of 10.5—11 for A47934 (16) (44) and A41030 (41) and actaplanin (Table 2) (28). A detailed review on the isolation of dalbaheptides has been written (14). Recovery from aqueous solution is made by ion pair (avoparcin) or butanol (teicoplanin) extraction. The described isolation schemes use ion-exchange matrices such as Dowex and Amberlite IR, acidic alumina, cross-linked polymeric adsorbents such as Diaion HP and Amberlite XAD, cation-exchange dextran gel (Sephadex), and polyamides in various sequences. Reverse-phase hplc, ion-exchange, or affinity resins may be used for further purification (14,89). 

A good separation of L-rhamnose, 2-acetamido-2-deoxy-D-glucose, D-glucose, and 2-amino-2-deoxy-D-glucose, eluted in that order, was obtained by Zeleznick80 on a small column packed with the highly cross-linked, dextran gel Sephadex G-25, with 62 15 25 (v/v) butyl alcohol-M acetic acid-water as the eluant however, the gel functioned more as a support for partition chromatography than as a molecular sieve. 

Exclusion Limit This is defined as the molecular mass of the smallest molecule that cannot diffuse into the. inner volume of the gel matrix. All molecules above this limit elute rapidly in a single zone. The exclusion limit of a typical gel, Sephadex G-50, is 30,000 daltons. All solute molecules having a molecular size greater than this value would pass directly through the column bed without entering the gel pores. 

Chang (64) used a porous styrene/divinylbenzene gel to determine small amounts of fatty acid dimers in tall oil. Hase and Harva (66) separated the monomeracid methyl esters from dimers and higher oligomers using a modified dextran gel SEPHADEX LH-20. 

Guanosine, adenine, HPLC-UV at 254 nm and Separation on dextran-based gels Sephadex... 

Fig. 8. Gel-filtration diagram of serum albumin prefractionated by ammonium sulfate precipitation. Gel, Sephadex G-200, 200-400 mesh buffer, 0.1 M Tris, 0.2 M NaCl, pH 8.0 column size, 5 X 110 cm elution rate, 40 ml/hr sample volume, 7 ml fraction volume, 10 ml. Ordinate, absorbancy at 278 mii abscissa, fraction number. (Pedersen, 1962.)...

The soluble linear dextran chains are cross-linked with epichlorohydrin in alkaline solution to yield a three-dimensional gel, which solidifies exothermically. The commercially available dextran gels (Sephadex) are very stable to chemical attack and can be heated up to 110°C in an autoclave for 40 min without impairment of properties. The gels swell to some extent in ethanol, ethylene glycol, formamide, A,A-dimethylformamide (DMF), and dimethylsuKoxide (DMSO). 

Sfiica impregnated with saturated and unsaturated hydrocarbons (squalene, paraffin oil), silicone and plant oils, complexing agents (silver ions, boric add and borates, unsaturated and aromatic compounds), tigands (EDTA, digitonin), and transition metal salts silanized silica gel impregnated with anionic and cationic surfactants Cross-linked, polymeric dextran gels (Sephadex)... 

Thin-layer chromatography of isolated serum proteins on a weakly cross-linked dextran gel (Sephadex G-200) has been reported to give Rf values linearly related to the logarithms of the molecular weights of the proteins (M28). 

G9. Guillemin, R., Yamazaki, E., Jutisz, M., and Sakiz, E., Presence dans un extrait de tissus hypothalamiques d une substance stimulant la sdcrdtion de I hormone hsrpophysaire thyr6otrope (T8H). Premifere purification par filtration sur gel Sephadex. Compt. Rend. 266, 1018-1020 (1962). 

Synthetic ion-exchange resins [213], silica-based exchangers [214] and activated alumina [209] have been most commonly used other materials used include cross-linked dextran gel (Sephadex) [215], fullerenes (especially Cis and Q,y)[216], polyurethane foam [217], PTFE turnings [218] or fibres [219], cigarette filters [220], functionalised cellulose [221], activated carbon [222], grape bagasse [223], rice husks [224] and bioorganisms (Saccharomyces cerevisiae) [225]. 

CM-Sephadex, calcium phosphate gel, Sephadex G-lOO, DEAE-Sepha-dex, hydroxyapatite [5]) [5, 6]... 

The whole plants of A. lingalatus were collected from Li-Jiang county, Yunnan Province. The butanol-soluble fraction of a 70% ethanol extract was chromatographed over Diaion HP-20, silica gel, Sephadex LH-20 and C8 reversed-phase silica gel to yield four new saponines 27-30, The structures of the saponins we isolated were determined by acidic and alkaline hydrolyses, esterification and various spectral analyses. The common aglycone to all new saponins was proved to be 3, 16a-dihydroxy-olean-12-en-28-oic acid, which connected a commone glucose unit at C3 and different sugar units at C2,. 

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