Gel cross-linking

Desirable properties of elastomers include elasticity, abrasion resistance, tensile strength, elongation, modulus, and processibiUty. These properties are related to and dependent on the average molecular weight and mol wt distribution, polymer macro- and microstmcture, branching, gel (cross-linking), and... 

Stationary phase Liquid, solid Ionic gel, cross-linked liquid Bonded phase Polar vs. nonpolar... 

Polyurethane Hydrogel Cross-Linked Polyacrylamide Gels Cross-Linked Polyacrylic Acid Gels... 

The most recent experimental work to settle the controversy regarding the factor B is the swelling pressure work of Van de Kraats (105,106). This author used poly( >-nitrophenyl methacrylate) gels, cross-linked in solution by aminolysis with hexamethylene diamine. A typical example of his results is shown in Fig. 14, where it is seen that % is a constant over a range in polymer concentration from 5 to 20%. 

Gels cross-linked with Anker s reagent, N,N -diallyl-tartardiamide, dissolve in 2% periodic acid in 20-30 min at 37°C. Anker (1970) asserts that the gels take a somewhat longer time to set (1 hr for a 7% gel), but are otherwise equivalent to methylenebisacrylamide cross-linked gels, and that the periodic acid does not quench the scintillation. 

Chemical (fixed) gels cross-linked polyacrylamide, bonded to capillary wall... 

Porath, J., Laas, T., Janson, J.-Ch. Agar derivates for chromatography, electrophoresis and gel-bound enzymes - III. Rigid agarose gels cross-linked with divinyl sulphone (DVS), /. Chromatogr., 1975, 103, 49-62. 

By immobilsation, the pH and temperature profiles of the enzymes may be shifted and the stability of the enzymes altered and in most cases the objective is towards enhancement of these properties. Methods used for the immobilization of enzymes fall into the following categories physical adsorption onto an inert carrier, inclusion in the lattices of a polymerized gel, cross-linking of the protein with a bifunctional reagent, and covalent binding to a reactive insoluble support (Figure 6.52). The selection of the carrier depends on the nature of the enzyme itself, as well as the particle size, surface area, molar ratio of hydrophilic to hydrophobic groups and chemical composition. 

The Expasy home page mentioned previously recommends using piperazine diacrylyl instead of bisacrylamids as a cross-linker. Gels cross-linked with piperazine diacrylyl apparently separate the proteins better and block less N-terminals. Fur ermore, gels cross-linked with piperazine diacrylyl can be silver stained better. The addition of 5 mM Na-thiosulfates into the running buffer is also done for better staining. 

The use of amylose gel cross-linked by epichlorohydrin for affinity chromatography of extracellular isoamylase of Pseudomonas amyloderamosa has been studied. The isoamylase was adsorbed well on the amylose gel and was eluted specifically with maltodextrin. The eluted enzyme was precipitated with ammonium sulphate to remove maltodextrin, and then the solution of the precipitate was dialysed and concentrated by vacuum filtration. By this procedure 96 mg of the enzyme were purified to homogeneity from 20 1 of culture broth in about 70% yield. 

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