Dialysis preparative

Electrophoresis of a crystalline preparation revealed one major enzymatically active component and a minor inactive one (Negelein and Wulff, 1937). The smaller, inactive constituent varied from 5% to 20% of the total protein. Re-examination of the electrophoretic properties of yeast ADH crystals confirmed the presence of one slow, presumably active, and one fast-moving, presumably inactive component. Their relative amounts did not change systematically with recrystallization as shown by area analysis. The percentage of inactive component was a function of age of the solution and duration of preliminary dialysis. Preparations dialyzed for 20 hours at pH 5 contained as much as 14 % to 25 % of the inactive component, while dialysis for 4 hours showed as little as 6 %. The second component was assumed to be an inactive transformation product of the active enzyme (Hayes and Velick, 1954). 

For this reason, glycoproteins must first be isolated from the biological matrix by dialysis, preparative chromatography, isoelectric focusing, and so forth or by a combination of several methods. For a structural determination, degradation steps such as a site-specific proteolysis (e.g., with trypsin), removal of oligosaccharides from the polypeptide (by an enzymatic hydrolysis or hydrazine... 

A test on bacterial endotoxins is also included in the Ph. Eur. because of water for the production of dialysis preparations. 

After preparation, colloidal suspensions usually need to undergo purification procedures before detailed studies can be carried out. A common technique for charged particles (typically in aqueous suspension) is dialysis, to deal witli ionic impurities and small solutes. More extensive deionization can be achieved using ion exchange resins. 

Other patents (81,82) coveted the preparation of cellulose solutions using NMMO and speculated about their use as dialysis membranes, food casings (sausage skins), fibers, films, paper coatings, and nonwoven binders. NMMO emerged as the best of the amine oxides, and its commercial potential was demonstrated by American Enka (83,84). Others (85) have studied the cellulose-NMMO system in depth one paper indicates that further strength increases can be obtained by adding ammonium chloride or calcium chloride to the dope (86). 

Wet spinning of this type of hoUow fiber is a weU-developed technology, especiaUy in the preparation of dialysis membranes for use in artificial kidneys. Systems that spin more than 100 fibers simultaneously on an around-the-clock basis are in operation. Wet-spun fibers are also used widely in ultrafiltration appUcations, in which the feed solution is forced down the bore of the fiber. Nitto, Asahi, Microgon, and Romicon aU produce this type of fiber, generaUy with diameters of 1—3 mm. 

Films or membranes of silkworm silk have been produced by air-drying aqueous solutions prepared from the concentrated salts, followed by dialysis (11,28). The films, which are water soluble, generally contain silk in the silk I conformation with a significant content of random coil. Many different treatments have been used to modify these films to decrease their water solubiUty by converting silk I to silk II in a process found usehil for enzyme entrapment (28). Silk membranes have also been cast from fibroin solutions and characterized for permeation properties. Oxygen and water vapor transmission rates were dependent on the exposure conditions to methanol to faciUtate the conversion to silk II (29). Thin monolayer films have been formed from solubilized silkworm silk using Langmuir techniques to faciUtate stmctural characterization of the protein (30). ResolubiLized silkworm cocoon silk has been spun into fibers (31), as have recombinant silkworm silks (32). 

Preparation of aqueous HOCl substantially free of CU from either aqueous CI2 or HOCl—salt solutions has been accompHshed by electro dialysis (qv) using semipermeable membranes (130). This method has limited potential because of the unavailabihty of stable anionic membranes. 

Fig. 5. Scanning electron micrographs of hoUow fiber dialysis membranes. Membranes in left panels are prepared from regenerated cellulose (Cuprophan) and those on the right from a copolymer of polyacrylonitrile. The ceUulosic materials are hydrogels and the synthetic thermoplastic forms a microreticulated open cell foam with a tight skin on the inner wall. Pictures at top are membrane cross sections those below are of the wall region. Dimensions as indicated.

R. Herraez-Heruandez, A. J. H. Eouter, N. C. van de Merbel and U. A. Th Brinkman, Automated on-line dialysis for sample preparation for gas cliromatogruphy determination of benzodiazepines in human plasma , 7. Pharm. Biomed. Anal. 14 1077-1087 (1996). 

The colloidal palladium solution is prepared as follows A solution of a palladium salt is added to a solution of an alkali salt of an acid of high molecular weight, the sodium salt of protalbinic acid being suitable. An excess of alkali dissolves the precipitate formed, and the solution contains tine palladium in the form of a hydrosol of its hydroxide. The solution is purified by dialysis, and the hydroxide reduced with hydrazine hydrate. On further dialysis and evaporation to dryness a water-soluble product is obtained, consisting of colloidal palladium and sodium protalbinate, the latter acting as a protective colloid. 

Luciferase-catalyzed luminescence of luciferin. Odontosyllis luciferin emits light in the presence of Mg2+, molecular oxygen and luciferase. The relationship between the luminescence intensity and the pH of the medium shows a broad optimum (Fig. 7.2.8). The luminescence reaction requires a divalent alkaline earth ion, of which Mg2+ is most effective (optimum concentration 30 mM). Monovalent cations such as Na+, K+, and NH have little effect, and many heavy metal ions, such as Hg2+, Cu2+, Co2+ and Zn2+, are generally inhibitory. The activity of crude preparations of luciferase progressively decreases by repeated dialysis and also by concentrating the solutions under reduced pressure. However, the decreased luciferase activity can be completely restored to the original activity by the addition of 1 mM HCN (added as KCN). The relationship between the concentration of HCN and the luciferase activity is shown in Fig. 7.2.9. Low concentrations of h and K3Fe(CN)6 also enhance luminescence, but their effects are only transient. 

The next approach was to reduce the polydispersity of the chain length by fractionation. In the earliest preparation, fractionation was performed by precipitation or by dialysis, but the results were not very satisfying. 

Schwendener, R. A., Asanger, M., and Weder, H. G. (1981). n-Alkylglucosides as detergents for the preparation of highly homogeneous bilayer liposomes of variable sizes (60-240 (p) applying defined rates of detergent removal by dialysis, Biochem. Biophys. Res. Commun.. 100, 1055-1062. 

Crude polysaccharide fraction (GL-2) was prepared from the leaves of P. ginseng by hot water extraction, ethanol precipitation and dialysis, and GL-2 was fractionated by Cetavlon precipitation and weakly acidic polysaccharide fraction (GL-4) was obtained[3]. GL-4IIb2 was purified from GL-4 by DEAE-Sepharose CL-6B as described previousely [3]. In order to remove the color-materials, GL-4IIb2 was further purified by Q-Sepharose (C1 form), and the major fraction, eluted with 0.3 M NaCl, was repurifled by gel filtration on Bio-gel P-30 column to obtain purified active polysaccharide, GL-4IIb2. ... 

The specimens were analyzed at spectrophotometer at 280 nm. Preparations were purified from salts by dialysis. Protein concentrations in the initial and purified enzyme preparations were determined by Lowry method [6]. 

Until this point, the sample preparation techniques under discussion have relied upon differences in polarity to separate the analyte and the sample matrix in contrast, ultraflltration and on-line dialysis rely upon differences in molecular size between the analyte and matrix components to effect a separation. In ultrafiltration, a centrifugal force is applied across a membrane filter which has a molecular weight cut-off intended to isolate the analyte from larger matrix components. Furusawa incorporated an ultrafiltration step into his separation of sulfadimethoxine from chicken tissue extracts. Some cleanup of the sample extract may be necessary prior to ultrafiltration, or the ultrafiltration membranes can become clogged and ineffective. Also, one must ensure that the choice of membrane filter for ultrafiltration is appropriate in terms of both the molecular weight cut-off and compatibility with the extraction solvent used. 

Separations in membrane processes result from differences in the transport rates of analytes or solvent molecules through a membrane interface. The transport rate is usually determined by the existence of a driving force, such as a concentration, pressure- or temperature gradient and the mobility and concentration of analytes within the Interface. The most useful membrane processes for sampld preparation are dialysis. 

GC, utilizing flame ionization detection (FID), has been used to measure diisopropyl methylphosphonate in meat, grain, or milk (Caton et al. 1994). Sample preparation steps include homogenization, filtration, dialysis, and extraction on a solid sorbent. Two common solid phase extractants, Tenax GC and octadecylsilane bonded silica gel (C18 Silica), were compared by Caton et al. (1994). They reported 70% recovery when using Tenax GC and 85% recovery when using C18 Silica. Sensitivity was not reported. Equilibrium experiments indicate that 8-10 mg of Tenax GC are required to achieve maximum recovery of each g of diisopropyl methylphosphonate (Caton et al. 1994). By extrapolating these... 

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