Exchange and Electrophoresis

In general, partition of components from a solution at a solid surface provides the principle that is most often exploited (adsorption is used only very rarely), but for amino acids and peptides, which can exist in charged forms in aqueous solutions, ion-exchange and electrophoresis separation are also available. Separation on the basis of molecular size is also used. 

Reaction of [TcBrJ-" with citric acid is reported to yield polymeric mono- and dicitrates and monomeric dicitrates of Tc(IV). Complex formation and hydrolysis of Tc(lV) were shown to be competitive reactions. Brown to violet solutions occurred, depending on the molar ratio of citratc/technetium and on the reaction time [370,371], The complex formation of Tc(IV) with nitrilotriacctic acid (H3iita), ethylc-nediaminctetraacetic acid (H4edta), and cyclohexanediaminetctraacetic acid (f data) were studied in aqueous solution by means of ion exchange and electrophoresis [372] and the complex composition of solid di- and trinuclear compounds containing H jnta were analyzed [373]. 

Purification techniques, methods for the purification of peptides and proteins. Analysis and purification of naturally occurring peptides and of synthetic peptides makes use of different separation techniques. Partitioning of the analyte between a solution and a solid phase is the most exploited principle. Ion-exchange and electrophoresis methods... 

Amino acids may be separated by various methods. Separation is achieved on the basis of such characteristics as adsorption, partition between partially miscible phases, ion-exchange and electrophoresis. Details of the techniques can be found in text books of practical biochemistry. 

Toxins were extracted with 0.1 N HCl or 75% EtOH acidified to pH 2 and treated with successive columns of charcoal, Bio-Gel P-2 and Bio-Rex 70. Toxins separated by the last column were identified by tic and electrophoresis. Relative abundance of each toxin was determined by monitoring the eluate from Bio-Rex 70 column by mouse assay. A fluorometric paralytic shellfish toxin analyzer was applied to samples which were too small to be followed by mouse assay. Toxins separated by the ion exchange column (Hitachi gel 3011C) were continuously aromatized by tei t-butylhydroperoxide and monitored by the fluorometer (1 ). 

Okada T. Nonaqueous ion-exchange chromatography and electrophoresis Approaches to nonaqueous solution chemistry and design of novel separation. Journal of Chromatography A1998 804 17-28. 

Analysis by SDS-polyacrylamide gel electrophoresis of purified NOS from isolated HC from rats injected with killed Corynebacterium parvum (H), and from the murine macrophage cell line RAW 264-7 (M) (courtesy of D. Stuehr, The Cleveland Clinic, Cleveland, OH) which was exposed to LPS and IFNy. Crude cytosols were separated using ion exchange and affinity 2 5 -ADP Sepharose chromatography. Last step by gel filtration is equivalent to separation by molecular weight. 

In contrast, CSPs have achieved great repute in the chiral separation of enantiomers by chromatography and, today, are the tools of the choice of almost all analytical, biochemical, pharmaceutical, and pharmacological institutions and industries. The most important and useful CSPs are available in the form of open and tubular columns. However, some chiral capillaries and thin layer plates are also available for use in capillary electrophoresis and thin-layer chromatography. The chiral columns and capillaries are packed with several chiral selectors such as polysaccharides, cyclodextrins, antibiotics, Pirkle type, ligand exchangers, and crown ethers. 

The chiral recognition mechanisms in NLC and NCE devices are similar to conventional liquid chromatography and capillary electrophoresis with chiral mobile phase additives. It is important to note here that, to date, no chiral stationary phase has been developed in microfluidic devices. As discussed above polysaccharides, cyclodextrins, macrocyclic glycopeptide antibiotics, proteins, crown ethers, ligand exchangers, and Pirkle s type molecules are the most commonly used chiral selectors. These compounds... 

Subtilisin BPN was prepared through a series of protein purification steps applied to the fermentation broth. These steps included ultrafiltration ethanol precipitation DEAE (diethyl-aminoethyl) Tris Acryl batch anionic exchange SP (sulfopropyl) Tris Acryl column cationic exchange and, concentration with an Amicon stirred cell. The enzyme purity was determined to be -951 via spectroscopic assays that measure the ratio of active enzyme to total protein. In addition, purity was verified via HPLC and SDS-page (sodium dodecyl sulfate polyacrylamide gel electrophoresis). 

Figure 1. A. The synthetic route that is used for the synthesis of L-Asn-Sepharose CL 6B affinity adsorbent. B SDS-polyacrylamide gel electrophoresis of caL-ASNase purification. Lane 1 E. coli crude extract after induction with 1 mM IPTG Lane 2 EcaL-ASNase purified according to the two-step procedure using cation-exchange and affinity chromatography.

The separation scientist with experience gained from a LC background may tend to limit the modes of electrochromatography to reversed phase (RP), normal phase, ion-exchange and, maybe, size-exclusion. Analysts from an electrophoretic background typically use the term "CE" in a much broader sense to include the main modes of capillary zone electrophoresis, micellar electrokinetic chromatography, capillary gel electrophoresis, isoelectric focusing and isotachophoresis. 

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