Separation Using Ion Exchange

However, the products are separated using ion-exchange columns and the starting material is a derivative rattier than a precursor of the racemic amino add, thus making the total process drcuitous since it involves several chemical steps in addition to die enzymatic resolution step. Furthermore, racemisation of the unwanted isomer is not easily accomplished. 

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 isolating the amino adds from Ihe fermentation broth, chromatographic separations using ion-exchange resins are the most important commercial method. Precipitation with compounds which yield insoluble salts with amino acids are also used. Purification is possible by crystallization through careful adjustment of the isoelectiicpoint, at which point the amino acid is least soluble. 

The majority of the chromatographic separations using ion exchangers are carried out in aqueous solutions because of the superior ionizing properties... 

Prior to any evaluation of the functional integrity of labeled molecules, they must be separated from unlabeled molecules that may still be present. This is especially important for hormones which can elicit physiological effects at minute concentrations. Separation is usually based on a physicochemical change in the molecule as a result of iodination. Figure 8-36 depicts one such separation using ion exchange chromatography and Table 8-8 lists a number of other methods that have also been used to successfully isolate various iodinated hormones. 

GP Miller, DI Norman, PL Frisch. A comment on arsenic species separation using ion exchange. Water Res 34 1397-1400, 2000. 

Muramatsu, Y., Uchida, S., Tagami, K., Yoshida, S., and Fujikawa, T. 1999. Determination of plutonium concentration and its isotopic ratio in environmental materials by ICP-MS after separation using ion-exchange and extraction chromatography. J Anal Atom Spectrom 14(5), 859-865. 

This is the enzyme responsible for activating methionine to the 5-adenosyl form in which it acts as a methyl donor. It may be assayed radiochemically using C labelled methionine and product separation using ion exchange. 

Sarfert FT, Etzel MR. Mass transfer limitations in protein separations using ion-exchange membranes. J Chromatogr 1997 764 3-20. 

---