Selection, displacement chromatography

A. Purification of an Antigenic Vaccine Protein by Selective Displacement Chromatography... 

Kundu A, Barnthouse KA, Cramer SM. Selective displacement chromatography of proteins. Biotech Bioeng 1997 56 119-29. 

Shukla AA, Hopfer RL, Chakravarti DN, Bortell E, Cramer SM. Purification of an antigenic vaccine protein by selective displacement chromatography. Biotech Prog 1998 14 92-101. 

One of the most rational means for displacing a broad zone is electrolyte desorption under the conditions of decreasing degree of ionization, i.e., when counterions are converted into dipolar ions, uncharged molecules and coions. This conversion corresponds to a sharp decrease in distribution coefficients of the desorbed substance. Hence, the displacement of equilibrium parame ters at a high rate of mass-exchange is one of the methods of selective stepwise chromatography. 

While much has been learned about the role and selection of the operation parameters in displacement chrcmatography (60-66), little is known yet about the rules of displacer selection and the means available to control the selectivity of the separation. The paucity of well characterized displacers and the lack of knowledge of the solute adsorption isotherms hinder most strongly the wider acceptance and use of displacement chromatography. In most cases, displacer selection is still done by trial-and-error. In the majority of modem displacement chromatographic publications a reversed-phase system was used to separate small polar molecules, antibiotics, oligopeptides and small proteins (52-66). 

The development of displacement separations has historically been an empirical process and even though chromatographic theory may guide the selection of operating conditions the final stage must involve experimental validation. Typically, several experiments will be carried out at or near the conditions determined by the theory. The final stage in the procedure is either experimental or numerical optimization of the displacement process to produce optimal yields, purities and productivities. At this point, the relative efficacy of selective and conventional displacement chromatography can also be evaluated. 

Carta, G., and Dinerman, A. (1994). Displacement chromatography of amino acids Effects of selectivity reversal. AlChE J. 40, 1618-1628. 

Thin-layer chromatography has been used as a selective, sensitive, reliable and simple separation method, and it has been proven a very useful method for optimisation of displacement chromatography 122), and in the determination of lipophilicity 123-25). 

Active ester formation by the mixed anhydride method is accompanied by the side reaction of esterification at the carbonate moiety of mixed anhydride 51 which generates mixed carbonate 52 (Scheme 12).This decreases the yields, but is more of a nuisance than an obstacle as the side products do not interfere with crystallization of the esters as the former are soluble in the crystallizing solvent. More mixed carbonate is formed from derivatives of the hindered amino acids and proline none is formed from a-unsubstituted acids. A-Hy-droxysuccinimide gives rise to much less byproduct than 4-nitrophenol other phenols generate intermediate amounts. Less byproduct is generated when the reagent is isopropyl chloroformate. The impurity can be readily removed from a solution of the ester by adsorption of the compounds on reverse-phase chromatography beads followed by separation by selective displacement. ... 

Experimental work of Kalasz et al. resulted in the statement of the characteristics and basic rules of displacement chromatography. They conceived properties of the fully developed displacement train, factors affecting displacement development, efficacy of separation, analysis of displaced fractions, determination of displacement diagrams from Langmuirian isotherms, as well as selection of the column, carrier, and displacer for displacement chromatography. Concentration of the sample is a particular feature of displacement chromatography. However, the displacer in the carrier is also definitely concentrated through the development of the displacement train. 

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