Low molecular weight displacers

Several of the important structural features of low molecular weight displacers have been identified on a polymethacrylate based cation exchange support (8 fj, particle size51)- This study made use of the displacer ranking plot described in Section V.C to rank homologous series of molecules which differ from each other in predominantly one structural characteristic. The 

The displacer ranking plot has also been employed to compare the affinity of low molecular weight displacers on various classes of ion-exchange materials.54 This study was carried out on three different stationary phases a polymethacrylate (PMA)-based stationary phase (Waters SP-8HR), an agarose-based material (Pharmacia High Performance SP Sepharose), and a hydrophilized PS-DVB support (POROS HS50). These phases are representative of different classes of stationary phases typically employed for protein chromatography. The displacers employed in this study were based on the 

FIGURE 17 Comparison of the effect of nonspecific interactions on displacer affinity in three classes of stationary phases. (Shukla et al.54) ranking of branched displacers based on PETMA4 — effect of hydrophobicity - aromaticity. Parameters (A) on Waters SP-8HR PE-DMABzCI4 O = 3.12, K = 70.2), PE-DMAHepl4 (u= 3.12, K = 40.0) PE-DMACyl4 (r= 3.1, K = 7.9), PETMA4 (v= 2.6, K = 

Preparative chromatography has achieved a unique position in the purification of biotechnology products on an industrial scale. As an increasing number of biotechnology products are approved by the Food and Drug Administration (FDA) and with the rapid increases in the scales at which these products are produced, there is a growing need for the design of downstream processes with fewer, more efficient steps. While elution chro- 

Dibner, M. D. (1997). Biotechnology and pharmaceuticals 10 years later. Biopbarmacology 10(9), 24-30. 

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TABLE 2 Low Molecular Weight Displacers ( < 2 kD) for the Ion-Exchange Displacement Chromatography of Proteins... 

In contrast to high molecular weight polyelectrolyte displacers, the efficacy of low molecular weight displacers is dependent on both mobile phase salt and displacer concentrations. This sensitivity to the operating conditions opens up the possibility of carrying out selective displacement where the products of interest can be selectively displaced, while the low affinity impurities can be desorbed in the induced salt gradient ahead of the displacement train and the high-affinity impurities either retained or desorbed in the displacer zone.43 A... 

For a given A value, the higher the A value, the better the displacer under those operating conditions. As expected, an increase in the A value as one moves along the x axis (which corresponds to lower displacer concentrations or lower salt concentrations) results in a decrease in the value of the dynamic affinity (A). This plot has been employed to rank the relative efficacy of displacers51,54 and to provide insight into the important structural features of low molecular weight displacers (Section VII). 

Jen, S. C. D., and Pinto, N. G. (1990). Use of the sodium salt of poly(vinyl) sulfonic acid as a low molecular weight displacer for protein separations by ion-exchange displacement chromatography. J. Chromatogr. 519, 87-98. 

Kundu, A., and Cramer, S. M. (1997). Low molecular weight displacers for high resolution protein separations. Anal. Biochem. 248, 111-116. 

Kundu A, Vunnum S, Jayaraman G et al. Protected amino acids as novel low-molecular-weight displacers in cation-exchange. Biotechnol Bioeng 1995 48 452-460. 

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