Equilibrium and Kinetics of High Molecular Weight Protein Uptake in Ion Exchange Chromatography

Abstract

Abstract-Equilibrium and kinetic experiments have been carried out in order to study the effect of protein size in the purification of high molecular weight (HMW) proteins by IEC. The current work focused on two proteins uptake by Q HyperZ chromatographic media. Bovine Serum Albumin (BSA) and ferritin have been selected due to their close isoelectric point (4.9 and 4.4 respectively) and their different molecular weight (66.5 and 450 kDa respectively). As usually reported in the literature, equilibrium uptake for BSA has been higher than for ferritin at the same buffer conditions (pH, ionic strength), suggesting complex phenomena for ferritin uptake. Moreover, contrary to the general rule in ion-exchange processes, ferritin uptake has not been really affected by the increase of NaCl concentration. In fact, no significant change in the ferritin uptake has been quantified with the increasing of salt concentration from 0 to 100 mM. However, the kinetics of ferritin ion exchange has showed a classical behaviour, according to the homogenous diffusion model. The determination of the effective diffusion coefficient for ferritin has been possible from transient uptake at different protein initial concentrations. Thus, in spite of its large size, ferritin seems to diffuse inside the macro-porous anion-exchange particles.

Effects of Particle Size on the Gas Uptake Kinetics and Physical Properties of Type III Porous Liquids

“…In particular, CO 2 uptake into a PL can be considered to occur in 4 stages as follows (Figure ). , (1) CO 2 molecules enter PDMS and diffuse through the liquid (bulk diffusion). (2) CO 2 molecules pass through a liquid boundary layer between the AF surface and the bulk liquid to arrive at the surface of the AF particles (layer diffusion), and simultaneously, some CO 2 molecules remain in the PDMS.…”