A rotating disk shear device was used to study the effect of interfacial shear on the structural integrity of human monoclonal antibodies of IgG4 isotype. Factors associated with the solution conditions (pH, ionic strength, surfactant concentration, temperature) and the interface (surface roughness) were studied for their effect on the rate of IgG4 monomer loss under high shear conditions. The structural integrity of the IgG4 was probed after exposure to interfacial shear effects by SDS-PAGE, IEF, dynamic light scattering, and peptide mapping by LC-MS. This analysis revealed that the main denaturation pathway of IgG4 exposed to these effects was the formation of large insoluble aggregates. Soluble aggregation, breakdown in primary structure, and chemical modifications were not detected. The dominant factors found to affect the rate of IgG4 monomer loss under interfacial shear conditions were found to be pH and the nanometer-scale surface roughness associated with the solid-liquid interface. Interestingly, temperature was not found to be a significant factor in the range tested (15-45 degrees C). The addition of surfactant was found to have a significant stabilizing effect at concentrations up to 0.02% (w/v). Implications of these findings for the bioprocessing of this class of therapeutic protein are briefly discussed.

Chromatography plays an important role in the downstream processing of proteins. Over the past years, there has been a steady move toward the adoption of more rigid, porous particles to combine ease of manufacture with increased levels of productivity. The latter is still constrained by the onset of compression where the level of wall support becomes incapable of withstanding flow-induced particle drag. In this study, we investigate how, by the installation of cylindrical column inserts, it is possible to enhance the level of wall support. Experiments were conducted to examine the effect of the position of the insert in the column, and also of the insert dimensions on the critical velocity at which the onset of compression occurs. It was found that when installed at the bottom of the column, inserts can provide up to a 20% increase in critical velocity without significantly affecting column hydrodynamics, as measured by the level of axial dispersion.

No abstract

Accounts of healings like the one reported concerning Bartimaeus present a challenge for preachers on Disability Awareness Sunday. This study illustrates how among experienced preachers sensing types and intuitive types approach the problem in different ways.