Nondiffusive Mechanisms Enhance Protein Uptake Rates in Ion Exchange Particles

Scanning confocal fluorescence microscopy and multiphoton fluorescence microscopy were used to image the uptake of the protein lysozyme into individual ion exchange chromatography particles in a packed bed in real time. Self-sharpening concentration fronts penetrating into the particles were observe...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2003-01, Vol.100 (2), p.420-425
Main Authors: Dziennik, S. R., Belcher, E. B., Barker, G. A., DeBergalis, M. J., Fernandez, S. E., Lenhoff, A. M.
Format: Article
Language:English
Subjects:
Adsorbents
Adsorption
Biological Sciences
Charge density
Diffusion
Diffusion coefficient
Fluorescence
Ion exchange
Ions
Isotherms
Medical imaging
Microscopy
Microscopy, Confocal
Muramidase - metabolism
Osmolar Concentration
Physical Sciences
Protein Transport
Protein uptake
Proteins
Steepest descent method
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Summary:Scanning confocal fluorescence microscopy and multiphoton fluorescence microscopy were used to image the uptake of the protein lysozyme into individual ion exchange chromatography particles in a packed bed in real time. Self-sharpening concentration fronts penetrating into the particles were observed at low salt concentrations in all of the adsorbents studied, but persisted to 100 mM ionic strength only in some materials. In other adsorbents, diffuse profiles were seen at these higher salt concentrations, with the transition region exhibiting a pronounced fluorescence peak at the front at intermediate salt concentrations. These patterns in the uptake profiles are accompanied by significant increases in protein uptake rates that are also seen macroscopically in batch uptake experiments. The fluorescence peak appears to be a concentration overshoot that may develop, in part, from an electrokinetic contribution to transport that also enhances the uptake rate. Further evidence for an electrokinetic origin is that the effect is correlated with high adsorbent surface charge densities. Predictions of a mathematical model incorporating the electrokinetic effect are in qualitative agreement with the observations. These findings indicate that mechanisms other than diffusion contribute to protein transport in oppositely charged porous materials and may be exploited to achieve rapid uptake in process chromatography.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0237084100