Hydrodynamic radius coincides with the slip plane position in the electrokinetic behavior of lysozyme
The zeta potential (ζ) is the effective charge energy of a solvated protein, describing the magnitude of electrostatic interactions in solution. It is commonly used in the assessment of adsorption processes and dispersion stability. Predicting ζ from molecular structure would be useful to the struct...
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Published in | Proteins, structure, function, and bioinformatics Vol. 86; no. 5; pp. 515 - 523 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
United States
Wiley Subscription Services, Inc
01.05.2018
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Subjects | |
Online Access | Get full text |
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Summary: | The zeta potential (ζ) is the effective charge energy of a solvated protein, describing the magnitude of electrostatic interactions in solution. It is commonly used in the assessment of adsorption processes and dispersion stability. Predicting ζ from molecular structure would be useful to the structure‐based molecular design of drugs, proteins, and other molecules that hold charge‐dependent function while remaining suspended in solution. One challenge in predicting ζ is identifying the location of the slip plane (XSP), a distance from the protein surface where ζ is theoretically defined. This study tests the hypothesis that the XSP can be estimated by the Stokes–Einstein hydrodynamic radius (Rh), using globular hen egg white lysozyme as a model system. Although the XSP and Rh differ in their theoretical definitions, with the XSP being the position of the ζ during electrokinetic phenomena (e.g., electrophoresis) and the Rh being a radius pertaining to the edge of solvation during diffusion, they both represent the point where water and ions no longer adhere to a molecule. This work identifies the limited range of ionic strengths in which the XSP can be determined using diffusivity measurements and the Stokes–Einstein equation. In addition, a computational protocol is developed for determining the ζ from a protein crystal structure. At low ionic strengths, a hyperdiffusivity regime exists, requiring direct measurement of electrophoretic mobility to determine ζ. This work, therefore, supports a basic tenant of EDL theory that the electric double layer during diffusion and electrophoresis are equivalent in the Stokes–Einstein regime. |
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Bibliography: | Funding information National Science Foundation, Grant/Award Number: DMR‐0907273; National Institutes of Health, Grant/Award Number: DP2‐OD‐006478 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0887-3585 1097-0134 |
DOI: | 10.1002/prot.25469 |