Analytical partitioning of poly(ethylene glycol)-modified proteins |
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Authors: | Cristina Delgado Martin Malmsten James M. Van Alstine |
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Affiliation: | aMolecular Cell Pathology, Royal Free Hospital School of Medicine, Rowland Hill Street, London NW3 2PF, UK;bInstitute for Surface Chemistry, P.O. Box 5607, S-114 86 Stockholm, Sweden;cDepartment of Chemistry, University of Alabama in Huntsville, Huntsville, AL 35899, USA |
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Abstract: | Covalently grafting proteins with varying numbers (n) of poly(ethylene glycol) molecules (PEGs) often enhances their biomedical and industrial usefulness. Partition between the phases in aqueous polymer two-phase systems can be used to rapidly characterize polymer-protein conjugates in a manner related to various enhancements. The logarithm of the partition coefficient (K) approximates linearity over the range 0<n<x. However, x varies with the nature of the conjugate (e.g., protein molecular mass) and such data analysis does not facilitate the comparison of varied conjugates. The known behavior of surface localized PEGs suggests a better correlation should exist between log K and the weight fraction of polymer in PEG-protein conjugates. Data from four independent studies involving three proteins (granulocyte-macrophage colony stimulation factor, bovine serum albumin and immunoglobulin G) has been found to support this hypothesis. Although somewhat simplistic, ‘weight fraction’ based analysis of partition data appears robust enough to accommodate laboratory to laboratory variation in protein, polymer and phase system type. It also facilitates comparisons between partition data involving disparate polymer-protein conjugates. |
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Keywords: | Partitioning Aqueous two-phase systems Poly(ethylene glycol) Proteins Immunoglobulin Bovine serum albumin |
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