Summary
Covalent attachment of polyethylene glycol (PEG) to proteins produces an increase in their partition coefficient (K) in PEG/dextran aqueous two-phase systems. At least for bovine serum albumin (BSA) and granulocyte-macrophage colony stimulating factor (GM-CSF) a linear relationship exists between log K of the conjugate and the number of PEG molecules attached to it (up to 20 PEG molecules for BSA and 3 for GM-CSF). The proportionality constant (i.e., the increment in log K per PEG molecule attached) is protein specific. For PEGGM-CSF conjugates, the proportionality constant increases with the concentration of the polymers (PEG and dextran up to 6%, w/w) in the two-phase system. A further increase in the polymer concentration up to 6.5% leads to a decrease in the proportionality constant. To explain these observations it is proposed that the interaction between the PEG-modified conjugate and the polymers in the phase system includes a positive interaction between the PEG attached to the PEG-modified conjugate and the PEG coils in the top phase, in addition to the excluded volume interactions generally accepted as the main interactions determining the partitioning of native proteins.
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Delgado, C. (1995). Partitioning of Polyethylene Glycol(PEG)-Protein Conjugates in PEG/Dextran Aqueous Two-Phase Systems. In: Rogers, R.D., Eiteman, M.A. (eds) Aqueous Biphasic Separations. Springer, Boston, MA. https://doi.org/10.1007/978-1-4615-1953-9_14
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DOI: https://doi.org/10.1007/978-1-4615-1953-9_14
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