Molecular thermodynamics for protein precipitation with a polyelectrolyte

Journal Article · Thu Jul 01 04:00:00 EDT 1999 · Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical

DOI:https://doi.org/10.1021/jp990455e· OSTI ID:682085

Jiang, J; Prausnitz, J M ^[1]

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1. Univ. of California, Berkeley, CA (United States). Chemical Engineering Dept.

A molecular-thermodynamic framework is developed for phase equilibria in an aqueous system containing a charged globular protein and an oppositely charged linear polyelectrolyte. The globular protein is represented by a spherical macroion with its coins; the linear polyelectrolyte is represented by a charged hard-sphere chain (polyion) with corresponding counterions. The potential of mean force contains Coulombic interactions between macroions, polyions, and small ions; long-range dispersion attractions between protein macroions; and hydrophobic macroion-polyion and macroion-macroion associations. Analytic expressions for thermodynamic properties are obtained, and liquid-liquid phase equilibria (precipitation) are calculated for model systems. Adding polyelectrolyte to a protein solution leads to precipitation, but further addition of polyelectrolyte leads to redissolution of the protein. This destabilization-restabilization phenomenon follows from electrostatic interactions with coupled polymer adsorption. The effects on phase equilibria of protein charge, protein size, association energy between protein-polyion, polyion chain length, and polyion charge density are investigated for model systems and compared with experimental data. Brief consideration is given to fractional precipitation for binary aqueous mixtures of proteins with different charge densities.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 682085
• Journal Information: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Journal Name: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical Journal Issue: 26 Vol. 103; ISSN 1089-5647; ISSN JPCBFK
• Country of Publication: United States
• Language: English

Related Subjects

55 BIOLOGY AND MEDICINE
BASIC STUDIES
ELECTROLYTES
GLOBULINS
PRECIPITATION
PROTEINS
THERMODYNAMICS