Regensburg 2013 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 33: Poster: Charged Soft Matter
CPP 33.2: Poster
Mittwoch, 13. März 2013, 16:30–18:30, Poster C
Coupling of surface charge and pH effects: charge inversion and reentrant condensation in protein solutions with multivalent cations — •Felix Roosen-Runge1, Benjamin Heck1, Fajun Zhang1, Oliver Kohlbacher2, and Frank Schreiber1 — 1Institut für Angewandte Physik, Universität Tübingen — 2Zentrum für Bioinformatik, Universität Tübingen
Charge regulation of proteins is a fundamental mechanism in biological systems, depending on the pH of the solution and condensation of counterions. We report on charge inversion and the related reentrant phase behavior in solutions of globular proteins with different multivalent metal cations [1,2], addressing the coupling of pH effects and charge regulation. For several proteins and both acidic and neutral metal salts, charge inversion as measured by electrophoretic light scattering is found to be a universal phenomenon, whose extent depends on the specific protein-salt combination. Reentrant phase diagrams show a much narrower phase-separated regime for acidic salts. The experimental findings are reproduced with good agreement by an analytical model accounting for ion condensation, pH effects due to metal hydrolysis and charge regulation of side chains. Using a DLVO picture, reentrant phase behavior can be explained. Finally, the relation of charge inversion and reentrant condensation is discussed, suggesting that pH variation in combination with multivalent cations provides control of both attractive and repulsive interactions between proteins.
[1] F. Zhang, et al., Soft Matter 8 (2012) 1313
[2] F. Zhang, et al., PRL 101 (2008) 148101