Dresden 2009 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 39: POSTERS Colloids and Liquids
CPP 39.3: Poster
Thursday, March 26, 2009, 17:00–19:30, P3
Novel charge-induced protein interactions in solution studied by SAXS/SANS — •Fajun Zhang1, Luca Ianeselli1, Maximilian W. A. Skoda2, Robert M. J. Jacobs3, Oliver Kohlbacher4, Sophie Weggler5, Andreas Hildebrandt5, and Frank Schreiber1 — 1Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany — 2ISIS, Rutherford Appleton Laboratory, UK — 3CRL, University of Oxford, UK — 4Zentrum für Bioinformatik Tübingen, Tübingen — 5Zentrum für Bioinformatik Saar, Saarbrücken
Proteins can be considered as very complex *colloids*. Their interactions in solution challenge our understanding from conventional colloidal science. Using a model protein, BSA, we have studied the influence of ionic strength and the nature of salt on protein interactions by SAS. For simple salts, protein interactions can be described using a theoretical model based on a screened Coulomb potential [1]. By using multivalent counterions, a novel reentrant condensation behavior is observed, which is caused by short-ranged electrostatic interactions between ions and acidic residues, mechanistically different from the case of DNA. A short-ranged attraction arises between counterion-bound proteins in the reentrant regime. Monte Carlo simulations and zeta-potential measurements under these strong electrostatic coupling conditions support an effective inversion of charge on surface side chains through binding of the multivalent counterions [2]. These observations provide a new way for tuning protein interactions in solution. [1] F. Zhang, et al., J. Phys. Chem. B. 2007, 111, 251. [2] F. Zhang, et al., Phys. Rev. Lett. 2008, 101, 148101.