Regensburg 2010 – scientific programme

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BP: Fachverband Biologische Physik

BP 36: Posters: Tissue Dynamics, Charge Effects, and Anomalous Transport

BP 36.9: Poster

Thursday, March 25, 2010, 17:15–20:00, Poster B2

Reentrant Condensation of protein solutions induced by Fe³⁺ and Al³⁺ — •Benjamin Heck, Fajun Zhang, and Frank Schreiber — Auf der Morgenstelle 10, Universitaet Tuebingen,72076 Tuebingen, Germany

The trivalent ions such as Fe³⁺ can be physiologically important and also relevant in the context of protein-aggregation diseases such as Alzheimer. Therefore it is important to understand their impact on protein interactions and phase behavior in solution. Using model globular proteins, we found that addition of Fe³⁺/Al³⁺ into protein solution leads to a reentrant phase behavior [1]. When salt concentration, c, is below a critical value, c<c*, proteins are negatively charged. The repulsive Coulomb interaction is dominating which stabilizes proteins in solution. Above c*, aggregation occurs because the effective surface charge of proteins is significantly reduced due to the binding of cations on the protein surface. Further increase salt concentration above a second critical value, c**, one finds redissolution which in a simple picture is interpreted as effective inversion of charges [1].Charge inversion takes place only for multivalent ions. Electrophoresis experiments confirm the effective charge inversion of proteins as a function of salt concentration. Small-angle X-ray scattering data further reveal a clear transition of interactions from repulsive to attractive and to repulsive again at c<c*, c*<c<c** and c**<c, respectively. [1] F. Zhang et al., Phys. Rev. Lett. 101 (2008) 148101