Dresden 2014 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 54: Poster Session 3

CPP 54.24: Poster

Donnerstag, 3. April 2014, 15:00–19:00, P2

Small differences with big impact: Reentrant phase behavior induced by multivalent cations in protein solutions — •Marcell Wolf, Fajun Zhang, Felix Roosen-Runge, and Frank Schreiber — Institut für Angewandte Physik, Auf der Morgenstelle 10, 72076 Tübingen

Subtle difference between proteins can lead to remarkably big differences in their resulting phase behavior. Using a multivalent cation, Y³⁺, a reentrant condensation (RC) with a liquid-liquid phase separation (LLPS) within the condensed regime has been established in a negatively charged protein system [1,2]. Here we compare the phase behavior of two serum albumins, BSA and HSA. They are highly similar in the primary structure but the comparison of the RC behavior shows a strong difference. The condensed regime and the LLPS region is much broader for a HSA system and the LLPS boundaries where also shifted to lower salt and protein concentrations (c_p), observed by optical microscopy. The major contribution of this changes can be explained by existence of dimers in BSA solutions, observed by GPC and DLS experiments. Due to the dimers a higher c_p is necessary to achieve the same monomer concentration than without dimers. In addition these will be also interactions between monomer and dimers which will also influence the phase behavior. Using an ellipsoid sticky hard sphere potential for fitting the data, determined by SAXS, the effective interaction was calculated [3]. [1] F. Zhang et al., PRL 101, 2008, 148101; [2] F. Zhang et al., Soft Matter 8, 2012, 1313; [3] M. Wolf et al. J. Mol. Liq., submitted.