Regensburg 2013 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 33: Poster: Charged Soft Matter

CPP 33.4: Poster

Mittwoch, 13. März 2013, 16:30–18:30, Poster C

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 behavior. Using a multivalent cation, yttrium chloride (YCl₃), 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 between the RC behavior of these two albumins shows that minor differences in the primary protein structure have a strong influence on such a system. The range of the condensed regime is much broader for HSA. Optical microscopy also shows a shift of the LLPS region to lower salt and protein concentrations in the case of HSA, where the LLPS region is much broader. The formation of clusters in the condensed regime and outside the LLPS region is systematically studied by SAXS, SLS/DLS and we observe that the cluster size is much smaller by using HSA. Differences of the primary structure between the two proteins leads to changes in the hydrophobicity and charge distribution of the proteins. These changes in BSA and HSA phase diagrams can be related to differences in protein structure. [1] F. Zhang et al., PRL 101, 2008, 148101; [2] F. Zhang et al., Soft Matter 8, 2012, 1313.