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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 22: Poster: Charged Soft Matter

CPP 22.1: Poster

Mittwoch, 28. März 2012, 11:00–13:00, Poster A

Liquid-liquid phase separation in protein solutions induced by YCl₃ — •Marcell Wolf¹, Fajun Zhang¹, Felix Roosen-Runge¹, Roland Roth², Maximilian W. A. Skoda³, Robert M. J. Jacobs⁴, and Frank Schreiber¹ — ¹Institut für Angewandte Physik, Universität Tübingen, Germany — ²Institut für Theoretische Physik, Universität Erlangen-Nürnberg, Germany — ³ISIS, RAL, Didcot, UK — ⁴CRL, University of Oxford, UK

Liquid-liquid phase separation (LLPS) in protein solutions plays an important role for protein crystallization. Phase diagrams of HSA and BSA with Yttrium Chloride (YCl₃) in the c_p and c_s plane were determined; a reentrant phase behavior [1] was observed. Here, we show that LLPS can be induced in protein solutions by using YCl₃ [2]. Phase boundaries were determined by UV and X-ray absorption. The effective protein-protein interaction upon LLPS was investigated by SAXS. By optical microscopy of the condensed regime the LLPS region was defined by the formation of liquid droplets. In the case of HSA no cluster formation was observed, whereas BSA formed clusters outside and at the LLPS borders. The reduced second virial coefficient B₂/B₂^HS for HSA decreased from a slightly negative value in the condensed regime below the critical value of -1.5 in the LLPS region. For BSA, more negative values were observed at the LLPS border than in between. This is consistent with other protein systems studied. LLPS for HSA and BSA by adding YCl₃ and the clustering in BSA solutions can be explained by a sufficient low and negative B₂/B₂^HS. [1] F. Zhang et al., PRL 101, 2008, 148101; [2] F. Zhang et al. Soft Matter, submitted.