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BP: Fachverband Biologische Physik

BP 23: Biopolymers and Biomaterials III (with CPP)

BP 23.10: Vortrag

Mittwoch, 16. März 2011, 17:30–17:45, ZEU 260

Liquid-liquid phase separation in protein solutions induced by multivalent counter ions — •Marcell Wolf, Fajun Zhang, Felix Roosen-Runge, Andrea Sauter, and Frank Schreiber — Institut für Angewandte Physik, Auf der Morgenstelle 10, Universität Tübingen, 72076 Tübingen, Germany

The liquid-liquid phase separation (LLPS) in concentrated protein solutions plays an important role for protein crystallization as well as protein-association related diseases, such as the sickle cell anemia and eye cataracts, etc [1]. Here, we show that the LLPS can be induced in protein solutions by using a multivalent salt like Yttrium Chloride (YCl₃). The phase diagram of proteins with YCl₃ in the c_p (protein concentration) - c_s (salt concentration) plane is determined. The protein solution undergoes a phase-separation upon adding salt up to a critical value c*. Further increasing c_s to c** the precipitates dissolve and the system turns back to a homogenous solution. This is a re-entrant phase behavior [2]. In the condensed regime between c* and c** the system is thermodynamically equivalent to the phase behavior of a hard sphere with short range interactions, which exhibits a stable gas-solid transition and a metastable LLPS. The phase boundary is determined by UV and X-ray absorption. The effective protein-protein interactions in solutions upon LLPS are investigated by SLS and SAXS. The resulting interaction potential has been compared and discussed based on the thermodynamic criteria. [1] J.D. Gunton, A. Shiryayev, D. L. Pagan, Protein Condensation, 2007, Cambridge University Press, [2] F. Zhang et al., Phys. Rev. Lett. 101 (2008) 148101