Dresden 2014 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 54: Poster Session 3
CPP 54.29: Poster
Thursday, April 3, 2014, 15:00–19:00, P2
Liquid-liquid phase separation in protein - PEG mixture — Saliba Barsaume1, •Fajun Zhang1, Michael Sztucki2, Roland Roth3, and Frank Schreiber1 — 1Institut für Angewandte Physik, Universität Tübingen, Germany — 2ESRF, Grenoble, France — 3Institut für Theoretische Physik, Universität Tübingen, Germany
We present a combined experimental and theoretical study of the liquid-liquid phase separation (LLPS) in protein-PEG mixture. Bovine gamma-globulin solutions mixed with PEG above a critical volume fraction undergo a LLPS at constant temperature. The partitioning of both protein and PEG has been determined which gives the binodal of LLPS. The critical point of the system has been extrapolated from the tie lines. The critical volume fraction is about 6% which is significantly lower than the theoretical value (13-23%) for colloidal systems with isotropic interaction. The resulting phase boundary is compared with the free volume theory for arbitrary shape (Y-Shape) of protein with a radius of gyration of 6.3 nm and the size ratio of 0.3-0.8 between PEG and protein. Furthermore, small angle X-ray scattering has been employed to determine the effective protein-protein interactions approaching LLPS. The reduced second virial coefficient has been determined for samples at the binodal and near the critical point of LLPS, which is further compared and discussed with the value predicted from colloidal theory.