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BP: Fachverband Biologische Physik
BP 10: Colloids and Complex Fluids III (Joint Session CPP/DY/BP)
BP 10.8: Talk
Monday, March 7, 2016, 17:00–17:15, H42
Phase behaviour and interactions in a three components γ-globulin based depletion interaction system — •Stefano Da Vela1, Fajun Zhang1, Sarah El-Asfar1, Christian Exner1, Michael Sztucki2, and Frank Schreiber1 — 1Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen — 2ESRF, Grenoble, France
Aqueous solutions of bovine γ-globulin with polyethylene glycol (PEG) added as non-interacting polymer, provide a tunable protein system for the study of depletion-driven phase behaviour: range and strength of the interaction are adjusted by appropriate choice of PEG molecular weight and concentration. An extensive study of the phase behaviour of the system for different effective attraction strengths reveals a set of conditions for which a Liquid-Liquid Phase Separation (LLPS) phase boundary emerges above the freezing temperature of the solvent. Addition of bovine serum albumin (BSA), results into an effective three components system. BSA, while not inducing depletion interaction on its own, appears to enhance it in presence of PEG, shifting the LLPS boundary to higher temperatures while being preferentially excluded from the resulting protein-dense liquid phase. In order to investigate the effect of BSA on the phase boundaries and on the interaction, phase diagrams as a function of temperature, protein and PEG concentration are presented together with small angle X-ray scattering data. Optical microscopy, turbidimetry and size exclusion chromatography are employed as supplementary techniques. The findings are relevant to the understanding of protein mixtures and their separation.