Berlin 2015 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 34: P6: Biomaterials and Biopolymers
CPP 34.9: Poster
Tuesday, March 17, 2015, 14:00–16:00, Poster C
A polyethylene glycol / γ-globulin mixture as a versatile depletion interaction system for the study of crowding effects — •Stefano Da Vela1, Fajun Zhang1, Christian Exner1, Saliba Barsaume1, Michael Sztucki2, and Frank Schreiber1 — 1Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen — 2ESRF, Grenoble, France
Bovine γ-globulin is a polyvalent antibody preparation consisting mainly of Immunoglobulin G (IgG), an anisotropic, Y-shaped protein. Solutions of γ-globulin, with polyethylene glycol (PEG) of variable molecular weights added as depletion agent, can be used as a model to study the effect of attractive particle-particle interactions with tunable range and strength. The phase behaviour is comparable to that of monoclonal antibody systems, with the appearance of a gas-liquid coexistence region accessible above the freezing temperature of water, within a range of PEG concentrations. However, the availability of large amounts of protein in the case of γ-globulin allows for an extensive exploration of its phase diagram: regions at high protein volume fraction and the possibility to realize arrested phase transitions are of particular interest. Moreover, by choosing appropriate PEG molecular weights and concentrations, the phase behaviour can be described in conditions beyond those of applicability of the Asakura-Oosawa model of depletion interactions. Typical phase diagrams as a function of PEG concentration and temperature are presented, while dynamic light scattering and small-angle x-ray scattering are employed to characterize the interaction.