Regensburg 2013 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 45: Colloids and Complex Liquids II

CPP 45.3: Vortrag

Donnerstag, 14. März 2013, 15:45–16:00, H40

Clustering in β-lactogloblin and lysozyme protein solutions studied by SAXS — •Bo Jing¹, Fajun Zhang¹, Felix Roosen-Runge¹, Michael Sztucki², and Frank Schreiber¹ — ¹Institute of Applied Physics, University of Tübingen — ²ESRF, Grenoble, France

The understanding of protein cluster formation provides insight into protein function, crystallization and protein aggregation induced diseases. β-lactoglobulin (BLG) is known to form dimers, tetramers, hexamers and octamers at certain pH, temperature, and salt concentrations. Here, we present SAXS measurements which indicate oligomer formation at high protein concentrations, in the absence of salt and other additives. Scattering curves of BLG solutions display a major correlation peak which shifts minimally to higher q-values with increasing protein concentration. This observation is indicative of cluster formation or, in this case, oligomerization. We draw a comparison with the well-studied lysozyme protein system, where we observed a more pronounced shift of the major correlation peak that has been associated with the formation of a dynamical cluster phase. In this system, the peak position also shows a temperature dependence not seen with BLG solutions. The SAXS data of both systems were fitted to elliptical form factors and two-Yukawa interaction potentials. We relate the different clustering models and contrasting temperature responses in these protein systems to differences in their interaction potential and the distinct properties of BLG and lysozyme proteins molecules. In this context, the shortcomings of isotropic interaction models and the need to consider patchy interactions are also discussed.