Dresden 2014 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 4: Crystallization, Nucleation and Self Assembly I

CPP 4.4: Vortrag

Montag, 31. März 2014, 10:15–10:30, ZEU 114

Real-Time Observation of Non-Classical Protein Crystallization Kinetics — •Andrea Sauter¹, Gudrun Lotze², Fajun Zhang¹, and Frank Schreiber¹ — ¹Universität Tübingen, Institut für Angewandte Physik — ²European Synchrotron Radiation Facility, F-38043 Grenoble Cedex 9, France

We present a real-time study of protein crystallization for beta-lactoglobulin in the presence of CdCl₂ by small angle X-ray scattering (SAXS) and optical microscopy. In the presence of CdCl₂ both classical and non-classical crystallization can be found depending on the concentration of protein and salt. A phase diagram region can be identified in which real-time SAXS demonstrates the existence of an intermediate state prior to crystallization that cannot be explained by classical nucleation theory. It shows as a minimum at 0.48 nm⁻¹ and a maximum at 0.7 nm⁻¹ which become visible in the scattering curves after several minutes. With time, this new feature becomes more pronounced. In the next step, Bragg peaks appear and the position of the minimum shifts towards larger q values. The minimum regresses again and in the end, only the contribution of the Bragg peaks is left. It can be concluded that an amorphous intermediate structure forms before crystallization starts and is consumed later by the growing crystals. Evolution and kinetics of the two components can be followed in real-time by X-ray scattering and microscopy.