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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 14: Crystallization, Nucleation and Self Assembly I
CPP 14.1: Talk
Tuesday, March 12, 2013, 09:30–09:45, H39
Protein clustering as a precursor of crystallization — •Fajun Zhang1, Andrea Sauter1, Marcell Wolf1, Felix Roosen-Runge1, Michael Sztucki2, Roland Roth3, and Frank Schreiber1 — 1Institut für Angewandte Physik, Universität Tübingen — 2ESRF, Grenoble, France — 3Institut für Theoretische Physik, Universität Tübingen
Protein clusters are normally considered as a major impurity for growth of high quality single crystals. Here we show that pre-assembled protein clusters formed via cation bridging can serve as a building block of crystallization. Globular proteins, human serum albumin and beta-lactoglobulin have been crystallized from solution in the presence of multivalent metal ions. These negatively charged globular proteins undergo a reentrant condensation phase behavior [1]. Crystallization near phase boundaries follows different mechanisms [2]. DLS and SAXS reveal the formation of protein clusters near both phase boundaries. Real time SAXS measurements demonstrate that protein clusters act as precursors of nucleation with a reduced energy barrier [3]. Crystallographic analysis provides direct evidence of the crystal structure and cation binding sites [2]. Although the binding sites do not necessarily form the crystal lattice, they enhance interactions between protein contacts. The limited binding number (2-4) ensures the flexibility of proteins within clusters, which is crucial for the conformation relaxation during nucleation. [1] F. Zhang, et al. Phys. Rev. Lett. 2008, 101, 148101. [2] F. Zhang, et al. J. Appl. Cryst. 2011, 44, 755. Soft Matter 2012,8, 1313. [3] F. Zhang, et al. Faraday Discuss. 2012, 159, 313.