Dresden 2020 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 21: Crystallization, Nucleation and Self-Assembly

CPP 21.2: Vortrag

Montag, 16. März 2020, 15:15–15:30, ZEU 255

Specific ion selection of protein crystal structures and growth — •Ralph Maier1, Christian Simo1, Aafiya Idrees1, Georg Zocher1, Fajun Zhang1, Thilo Stehle1,2, and Frank Schreiber11Universität Tübingen, Germany — 2Vanderbilt University School of Medicine, Nashville, USA

We study protein crystallization in aqueous solutions of β-lactoglobulin (BLG) with ZnCl2 by microscopy and small angle X-ray scattering (SAXS). This system is compared to a previously investigated system of BLG with another divalent salt (CdCl2). Both systems exhibit a reentrant condensation phase behavior with phase transitions at the salt concentration (cs) c* and pseudo - c** and a morphology change of the resulting crystals by increasing cs [1]. Importantly, in contrast to BLG with Cd where all crystals share the same structure [2], the morphology change with Zn is accompanied by a change of the crystal structure as verified by SAXS measurements. While the needle-like crystals nucleate in a P3221 structure, the structure of the more compact crystals, which is similar as for Cd, could not yet been resolved due to twin crystals for Cd. Interestingly, for BLG-Cd, a two-step crystallization mechanism has been proposed and an intermediate phase between the initial solution and the final crystal was identified by a specific SAXS correlation peak, which, however, has not yet been observed for Zn [2] despite forming the similar structure. This provides a model system to investigate different crystallization pathways leading to different structures. [1] Sauter et al., J. Am. Chem. Soc., 2015, 137, 1485-1491. [2] Sauter et al., Cryst. Growth Des., 2014, 14, 6357-6366.

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