Phase Behaviour and Associated Dynamics of Protein Solutions Manipulated by Ions
F. Zhang
1, T. Seydel
2, F. Roosen-Runge
1, M. Hennig
2, M. Wolf
1, A. Sauter
1, R. Jacobs
3, and F. Schreiber
11Institut für Angewandte Physik, Uni Tübingen, 72076 Tübingen, Germany
2ILL, B.P. 156, 38042, France
3Department of Chemistry, Oxford University, Oxford OX1 3TA, United Kingdom E-Mail: frank.schreiber@uni-tuebingen.de
We will discuss how mono- and multivalent ions can be used to manipulate the interactions and the associated phase behaviour as well as the associated diffusion dynamics of aqueous protein solutions. In particular, we show that multivalent ions do not only influence the ionic strength and the effective interactions in aqueous solutions [1], but lead to qualitatively new effects. Specific attention will be given to the "reentrant condensation" of proteins [2,3] and its relationship with liquid-liquid phase separation and crystallization. In this context, we attempt to rationalize crystallization controlled by trivalent ions [4,5].
We will first focus on results obtained by elastic scattering, in particular SANS using contrast variation in comparison with SAXS and ASAXS, extracting information on the ionic and water shell around the proteins (based on the form factor) as well as the interactions (based on the structure factor) [6].
Second, we will discuss the consequences on the dynamics of these systems for different salt concentrations (i.e. with difference effective interactions), different crowding conditions (protein concentration) and also near salt-induced phase transitions. This involves both quasi- elastic neutron scattering (QENS) [7] as well as dynamic light scattering techniques (DLS) [8].
References
[1] F. Zhang et al., J. Phys. Chem. B 111 (2007) 251 [2] F. Zhang et al., Phys. Rev. Lett. 101 (2008) 148101
[3] F. Zhang et al., Proteins: Structure, Function, and Bioinformatics, 78 (2010) 3450 [4] F. Zhang et al., J. Appl. Cryst. 44 (2011) 755
[5] F. Zhang et al., Soft Matter 8 (2012) 1313
[6] F. Zhang et al., Phys. Chem. Chem. Phys. 14 (2012) 2483 [7] F. Roosen-Runge et al. PNAS 108 (2011) 11815
[8] M. Heinen et al., Soft Matter 8 (2012) 1404
