Dresden 2017 – wissenschaftliches Programm
CPP 51.4: Poster
Mittwoch, 22. März 2017, 18:30–21:00, P3
Effect of weakly/strongly interacting cation mixtures on LCST-LLPS in protein solutions — •Olga Matsarskaia1, Nirzari Ann1, Felix Roosen-Runge2, Johannes Möller3, Fajun Zhang1, and Frank Schreiber1 — 1Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen — 2Institut Laue-Langevin, Grenoble, France — 3ESRF, Grenoble, France
In the presence of trivalent cations, negatively charged globular proteins show a rich phase behaviour including reentrant condensation, crystallisation, clustering  and lower critical solution temperature metastable liquid-liquid phase separation (LCST-LLPS) . Here, we present a systematic study of the influence of mixtures of varying ratios of Ho3+/La3+. Small-angle X-ray scattering (SAXS) data reveal that the interaction between BSA and the small cation Ho3+ is very strong, while the large La3+ interacts only weakly, which can be partly attributed to cation size effects. Using a combination of temperature-dependent UV-Vis as well as ζ potential measurements, we furthermore show that an increasing Ho3+/La3+ ratio systematically shifts the LCST to lower values. Our findings imply that cation size and other cation-specific effects can be a sensitive tool to fine-tune protein-protein interactions and phase behaviour in solution.
 Zhang et al. Pure & Appl. Chem. 2014, 86, 191-202;  Matsarskaia et al. JPCB 2016, 120, 7731-7736.