Regensburg 2016 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

CPP: Fachverband Chemische Physik und Polymerphysik

CPP 43: Poster: The Physics of Water Interactions with Biological Matter

CPP 43.10: Poster

Mittwoch, 9. März 2016, 18:15–21:00, Poster B2

Lower critical solution temperature behaviour in protein solutions caused by cation-induced hydration effects — •Olga Matsarskaia¹, Michal Braun¹, Felix Roosen-Runge², Marcell Wolf¹, Roland Roth³, Fajun Zhang¹, and Frank Schreiber¹ — ¹Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen — ²Institut Laue-Langevin, Grenoble, France — ³Institut für Theoretische Physik, Universität Tübingen

Upper and lower critical solution temperatures (UCST / LCST) are well known in systems such as mixtures of organic liquids. Here, we demonstrate for the first time an LCST in an aqueous protein (bovine serum albumin, BSA) solution which is induced by trivalent metal cations such as Y³⁺. The LCST manifests itself as a liquid-liquid phase separation (LLPS) above a certain temperature. Supported by calorimetric data, in their contribution we rationalise the mechanism behind this new case of LCST as follows. It is known from crystal structures that the Y³⁺ cations bind to negatively charged carboxyl groups of acidic residues on the protein surface and can bridge protein molecules [1]. Both Y³⁺ and carboxyl groups are strongly hydrated. For protein-cation binding to occur, both binding partners need to shed their hydration shells. Hydration water molecules are thus released into bulk water, increasing the entropy of the system. With increasing temperature, this entropy-driven binding process becomes more efficient, inducing a short-range attraction into the system which ultimately leads to LLPS.

[1] Zhang et al. (2011). J. Appl. Cryst., 44, 755.