Cation-Induced Hydration Effects Cause Lower Critical Solution Temperature Behavior in Protein Solutions

Research output: Contribution to journalArticle


The phase behavior of protein solutions is important for numerous phenomena in biology and soft matter. We report a lower critical solution temperature (LCST) phase behavior of aqueous solutions of a globular protein induced by multivalent metal ions around physiological temperatures. The LCST behavior manifests itself via a liquid-liquid phase separation of the protein-salt solution upon heating. Isothermal titration calorimetry and zeta-potential measurements indicate that here cation-protein binding is an endothermic, entropy-driven process. We offer a mechanistic explanation of the LCST. First, cations bind to protein surface groups driven by entropy changes of hydration water. Second, the bound cations bridge to other protein molecules, inducing an entropy-driven attraction causing the LCST. Our findings have general implications for condensation, LCST, and hydration behavior of (bio)polymer solutions as well as the understanding of biological effects of (heavy) metal ions and their hydration.


  • Olga Matsarskaia
  • Michal K. Braun
  • Felix Roosen-Runge
  • Marcell Wolf
  • Fajun Zhang
  • Roland Roth
  • Frank Schreiber
External organisations
  • University of Tübingen
  • Institut Laue Langevin
Original languageEnglish
Pages (from-to)7731-7736
Number of pages6
JournalJournal of Physical Chemistry B
Issue number31
Publication statusPublished - 2016 Aug 11
Publication categoryResearch
Externally publishedYes