Berlin 2018 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 68: Crystallization, Nucleation and Self-Assembly I

CPP 68.4: Talk

Thursday, March 15, 2018, 12:30–12:45, C 230

Salt-induced temperature-dependent protein cluster formation: access to binding entropies and enthalpies — •Christian Beck^1,2, Marco Grimaldo¹, Michal Braun², Fajun Zhang², Felix Roosen-Runge³, Frank Schreiber², and Tilo Seydel¹ — ¹Institut Laue Langevin, Grenoble, France — ²IAP, University of Tübingen, Tübingen, Germany — ³Physical Chemistry, Lund University, Lund, Sweden

With increasing Yttrium Chloride (YCl₃) salt concentration c_s, aqueous Bovine Serum Albumin (BSA) protein solutions subsequently change from a visually transparent (regime I) to a turbid phase (regime II) and back to a transparent phase (regime III: reentrant dissolution). Within regime II, a lower critical solution temperature (LCST) associated with a liquid-liquid phase separation (LLPS) can be observed. Quasi-elastic neutron scattering (QENS) data as a function of c_s and the protein concentration c_p lend support to the formation of protein clusters when approaching regime II [1]. By applying the Wertheim theory for patchy particles [2] and the Flory-Stockmeyer cluster size distribution function, it is possible to describe the temperature dependent cluster formation quantitatively. The ion-binding and protein-protein bridging entropies and enthalpies associated with the clusters can be determined directly from a simultaneous fit of the model to a large set of QENS spectra for different c_p, c_s, and T. The results are compared with calorimetry measurements [3]. [1]Grimaldo, M. et al, JPCL 6 (2015) 2577; [2]Wertheim, M., J. Stat. Phys. 1984, 35, 19-34; [3]Matsarskaia, O. et al, J. Phys. Chem. B 120 (2016) 7731