Berlin 2015 – scientific programme
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BP: Fachverband Biologische Physik
BP 52: Protein structure and dynamics II
BP 52.5: Talk
Friday, March 20, 2015, 11:00–11:15, H 1028
Phase behavior of dense lysozyme solutions — •Julian Schulze1, Johannes Möller1, Michael Paulus1, Julia Nase1, Metin Tolan1, and Roland Winter2 — 1Fakultät Physik/Delta, Technische Universität Dortmund, 44221 Dortmund , Germany — 2Fakultät für Chemie und Chemische Biologie, Technische Universität Dortmund, 44221 Dortmund, Germany
In previous studies, small angle X-ray scattering (SAXS) in combination with liquid-state theoretical approaches and DLVO theory was used to study the intermolecular interaction potential, V(r), of lysozyme solutions under the influence of varying environmental conditions as protein concentration c, temperature T, pressure p or salt concentration I. While the repulsive Coulomb term of the DLVO potential remains almost constant as a function of p, the depth of the attractive part, J(p), exhibits a non-monotonic p-dependence with a minimum at 1.5 kbar at selected T. Adding 0.5 M NaCl leads to more prominent short range interactions, especially at high c and low T. Here, the homogeneous protein solution becomes turbid due to formation of a metastable liquid-liquid phase separation (LLPS) region, where lysozyme forms small droplets of high concentration within the more dilute liquid phase. At elevated pressures, this l-l phase separation is suppressed, but due to the non-monotonic behavior of J(p), a further pressure increase leads to a re-entrant LLPS. The analysis of the SAXS data allows the construction of the c-p-T phase diagram of lysozyme solutions. As crystallization occurs in this c-p-T region as well, the diagram will help optimize crystallization conditions.