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BP: Fachverband Biologische Physik

BP 10: Posters DY - Fluid Physics, Active Matter, Complex Fluids, Soft Matter and Glasses (joint session DY/BP)

BP 10.13: Poster

Montag, 22. März 2021, 14:00–16:30, DYp

The thermodynamics and kinetics of protein crystallization probed by isothermal microcalorimetry — Lorena Hentschel, •Jan Hansen, Florian Platten, and Stefan U. Egelhaaf — Condensed Matter Physics Laboratory, Heinrich Heine University, Düsseldorf, Germany

During a first-order phase transition, a thermodynamic system releases or absorbs latent heat. Despite their fundamental importance, the heat or enthalpy change occurring during protein crystallization has been directly measured only in a few cases, and the associated entropy change can only be determined indirectly. Here, the thermodynamics and kinetics of tetragonal lysozyme crystallization are studied for various physicochemical solution parameters. Direct microcalorimetric and indirect van't Hoff enthalpy determinations quantitatively agree, suggesting a two-state crystallization process. Assuming that crystals are electrostatically neutral, the weak dependences of the crystallization enthalphy and entropy on salt concentration and pH value are explained by a Poisson-Boltzmann model. Furthermore, the calorimetric signal is related to the concentration change during nucleation and growth, from which the induction time and the growth rate are inferred. Their dependences on the chemical potential are in line with previous findings and can be modelled by classical nucleation theory and 2D growth models, respectively.