Protein solutions approaching phase separation and dynamical arrest

• Applicant: Dr. Florian Platten
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
• Term: from 2019 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 420474065

Colloids with short-ranged attractions exhibit an extremely rich thermodynamic and dynamical behavior. This includes, e.g. metastable liquid-liquid phase separation buried inside the fluid-solid coexistence region as well as dynamical arrest. According to the extended law of corresponding states (ELCS), all systems of this kind obey the same equation of state that is a function of only three reduced parameters, namely density, temperature and second virial coefficient. It has been claimed that all thermodynamic and dynamical properties are determined by the ELCS. However, its full predictive capability has not been tested experimentally. This is, in particular, due to the scarcity of knowledge on the role of dynamical arrest and the collective dynamics in the vicinity of the phase boundaries. Protein solutions dominated by short-ranged attractions represent a convenient experimental model system to study critical phenomena and non-equilibrium behavior. We will focus on protein solutions approaching phase separation and arrest. Using light scattering as well as digital Fourier microscopy, their static structure factor and intermediate scattering function will be examined at the length scales of condensation. Furthermore, the non-equilibrium evolution of these properties will be monitored after quenches into the metastable or unstable region. Thus, the microstructural processes that govern phase separation and arrest will be explored. Our experiments on the structure, dynamics and kinetics of short-ranged attractive systems will serve as a basis for scrutinizing the predictive power of the ELCS and its limits. This work will hence contribute to a deeper understanding of protein condensation phenomena in general and might be relevant not only to statistical physics, but also to medicine, pharmaceutical industry and food engineering.

• DFG Programme: Research Grants