Protein phase behavior in electric fields

• Applicants: Dr. Kyongok Kang; Dr. Florian Platten
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495795796

Protein self-assembly is relevant for many processes in nature and in industry, like the pathogenesis of several widespread diseases, the growth of diffraction-quality protein crystals, the texture of protein-based food products as well as the formulation and storage of proteinaceous drugs. External electric fields have been used to manipulate the number and size of protein crystals, to destabilize amyloid fibrils, and to preserve protein-based food products. Electric fields will affect protein solutions, similar to their effects on polyelectrolytes, by polarization of the proteins and their electric double layers, internal electric stresses, hydrodynamic friction forces and alignment of the proteins. However, the influence of electric fields on the collective behavior of protein solutions has as yet not been systematically explored. In particular, only little is known about the frequency and field strength dependence of the structural and dynamical properties of protein solutions as well as the phase boundaries and the occurrence of field-induced new states, such as liquid-crystalline domains and linearly extended aggregates. The goal of the present project is to obtain a fundamental understanding of the phase behavior of protein solutions in electric fields. We aim at establishing a comprehensive experimental picture by a suitable choice of systems and research methods. To this end, the influence of electric fields on the three different kinds of protein solutions will be examined: (A) systems dominated by short-ranged attractions, (B) systems with additional long-ranged repulsions, and (C) binary protein mixtures. In addition, model proteins will be used differing in their shape, size, structural flexibility, degree of unfolding, conformational stability and surface properties. These model systems can thus be considered representative for many proteins in general. The condensed states will be studied on various length scales: their rich morphologies by light microscopy, the form and structure factor of protein solutions by means of small-angle X-ray scattering, the collective dynamics of the solution by dynamic light scattering, and the secondary and tertiary structure of single proteins by circular dichroism spectroscopy. The experimental results will be summarized in state diagrams, based on which the kinetics of phase transitions will be analyzed by scattering techniques and video microscopy with special emphasis on the formation of field-induced new states. The results of this work will help to elucidate the mechanisms of electric-field induced protein condensation processes and could thus not only be relevant for biophysical chemistry, but also for medicine, pharmaceutical industry and food processing.

• DFG Programme: Research Grants
• International Connection: Denmark
• Cooperation Partner: Professor Dr. Jan Skov Pedersen