The article provides information on translational diffusion of unstructured αS-casein and hard globular α-chymotrypsin as a tool for evaluating intermolecular interactions in aqueous protein solutions. The self- and mutual diffusion coefficients of proteins were obtained using Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR) and Dynamic Light Scattering (DLS) methods. The theoretical description of the experimental data was based on the friction formalism of nonequilibrium thermodynamics [1]. As a result, sets of virial coefficients containing information on various types and contributions of intermolecular interactions were obtained. Also, the second virial coefficients were calculated from the model of the protein - protein potential of mean force, that contains description of charge - charge, charge - dipole, dipole - dipole potentials, dispersion Hamaker and the mean force osmotic-attraction potentials [2]. The proposed complex approach to the study of protein interactions made it possible to estimate the contribution of various interactions and described the intermolecular interactions of proteins that are fundamentally different in shape and structure.
protein-protein interactions, second virial coefficient, translational diffusion, NMR PFG, DLS
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