Dynamics of proteins in aqueous solutions - recent advances using high-resolution spectroscopy
Résumé
Novel high resolution neutron spectrometers permit new types of experiments probing several hierarchically superimposed levels of protein dynamics on the molecular length scale. Notably, the high cold neutron flux delivered to the samples opens up the possibility to investigate proteins suspended in aqueous solutions.
In this way, the nanosecond time scale internal motion of proteins and other macromolecules in aqueous solutions at comparatively low concentrations of 50 to 200 mg/ml can be explored [1,2]. These novel types of experiments allow to investigate the in-solution internal dynamics
of proteins and its difference to the previously studied hydrated macromolecular powder dynamics. Simultaneously, the superimposed global center-of-mass motions can be measured and separated into the rotational and translational diffusion contributions [3]. This center-of-mass diffusion can be interpreted in terms of concepts from colloid physics [4,5]. High-resolution incoherent neutron scattering provides a unique access to the short-time self-diffusion of proteins and other macromolecules in aqueous solutions [4]. On this time scale, hydrodynamic and electrostatic interactions prevail, as opposed to the longer time scales accessible for instance by nuclear magnetic resonance experiments, on which direct interactions (collisions) between the suspended proteins dominate.
The new possibilities permit to address the current topics [1-10], amongst others, of macromolecular crowding [4], of “patchy” colloid physics [5,6], of protein cluster formation [2,5], of protein unfolding [7,8], of the in situ study of dynamic precursor processes to the crystallization of proteins from aqueous solutions, and of intrinsically disordered proteins [9]. The talk will present a selection of recent results highlighting the link between protein
biophysics and colloid physics.
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[5] M. Grimaldo et al., J.Phys.Chem.Lett. 6, 2577 (2015).
[6] F.Roosen-Runge et al., Sci.Rep. 4, 7016 (2014).
[7] M. Grimaldo et al., Phys.Chem.Chem.Phys. 17, 4645 (2015).
[8] M. Hennig et al., Soft Matter 8, 1404 (2012).
[9] S. Lenton et al., Biophys.J. 112, 1586 (2017).
[10] T. Seydel, Dynamics of biological systems, in: F. Fernandez-Alonso, D.L. Price (Eds.),
Experimental Methods in the Physical Sciences, vol.49, Academic Press 2017, pp.77-128