Revitalizing an important field in biophysics: The new frontiers of molecular crowding

Taking into account the presence of the crowded environment of a macromolecule has been an important goal of biology over the past 20 years. Molecular crowding affects the motions, stability and the kinetic behaviour of proteins. New powerful approaches have recently been developed to study molecular crowding, some of which make use of the synchrotron radiation light. The meeting “New Frontiers in Molecular Crowding” was organized in July 2022at the European Synchrotron Radiation facility of Grenoble to discuss the new frontiers of molecular crowding. The workshop brought together researchers from different disciplines to highlight the new developments of the field, including areas where new techniques allow the scientists to gain unprecedently expected information. A key conclusion of the meeting was the need to build an international and interdisciplinary research community through enhanced communication, resource-sharing, and educational initiatives that could let the molecular crowding field flourish further

Anharmonic onsets in polypeptides revealed by neutron scattering: Experimental evidences and quantitative description of energy resolution dependence

International audienceNeutron scattering measurements on protein powders reveal two deviations from harmonic dynamics at low temperature, whose molecular origin, physical nature and biological relevance are still matter of discussion. In this study we present a new experimental and theoretical approach to evidence the resolution dependence of anharmonic onsets: the use of strategically selected homomeric polypeptides allows revealing the exact resolution dependence; a two-site energy landscape model, where resolution effects are explicitly taken into account, is able to interpret quantitatively the experimental data in terms of energy landscape parameters. The energetic description provided by this analysis, together with recent experimental evidences obtained on chemically and structurally different peptide systems, allows us to connect the protein/water energy landscape structure with the two-wells water interaction potential proposed to explain the low-density→high-density liquid-liquid transition observed in supercooled water

Probing the dynamics of biological matter by elastic, quasi-elastic, and inelastic neutron scattering

The so-called function-structure-dynamics paradigm established that a close relationship links the way biological molecules work (function), their 3-dimensional organization (structure) and the changes of this organization in time (dynamics), which characterize biomolecules as highly dynamic objects. A typical example of protein dynamics is provided by protein reactions with substrates: equilibrium thermal fluctuations of protein structure are necessary to allow the access of substrates to the active site, where the functional reaction occurs. Neutron scattering is a powerful technique to study equilibrium protein structural dynamics. The incoherent structure factor, which is dominant in neutron scattering from biological matter, is related to the time-position self correlation function of protein/solvent nuclei. Here the basic theory of neutron scattering and the principles of the technologies used to measure it are described. Some selected applications of neutron scattering for investigating the structural dynamics of biological molecules are also reviewed

Role of hydration water in the onset of protein structural dynamics

International audienceProteins are the molecular workhorses in a living organism. Their 3D structures are animated by a multitude of equilibrium fluctuations and specific out-of-equilibrium motions that are required for proteins to be biologically active. When studied as a function of temperature, functionally relevant dynamics are observed at and above the so-called protein dynamical transition (~240 K) in hydrated, but not in dry proteins. In this review we present and discuss the main experimental and computational results that provided evidence for the dynamical transition, with a focus on the role of hydration water dynamics in sustaining functional protein dynamics. The coupling and mutual influence of hydration water dynamics and protein dynamics are discussed and the hypotheses illustrated that have been put forward to explain the physical origin of their onsets

Anharmonic activations in proteins and peptide model systems and their connection with supercooled water termodynamics

International audienc

Anharmonic activations in proteins and peptide model systems and their connection with supercooled water termodynamics

International audienc

The boson peak of deeply cooled confined water reveals the existence of a low-temperature liquid-liquid crossover.

International audienceThe Boson peak of deeply cooled water confined in the pores of a silica xerogel is studied by inelastic neutron scattering at different hydration levels to separate the contributions from matrix, water on the pore surfaces and "internal" water. Our results reveal that at high hydration level, where the contribution from internal water is dominant, the temperature dependence of the Boson peak intensity shows an inflection point at about 225 K. The complementary use of differential scanning calorimetry to describe the thermodynamics of the system allows identifying the inflection point as the signature of a water liquid-liquid crossover