Role of Hydration Layer in Dynamical Transition in Proteins: Insights from Translational Self-Diffusivity

Abstract

Elucidation of the role of hydration water underpinning dynamical crossover in proteins has proven challenging. Indeed, many contradictory findings in the literature seek to establish either causal or correlative links between water and protein behavior. Here, via molecular dynamics, we compute the temperature dependence of mean-square displacement and translational self-diffusivities for both hen egg white lysozyme and its hydration layer from 190 to 300 K. We find that the protein's mobility increases sharply at ∼230 K, indicating dynamical onset; concerted motion with hydration-water molecules is evident up to ∼285 K, confirming dynamical correlation between them. Exploring underlying mechanisms of such concerted motion, we scrutinize the water-protein hydrogen-bonding network as a function of temperature, noting sharp deviation from linearity of the hydrogen bond number's profile with temperature originating near the protein dynamical transition. Our studies reveal a common temperature profile/dependence of self-diffusivity values of the protein, hydration water, and the bulk solvent, originating from a common dependence on the bulk solvent viscosity, η. The key mechanistic role adopted by the protein-water hydrogen bond network in relation to the onset of proteins' dynamical transition is also discussed.

Self-Diffusion of Individual Adsorbed Water Molecules at Rutile (110) and Anatase (101) TiO2 Interfaces from Molecular Dynamics

“…Many other theoretical studies have been systematically investigated on this surface, such as the nature of layered water structure [20] ionic adsorptions [21] viscosity and self-diffusion of the water layers{Formatting Citation} and dielectric properties of the interface. As one of the particular interest areas of study of the authors, diffusivity was reported to increase further away from the surface going toward bulk-like values [22] which is in accordance with the experimental measurements of Mamontov et al [23,24].…”

Mechanisms of Iodide–Triiodide Exchange Reactions in Ionic Liquids: A Reactive Molecular-Dynamics Exploration

“…It is important to note that here, this MSD-sampling time was selected to be ~20–150 times the bond-exchange events’ timescales, although sufficiently long for adequate statistical sampling of such MSDs; this affords recording of rather dramatic instances of lower diffusivities at 450 and 550 K with the shoulder, or “hump”, in the 0–0.2 × 10 −9 m 2 /s region clearly discernible when motion is slowed due to involvement in reaction events. Also, the distributions in Figure 3b are clearly non-Gaussian, with a tail at higher self-diffusivities and temperatures similar to that seen in [29] for individual water molecules in hydration layers.…”

“…In Figure 5, Arrhenius plots are provided for both the number of reactions per nanosecond, N , and self-diffusivity [29], D (from Figure 3), with good fit. A Student’s t -test on the resulting N - and D - activation energies of 5.12 and 4.88 kJ/mol (or 0.053 and 0.048 eV), respectively, establishes non-rejection of the null hypothesis H 0 with respective linear-regression activation-energy uncertainties of 0.43 and 0.41 kJ/mol.…”

Water dynamics in human cancer and non-cancer tissues

“…In a highly crowded intracellular medium or within tissues, water displays particular properties, different from those of the bulk water -water diffusion is not a purely random process, being restricted due to its high viscosity and macromolecular crowding. This interfacial water is known to play a fundamental role, through the maintenance of the stable three-dimensional conformation of biomolecules and biological clusters, [1][2][3][4][5][6] and any changes in its structural or dynamical profiles are expected to have substantial consequences at the functional level. Furthermore, the dynamical behaviour of water determines the biomechanical properties of cells and the cellular architecture which are associated with cancer initiation, progression, invasiveness and metastasis.…”