[NMR paper] Hydration-Dependent Dynamical Modes in Xyloglucan from Molecular Dynamics Simulation of 13C NMR Relaxation Times and their Distributions.

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Hydration-Dependent Dynamical Modes in Xyloglucan from Molecular Dynamics Simulation of 13C NMR Relaxation Times and their Distributions.

Related Articles Hydration-Dependent Dynamical Modes in Xyloglucan from Molecular Dynamics Simulation of 13C NMR Relaxation Times and their Distributions.

Biomacromolecules. 2018 Apr 24;:

Authors: Chen P, Terenzi C, Furo I, Berglund LA, Wohlert J

Abstract
Macromolecular dynamics in biological systems, which play a crucial role for biomolecular function and activity at ambient temperature, depend strongly on hydration. Yet, a generally accepted quantitative model of hydration-dependent phenomena based on local relaxation and diffusive dynamics of both polymer and its hydration water is still missing. In this work, atomistic-scale spatial distributions of motional modes are calculated using molecular dynamics (MD) simulations of hydrated xyloglucan (XG). These are shown to reproduce experimental hydration-dependent 13C NMR longitudinal relaxation times (T1) at room temperature, and relevant features of their broad distributions, which are indicative of locally heterogeneous polymer reorientational dynamics. At low hydration, the self-diffusion behavior of water shows water molecules confined to particular locations in the randomly aggregated XG network while the average polymer segmental mobility remains low. Upon increasing water content, the hydration network becomes mobile and fully accessible for individual water molecules, and the motion of hydrated XG segments becomes faster. Yet, the polymer network retains a heterogeneous gel-like structure even at the highest level of hydration. We show that the observed distribution of relaxations times arises because of the spatial heterogeneity of chain mobility that in turn is a result of heterogeneous distribution of water and chain-chain interactions. Our findings contribute to the picture of hydration-dependent dynamics in other macromolecules such as proteins, DNA and synthetic polymers, and hold important implications for the mechanical properties of polysaccharide matrices in plants and plant-based materials.


PMID: 29688710 [PubMed - as supplied by publisher]



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