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Issue 16, 2007
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Separable cooperative and localized translational motions of water confined by a chemically heterogeneous environment

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Abstract

We report quasi-elastic neutron scattering experiments at two resolutions that probe timescales of picoseconds to nanoseconds for the hydration dynamics of water, confined in a concentrated solution of N-acetyl-leucine-methylamide (NALMA) peptides in water over a temperature range of 248 K to 288 K. The two QENS resolutions used allow for a clean separation of two observable translational components, and ultimately two very different relaxation processes, that become evident when analyzed under a combination of the jump diffusion model and the relaxation cage model. The first translational motion is a localized β-relaxation process of the bound surface water, and exhibits an Arrhenius temperature dependence and a large activation energy of ∼8 kcal mol−1. The second non-Arrhenius translational component is a dynamical signature of the α-relaxation of more fluid water, exhibiting a glass transition temperature of ∼116 K when fit to the Volger Fulcher Tamman functional form. These peptide solutions provide a novel experimental system for examining confinement in order to understand the dynamical transition in bulk supercooled water by removing the unwanted interface of the confining material on water dynamics.

Graphical abstract: Separable cooperative and localized translational motions of water confined by a chemically heterogeneous environment

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Publication details

The article was received on 22 Nov 2006, accepted on 15 Jan 2007 and first published on 06 Feb 2007


Article type: Paper
DOI: 10.1039/B616997J
Citation: Phys. Chem. Chem. Phys., 2007,9, 1962-1971
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    Separable cooperative and localized translational motions of water confined by a chemically heterogeneous environment

    C. Malardier-Jugroot and T. Head-Gordon, Phys. Chem. Chem. Phys., 2007, 9, 1962
    DOI: 10.1039/B616997J

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