Molecular dynamics in hydrated sodium alginate by quasielastic and elastic neutron scattering

Tripadus, V.; Zanotti, Jean-Marc; Statescu, M.; Constantinescu, O.; Mitra, Saibal; Aranghel, D.

doi:10.1016/j.chemphys.2009.09.015

Cited by 2 publications

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“…9 The molecular structure and dynamics of water-alginate systems depend on the alginate concentration, temperature, chain length, and nature of the counterion. Monovalent cations form soluble mixtures with alginic acid.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Neutron scattering experiments have demonstrated that water determines the confirmation as well as the flexibility of alginate chains. 9 The molecular structure and dynamics of water-alginate systems depend on the alginate concentration, temperature, chain length, and nature of the counterion. Monovalent cations form soluble mixtures with alginic acid.…”

Section: ■ Introductionmentioning

confidence: 99%

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Hydration of Sodium Alginate in Aqueous Solution

et al. 2014

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Alginates are naturally occurring biocompatible polysaccharides. They have a broad range of applications, mainly in connection to their ability to control the rheology of aqueous solutions. Specifically, addition of a small amount of alginate (10% wt) leads to a ∼100-fold increase in viscosity. Here we explore whether that pronounced retardation of the long-range correlations is accompanied by molecularlevel changes of the water structure. We employ viscometry, dielectric spectroscopy (DS) and femtosecond infrared (fs-IR) pump−probe spectroscopy to study water dynamics in sodium alginate solutions. Remarkably, despite the large rheological effects of alginates in solution, the rotational dynamics of water are remarkably similar to those observed in bulk water. Only a small subensemble of water molecules is slowed down significantly, amounting to 6 ± 2 water molecules per saccharide unit. Furthermore, DS measurements reveal an additional ∼5 water molecules to be slowed down by the counterion (Na + ). Our results reveal that the effect of alginate on the dynamics of water is restricted to the first hydration shell. This indicates that the large viscosity increase is determined by the polysaccharide network, with large water pools present between the polysaccharide chains. ■ INTRODUCTIONAlginate is a water-soluble polysaccharide, which is isolated from brown algal species. It is built up of two uronic acids residues, L-guluronic (G) and D-mannuronic acid (M). Alginates are biodegradable, biocompatible, and nontoxic. Their most important property is related to their viscosifying, stabilizing and gelling properties as well as their ability to retain water. Owing to these properties, they have a broad range of applications, mainly in food industry as thickeners, stabilizing agents and emulsifiers 1 and they are also used in the cosmetic and drug industry. 2 Thus, it is of technological interest to understand the mechanism of how alginate affects the overall dynamics of soft matter samples. Such insights are also interesting from a fundamental point of view. Already in relatively small amounts, alginate has a dramatic effect on the rheology of aqueous solutions (Figure 1) − the question that presents itself is how the alginate interacts with water to bring about such large changes: can the local interactions of the alginate with the water be related to the global effect of the polysaccharide on the rheological properties?While the hydration of monosaccharides or disaccharides has been studied intensively, 3−6 there are only few reports on the water dynamics in the hydrations shell of polysaccharides. 7,8 In particular, the effect of polyelectrolyte-based polysaccharides on the dynamics of water are of paramount interest, as in principle Coulomb forces may lead to longer-ranged interactions, compared to neutral polysaccharides. Naturally, the hydration water itself plays an important role in structure, dynamics, and functionality of biomolecules as the hydrating water molecules determine charge screening and the dissocia...

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Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%