Interactions in saccharide/cation/water systems: Insights from density functional theory

Abstract

Interactions between saccharides and ions in aqueous solutions are of great importance in many fi elds (chem istry, physico-chernistry, biology, food industries). Thus, this work proposes to develop a methodology dealing with the characterization and the understanding of interactions between saccharides and cations in presence of water molecules, by a quantum mechanics approach. In the fi rst part, the saccharide hydration properties (xylose, glucose, sucrose) in pure water are deterrnined. Results show that the saccharide coordination numbers, as well as the saccharides hydration enthalpy, increase with the saccharide hydrophilic group number. In the second par t, the influence of cations on saccharides hydration properties, and inversely, is evaluated. In sac charide/cation/water systems, the decrease in hydration enthalpy of cations and saccharides shows that both species are dehydrated and that saccharide dehydration depends on the nature of the cation. The dehydration sequenoe of saccharides was explained from the study of saccharide/cation interactions.

Advances in the Understanding of the Transfer of Saccharides through NF Membranes in the Presence of Electrolytes by Coupling Quantum Mechanics and Thermodynamic Methods

“…In our previous works, the solute hydration properties (ions and saccharides) in pure water and in mixture were studied via a full geometry optimization using the DFT method [ 24 , 25 , 26 ]. First, the ion coordination number, CN , which is defined as the number of water molecules directly bonded to the central ion in its solvation first layer, was determined [ 25 ].…”

“…First, the ion coordination number, CN , which is defined as the number of water molecules directly bonded to the central ion in its solvation first layer, was determined [ 25 ]. Then, the number of interactions between the cation and the oxygen, n inter S/C+ , defined as the number of oxygen belonging to the saccharide in direct interaction with the ion, was calculated [ 26 ]. Results concerning the ion coordination number and the number of interactions between glucose and different cations are given in Table 5 [ 25 , 26 ].…”

“…Then, the number of interactions between the cation and the oxygen, n inter S/C+ , defined as the number of oxygen belonging to the saccharide in direct interaction with the ion, was calculated [ 26 ]. Results concerning the ion coordination number and the number of interactions between glucose and different cations are given in Table 5 [ 25 , 26 ]. In saccharide/cation/water systems, results showed that saccharides are all the more dehydrated as the number of saccharide/cation interactions increases, n inter S/C+ [ 26 ].…”

“…First, the computation of the ion hydration properties in water confirmed that the presence of an anion (Cl − or SO 4 2− ) does not lead to a change in the first cation hydration layer (Na + , K + , Mg 2+ and Ca 2+ ) [ 25 ]. Considering this last point, the saccharide/electrolyte interactions have been characterized in saccharide/cation/water systems showing that in such systems, cations and saccharides are both dehydrated [ 26 ]. In agreement with the results obtained from the volumetric properties, quantum mechanics calculations have shown that the saccharide dehydration increases with the ion valence and that the saccharide dehydration increases according to the following sequences: Na + < K + and Mg 2+ < Ca 2+ .…”

“…The envisaged methodology is based on the comparison of the hydration properties obtained by experimental and theoretical approaches (volumetric properties from a thermodynamic method and quantum mechanics data) with the mass transfer of saccharides through an NF membrane. Thus, correlations between the solute hydration properties obtained at different scales [ 23 , 24 , 25 , 26 ] and the mass transfer parameters, which characterize the impact of the electrolyte on the saccharide transfer, are investigated to improve the understanding of the impact of the nature (cation, anion, size, valence, etc.) and the concentration of the ions.…”