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Structure of alginate gels: interaction of diuronate units with divalent cations from density functional calculations.

Structure of alginate gels: interaction of diuronate units with divalent cations from density... The complexation of (1→4) linked α-L-guluronate (G) and β-D-mannuronate (M) disaccharides with Mg(2+), Ca(2+), Sr(2+), Mn(2+), Co(2+), Cu(2+), and Zn(2+) cations have been studied with quantum chemical density functional theory (DFT)-based method. A large number of possible cation-diuronate complexes, with one and two GG or MM disaccharide units and with or without water molecules in the inner coordination shells have been considered. The computed bond distances, cation interaction energies, and molecular orbital composition analysis revealed that the complexation of the transition metal (TM) ions to the disaccharides occurs via the formation of strong coordination-covalent bonds. On the contrary, the alkaline earth cations form ionic bonds with the uronates. The unidentate binding is found to be the most favored one in the TM hydrated and water-free complexes. By removing water molecules, the bidentate chelating binding also occurs, although it is found to be energetically less favored by 1 to 1.5 eV than the unidentate one. A good correlation is obtained between the alginate affinity trend toward TM cations and the interaction energies of the TM cations in all studied complexes, which suggests that the alginate affinities are strongly related to the chemical interaction strength of TM cations-uronate complexes. The trend of the interaction energies of the alkaline earth cations in the ionic complexes is opposite to the alginate affinity order. The binding strength is thus not a limiting factor in the alginate gelation in the presence of alkaline earth cations at variance with the TM cations. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Biomacromolecules Pubmed

Structure of alginate gels: interaction of diuronate units with divalent cations from density functional calculations.

Biomacromolecules , Volume 13 (6): 9 – Feb 12, 2013

Structure of alginate gels: interaction of diuronate units with divalent cations from density functional calculations.


Abstract

The complexation of (1→4) linked α-L-guluronate (G) and β-D-mannuronate (M) disaccharides with Mg(2+), Ca(2+), Sr(2+), Mn(2+), Co(2+), Cu(2+), and Zn(2+) cations have been studied with quantum chemical density functional theory (DFT)-based method. A large number of possible cation-diuronate complexes, with one and two GG or MM disaccharide units and with or without water molecules in the inner coordination shells have been considered. The computed bond distances, cation interaction energies, and molecular orbital composition analysis revealed that the complexation of the transition metal (TM) ions to the disaccharides occurs via the formation of strong coordination-covalent bonds. On the contrary, the alkaline earth cations form ionic bonds with the uronates. The unidentate binding is found to be the most favored one in the TM hydrated and water-free complexes. By removing water molecules, the bidentate chelating binding also occurs, although it is found to be energetically less favored by 1 to 1.5 eV than the unidentate one. A good correlation is obtained between the alginate affinity trend toward TM cations and the interaction energies of the TM cations in all studied complexes, which suggests that the alginate affinities are strongly related to the chemical interaction strength of TM cations-uronate complexes. The trend of the interaction energies of the alkaline earth cations in the ionic complexes is opposite to the alginate affinity order. The binding strength is thus not a limiting factor in the alginate gelation in the presence of alkaline earth cations at variance with the TM cations.

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ISSN
1525-7797
DOI
10.1021/bm300420z
pmid
22571325

Abstract

The complexation of (1→4) linked α-L-guluronate (G) and β-D-mannuronate (M) disaccharides with Mg(2+), Ca(2+), Sr(2+), Mn(2+), Co(2+), Cu(2+), and Zn(2+) cations have been studied with quantum chemical density functional theory (DFT)-based method. A large number of possible cation-diuronate complexes, with one and two GG or MM disaccharide units and with or without water molecules in the inner coordination shells have been considered. The computed bond distances, cation interaction energies, and molecular orbital composition analysis revealed that the complexation of the transition metal (TM) ions to the disaccharides occurs via the formation of strong coordination-covalent bonds. On the contrary, the alkaline earth cations form ionic bonds with the uronates. The unidentate binding is found to be the most favored one in the TM hydrated and water-free complexes. By removing water molecules, the bidentate chelating binding also occurs, although it is found to be energetically less favored by 1 to 1.5 eV than the unidentate one. A good correlation is obtained between the alginate affinity trend toward TM cations and the interaction energies of the TM cations in all studied complexes, which suggests that the alginate affinities are strongly related to the chemical interaction strength of TM cations-uronate complexes. The trend of the interaction energies of the alkaline earth cations in the ionic complexes is opposite to the alginate affinity order. The binding strength is thus not a limiting factor in the alginate gelation in the presence of alkaline earth cations at variance with the TM cations.

Journal

BiomacromoleculesPubmed

Published: Feb 12, 2013

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