Exploring the molecular basis for the metal-mediated assembly of alginate gels

Matthew B Stewart; Stephen R Gray; Todor Vasiljevic; John D Orbell

doi:10.1016/j.carbpol.2013.11.034

Exploring the molecular basis for the metal-mediated assembly of alginate gels

Carbohydr Polym. 2014 Feb 15:102:246-53. doi: 10.1016/j.carbpol.2013.11.034. Epub 2013 Dec 4.

Authors

Matthew B Stewart¹, Stephen R Gray², Todor Vasiljevic³, John D Orbell⁴

Affiliations

¹ Institute for Sustainability and Innovation (ISI), Victoria University, PO Box 14428, Melbourne, VIC 8001, Australia; College of Engineering and Science, Victoria University, PO Box 14428, Melbourne, VIC 8001, Australia. Electronic address: Matthew.Stewart@vu.edu.au.
² Institute for Sustainability and Innovation (ISI), Victoria University, PO Box 14428, Melbourne, VIC 8001, Australia; College of Engineering and Science, Victoria University, PO Box 14428, Melbourne, VIC 8001, Australia. Electronic address: Stephen.Gray@vu.edu.au.
³ Institute for Sustainability and Innovation (ISI), Victoria University, PO Box 14428, Melbourne, VIC 8001, Australia; College of Health and Biomedicine, Victoria University, PO Box 14428, Melbourne, VIC 8001, Australia. Electronic address: Todor.Vasiljevic@vu.edu.au.
⁴ Institute for Sustainability and Innovation (ISI), Victoria University, PO Box 14428, Melbourne, VIC 8001, Australia; College of Engineering and Science, Victoria University, PO Box 14428, Melbourne, VIC 8001, Australia. Electronic address: John.Orbell@vu.edu.au.

PMID: 24507279
DOI: 10.1016/j.carbpol.2013.11.034

Abstract

The binding of sodium and calcium ions to single and multiple poly-G decamer strands has been modelled by conducting a series of molecular dynamics simulations. Implications for metal mediated inter-strand interactions and gel assembly have been explored by systematically introducing up to three strands into each of these simulations. A particular emphasis has been placed on revealing intrinsic binding modes by an unbiased initial positioning of the metal ions. The results have revealed binding modes that provide a rationale for the observed gelling of alginate by calcium rather than sodium ions. A number of junction zones involving calcium ions have been identified that result in chain aggregation. This includes a distinctive perpendicular motif that appears to be ubiquitous in previously reported AFM images of open 3-D alginate networks. The coordination geometries of the metal ions have been characterised and the metal-mediated junctions between associated strands are described in detail.

Keywords: Alginate gels; Calcium coordination; Molecular dynamics; Sodium alginate.