Opening the Egg Box: NMR spectroscopic analysis of the interactions between s-block cations and kelp monosaccharides

Rowbotham, Jack; Greenwell, Chris; Dyer, Philip W.

doi:10.1039/d0dt04375c

Opening the Egg Box: NMR spectroscopic analysis of the interactions between s-block cations and kelp monosaccharides

Rowbotham, Jack; Greenwell, Chris; Dyer, Philip W.

Authors

Jack Rowbotham

Professor Chris Greenwell chris.greenwell@durham.ac.uk
Head Of Department

Professor Philip Dyer p.w.dyer@durham.ac.uk
Professor

Abstract

The best-known theory accounting for metal-alginate complexation is the so-called “Egg Box” model. In order to gain greater insight into the metal-saccharide interactions that underpin this model, the coordination chemistry of the corresponding monomeric units of alginate, L-guluronate (GulA) and D-mannuronate (ManA) have been studied herein. GulA and ManA were exposed to solutions of different s-block cations and then analysed by 1H and 13C NMR spectroscopy. It was found that the α/β ratio of the pyranose anomeric equilibria of GulA showed large pertubations from the starting value (α/β = 0.21 ± 0.01) upon contact with 1.0 M Ca2+, Sr2+, and Ba2+ (α/β = 1.50 ± 0.03, 1.20 ± 0.02, and 0.58 ± 0.02, respectively) at pD 7.9, but remained almost constant in the presence of Na+, K+, and Mg2+ (α/β = 0.24 ± 0.01, 0.19 ± 0.01, and 0.26 ± 0.01, respectively). By comparison, no significant changes were observed in the α/β ratios of ManA and related mono-uronates D-glucuronate (GlcA) and D-galacturonate (GalA) in the presence of all of the metal ions surveyed. Analysis of the 1H and 13C coordination chemical shift patterns indicate that the affinity of α-GulA for larger divalent cations is a consequence of the unique ax-eq-ax arrangement of hydroxyl groups found for this uronate anomer.

Citation

Rowbotham, J., Greenwell, C., & Dyer, P. W. (2021). Opening the Egg Box: NMR spectroscopic analysis of the interactions between s-block cations and kelp monosaccharides. Dalton Transactions, 50(38), 13246-13255. https://doi.org/10.1039/d0dt04375c

Journal Article Type	Article
Acceptance Date	Sep 6, 2021
Online Publication Date	Sep 6, 2021
Publication Date	Oct 14, 2021
Deposit Date	Sep 6, 2021
Publicly Available Date	Sep 6, 2021
Journal	Dalton Transactions
Print ISSN	1477-9226
Electronic ISSN	1477-9234
Publisher	Royal Society of Chemistry
Peer Reviewed	Peer Reviewed
Volume	50
Issue	38
Pages	13246-13255
DOI	https://doi.org/10.1039/d0dt04375c