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

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Opening the Egg Box: NMR spectroscopic analysis of the interactions between s-block cations and kelp monosaccharides
Dalton Transactions ( IF 3.5 ) Pub Date : 2021-09-06 , DOI: 10.1039/d0dt04375c
Jack S Rowbotham _{1,

2} , H Christopher Greenwell _{1,

3} , Philip W Dyer ₁

Affiliation

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.

中文翻译：

打开蛋盒：s-嵌段阳离子和海带单糖相互作用的核磁共振光谱分析

解释金属-藻酸盐络合的最著名的理论是所谓的“蛋盒”模型。为了更深入地了解支撑该模型的金属-糖类相互作用，本文研究了藻酸盐、L-古洛糖醛酸盐( GulA ) 和D-甘露糖醛酸盐 ( ManA ) 的相应单体单元的配位化学。GulA和ManA暴露于不同 s-嵌段阳离子的溶液中，然后通过¹ H 和¹³ C NMR 光谱进行分析。发现GulA的吡喃糖异头平衡的α / β比值^{与 1.0 M Ca 2+}、Sr ²⁺和 Ba ²⁺接触后，从起始值 ( α / β = 0.21 ± 0.01)开始出现较大的波动（α / β = 1.50 ± 0.03、1.20 ± 0.02 和 0.58 ± 0.02 ，分别）在 pD 7.9，但在存在 Na ⁺、K ⁺和 Mg ²⁺的情况下几乎保持不变（α / β = 0.24 ± 0.01、0.19 ± 0.01 和 0.26 ± 0.01，分别）。相比之下，ManA和相关的单糖醛酸D的α / β比率没有观察到显着变化-葡萄糖醛酸 ( GlcA ) 和D-半乳糖醛酸( GalA ) 在所有调查的金属离子存在下。对¹ H 和¹³ C 配位化学位移模式的分析表明，α -GulA对较大二价阳离子的亲和力是这种糖醛酸异头物发现的羟基的独特 ax-eq-ax 排列的结果。

更新日期：2021-09-10

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