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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。GulAManA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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