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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Comparison of the Ca2+ complexing properties of isosaccharinate and gluconate - is gluconate a reliable structural and functional model of isosaccharinate?
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Comparison of the Ca2+ complexing properties of isosaccharinate and gluconate - is gluconate a reliable structural and functional model of isosaccharinate?

机译：对异升糖和葡萄糖酸盐的Ca2 +络合性质的比较 - 葡萄糖酸盐是异糖素的可靠结构和功能模型吗？

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摘要

The calcium complexation and acid-base properties of alpha-D-isosaccharinate (Isa(-)) in neutral and in (hyper) alkaline solutions have been investigated via potentiometric titrations, multinuclear NMR, ESI-MS and quantum chemical calculations. Isa- is the primary alkaline degradation product of cellulose, and may be present in radioactive waste repositories and therefore, it could contribute to the mobilization of radioactive nuclei. Because of its limited availability, D-gluconate (Gluc(-)) is commonly used as a structural and functional model of Isa-. Therefore, the thermodynamic and structural data obtained for Isa- were compared with those of Gluc-. The formation constants of the CaIsa(+) and CaGluc(+) complexes present in neutral solutions are practically identical, but the binding sites are in different positions and the CaIsa(2)(0) solution species cannot be detected. The stepwise formation constant of the CaIsaH(-1)(0) complex (forming in alkaline medium) is somewhat larger than that of CaGlucH(-1)(0), which is in line with the observation that IsaH(-1)(2-) is a stronger base than GlucH(-1)(2-). The most striking difference is that, unlike Gluc(-), Isa- does not form polynuclear complexes with Ca2+. The structural reason for this is that the alcoholate groups on C2 and C3 adjacent to the carboxylate moiety on Gluc(-) are able to simultaneously bind Ca2+, making the formation of polynuclear Ca-complexes possible. On Isa(-), only the alcoholate on C2 is involved, while the other one on C6 is not (supposedly for steric reasons). In conclusion, during the interactions of Gluc(-) and Isa(-) with Ca2+, differences rather than similarities prevail.
机译：通过电位滴定，多核NMR，ESI-MS和量子化学计算，研究了中性和（HEAD）碱性溶液中α-D-异升（ISA（））的钙络合和酸碱性质。 ISA-是纤维素的主要碱性降解产物，并且可能存在于放射性废物储存库中，因此，它可能有助于动员放射性核。由于其有限的可用性，D-葡萄糖酸盐（Gluc（））通常用作ISA-的结构和功能模型。因此，与ISA-与Gluc-相比获得的热力学和结构数据。中性溶液中存在的Caisa（+）和Cagluc（+）复合物的形成常数实际上是相同的，但结合位点处于不同的位置，并且不能检测到Caisa（2）（0）溶液物质。 Caisah（-1）（0）复合物（在碱性培养基中形成）的逐步形成常数略大于Cagluch（-1）（0）的略大，这与ISAH（-1）（ 2-）是比gluch（-1）（2-）的更强的基础。最引人注目的差异是，与Gluc（ - ）不同，ISA-不与CA2 +形成多核配合物。为此的结构原因是邻近Gluc（ - - ）羧酸盐部分邻近的C2和C3上的醇组能够同时结合Ca 2+，使得形成多核性Ca-配合物。在ISA（ - ）中，只有C2上的醇化物，而另一个ON C6不是（如上所述的原因）。总之，在Gluc（ - ）和ISA（ - ）与CA2 +的相互作用期间，差异而非相似性占上风。

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