Characterization of Functional Groups in Estuarine Dissolved Organic Matter by DNP-enhanced 15N and 13C Solid-State NMR,ChemPhysChem

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Characterization of Functional Groups in Estuarine Dissolved Organic Matter by DNP-enhanced 15N and 13C Solid-State NMR
ChemPhysChem ( IF 2.3 ) Pub Date : 2021-07-12 , DOI: 10.1002/cphc.202100334
Florian Venel ₁ , Hiroki Nagashima _{1,

2} , Andrew G M Rankin _{1,

3} , Christelle Anquetil ₄ , Vytautas Klimavicius _{5,

6} , Torsten Gutmann ₅ , Gerd Buntkowsky ₅ , Sylvie Derenne ₄ , Olivier Lafon _{1,

7} , Arnaud Huguet ₄ , Frédérique Pourpoint ₁

Affiliation

Estuaries are key ecosystems with unique biodiversity and are of high economic importance. Along the estuaries, variations in environmental parameters, such as salinity and light penetration, can modify the characteristics of dissolved organic matter (DOM). Nevertheless, there is still limited information about the atomic-level transformations of DOM in this ecosystem. Solid-state NMR spectroscopy provides unique insights into the nature of functional groups in DOM. A major limitation of this technique is its lack of sensivity, which results in experimental time of tens of hours for the acquisition of ¹³C NMR spectra and generally precludes the observation of ¹⁵N nuclei for DOM. We show here how the sensitivity of solid-state NMR experiments on DOM of Seine estuary can be enhanced using dynamic nuclear polarization (DNP) under magic-angle spinning. This technique allows the acquisition of ¹³C NMR spectra of these samples in few minutes, instead of hours for conventional solid-state NMR. Both conventional and DNP-enhanced ¹³C NMR spectra indicate that the ¹³C local environments in DOM are not strongly modified along the Seine estuary. Furthermore, the sensitivity gain provided by the DNP allows the detection of ¹⁵N NMR signal of DOM, in spite of the low nitrogen content. These spectra reveal that the majority of nitrogen is in the amide form in these DOM samples and show an increased disorder around these amide groups near the mouth of the Seine.

中文翻译：

通过 DNP 增强的 15N 和 13C 固态核磁共振表征河口溶解有机物中的官能团

河口是具有独特生物多样性的关键生态系统，具有很高的经济重要性。沿着河口，环境参数的变化，如盐度和光穿透，可以改变溶解有机物 (DOM) 的特征。尽管如此，关于这个生态系统中 DOM 原子级转换的信息仍然有限。固态核磁共振光谱提供了对 DOM 中官能团性质的独特见解。这种技术的一个主要限制是它缺乏灵敏度，这导致获取¹³ C NMR 光谱的实验时间为数十小时，并且通常无法观察到¹⁵DOM 的 N 个核。我们在这里展示了如何使用魔角旋转下的动态核极化 (DNP) 来提高固态 NMR 实验对塞纳河口 DOM 的灵敏度。这种技术允许在几分钟内获得这些样品的¹³ C NMR 光谱，而不是传统的固态 NMR 需要几个小时。常规和 DNP 增强的¹³ C NMR 光谱均表明，DOM 中的¹³ C 局部环境并未沿塞纳河口发生强烈变化。此外，DNP 提供的灵敏度增益允许检测¹⁵尽管氮含量低，但 DOM 的 N NMR 信号。这些光谱表明，这些 DOM 样品中的大部分氮以酰胺形式存在，并显示在塞纳河口附近这些酰胺基团周围的无序性增加。

更新日期：2021-09-15

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