Unraveling structural conundrum of organic nitrogen in soil and sediment organic matter using advanced solid-state NMR: insights into formation mechanisms of stabilized nitrogen

智力优势。氮（N）循环是自然界中涉及氮和含氮化合物转化的地球化学循环。氮对许多生物过程至关重要，对地球上的任何生命都至关重要。例如，氮是蛋白质、氨基酸的组成部分之一，也是构成所有生命遗传密码的碱基的关键组成部分，如DNA和RNA。因此，氮循环是地球化学中最重要的课题之一，了解氮循环有助于控制自然界和自然界。s N平衡。土壤或沉积物中的氮大部分是有机氮。常规的15 N交叉极化/魔角旋转技术已广泛应用于土壤/沉积物有机质（SOM）中有机氮的研究，但该技术固有的缺陷限制了对有机氮结构的深入了解。该项目的目标是：a）开发一种改进的先进的固态协议，用于调查有机氮的形式在SOM中，B）调查不同的有机氮的形式的分布，特别是在SOM中的杂环N的存在和丰度，并可能c）使用新的和先进的固态NMR技术调查生物难降解的N的形成的机制。我们将主要关注但不限于两个样品，IHSS Pony Lake（南极洲）参考样品和一个硬沥青岩，这两个样品都含有相对较高的N。 通过使用适当的模型化合物以最大化交叉极化来改进常规的15 N交叉极化/魔角旋转（CP/MAS）;开发一些15 N光谱编辑技术以选择特定的官能团，并使用饱和脉冲诱导的偶极交换与再耦合来分析共价结合的N。将使用这些改进的NMR技术检查不同形式的有机N的相对比例。杂环N的存在和丰度，这可能被低估的常规15 N CP/MAS，也将使用这些技术进行研究。该项目有望在理解SOM中有机氮的性质方面取得重大进展。它将揭示不同形态有机氮的相对比例的更准确的信息。新的或改进的核磁共振技术表征有机质中的有机氮将为我们提供一个重要的工具，研究有机质中的有机氮，奠定了基础，显着提高氮的地球化学的理解。本计画将培养一位研究生应用、改良及发展先进的固态核磁共振技术于地球化学。它还将影响到公共宣传计划的内容以及大学和研究生一级的教育宣传。更广泛的影响。本计画将培养一位研究生应用、改良及发展先进的固态核磁共振技术于地球化学。它还将影响到公共宣传计划的内容以及大学和研究生一级的教育宣传。

Intellectual Merit. The nitrogen (N) cycle is a biogeochemical cycle involving the transformation of nitrogen and nitrogen-containing compounds in nature. Nitrogen is essential for many biological processes and is crucial for any life on earth. For example, nitrogen is one of the building blocks of proteins, amino acids, and is a key component of the bases that make up the genetic code of all life, such as DNA and RNA. Therefore, N cycle is one of the most important topics in biogeochemistry and understanding the N cycle can help control both the nature?s N balance. Most of N in soils or sediments is organic. While routine 15N cross polarization/magic angle spinning technique has been extensively applied to the investigations of organic N in soil/sediment organic matter (SOM), the inherent drawbacks of this technique have so far provided limited insight into the structures of organic N. The objectives of the project are: a) to develop an improved advanced solid-state protocol for investigating organic N forms in SOM, b) to investigate the distributions of different organic N forms and in particular the presence and abundance of heterocyclic N in SOM, and possibly c) to investigate the mechanisms underlying the formation of biologically refractory N using the new and advanced solid-state NMR techniques. We will primarily focus on, but not are limited to, two samples, an IHSS Pony Lake (Antarctica) Reference and a gilsonite, both of which contain relatively high N.The work on the new and improved advanced solid-state NMR techniques will include improvement of routine 15N cross polarization/magic angle spinning (CP/MAS) by using appropriate model compounds to maximize cross polarization; development of some 15N spectral-editing techniques to select specific functional groups and analysis of covalently-bound N using saturation-pulse induced dipolar exchange with recoupling. The relative proportions of different forms of organic N will be examined using these improved NMR techniques. The presence and abundance of heterocyclic N, which could be underestimated by routine 15N CP/MAS, will also be investigated using these techniques. The project promises significant advances in understanding the nature of organic N in SOM. It will reveal more accurate information on the relative proportions of different forms of organic N. The new or improved NMR techniques for characterizing organic N in SOM will provide us with a critical tool for research on organic N in SOM, laying the foundations for a significantly improved understanding of nitrogen biogeochemistry.Broader Impacts. This project will train a graduate student in applying, improving and developing advanced solid-state NMR techniques for biogeochemistry. It will also influence the content of planned public outreach and educational outreach at the college and graduate levels by the PI. Broader Impacts. This project will train a graduate student in applying, improving and developing advanced solid-state NMR techniques for biogeochemistry. It will also influence the content of planned public outreach and educational outreach at the college and graduate levels by the PI.