Description of Dissolved Organic Matter Transformational Networks at the Molecular Level
Description of Dissolved Organic Matter Transformational Networks at the Molecular Level
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DOI：
10.1021/acs.est.2c04715
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发表时间：
2023-02-01
影响因子：
11.4
通讯作者：
Fernandez-Lima，Francisco
中科院分区：
文献类型：
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作者：
Leyva，Dennys;Tariq，Muhammad Usman;Fernandez-Lima，Francisco
溶解有机物(DOM)是全球碳循环的重要组成部分。解读DOM的结构足迹是在机械水平上理解其生物地球化学转化的关键。尽管大量的研究提高了我们对DOM化学组成的了解，但它的三维图像在很大程度上仍然没有被揭示。在这项工作中，我们使用高分辨率迁移率和超高分辨率傅立叶变换离子回旋共振串联质谱仪(FT-ICR MS/MS)比较了来自三个不同淡水生态系统的四个固相萃取(SPE)DOM样品。通过连续积累选定的离子碰撞诱导解离(CASI-CID)FT-ICR MS/MS，根据名义质量水平的中性损失确定了结构家族。对结构家族的比较表明，该样本组的结构足迹不同。用Cytoscape软件进行的结构家族表示显示了DOM样本之间的特征聚集模式，从而证实了结构水平上的明显差异(四个样本中只有10%是共同的)。中性损失功能水平的分析表明，水合作用和羧化作用是三个生态系统中普遍存在的转化过程。相反，由于上游木质素的广泛生物降解，涉及甲氧基部分的转化机制可能在河口系统中受到限制。在结构家族描述中包括同分异构体含量(在化学式水平上的迁移率测量)，表明可能存在其他转化途径和/或来源变化，并解释了观察到的差异。虽然需要评估更多和不同类型的DOM样品的结构特征并将其添加到这个数据库中，但这里提供的结果表明，Graph-DOM是一个强大的工具，能够提供关于DOM化学足迹的新信息，其基础是通过碎裂路径和碰撞截面产生的前体分子的结构互连。
Dissolved Organic Matter (DOM) is an important component of the global carbon cycle. Unscrambling the structural footprint of DOM is key to understand its biogeochemical transformations at the mechanistic level. Although numerous studies have improved our knowledge of DOM chemical makeup, its three-dimensional picture remains largely unrevealed. In this work, we compare four solid phase extracted (SPE) DOM samples from three different freshwater ecosystems using high resolution mobility and ultrahigh-resolution Fourier transform ion cyclotron resonance tandem mass spectrometry (FT-ICR MS/MS). Structural families were identified based on neutral losses at the level of nominal mass using continuous accumulation of selected ions-collision induced dissociation (CASI-CID)FT-ICR MS/MS. Comparison of the structural families indicated dissimilarities in the structural footprint of this sample set. The structural family representation using Cytoscape software revealed characteristic clustering patterns among the DOM samples, thus confirming clear differences at the structural level (Only 10% is common across the four samples.). The analysis at the level of neutral loss-based functionalities suggests that hydration and carboxylation are ubiquitous transformational processes across the three ecosystems. In contrast, transformation mechanisms involving methoxy moieties may be constrained in estuarine systems due to extensive upstream lignin biodegradation. The inclusion of the isomeric content (mobility measurements at the level of chemical formula) in the structural family description suggests that additional transformation pathways and/or source variations are possible and account for the dissimilarities observed. While the structural character of more and diverse types of DOM samples needs to be assessed and added to this database, the results presented here demonstrate that Graph-DOM is a powerful tool capable of providing novel information on the DOM chemical footprint, based on structural interconnections of precursor molecules generated by fragmentation pathways and collisional cross sections.