A major bottleneck in metabolomics is the annotation of a molecular formula as a first step to a tentative structure assignment of known and unknown metabolites. The direct observation of an isotopic fine structure (IFS) provides the ability to confidently assign an unknown's molecular formula out of a complex mass spectrum. However, the majority of mass spectrometers deployed for metabolomic studies do not have sufficient resolving power and high-fidelity isotope ratios in the mass range of interest to determine molecular formulas from IFS data. To increase the number of unknowns for which IFS can be determined, a segmented "boxcar" approach using a selection quadrupole as a broadband mass filter is used. In this longer, enhanced dynamic range discovery experiment, selected ions in a specific mass range are accumulated before detection by the analyzer cell. The mass filter window is then moved across the entire mass range resulting in a composite mass spectrum covering the m/z range of interest for phenomics research. The effectiveness of the FIA-CASI-FTMS workflow utilizing IFS for molecular formula assignment is realized with the implementation of the dynamically harmonized cell, which distinguishes the approach from other segmented workflows because of the analytical properties of the cell. The discovery approach was applied to a human plasma sample to confidently assign an unknown molecular formula as part of the quest to illuminate its metabolic "dark matter" via high-fidelity IFS ratio determinations. The FIA-CASI-FTMS workflow showed a 2.6-fold increase in both matching with the Human Metabolome Database and an increase in the IFS pattern.

中文翻译：

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用于发现代谢组学中精确质量分析的增强同位素精细结构方法：FIA-CASI-FTMS。

代谢组学的一个主要瓶颈是分子式的注释，这是对已知和未知代谢物进行初步结构分配的第一步。同位素精细结构 (IFS) 的直接观察提供了从复杂质谱中可靠地确定未知分子式的能力。然而，用于代谢组学研究的大多数质谱仪在感兴趣的质量范围内没有足够的分辨率和高保真同位素比，无法根据 IFS 数据确定分子式。为了增加可确定 IFS 的未知数，使用了使用选择四极杆作为宽带质量过滤器的分段“箱车”方法。在这个更长的、增强的动态范围发现实验中，特定质量范围内的选定离子在被分析器单元检测之前被累积。然后，质量过滤器窗口在整个质量范围内移动，从而产生一个复合质谱，覆盖了表型组学研究感兴趣的 m/z 范围。利用 IFS 进行分子式分配的 FIA-CASI-FTMS 工作流程的有效性通过动态协调单元格的实施来实现，由于单元格的分析特性，该方法将方法与其他分段工作流程区分开来。该发现方法应用于人类血浆样本，以自信地指定未知分子式，作为通过高保真 IFS 比率测定阐明其代谢“暗物质”的一部分。FIA-CASI-FTMS 工作流程显示 2。