Element-Selective Targeting of Nutrient Metabolites in Environmental Samples by Inductively Coupled Plasma Mass Spectrometry and Electrospray Ionization Mass Spectrometry
Element-Selective Targeting of Nutrient Metabolites in Environmental Samples by Inductively Coupled Plasma Mass Spectrometry and Electrospray Ionization Mass Spectrometry
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DOI：
10.3389/fmars.2021.630494
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发表时间：
2021-05
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影响因子：
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通讯作者：
Jingxuan Li;R. Boiteau;L. Babcock-Adams;Marianne Acker;Zhongchang Song;M. McIlvin;D. Repeta
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作者：
Jingxuan Li;R. Boiteau;L. Babcock-Adams;Marianne Acker;Zhongchang Song;M. McIlvin;D. Repeta
结合除碳、氮、氢和氧之外的元素的金属可以通过电感耦合质谱法（ICPMS）选择性地检测。当与色谱分离和常规电喷雾电离质谱（ESIMS）并行使用时，ICPMS允许分析人员快速发现，表征和鉴定携带营养元素（P，S，痕量金属;“营养代谢物”）的目标代谢物，这对微生物生物地球化学循环的研究特别感兴趣。该方法已被应用于海洋中铁载体和其他痕量金属有机配体的研究。最初的方法使用质量搜索算法，该算法依赖于铁、铜和镍的稳定同位素体的比率，将ESIMS收集的质谱分配给ICPMS检测到的携带这些元素的代谢物。然而，虽然基于同位素的质量分配算法在表征包含一些痕量金属的代谢物方面非常成功，但它们没有实现ICPMS/ESIMS方法的全部潜力，因为它们不能用于分配具有单一同位素元素或稳定同位素比例未知的元素的代谢物的分子离子。在这里，我们报告了一个修订后的ICPMS/ESIMS方法，它结合了一些变化的仪器硬件的配置，提高了灵敏度的方法的一个因素4-5，并允许更准确的定量代谢物。我们还描述了一套新的质量搜索算法，可以找到和表征携带单一同位素元素的代谢物。我们使用新的方法来确定在实验室培养的弧菌cyclitrophicus和海水样品收集在北太平洋的铁载体，并分配分子离子的单一同位素钴和碘营养代谢产物的提取物的实验室培养的海洋蓝藻Prochorococcus MIT 9215。
Metabolites that incorporate elements other than carbon, nitrogen, hydrogen and oxygen can be selectively detected by inductively coupled mass spectrometry (ICPMS). When used in parallel with chromatographic separations and conventional electrospray ionization mass spectrometry (ESIMS), ICPMS allows the analyst to quickly find, characterize and identify target metabolites that carry nutrient elements (P, S, trace metals; “nutrient metabolites”), which are of particular interest to investigations of microbial biogeochemical cycles. This approach has been applied to the study of siderophores and other trace metal organic ligands in the ocean. The original method used mass search algorithms that relied on the ratio of stable isotopologues of iron, copper and nickel to assign mass spectra collected by ESIMS to metabolites carrying these elements detected by ICPMS. However, while isotopologue-based mass assignment algorithms were highly successful in characterizing metabolites that incorporate some trace metals, they do not realize the whole potential of the ICPMS/ESIMS approach as they cannot be used to assign the molecular ions of metabolites with monoisotopic elements or elements for which the ratio of stable isotopes is not known. Here we report a revised ICPMS/ESIMS method that incorporates a number of changes to the configuration of instrument hardware that improves sensitivity of the method by a factor of 4–5, and allows for more accurate quantitation of metabolites. We also describe a new suite of mass search algorithms that can find and characterize metabolites that carry monoisotopic elements. We used the new method to identify siderophores in a laboratory culture of Vibrio cyclitrophicus and a seawater sample collected in the North Pacific Ocean, and to assign molecular ions to monoisotopic cobalt and iodine nutrient metabolites in extracts of a laboratory culture of the marine cyanobacterium Prochorococcus MIT9215.