Environmental and Biological Sciences Division Pacific Northwest National Laboratory, Richland, Washington 99352, United States.
J Am Soc Mass Spectrom. 2021 Mar 3;32(3):648-652. doi: 10.1021/jasms.0c00251. Epub 2020 Dec 1.
Many organisms process carbon and other nutrients to generate energy through aerobic respiration where organic carbon compounds are broken down and oxygen is consumed, producing carbon dioxide and water. Respiration is indicative of active metabolism, and respiration rates are proportional to the amount of living biomass in an ecosystem. Although there are many methods for measuring respiration rates in the laboratory, current systems, such as infrared gas analyzers, are limited in their ability to independently resolve isotopomer fluxes across a range of relevant gases including both CO and O in real-time. Therefore, monitoring of biological respiration in real time under controlled laboratory conditions would enable better understanding of cellular physiology. To address this challenge, we developed a real time mass spectrometry (RTMS) manifold that simultaneously measures production and consumption of multiple gases and their isotopologues in seconds with the speed and sensitivity necessary to characterize rapidly changing respiration events as they occur. This universal manifold can be fitted to a variety of instruments and affords the same analytical precision and accuracy of the instrument while allowing for the real time measurements. Here, we paired the manifold to a single quad MS with an electron impact (EI) source operated in scan mode to detect extracted target gases by their respective masses (e.g., CO at mass 44, CO at 45). We demonstrated applicability of the RTMS instrument to different biological ecosystems (bacterial cultures, plants, and soil), and in all cases, we were able to detect simultaneous and rapid measurements of multiple gases in real time, providing novel insights into complex respiratory metabolism and the influence of biological and environmental factors.
许多生物通过有氧呼吸来处理碳和其他营养物质以产生能量，在有氧呼吸中，有机碳化合物被分解，氧气被消耗，产生二氧化碳和水。呼吸是活跃代谢的指标，呼吸速率与生态系统中活生物质的量成正比。虽然有许多在实验室中测量呼吸速率的方法，但目前的系统，如红外气体分析仪，在独立解析一系列相关气体（包括 CO 和 O）的同位素通量方面能力有限，无法实时进行。因此，在受控的实验室条件下实时监测生物呼吸将有助于更好地理解细胞生理学。为了解决这个挑战，我们开发了一种实时质谱（RTMS）歧管，它可以在几秒钟内同时测量多种气体及其同位素的产生和消耗，其速度和灵敏度足以在呼吸事件发生时实时表征其快速变化。这种通用歧管可以适配各种仪器，并在允许实时测量的同时保持与仪器相同的分析精度和准确性。在这里，我们将歧管与具有电子冲击（EI）源的单四极杆 MS 配对，以扫描模式操作，通过各自的质量来检测提取的目标气体（例如，质量为 44 的 CO，质量为 45 的 CO）。我们证明了 RTMS 仪器适用于不同的生物生态系统（细菌培养物、植物和土壤），在所有情况下，我们都能够实时检测多种气体的同时快速测量，为复杂的呼吸代谢以及生物和环境因素的影响提供了新的见解。
