Ruttkies Christoph, Schymanski Emma L, Strehmel Nadine, Hollender Juliane, Neumann Steffen, Williams Antony J, Krauss Martin
Department of Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120, Halle, Germany.
Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, 6 avenue du Swing, 4367, Belvaux, Luxembourg.
Anal Bioanal Chem. 2019 Jul;411(19):4683-4700. doi: 10.1007/s00216-019-01885-0. Epub 2019 Jun 17.
Liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) is increasingly popular for the non-targeted exploration of complex samples, where tandem mass spectrometry (MS/MS) is used to characterize the structure of unknown compounds. However, mass spectra do not always contain sufficient information to unequivocally identify the correct structure. This study investigated how much additional information can be gained using hydrogen deuterium exchange (HDX) experiments. The exchange of "easily exchangeable" hydrogen atoms (connected to heteroatoms), with predominantly [M+D] ions in positive mode and [M-D] in negative mode was observed. To enable high-throughput processing, new scoring terms were incorporated into the in silico fragmenter MetFrag. These were initially developed on small datasets and then tested on 762 compounds of environmental interest. Pairs of spectra (normal and deuterated) were found for 593 of these substances (506 positive mode, 155 negative mode spectra). The new scoring terms resulted in 29 additional correct identifications (78 vs 49) for positive mode and an increase in top 10 rankings from 80 to 106 in negative mode. Compounds with dual functionality (polar head group, long apolar tail) exhibited dramatic retention time (RT) shifts of up to several minutes, compared with an average 0.04 min RT shift. For a smaller dataset of 80 metabolites, top 10 rankings improved from 13 to 24 (positive mode, 57 spectra) and from 14 to 31 (negative mode, 63 spectra) when including HDX information. The results of standard measurements were confirmed using targets and tentatively identified surfactant species in an environmental sample collected from the river Danube near Novi Sad (Serbia). The changes to MetFrag have been integrated into the command line version available at http://c-ruttkies.github.io/MetFrag and all resulting spectra and compounds are available in online resources and in the Electronic Supplementary Material (ESM). Graphical abstract.
液相色谱与高分辨率质谱联用（LC-HRMS）在复杂样品的非靶向分析中越来越受欢迎，其中串联质谱（MS/MS）用于表征未知化合物的结构。然而，质谱图并不总是包含足够的信息来明确鉴定正确的结构。本研究调查了使用氢氘交换（HDX）实验可以获得多少额外信息。观察到“易于交换”的氢原子（与杂原子相连）发生交换，在正模式下主要产生[M+D]离子，在负模式下产生[M-D]离子。为了实现高通量处理，新的评分项被纳入计算机辅助碎片分析工具MetFrag。这些评分项最初在小数据集上开发，然后在762种具有环境意义的化合物上进行测试。在这些物质中的593种（506个正模式，155个负模式光谱）中发现了成对的光谱（正常光谱和氘代光谱）。新的评分项在正模式下额外产生了29个正确鉴定结果（从49个增加到78个），在负模式下前10名的排名从80提高到106。与平均0.04分钟的保留时间（RT）变化相比，具有双重功能（极性头部基团、长的非极性尾部）的化合物表现出高达几分钟的显著保留时间（RT）变化。对于一个包含80种代谢物的较小数据集，当纳入HDX信息时，正模式（57个光谱）下前10名的排名从13提高到24，负模式（63个光谱）下从14提高到31。使用目标物以及在从塞尔维亚诺维萨德附近的多瑙河采集的环境样品中初步鉴定的表面活性剂种类，证实了标准测量的结果。对MetFrag的更改已集成到可从http://c-ruttkies.github.io/MetFrag获得的命令行版本中，所有生成的光谱和化合物可在在线资源以及电子补充材料（ESM）中获取。图形摘要。
