Nordström Anders, Want Elizabeth, Northen Trent, Lehtiö Janne, Siuzdak Gary
Department of Molecular Biology and The Center for Mass Spectrometry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla California 92037, USA.
Anal Chem. 2008 Jan 15;80(2):421-9. doi: 10.1021/ac701982e. Epub 2007 Dec 18.
A multiple ionization mass spectrometry strategy is presented based on the analysis of human serum extracts. Chromatographic separation was interfaced inline with the atmospheric pressure ionization techniques electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) in both positive (+) and negative (-) ionization modes. Furthermore, surface-based matrix-assisted laser desorption/ionization (MALDI) and desorption ionization on silicon (DIOS) mass spectrometry were also integrated with the separation through fraction collection and offline mass spectrometry. Processing of raw data using the XCMS software resulted in time-aligned ion features, which are defined as a unique m/z at a unique retention time. The ion feature lists obtained through LC-MS with ESI and APCI interfaces in both +/- ionization modes were compared, and unique ion tables were generated. Nonredundant, unique ion features, were defined as mass numbers for which no mass numbers corresponding to M + H, M - H, or M + Na were observed in the other ionization methods at the same retention time. Analysis of the extracted serum using ESI for both (+) and (-) ions resulted in >90% additional unique ions being detected in the (-) ESI mode. Complementing the ESI analysis with APCI resulted in an additional approximately 20% increase in unique ions. Finally, ESI/APCI ionization was combined with fraction collection and offline-MALDI and DIOS mass spectrometry. The parts of the total ion current chromatograms in the LC-MS acquired data corresponding to collected fractions were summed, and m/z lists were compiled and compared to the m/z lists obtained from the DIOS/MALDI spectra. It was observed that, for each fraction, DIOS accounted for approximately 50% of the unique ions detected. These results suggest that true global metabolomics will require multiple ionization technologies to address the inherent metabolite diversity and therefore the complexity in and of metabolomics studies.
基于对人血清提取物的分析，提出了一种多电离质谱策略。色谱分离与大气压电离技术电喷雾电离（ESI）和大气压化学电离（APCI）在线联用，采用正（+）和负（-）电离模式。此外，基于表面的基质辅助激光解吸/电离（MALDI）和硅上解吸电离（DIOS）质谱也通过馏分收集和离线质谱与分离相结合。使用XCMS软件处理原始数据产生了时间对齐的离子特征，其定义为在唯一保留时间的唯一质荷比。比较了在+/-电离模式下通过带有ESI和APCI接口的LC-MS获得的离子特征列表，并生成了唯一离子表。非冗余的唯一离子特征定义为在相同保留时间的其他电离方法中未观察到对应于M + H、M - H或M + Na的质荷比的质量数。对提取的血清进行ESI正离子和负离子分析，结果在负离子ESI模式下检测到的独特离子增加了90%以上。用APCI补充ESI分析，独特离子又增加了约20%。最后，将ESI/APCI电离与馏分收集以及离线MALDI和DIOS质谱相结合。将LC-MS采集数据中与收集馏分相对应的总离子流色谱图部分进行求和，编制质荷比列表，并与从DIOS/MALDI光谱获得的质荷比列表进行比较。观察到，对于每个馏分，DIOS占检测到的独特离子的约50%。这些结果表明，真正的全代谢组学将需要多种电离技术来应对固有的代谢物多样性，从而解决代谢组学研究中的复杂性问题。
