Ion Mobility Derived Collision Cross Sections to Support Metabolomics Applications

Abstract

Metabolomics is a rapidly evolving analytical approach in life and health sciences. The structural elucidation of the metabolites of interest remains a major analytical challenge in the metabolomics workflow. Here, we investigate the use of ion mobility as a tool to aid metabolite identification. Ion mobility allows for the measurement of the rotationally averaged collision cross-section (CCS), which gives information about the ionic shape of a molecule in the gas phase. We measured the CCSs of 125 common metabolites using traveling-wave ion mobility-mass spectrometry (TW-IM-MS). CCS measurements were highly reproducible on instruments located in three independent laboratories (RSD < 5% for 99%). We also determined the reproducibility of CCS measurements in various biological matrixes including urine, plasma, platelets, and red blood cells using ultra performance liquid chromatography (UPLC) coupled with TW-IM-MS. The mean RSD was < 2% for 97% of the CCS values, compared to 80% of retention times. Finally, as proof of concept, we used UPLC–TW-IM-MS to compare the cellular metabolome of epithelial and mesenchymal cells, an in vitro model used to study cancer development. Experimentally determined and computationally derived CCS values were used as orthogonal analytical parameters in combination with retention time and accurate mass information to confirm the identity of key metabolites potentially involved in cancer. Thus, our results indicate that adding CCS data to searchable databases and to routine metabolomics workflows will increase the identification confidence compared to traditional analytical approaches.

Enhanced lipid isomer separation in human plasma using reversed-phase UPLC with ion-mobility/high-resolution MS detection

“…Using ion mobility, collisional crosssections (CCSs) of ions can be calculated, and besides accurate mass, fragmentation information, and retention time (Rt), these CCS values can be added to a searchable library for a routine work fl ow to increase the identifi cation confi dence. It was recently demonstrated that the CCS values are highly reproducible even using different machines ( 35 ).…”

Challenges in Separations of Proteins and Small Biomolecules and the Role of Modern Mass Spectroscopy Tools for Solving Them, as Well as Bypassing Them, in Structural Analytical Studies of Complex Biomolecular Mixtures

“…Instead, a brief overview of the utility of separation techniques in metabolomic analyses and challenges in related LC-MS analyses. In Table 5, a partial dataset of a typical metabolomic experiment is shown [73]. Metabolomic experiments are typically conducted in LC-IMS (ion mobility mass spectroscopy) setting, because collision cross-section (CCS) values are used together with m/z and R t data for reliable identification of metabolites from various databases (see Table 5).…”

“…The most commonly used databases are HMDB (Human Metabolome Database) [74], METLIN [75] and in-house databases. Typical tolerance parameters are ∆ppm < 10, R t range < 0.3 s and CCS < 5 Å 2 [73].…”

Ion Mobility in Clinical Analysis: Current Progress and Future Perspectives

“…More recently, LC-TWIMS-MS allowed resolution of coeluting lipid isomers in human plasma extracts, showing the potential for this technique to improve clinical LC-MS methods both qualitatively and quantitatively (68 ). Collection of ion mobility-derived CCS values can further improve lipidomics specificity, especially with complex biological samples or when performing MALDI imaging studies that offer no chromatographic separation (69 ). Beyond commonly analyzed compounds such as carbohydrates and lipids, several other clinically relevant compound classes have been analyzed with IMS.…”