Recent additions and access to a multidimensional lipidomic database containing liquid chromatography, ion mobility spectrometry, and tandem mass spectrometry information

Abstract

The importance of lipids in biology continues to grow with their recent linkages to more diseases and conditions, microbiome fluctuations, and environmental exposures. These associations have motivated researchers to evaluate lipidomic changes in numerous matrices and studies. Lipidomic analyses, however, present numerous challenges as lipid species have broad chemistries that require different extraction methods and instrumental analyses to evaluate and separate their many isomers and isobars. Increasing knowledge about different lipid characteristics is therefore crucial for improving their separation and identification. Here, we present a multidimensional database for lipids analyzed on a platform combining reversed-phase liquid chromatography, drift tube ion mobility spectrometry, collision-induced dissociation, and mass spectrometry (RPLC-DTIMS-CID-MS). This platform and the different separation characteristics it provides enables more confident lipid annotations when compared to traditional tandem mass spectrometry platforms, especially when analyzing highly isomeric molecules such as lipids. This database expands on our previous publication containing only human plasma and bronchoalveolar lavage fluid lipids and provides experimental RPLC retention times, IMS collision cross section (CCS) values, and m/z information for 877 unique lipids from additional biofluids and tissues. Specifically, the database contains 1504 precursor [M + H]⁺, [M + NH₄]⁺, [M + Na]⁺, [M-H]^-, [M-2H]^2-, [M + HCOO]^-, and [M + CH₃COO]^- ion species and their associated CID fragments which are commonly targeted in clinical and environmental studies, in addition to being present in the chloroform layer of Folch extractions. Furthermore, this multidimensional RPLC-DTIMS-CID-MS database spans 5 lipid categories (fatty acids, sterols, sphingolipids, glycerolipids, and glycerophospholipids) and 24 lipid classes. We have also created a webpage (tarheels.live/bakerlab/databases/) to enhance the accessibility of this resource which will be populated regularly with new lipids as we identify additional species and integrate novel standards.

Keywords: Collision cross section; Database; Ion mobility spectrometry; Lipidomics; Lipids; Mass spectrometry; Reverse phase liquid chromatography (RPLC).

Fig. 1

RPLC-IMS-CID-MS lipid database information. This database contains 1504 precursor ion species from 877 unique lipids from five lipid categories (pie chart) and 24 classes abbreviated in the stacked bar graph. Class abbreviations are defined in the “Abbreviation” section of the manuscript. Ion species are given for both ionization modes with positive mode species in magenta and negative mode in purple

Fig. 2

Collision cross section (CCS) versus m/z trendlines of all the unique lipids in the database. Lipids species in both A negative ionization mode and B positive mode illustrate unique lipid class relationships