U.S. Department of Energy

Pacific Northwest National Laboratory

Development of a SLIM SUPER TWIM-MS Application Platform for Multi-Omics

Introduction 

Structures for lossless ion manipulations (SLIM) have been recently developed for traveling wave ion mobility (TWIM) experiments with a range of capabilities including serpentine long path separations (>100 m), trapping of large ion populations (>109 ions), and compression ratio ion mobility programming (CRIMP) for increased sensitivity. These capabilities have demonstrated remarkable improvements in separation of isomeric lipids, peptides, and metabolites. 
In this work, we evaluate the development of a SLIM TWIM-MS platform specifically designed for application in multi-omic analysis of complex biological samples. This system is designed to overcome challenges in conventional IM-MS analysis, including the ability to precisely target a narrow mobility window for extended analysis. This presentation will highlight the hardware and software innovations required for such experiments.

Methods 

A homebuilt SLIM system, coupled with Agilent 6538 QTOF-MS, is evaluated for its capabilities in ultrahigh resolution IM separations. The custom SLIM utilizes four different traveling wave (TW) inputs, designed for multiple accumulation regions and peak compression. Switches are placed to allow multiple passes of ions within a targeted mobility range and to control trapping events. Instrument control and data acquisition are performed with in-house developed software. Experiments involve a one pass (12.3 m path length) prescan to obtain initial drift time information and mass spectra. A targeted range is then selected for further analysis, which can include multiple separation passes for improved resolution followed by compression to reduce diffusional broadening and prevent excessive narrowing of the mobility range studied.

Preliminary Data 

The SLIM IM-MS applications system is evaluated for its capabilities in the analysis of complex mixtures, specifically for accumulation of a large initial ion population, concentration of a targeted mobility range, and long path separations providing improved resolution. 
Acquisition of a prescan (small ion population, single pass separation) produces initial drift time information and mass spectra to define regions of interest. A user-defined experiment (i.e., number of passes, compression, etc.) then begins with accumulation of a large initial ion population in a 6 m region; preliminary experiments have demonstrated SLIM accumulation of >109 ions using low-amplitude TWs. The ability to accumulate such a large ion population provides increased dynamic range for the analysis of complex mixtures, in which key components may be present at low concentrations. This SLIM-based trapping capacity overcomes the challenge of limited ion capacity encountered in conventional pulsed IM instrumentation. 
The in-house developed software can then control TW parameters and switches for precision control of trapping, cycling, and compression as per the defined experiment. Single pass SLIM (performed with a similar SLIM design having a 13 m separation path) has demonstrated dramatic improvements in resolution with increased path length for isomeric cis/trans lipids, leucine/isoleucine-containing peptides, reverse sequence peptides, and metabolites such as sugars. Multiple pass separations, with path lengths in excess of >100 m, provide further improvements in resolution and the detection of previously unobserved conformers. In addition, CRIMP has demonstrated increased signal intensity by merging several adjacent traveling traps. This reduces the effects of diffusional broadening that occur with long path separations and improves sensitivity for trace components in mixtures.
These capabilities are integrated into a  multi-pass serpentine ultra-long path for extended resolution (SUPER) SLIM TWIM-MS system that will be evaluated for analysis of complex biological samples with a multi-omic approach (e.g., metabolomics, proteomics, lipidomics).

Novel Aspect

First use of SLIM TWIM-MS application platform for multi-omic analysis of complex mixtures

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