Nanospray Desorption Electrospray Ionization (Nano-DESI) Mass Spectrometry Imaging with High Ion Mobility Resolution

Untargeted separationof isomeric and isobaric species in massspectrometry imaging (MSI) is challenging. The combination of ionmobility spectrometry (IMS) with MSI has emerged as an effective strategyfor differentiating isomeric and isobaric species, which substantiallyenhances the molecular coverage and specificity of MSI experiments.In this study, we have implemented nanospray desorption electrosprayionization (nano-DESI) MSI on a trapped ion mobility spectrometry(TIMS) mass spectrometer. A new nano-DESI source was constructed,and a specially designed inlet extension was fabricated to accommodatethe new source. The nano-DESI-TIMS-MSI platform was evaluated by imagingmouse brain tissue sections. We achieved high ion mobility resolutionby utilizing three narrow mobility scan windows that covered the majorityof the lipid molecules. Notably, the mobility resolution reachingup to 300 in this study is much higher than the resolution obtainedin our previous study using drift tube IMS. High-resolution TIMS successfullyseparated lipid isomers and isobars, revealing their distinct localizationsin tissue samples. Our results further demonstrate the power of high-mobility-resolutionIMS for unraveling the complexity of biomolecular mixtures analyzedin MSI experiments.

Automated summary

Untargeted separation of isomeric and isobaric species in mass spectrometry imaging is challenging. This study implemented nano-DESI MSI on a TIMS mass spectrometer and achieved high ion mobility resolution, successfully separating lipid isomers and isobars and revealing their distinct localizations in tissue samples. The results demonstrate the power of high-mobility-resolution IMS for analyzing complex biomolecular mixtures in MSI experiments.