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Topic: MS DIAL/Lipidomics-confusing annotation & weird spectra pattern in TG species (Read 55 times) previous topic - next topic

MS DIAL/Lipidomics-confusing annotation & weird spectra pattern in TG species

Hi everyone,

Thank you very much for stopping by and reading my confusions!

I recently applied MS-DIAL 5.1.230912 to process my untargeted lipidomics data (.wiff2 files acquired by UHPLC-ZenoTOF 7600 system under the mode of information dependent acquisition), with a major focus on lipid droplet-associated lipid species (MAG, DAG, TAG, CE etc.).

As I went through the results of my pooled QC samples, I noticed a considerable amount of identified lipid species were annotated with the prefix "w/o MS2", yet the MS2 spectra information of such species could readlily be exported and clearly documented in the alignment results (Could this be the cue suggesting my mass spectrometry acquisition parameters were working fine?). It confused me why MS-DIAL was labeling these lipid species with "w/o MS2" prefixes when their MS2 spectra information were intact.

Subsequently, I filtered TG species (by the Ontology filter in the ion table) to have a more careful look on the "w/o MS2" TGs. As I looked through the "Measured vs Reference" spectra panel on the right (I assume the panel displayed MS1 spectra since I could see the m/z of the precursor ion), I found that a majority of the "w/o MS2" TGs all had a weird MS1 product ion peak that usually occupied 100% of peak relative abundance, with the m/z ratio of 59.06. However, for those TG species that matched reference spectra, the m/z 59.06 peak could no longer be prominently observed (Please check the attachment picture for details). I wonder what was the actual chemical formula this specific product ion, and whether the appearance of this product ion indicated/represented the existence of a specific category of lipid (it can represent TG or other lipid classes).

Thanks again for your time and patience, I'm very much welcome with your inspirational reply and advice!

 

Re: MS DIAL/Lipidomics-confusing annotation & weird spectra pattern in TG species

Reply #1
Further information: the m/z 59.06 peak were more frequently observed in TG species with the [M+Na+] adduct ion. But it could also be observed in [M+NH4+] TG species. So far I cannot exclude the contribution of adduct type in promoting the production of the m/z 59.06 product ion.