Automated molecular formula determination by tandem mass spectrometry (MS/MS)

Abstract

Automated software was developed to analyze the molecular formula of organic molecules and peptides based on high-resolution MS/MS spectroscopic data. The software was validated with 96 compounds including a few small peptides in the mass range of 138-1569 Da containing the elements carbon, hydrogen, nitrogen and oxygen. A Micromass Waters Q-TOF Ultima Global mass spectrometer was used to measure the molecular masses of precursor and fragment ions. Our software assigned correct molecular formulas for 91 compounds, incorrect molecular formulas for 3 compounds, and no molecular formula for 2 compounds. The obtained 95% success rate indicates high reliability of the software. The mass accuracy of the precursor ion and the fragment ions, which is critical for the success of the analysis, was high, i.e. the accuracy and the precision of 850 data were 0.0012 Da and 0.0016 Da, respectively. For the precursor and fragment ions below 500 Da, 60% and 90% of the data showed accuracy within #0.001 Da and #0.002 Da, respectively. The precursor and fragment ions above 500 Da showed slightly lower accuracy, i.e. 40% and 70% of them showed accuracy within #0.001 Da and #0.002 Da, respectively. The molecular formulas of the precursor and the fragments were further used to analyze possible mass spectrometric fragmentation pathways, which would be a powerful tool in structural analysis and identification of small molecules. The method is valuable in the rapid screening and identification of small molecules such as the dereplication of natural products, characterization of drug metabolites, and identification of small peptide fragments in proteomics. The analysis was also extended to compounds that contain a chlorine or bromine atom.

Advances in structure elucidation of small molecules using mass spectrometry

“…Another approach used accurate masses from MS/MS product ions during the investigation of fragmentation processes of some natural products [189, 190]. Sirius Starburst [183] is a freely available software that combines MS/MS fragment and element ratio information with elemental composition determinations.…”

Computational mass spectrometry for small molecules

“…Tandem or multiple-stage MS can give additional information about the molecular formula of the intact compound: We can exclude all molecular formulas of the compound if, for one of the fragment (product ion) peaks, we cannot find a sub-formula that explains this peak [143][146]. Unfortunately, such approaches are susceptible to noisy data.…”

New Dereplication Method Applied to NMR-Based Metabolomics on DifferentFusariumSpecies Isolated from Rhizosphere ofSenna spectabilis

“…1,2 Classic dereplication methods use biological screening processes followed by databases queries in order to evaluate the data obtained on the state of the art technologies and hyphenated protocols, such as liquid chromatography coupled to a diode array detector with high-resolution mass spectrometry (LC-DAD-HRMS) and LC-DAD-NMR (nuclear magnetic resonance), LC-DAD-MS/MS (tandem mass spectrometry). [4][5][6][7][8] More recently, several other tools have been developed, aiming to achieve efficient and more factual paths for metabolite elucidation through analysis of high-resolution metabolite profiling. 7 Among the enhancements in the dereplication process, we highlight 2D 13 C NMR, high throughput screening (HTS), bioinformatics, MS/MS molecular networking applied to the omics sciences (genomics, proteomics, metabolomics), as well as chemometrics and other statistical tools, such as partial least-square discriminant analysis (PLS-DA), statistical total correlation spectroscopy (STOCSY).…”