Mass Spectral Library of Acylcarnitines Derived from Human Urine

Abstract

We describe the creation of a mass spectral library of acylcarnitines and conjugated acylcarnitines from the LC–MS/MS analysis of six NIST urine reference materials. To recognize acylcarnitines, we conducted in-depth analyses of fragmentation patterns of acylcarnitines and developed a set of rules, derived from spectra in the NIST17 Tandem MS Library and those identified in urine, using the newly developed hybrid search method. Acylcarnitine tandem spectra were annotated with fragments from carnitine and acyl moieties as well as neutral loss peaks from precursors. Consensus spectra were derived from spectra having similar retention time, fragmentation pattern, and the same precursor m/z and collision energy. The library contains 157 different precursor masses, 586 unique acylcarnitines, and 4 332 acylcarnitine consensus spectra. Furthermore, from spectra that partially satisfied the fragmentation rules of acylcarnitines, we identified 125 conjugated acylcarnitines represented by 987 consensus spectra, which appear to originate from Phase II biotransformation reactions. To our knowledge, this is the first report of conjugated acylcarnitines. The mass spectra provided by this work may be useful for clinical screening of acylcarnitines as well as for studying relationships among fragmentation patterns, collision energies, structures, and retention times of acylcarnitines. Further, these methods are extensible to other classes of metabolites.

Open Access Repository-Scale Propagated Nearest Neighbor Suspect Spectral Library for Untargeted Metabolomics

“…Although close in value, based on accurate mass defects, the observed mass difference does not correspond to a loss of C (12.000 Da), but rather a combination that corresponds to the loss of C 2 H 2 and gain of O. As the typical carnitine fragmentation pattern is conserved, 13 we can determine that these changes occur in the fatty acid portion of the molecule, and thus, that this is likely a hydroxybutanoic acid carnitine derivative. Additionally, we can observe a characteristic 3-hydroxy fragment ion with a mass of 145.050 Da, 20 leading to the final interpretation of 3-hydroxybutyrylcarnitine.…”

“…Comparison of 1 H-13 C HSQC spectra (600 MHz, CDCl 3 ) of apratoxin A (top) and its related suspect (apratoxin A -26.015 Da; bottom). The 1 H- 13 C correlations associated with the proline ring (turquoise boxes) are notably absent in the suspect. Based on the MS/MS fragmentation pattern, the suspect also possesses one less methyl group in the polyketide portion of the molecule: this is possibly explained by an isopropyl rather than a tert-butyl group at the initiating terminus, as seen in apratoxin C.…”

“…11 These strategies can also be used to generate new libraries of MS/MS reference spectra of potentially related MS/MS annotations from analog molecules that can subsequently be reused by the community. For example, small reference spectral libraries of human milk oligosaccharides 12 and urine acylcarnitines 13 were produced using an analog searching strategy (although the user licenses of these libraries restrict their redistribution). We hypothesized that the benefits of this approach could be further increased by considering analog matches across extremely large collections of MS/MS spectra to maximize the number of relevant spectrum links that can be found.…”

Comprehensive Analysis of Tryptic Peptides Arising from Disulfide Linkages in NISTmAb and Their Use for Developing a Mass Spectral Library

“…All detectable MS1 ions in a LC–MS run were analyzed with an in-house program, NIST ProMS. 25 In a LC–MS peptide mapping analysis, each peptide ion can be detected via a set of MS1 (LC–MS) peaks with specific isotopes, abundance, and retention times (RT). This set of peaks is denoted as an ion cluster by ProMS.…”

Analytical approaches for studying oxygenated lipids in the search of potential biomarkers by LC-MS

“…Regarding SP (2OH), they have been studied in metabolic syndrome [31], AD [19], neurological outcome in cardiac arrest [32] and cholangiocarcinoma [33]. As for acyl-L-carnitines, considerable effort has been taken to develop new methods for their comprehensive profiling including CAR (3OH) and CAR (DC) species [20,21,35,38,34,39,36,37]. Various CAR (3OH) and CAR (DC) have been found to be implicated in inborn errors of metabolism [20], diabetes mellitus and metabolic syndrome [21,38,34] among others (Supporting Table S1.1).…”