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Grossert JS, Crowell AMJ, Boschi D, Lolli ML, White RL. Tandem mass spectrometry of homologous 3-hydroxyfurazan and nitrile amino acids: Analysis of cooperative interactions and fragmentation processes. JOURNAL OF MASS SPECTROMETRY : JMS 2024; 59:e5043. [PMID: 38789127 DOI: 10.1002/jms.5043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 04/23/2024] [Accepted: 05/06/2024] [Indexed: 05/26/2024]
Abstract
The assignment of structure by tandem mass spectrometry (MS/MS) relies on the interpretation of the fragmentation behavior of gas-phase ions. Mass spectra were acquired for a series of heterocyclic mimetics of acidic amino acids and a related series of nitrile amino acids. All amino acids were readily protonated or deprotonated by electrospray ionization (ESI), and distinctive fragmentation processes were observed when the ions were subjected to collision-induced dissociation (CID). The deprotonated heterocycles showed bond cleavages of the 3-hydroxyfurazan ring with formation of oxoisocyanate and the complementary deprotonated nitrile amino acid. Further fragmentation of the deprotonated nitrile amino acids was greatly dependent on the length of the alkyl nitrile side chain. Competing losses of CO2 versus HCN occurred from α-cyanoglycinate (shortest chain), whereas water was lost from 2-amino-5-cyanopentanoate (longest chain). Interestingly, loss of acrylonitrile by a McLafferty-type fragmentation process was detected for 2-amino-4-cyanobutanoate, and several competing processes were observed for β-cyanoalanate. In one process, cyanide ion was formed either by consecutive losses of ammonia, carbon dioxide, and acetylene or by a one-step decarboxylative elimination. In another, complementary ions were obtained from β-cyanoalanate by loss of acetonitrile or HN=CHCO2H. Fragmentation of the protonated 3-hydroxyfurazan and nitrile amino acids resulted in the cumulative loss (H2O + CO), a loss that is commonly observed for protonated aliphatic α-amino acids. Overall, the distinct fragmentation behavior of the multifunctional 3-hydroxyfurazan amino acids correlated with the charged site, whereas fragmentations of the deprotonated nitrile amino acids showed cooperative interactions between the nitrile and the carboxylate groups.
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Affiliation(s)
- J Stuart Grossert
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Andrew M J Crowell
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Donatella Boschi
- Dipartimento di Scienza e Tecnologia del Farmaco (DSTF), Università degli Studi di Torino, Torino, Italy
| | - Marco L Lolli
- Dipartimento di Scienza e Tecnologia del Farmaco (DSTF), Università degli Studi di Torino, Torino, Italy
| | - Robert L White
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada
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Zhang X, Cheng S. Intramolecular Halogen Atom Coordinated H Transfer via Ion-Neutral Complex in the Gas Phase Dissociation of Protonated Dichlorvos Derivatives. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:2246-2254. [PMID: 28681359 DOI: 10.1007/s13361-017-1736-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2017] [Revised: 05/25/2017] [Accepted: 06/08/2017] [Indexed: 06/07/2023]
Abstract
Intramolecular halogen atom coordinated H transfer reaction in the gas phase dissociation of protonated dichlorvos derivatives has been explored by electrospray ionization tandem mass spectrometry. Upon collisional activation, protonated dichlorvos underwent dissociation reaction via cleavage of the P-O bond to give reactive ion-neutral complex (INC) intermediate, [dimethoxylphosphinoylium + dichloroacetaldehyde]. Besides direct dissociation of the complex, intramolecular chlorine atom coordinated H transfer reaction within the complex takes place, leading to the formation of protonated dimethyl chlorophosphate. To investigate the fragmentation mechanism, deuterium-labeled experiments and several other halogen-substituted (Br and F) analogs of dichlorvos were prepared and evaluated, which display a similar intramolecular halogen transfer. Density functional theory (DFT)-based calculations were performed and the computational results also support the mechanism. Graphical Abstract ᅟ.
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Affiliation(s)
- Xiaoping Zhang
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang, 330013, People's Republic of China.
| | - Shuai Cheng
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang, 330013, People's Republic of China
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Kappelmann J, Klein B, Geilenkirchen P, Noack S. Comprehensive and accurate tracking of carbon origin of LC-tandem mass spectrometry collisional fragments for 13C-MFA. Anal Bioanal Chem 2017; 409:2309-2326. [PMID: 28116490 PMCID: PMC5477699 DOI: 10.1007/s00216-016-0174-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 12/03/2016] [Accepted: 12/21/2016] [Indexed: 01/20/2023]
Abstract
In recent years the benefit of measuring positionally resolved 13C-labeling enrichment from tandem mass spectrometry (MS/MS) collisional fragments for improved precision of 13C-Metabolic Flux Analysis (13C-MFA) has become evident. However, the usage of positional labeling information for 13C-MFA faces two challenges: (1) The mass spectrometric acquisition of a large number of potentially interfering mass transitions may hamper accuracy and sensitivity. (2) The positional identity of carbon atoms of product ions needs to be known. The present contribution addresses the latter challenge by deducing the maximal positional labeling information contained in LC-ESI-MS/MS spectra of product anions of central metabolism as well as product cations of amino acids. For this purpose, we draw on accurate mass spectrometry, selectively labeled standards, and published fragmentation pathways to structurally annotate all dominant mass peaks of a large collection of metabolites, some of which with a complete fragmentation pathway. Compiling all available information, we arrive at the most detailed map of carbon atom fate of LC-ESI-MS/MS collisional fragments yet, comprising 170 intense and structurally annotated product ions with unique carbon origin from 76 precursor ions of 72 metabolites. Our 13C-data proof that heuristic fragmentation rules often fail to yield correct fragment structures and we expose common pitfalls in the structural annotation of product ions. We show that the positionally resolved 13C-label information contained in the product ions that we structurally annotated allows to infer the entire isotopomer distribution of several central metabolism intermediates, which is experimentally demonstrated for malate using quadrupole-time-of-flight MS technology. Finally, the inclusion of the label information from a subset of these fragments improves flux precision in a Corynebacterium glutamicum model of the central carbon metabolism.
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Affiliation(s)
- Jannick Kappelmann
- Institute of Bio- and Geosciences, IBG-1: Biotechnology, Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
| | - Bianca Klein
- Institute of Bio- and Geosciences, IBG-1: Biotechnology, Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
| | - Petra Geilenkirchen
- Institute of Bio- and Geosciences, IBG-1: Biotechnology, Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
| | - Stephan Noack
- Institute of Bio- and Geosciences, IBG-1: Biotechnology, Forschungszentrum Jülich GmbH, Jülich, 52425, Germany.
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LeBlanc LM, Powers SW, Grossert JS, White RL. Competing fragmentation processes of β-substituted propanoate ions upon collision-induced dissociation. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:2133-2144. [PMID: 27476993 DOI: 10.1002/rcm.7699] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 07/22/2016] [Accepted: 07/22/2016] [Indexed: 06/06/2023]
Abstract
RATIONALE When subjected to collisional activation, gas-phase carboxylate ions typically undergo decarboxylation. However, alternative fragmentation processes dominate when the carboxylate group is located within certain structural motifs. In this work, the fragmentation processes of β-substituted carboxylate ions are characterized to improve correlations between reactivity and structure. METHODS Mass spectra were collected using both ion trap and triple quadrupole mass spectrometers operating in the negative ion mode; collision-induced dissociation (CID) of ions was used to study the relationship between product ions and the structures of their precursor ions. Quantum mechanical computations were performed on a full range of reaction geometries at the MP2/6-311++G(2d,p)//B3LYP/6-31++G(2d,p) level of theory. RESULTS For a series of β-substituted carboxylate ions, a product ion corresponding to the anion of the β-substituent was obtained upon CID. Detailed computations indicated that decarboxylative elimination and at least one other fragmentation mechanism had feasible energetics for the formation of substituent anions differing in their gas-phase basicities. Predicted energetics for anti- and synperiplanar alignments in the transition structures for decarboxylative elimination correlated with the positions of crossover points in breakdown curves acquired for conformationally constrained ions. CONCLUSIONS The feasibility of more than one mechanism was established for the fragmentation of β-substituted propanoates. The contribution of each mechanistic pathway to the formation of the substituent anion was influenced by structural variations and conformational constraints, but mostly depended on the nature of the substituent. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Luc M LeBlanc
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, Canada, B3H 4R2
| | - Sean W Powers
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, Canada, B3H 4R2
| | - J Stuart Grossert
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, Canada, B3H 4R2
| | - Robert L White
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, Canada, B3H 4R2.
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LeBlanc LM, Crowell AMJ, Grossert JS, White RL. Phenyl group participation in rearrangements during collision-induced dissociation of deprotonated phenoxyacetic acid. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:2293-2301. [PMID: 26522323 DOI: 10.1002/rcm.7395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 08/11/2015] [Accepted: 09/10/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE The identification of trace constituents in biological and environmental samples is frequently based on the fragmentation patterns resulting from the collision-induced dissociation (CID) of gas-phase ions. Credible mechanistic characterization of fragmentation processes, including rearrangements, is required to make reliable assignments for structures of precursor and product ions. METHODS Mass spectra were collected using both ion trap and triple quadrupole mass spectrometers operating in the negative ion mode. Precursor ion scans and CID of ions generated in-source were used to establish precursor-product ion relationships. Density functional theory (DFT) computations were performed at the MP2/6-311++G(2d,p)//B3LYP/6-31++G(2d,p) level of theory. RESULTS Product ions at m/z 93 and 107 obtained upon CID of phenoxyacetate were attributed to phenoxide and o-methylphenoxide, respectively. An isotopic labeling experiment and computations showed that the phenoxide ion was formed by intramolecular displacement with formation of an α-lactone and also by a Smiles rearrangement. Rearrangement of phenoxyacetate via the ion-neutral complex formed in the α-lactone displacement pathway gave the isomeric o-hydroxyphenylacetate ion which yielded o-methylphenoxide upon decarboxylation. Computations provided feasible energetics for these pathways. CONCLUSIONS Previously unrecognized and energetically favorable rearrangements during the collision-induced fragmentation of phenoxyacetate have been characterized using isotopic labeling and DFT computations. Notably, the phenyl substituent plays an indispensable role in each rearrangement process resulting in multiple pathways for the fragmentation of phenoxyacetate.
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Affiliation(s)
- Luc M LeBlanc
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Andrew M J Crowell
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
| | - J Stuart Grossert
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Robert L White
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
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Wright PA, Alex A, Pullen FS. Can computational chemistry be used to predict CID fragmentation of anions? RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:2309-2315. [PMID: 26522325 DOI: 10.1002/rcm.7394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 09/10/2015] [Accepted: 09/10/2015] [Indexed: 06/05/2023]
Affiliation(s)
| | - Alexander Alex
- Evenor Consulting Ltd, The New Barn, Mill Lane, Eastry, UK
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Cao X, Zhu K, Song Q, Wang C, Wang Y, Cai R, Lin Y, Tang F, Zhang M, Mo W. Proton-bound complex mediating retro-Michael-type fragmentation of protonated 3-substituted oxindoles in the Orbitrap high-energy collisional dissociation cell. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:515-520. [PMID: 26160417 DOI: 10.1002/rcm.7128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 12/12/2014] [Accepted: 12/15/2014] [Indexed: 06/04/2023]
Abstract
RATIONALE Oxindole derivatives are valuable building blocks for indole chemistry. Systematically exploring the fragmentation behavior of the protonated 3-pyrazole-substituted oxindoles by kinetic methods combined with density functional theory (DFT) calculations is useful for further understanding their basic properties, and might provide some insights into their reactivity trends in synthesis and metabolism. METHODS All high-resolution high-energy collision-induced dissociation tandem mass spectrometry (CID-MS/MS) experiments were carried out using electrospray ionization hybrid Quadrupole-Orbitrap mass spectrometry in positive ion mode. Theoretical calculations were carried out by the DFT method at the B3LYP level with the 6-311G (d, p) basis set in the Gaussian 03 package of programs. RESULTS In the fragmentation of protonated 3-pyrazole-substituted oxindoles, the characterized protonated 3-(3-methyl-5-oxo-1H-pyrazol-4(5H)-ylidene)indolin-2-one derivatives and the protonated 5-methylpyrazolone were observed, which were proposed from the cleavage of the C(β)-C(γ) bond in a retro-Michael reaction. With the kinetic plot, a linear correlation was established between the intensities of this two competitive product ions and the difference in proton affinities of the corresponding neutral molecules, which demonstrated that the retro-Michael reaction was mediated by a proton-bound complex. CONCLUSIONS Using the kinetic method combined with theoretical calculations, a proton-bound complex mediating retro-Michael reaction was proposed for the fragmentation of protonated 3-pyrazole-substituted oxindoles in the high-energy collisional dissociation tandem mass spectrometry for the first time, which provided potential evidence to further understand their intrinsic bioactivities.
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Affiliation(s)
- Xiaoji Cao
- Research Center of Analysis and Measurement, Zhejiang University of Technology, 18 Chaowang Rd, Hangzhou, Zhejiang, 310014, P.R. China
| | - Kundan Zhu
- College of Chemical Engineering, Zhejiang University of Technology, 18 Chaowang Rd, Hangzhou, Zhejiang, 310014, P.R. China
| | - Qingbao Song
- College of Chemical Engineering, Zhejiang University of Technology, 18 Chaowang Rd, Hangzhou, Zhejiang, 310014, P.R. China
| | - Chenlu Wang
- College of Chemical Engineering, Zhejiang University of Technology, 18 Chaowang Rd, Hangzhou, Zhejiang, 310014, P.R. China
| | - Ye Wang
- College of Chemical Engineering, Zhejiang University of Technology, 18 Chaowang Rd, Hangzhou, Zhejiang, 310014, P.R. China
| | - Ruonan Cai
- College of Chemical Engineering, Zhejiang University of Technology, 18 Chaowang Rd, Hangzhou, Zhejiang, 310014, P.R. China
| | - Yan Lin
- College of Chemical Engineering, Zhejiang University of Technology, 18 Chaowang Rd, Hangzhou, Zhejiang, 310014, P.R. China
| | - Fangliang Tang
- Hangzhou Environmental Monitoring Control Station, Hangzhou, Zhejiang, 310014, P.R. China
| | - Ming Zhang
- Hangzhou Environmental Monitoring Control Station, Hangzhou, Zhejiang, 310014, P.R. China
| | - Weimin Mo
- Research Center of Analysis and Measurement, Zhejiang University of Technology, 18 Chaowang Rd, Hangzhou, Zhejiang, 310014, P.R. China
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Yao L, Chai Y, Sun C, Pan Y. Competitive proton and hydride transfer reactions via ion-neutral complexes: fragmentation of deprotonated benzyl N-phenylcarbamates in mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2015; 50:364-370. [PMID: 25800018 DOI: 10.1002/jms.3537] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 10/28/2014] [Accepted: 10/31/2014] [Indexed: 06/04/2023]
Abstract
The gas-phase chemistry of deprotonated benzyl N-phenylcarbamates was investigated by electrospray ionization tandem mass spectrometry. Characteristic losses of a substituted phenylcarbinol and a benzaldehyde from the precursor ion were proposed to be derived from an ion-neutral complex (INC)-mediated competitive proton and hydride transfer reactions. The intermediacy of the INC consisting of a substituted benzyloxy anion and a phenyl isocyanate was supported by both ortho-site-blocking experiments and density functional theory calculations. Within the INC, the benzyloxy anion played the role of either a proton abstractor or a hydride donor toward its neutral counterpart. Relative abundances of the product ions were influenced by the nature of the substituents. Electron-withdrawing groups at the N-phenyl ring favored the hydrogen transfer process (including proton and hydride transfer), whereas electron-donating groups favored direct decomposition to generate the benzyloxy anion (or substituted benzyloxy anion). By contrast, electron-withdrawing and electron-donating substitutions at the O-benzyl ring exhibited opposite effects.
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Affiliation(s)
- Liqing Yao
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, Zhejiang, China
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Cao X, Zhang F, Zhu K, Ye X, Shen L, Chen J, Mo W. Identifying the proton transfer reaction mechanism via a proton-bound dimeric intermediate for esomeprazoles by a kinetic method combined with density functional theory calculations. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2014; 28:1045-1050. [PMID: 24677526 DOI: 10.1002/rcm.6877] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 01/13/2014] [Accepted: 02/19/2014] [Indexed: 06/03/2023]
Abstract
RATIONALE Esomeprazole analogs are a class of important proton pump inhibitors for the treatment of gastro-esophageal reflux diseases. Understanding the fragmentation reaction mechanism of the protonated esomeprazole analogs will facilitate the characterization of their complex metabolic fate in humans. In this paper, the kinetic method and theoretical calculations were applied to evaluate the fragmentation of protonated esomeprazole analogs. METHODS All collision-induced dissociation (CID) mass spectrometry experiments were carried out using electrospray ionization (ESI) ion trap mass spectrometry in positive ion mode. Also the accurate masses of fragments were measured on by ESI quadrupole time-of-flight (QTOF) MS in positive ion mode. Theoretical calculations were carried out by the density functional theory (DFT) method with the 6-31G(d) basis set in the Gaussian 03 program. RESULTS In the fragmentation of the protonated esomeprazole analogs, C-S bond breakage is observed, which gives rise to protonated 2-(sulfinylmethylene)pyridines and protonated benzimidazoles. DFT calculations demonstrate that the nitrogen atom of the pyridine part is the thermodynamically most favorable protonation site, and the C-S bond cleavage is triggered by the transfer of this ionizing proton from the nitrogen atom of the pyridine part to the carbon atom of the benzimidazole part to which the sulfinyl is attached. Moreover, with the kinetic plot, the intensity ratios of two protonated product ions yield a linear relationship with the differences in proton affinities of the corresponding neutral molecules, which provides strong experimental evidence that the reaction proceeds via proton-bound 2-(sulfinylmethylene)pyridine/benzimidazole complex intermediates. CONCLUSIONS The kinetic method combined with theoretical calculations was successfully applied to probe the proton transfer reaction by proton-bound 2-(sulfinylmethylene)pyridine/benzimidazole complexes in the fragmentation of protonated esomeprazole analogs by ESI CID MS, which is a strong evidence that the kinetic method can be applied in identifying a proton-bound dimeric intermediate in the fragmentation of protonated ions.
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Affiliation(s)
- Xiaoji Cao
- Research Center of Analysis and Measurement, Zhejiang University of Technology, 18 Chaowang Rd, Hangzhou, Zhejiang, 310014, P.R. China
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Gillis EAL, Grossert JS, White RL. Rearrangements leading to fragmentations of hydrocinnamate and analogous nitrogen-containing anions upon collision-induced dissociation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:388-397. [PMID: 24408178 DOI: 10.1007/s13361-013-0788-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 11/14/2013] [Accepted: 11/18/2013] [Indexed: 06/03/2023]
Abstract
Tandem mass spectrometry (MS/MS) confirmed decarboxylation as the major collision-induced dissociation (CID) pathway of deprotonated hydrocinnamic acid (C6H5CH2CH2CO2H), N-phenylglycine (C6H5NHCH2CO2H) and 3-pyridin-2-ylpropanoic acid (C5H4NCH2CH2CO2H). The structure and stability of isomeric precursor and product anions were examined using density functional theory and ab initio methods. Geometry optimizations and frequency calculations were performed using the B3LYP/6-31++G(2d,p) level of theory and basis set with additional single point energies calculated at the MP2/6-311++G(2d,p) level. The formation of a delocalized product anion by carboxyl group-mediated migration of a benzylic proton to the ortho position of the ring and subsequent Cα-CO2(-) bond cleavage was energetically more favorable than direct decarboxylation and rearrangements of anions within ion-neutral complexes with carbon dioxide. The energy barrier for rearrangement of the delocalized product anion to the more stable benzylic anion was lowest in the fragmentation pathway of 3-pyridin-2-ylpropanoate. More energetically demanding fragmentation processes were indicated by the formation of other product anions at higher collision energy. Computations supported the feasibility of the formation of hydroxycarbonyl, styrene, and phenide ions from the benzylic anion of hydrocinnamate and the corresponding product anions from the nitrogen-containing analogues. The loss of dihydrogen from decarboxylated 3-pyridin-2-ylpropanoate was characterized computationally as hydride abstraction of an aryl proton. Overall, the results highlight the importance of exploring rearrangements in the fragmentation pathways of ions formed by electrospray ionization (ESI).
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Affiliation(s)
- Elizabeth A L Gillis
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
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Tovstiga TE, Gillis EAL, Grossert JS, White RL. Characterization of multiple fragmentation pathways initiated by collision-induced dissociation of multifunctional anions formed by deprotonation of 2-nitrobenzenesulfonylglycine. JOURNAL OF MASS SPECTROMETRY : JMS 2014; 49:168-177. [PMID: 24677307 DOI: 10.1002/jms.3324] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 12/08/2013] [Accepted: 12/11/2013] [Indexed: 06/03/2023]
Abstract
The correlation of anion structure with the fragmentation behavior of deprotonated nitrobenzenesulfonylamino acids was investigated using tandem mass spectrometry, isotopic labeling and computational methods. Four distinct fragmentation pathways resulting from the collision-induced dissociation (CID) of deprotonated 2-nitrobenzenesulfonylglycine (NsGly) were characterized. The unusual loss of the aryl nitro substituent as HONO was the lowest energy process. Subsequent successive losses of CO, HCN and SO2 indicated that an ortho cyclization reaction had accompanied loss of HONO. Other pathways involving rearrangement of the ionized sulfonamide group, dual bond cleavage and intramolecular nucleophilic displacement were proposed to account for the formation of phenoxide, arylsulfinate and arylsulfonamide product ions at higher collision energies. The four distinct fragmentation pathways were consistent with precursor-product relationships established by CID experiments, isotopic labeling results and the formation of analogous product ions from 2,4-dinitrobenzenesulfonylglycine and the Ns derivatives of alanine and 2-aminoisobutyric acid. The computations confirmed a low barrier for ortho cyclization with loss of HONO and feasible energetics for each reaction step in the four pathways. Computations also indicated that three of the fragmentation pathways started from NsGly ionized at the carboxyl group. Overall, the pathways identified for the fragmentation of the NsGly anion differed from processes reported for anions containing a single functional group, demonstrating the importance of functional group interactions in the fragmentation pathways of multifunctional anions.
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Affiliation(s)
- Tara E Tovstiga
- Department of Chemistry, Dalhousie University, 6274 Coburg Rd., PO Box 15000, Halifax, NS B3H 4R2, Canada
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Simakov A, Miller GBS, Bunkan AJC, Hoffmann MR, Uggerud E. The dissociation of glycolate—astrochemical and prebiotic relevance. Phys Chem Chem Phys 2013; 15:16615-25. [DOI: 10.1039/c3cp51638e] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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