1
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Gutiérrez-Quintanilla A, Moge B, Compagnon I, Noble JA. Vibrational and electronic spectra of protonated vanillin: exploring protonation sites and isomerisation. Phys Chem Chem Phys 2024; 26:15358-15368. [PMID: 38767194 DOI: 10.1039/d3cp05573f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Photofragmentation spectra of protonated vanillin produced under electrospray ionisation (ESI) conditions have been recorded in the 3000-3700 cm-1 (vibrational) and 225-460 nm (electronic) ranges, using room temperature IRMPD (infrared multiphoton dissociation) and cryogenic UVPD (ultraviolet photodissociation) spectroscopies, respectively. The cold (∼50 K) electronic UVPD spectrum exhibits very well resolved vibrational structure for the S1 ← S0 and S3 ← S0 transitions, suggesting long excited state dynamics, similar to its simplest analogue, protonated benzaldehyde. The experimental data were combined with theoretical calculations to determine the protonation site and configurational isomer observed in the experiments.
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Affiliation(s)
- Alejandro Gutiérrez-Quintanilla
- CNRS, Aix Marseille Univ., PIIM, Physique des Interactions Ioniques et Moléculaires, UMR 7345, 13397 Marseille, France.
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, Pau, France
| | - Baptiste Moge
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - Isabelle Compagnon
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - Jennifer A Noble
- CNRS, Aix Marseille Univ., PIIM, Physique des Interactions Ioniques et Moléculaires, UMR 7345, 13397 Marseille, France.
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2
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Fu D, Habtegabir SG, Wang H, Feng S, Han Y. Understanding of protomers/deprotomers by combining mass spectrometry and computation. Anal Bioanal Chem 2023:10.1007/s00216-023-04574-1. [PMID: 36737499 DOI: 10.1007/s00216-023-04574-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 01/19/2023] [Accepted: 01/27/2023] [Indexed: 02/05/2023]
Abstract
Multifunctional compounds may form different prototropic isomers under different conditions, which are known as protomers/deprotomers. In biological systems, these protomer/deprotomer isomers affect the interaction modes and conformational landscape between compounds and enzymes and thus present different biological activities. Study on protomers/deprotomers is essentially the study on the acidity/basicity of each intramolecular functional group and its effect on molecular structure. In recent years, the combination of mass spectrometry (MS) and computational chemistry has been proven to be a powerful and effective means to study prototropic isomers. MS-based technologies are developed to discriminate and characterize protomers/deprotomers to provide structural information and monitor transformations, showing great superiority than other experimental methods. Computational chemistry is used to predict the thermodynamic stability of protomers/deprotomers, provide the simulated MS/MS spectra, infrared spectra, and calculate collision cross-section values. By comparing the theoretical data with the corresponding experimental results, the researchers can not only determine the protomer/deprotomer structure, but also investigate the structure-activity relationship in a given system. This review covers various MS methods and theoretical calculations and their devotion to isomer discrimination, structure identification, conformational transformation, and phase transition investigation of protomers/deprotomers.
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Affiliation(s)
- Dali Fu
- State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering and Environment, China University of Petroleum-Beijing, Beijing, 102249, People's Republic of China
| | - Sara Girmay Habtegabir
- State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering and Environment, China University of Petroleum-Beijing, Beijing, 102249, People's Republic of China
| | - Haodong Wang
- State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering and Environment, China University of Petroleum-Beijing, Beijing, 102249, People's Republic of China
| | - Shijie Feng
- State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering and Environment, China University of Petroleum-Beijing, Beijing, 102249, People's Republic of China
| | - Yehua Han
- State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering and Environment, China University of Petroleum-Beijing, Beijing, 102249, People's Republic of China.
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3
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Koopman J, Grimme S. Calculation of Mass Spectra with the QCxMS Method for Negatively and Multiply Charged Molecules. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:2226-2242. [PMID: 36343304 DOI: 10.1021/jasms.2c00209] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Analysis and validation of a mass spectrometry (MS) experiment are usually performed by comparison to reference spectra. However, if references are missing, measured spectra cannot be properly matched. To close this gap, the Quantum Chemical Mass Spectrometry (QCxMS) program has been developed. It enables fully automatic calculations of electron ionization (EI) and positive ion collision-induced dissociation (CID) mass spectra of singly charged molecular ions. In this work, the extension to negative and multiple ion charge for the CID run mode is presented. QCxMS is now capable of calculating structures carrying any charge, without the need for pretabulated fragmentation pathways or machine learning of database spectra. Mass spectra of four single negatively charged and two multiple positively charged organic ions with molecular sizes from 12 to 92 atoms were computed and compared to reference spectra. The underlying Born-Oppenheimer molecular dynamics (MD) calculations were conducted using the semiempirical quantum mechanical GFN2-xTB method, while for some small molecules, ab initio DFT-based MD simulations were performed. Detailed insights into the fragmentation pathways were gained, and the effects of the computed charge assignments on the resulting spectrum are discussed. Especially for the negative ion mode, the influence of the deprotonation site to create the anion was found to be substantial. Doubly charged fragments could successfully be calculated fully automatically for the first time, while higher charged structures introduced severe assignment problems. Overall, this extension of the QCxMS program further enhances its applicability and underlines its value as a sophisticated toolkit for CID-based tandem MS structure elucidation.
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Affiliation(s)
- Jeroen Koopman
- Mulliken Center for Theoretical Chemistry, Institute for Physical and Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115Bonn, Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, Institute for Physical and Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115Bonn, Germany
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4
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Wachełko O, Szpot P, Tusiewicz K, Nowak K, Chłopaś-Konowałek A, Zawadzki M. An ultra-sensitive UHPLC-QqQ-MS/MS method for determination of 54 benzodiazepines (pharmaceutical drugs, NPS and metabolites) and z-drugs in biological samples. Talanta 2022; 251:123816. [DOI: 10.1016/j.talanta.2022.123816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 07/25/2022] [Accepted: 08/02/2022] [Indexed: 11/28/2022]
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5
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Sepman H, Tshepelevitsh S, Hupatz H, Kruve A. Protomer Formation Can Aid the Structural Identification of Caffeine Metabolites. Anal Chem 2022; 94:10601-10609. [PMID: 35861491 PMCID: PMC9352149 DOI: 10.1021/acs.analchem.2c00257] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
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The structural annotation of isomeric metabolites remains
a key
challenge in untargeted electrospray ionization/high-resolution mass
spectrometry (ESI/HRMS) metabolomic analysis. Many metabolites are
polyfunctional compounds that may form protomers in electrospray ionization
sources and therefore yield multiple peaks in ion mobility spectra.
Protomer formation is strongly structure-specific. Here, we explore
the possibility of using protomer formation for structural elucidation
in metabolomics on the example of caffeine, its eight metabolites,
and structurally related compounds. It is observed that two-thirds
of the studied compounds formed high- and low-mobility species in
high-resolution ion mobility. Structures in which proton hopping was
hindered by a methyl group at the purine ring nitrogen (position 3)
yielded structure-indicative fragments with collision-induced dissociation
(CID) for high- and low-mobility ions. For compounds where such a
methyl group was not present, a gas-phase equilibrium could be observed
for tautomeric species with two-dimensional ion mobility. We show
that the protomer formation and the gas-phase properties of the protomers
can be related to the structure of caffeine metabolites and facilitate
the identification of the structural isomers.
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Affiliation(s)
- Helen Sepman
- Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16, 106 91 Stockholm, Sweden
| | - Sofja Tshepelevitsh
- Institute of Chemistry, University of Tartu, Ravila 14a, Tartu 50411, Estonia
| | - Henrik Hupatz
- Institut für Chemie und Biochemie, Freie Universität Berlin, Arnimallee 20, 14195 Berlin, Germany
| | - Anneli Kruve
- Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16, 106 91 Stockholm, Sweden
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6
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Ucur B, Maccarone AT, Ellis SR, Blanksby SJ, Trevitt AJ. Solvent-Mediated Proton-Transfer Catalysis of the Gas-Phase Isomerization of Ciprofloxacin Protomers. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:347-354. [PMID: 35014802 DOI: 10.1021/jasms.1c00331] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Understanding how neutral molecules become protonated during positive-ion electrospray ionization (ESI) mass spectrometry is critically important to ensure analytes can be efficiently ionized, detected, and unambiguously identified. The ESI solvent is one of several parameters that can alter the dominant site of protonation in polyfunctional molecules and thus, in turn, can significantly change the collision-induced dissociation (CID) mass spectra relied upon for compound identification. Ciprofloxacin─a common fluoroquinolone antibiotic─is one such example whereby positive-ion ESI can result in gas-phase [M + H]+ ions protonated at either the keto-oxygen or the piperazine-nitrogen. Here, we demonstrate that these protonation isomers (or protomers) of ciprofloxacin can be resolved by differential ion mobility spectrometry and give rise to distinctive CID mass spectra following both charge-directed and charge-remote mechanisms. Interaction of mobility-selected protomers with methanol vapor (added via the throttle gas supply) was found to irreversibly convert the piperazine N-protomer to the keto-O-protomer. This methanol-mediated proton-transport catalysis is driven by the overall exothermicity of the reaction, which is computed to favor the O-protomer by 93 kJ mol-1 (in the gas phase). Conversely, gas phase interactions of mobility-selected ions with acetonitrile vapor selectively depletes the N-protomer ion signal as formation of stable [M + H + CH3CN]+ cluster ions skews the apparent protomer population ratio, as the O-protomer is unaffected. These findings provide a mechanistic basis for tuning protomer populations to ensure faithful characterization of multifunctional molecules by tandem mass spectrometry.
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Affiliation(s)
- Boris Ucur
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Alan T Maccarone
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Shane R Ellis
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
- Illawarra Health and Medical Research Institute, Wollongong, New South Wales 2522, Australia
| | - Stephen J Blanksby
- Central Analytical Research Facility and School of Chemistry and Physics, Queensland University of Technology, Brisbane 4001, Australia
| | - Adam J Trevitt
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
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7
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Mashmoushi N, Juhász DR, Coughlan NJA, Schneider BB, Le Blanc JCY, Guna M, Ziegler BE, Campbell JL, Hopkins WS. UVPD Spectroscopy of Differential Mobility-Selected Prototropic Isomers of Rivaroxaban. J Phys Chem A 2021; 125:8187-8195. [PMID: 34432451 DOI: 10.1021/acs.jpca.1c05564] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two ion populations of protonated Rivaroxaban, [C19H18ClN3O5S + H]+, are separated under pure N2 conditions using differential mobility spectrometry prior to characterization in a hybrid triple quadrupole linear ion trap mass spectrometer. These populations are attributed to bare protonated Rivaroxaban and to a proton-bound Rivaroxaban-ammonia complex, which dissociates prior to mass-selecting the parent ion. Ultraviolet photodissociation (UVPD) and collision-induced dissociation (CID) studies indicate that both protonated Rivaroxaban ion populations are comprised of the computed global minimum prototropic isomer. Two ion populations are also observed when the collision environment is modified with 1.5% (v/v) acetonitrile. In this case, the protonated Rivaroxaban ion populations are produced by the dissociation of the ammonium complex and by the dissociation of a proton-bound Rivaroxaban-acetonitrile complex prior to mass selection. Again, both populations exhibit a similar CID behavior; however, UVPD spectra indicate that the two ion populations are associated with different prototropic isomers. The experimentally acquired spectra are compared with computed spectra and are assigned to two prototropic isomers that exhibit proton sharing between distal oxygen centers.
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Affiliation(s)
- Nour Mashmoushi
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.,Waterloo Institute for Nanotechnology, University of 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Daniel R Juhász
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Neville J A Coughlan
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.,Waterloo Institute for Nanotechnology, University of 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | | | | | - Mircea Guna
- SCIEX, 71 Four Valley Drive, Concord, Ontario L4K 4V8, Canada
| | - Blake E Ziegler
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.,Watermine Innovation, Waterloo, Ontario N0B 2T0, Canada
| | - J Larry Campbell
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.,Watermine Innovation, Waterloo, Ontario N0B 2T0, Canada.,Bedrock Scientific, Milton, Ontario L6T 6J9, Canada
| | - W Scott Hopkins
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.,Waterloo Institute for Nanotechnology, University of 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.,Watermine Innovation, Waterloo, Ontario N0B 2T0, Canada.,Centre for Eye and Vision Research, New Territories 999077, Hong Kong
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8
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Batista PR, Penna TC, Ducati LC, Correra TC. p-Aminobenzoic acid protonation dynamics in an evaporating droplet by ab initio molecular dynamics. Phys Chem Chem Phys 2021; 23:19659-19672. [PMID: 34524295 DOI: 10.1039/d1cp01495a] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Protonation equilibria are known to vary from the bulk to microdroplet conditions, which could induce many chemical and physical phenomena. Protonated p-aminobenzoic acid (PABA + H+) can be considered a model for probing the protonation dynamics in an evaporating droplet, as its protonation equilibrium is highly dependent on the formation conditions from solution via atmospheric pressure ionization sources. Experiments using diverse experimental techniques have shown that protic solvents allow formation of the O-protomer (PABA protonated in the carboxylic acid group) stable in the gas phase, while aprotic solvents yield the N-protomer (protonated in the amino group) that is the most stable protomer in solution. In this work, we explore the protonation equilibrium of PABA solvated by different numbers of water molecules (n = 0 to 32) using ab initio molecular dynamics. For n = 8-32, the protonation is either at the NH2 group or in the solvent network. The solvent network interacts with the carboxylic acid group, but there is no complete proton transfer to form the O-protomer. For smaller clusters, however, solvent-mediated proton transfers to the carboxylic acid were observed, both via the Grotthuss mechanism and the vehicle or shuttle mechanism (for n = 1 and 2). Thermodynamic considerations allowed a description of the origins of the kinetic trapping effect, which explains the observation of the solution structure in the gas phase. This effect likely occurs in the final evaporation steps, which are outside the droplet size range covered by previous classical molecular dynamics simulations of charged droplets. These results may be considered relevant in determining the nature of the species observed in the ubiquitous ESI based mass spectrometry analysis, and in general for droplet chemistry, explaining how protonation equilibria are drastically changed from bulk to microdroplet conditions.
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Affiliation(s)
- Patrick R Batista
- Department of Fundamental Chemistry, Institute of Chemistry - University of São Paulo, Av. Prof. Lineu Prestes, 748, Cidade Universitária, São Paulo, SP, Brazil.
| | - Tatiana C Penna
- Department of Fundamental Chemistry, Institute of Chemistry - University of São Paulo, Av. Prof. Lineu Prestes, 748, Cidade Universitária, São Paulo, SP, Brazil.
| | - Lucas C Ducati
- Department of Fundamental Chemistry, Institute of Chemistry - University of São Paulo, Av. Prof. Lineu Prestes, 748, Cidade Universitária, São Paulo, SP, Brazil.
| | - Thiago C Correra
- Department of Fundamental Chemistry, Institute of Chemistry - University of São Paulo, Av. Prof. Lineu Prestes, 748, Cidade Universitária, São Paulo, SP, Brazil.
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9
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Schorr P, Kovačević B, Volmer DA. Overestimation of 3α- over 3β -25-Hydroxyvitamin D 3 Levels in Serum: A Mechanistic Rationale for the Different Mass Spectral Properties of the Vitamin D Epimers. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:1116-1125. [PMID: 33780622 DOI: 10.1021/jasms.1c00054] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The metabolism of vitamin D3 includes a parallel C-3 epimerization pathway-in addition to the standard metabolic processes for vitamin D3-reversing the stereochemical configuration of the -OH group at carbon-3 (β→α). While the biological function of the 3α epimer has not been elucidated yet, the additional species cannot be neglected in the analytical determination of vitamin D3, as it has the potential to introduce analytical errors if not properly accounted for. Recently, some inconsistent mass spectral behavior was seen for the 25-hydroxyvitamin D3 (25(OH)D3) epimers during quantification using electrospray LC-MS/MS. The present work extends that of Flynn et al. ( Ann. Clin. Biochem. 2014, 51, 352-559) and van den Ouweland et al. ( J. Chromatogr. B 2014, 967, 195-202), who reported larger electrospray ionization response factors for the 3α epimer of 25(OH)D3 in human serum samples as compared to the regular 3β variant. The present work was concerned with the mechanistic reasons for these differences. We used a combination of electrospray ionization, atmospheric pressure chemical ionization, and density functional theory calculations to uncover structural dissimilarities between the epimers. A plausible mechanism is described based on intramolecular hydrogen bonding in the gas phase, which creates a small difference of proton affinities between the epimers. More importantly, this mechanism allows the explanation of the different ionization efficiencies of the epimers based on kinetic control of the ionization process, where ionization initially takes place at the hydroxyl group with subsequent proton transfer to a basic carbon atom. The barrier for this transfer differs between the epimers and is in direct competition with H2O elimination from the protonated hydroxyl group. The "hidden" site of high gas phase basicity was revealed through computational calculations and appears to be inaccessible via direct protonation.
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Affiliation(s)
- Pascal Schorr
- Department of Chemistry, Humboldt University Berlin, 12489 Berlin, Germany
| | - Borislav Kovačević
- Group for Computational Life Sciences, Ruđer Bošković Institute, 10000 Zagreb, Croatia
| | - Dietrich A Volmer
- Department of Chemistry, Humboldt University Berlin, 12489 Berlin, Germany
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10
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Zheng Z, Attygalle AB. Impact of Ambient Vapors Present in an Electrospray Ionization Source on Gas-Phase Ion Structures. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:725-735. [PMID: 33606934 DOI: 10.1021/jasms.0c00430] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
According to current consensus, structures of protomeric (or deprotomeric) tautomers of gaseous ions generated by electrospray ionization depend primarily on the nature of the spray solvent. To probe the effect of the spray solvent on protonation, 4-aminobenzoic acid (PABA) has often been selected as the model compound. It is widely accepted that the protonation in the gas phase takes place primarily on the carbonyl oxygen atom when the sample is sprayed in methanol and on the nitrogen atom when acetonitrile is used as the spray solvent. Although this observation is valid, our current results indicate that the determination of the predominant protomer in the gas phase by the spray solvent is an indirect effect moderated by the solvent vapor molecules present in the ambient ion source. To investigate real-time changes in protomer distributions due to solvents, we used ion-mobility mass spectrometry (IM-MS). Initially, when a PABA solution in methanol was electrosprayed, the ion-mobility arrival-time profile recorded showed essentially one peak for the O-protomer. However, when acetonitrile or acetone vapors were introduced to the ambient-pressure ion source via the flowing desolvation gas, the intensity of the O-protomer peak diminished rapidly, and the N-protomer signal became dominant. The moment the acetonitrile (or acetone) vapors were removed from the ion source, the protomer-distribution signals began gradually reverting back to their original intensities. Furthermore, when PABA samples in methanol and acetonitrile were electrosprayed separately via a dual-sprayer setup, which allowed for the selective blocking of the gaseous ion-generation cascade of charged droplets from either sprayer, the predominant signal corresponded only to the N-protomer, irrespective of the position of the mechanical barrier. Because the mechanical barrier prevents only the gaseous ion formation, but not the physical access of solvent vapors to the ion source, it is evident that the solvent vapor that engulfs the ion source is the governing factor that decides the protomer distribution, not the nature of the spray solvent. Noticeably, acetonitrile wields a stronger effect on the manifested protomer distribution than many other solvents, including methanol, water, hexanes, and toluene. Apparently, the so-called "memory" of the solution-phase structures and the phenomenon described as "kinetic trapping" are both due to indirect effects caused by the solvent vapor engulfing the atmospheric-pressure ion source. Moreover, the so-called "memory" effect can either be "saved" or "erased" by exposing the initially formed gaseous ions to different solvent vapors from an alternative source.
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Affiliation(s)
- Zhaoyu Zheng
- Center for Mass Spectrometry, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
| | - Athula B Attygalle
- Center for Mass Spectrometry, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
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11
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Jiang F, Liu Q, Li Q, Zhang S, Qu X, Zhu J, Zhong G, Huang M. Signal Drift in Liquid Chromatography Tandem Mass Spectrometry and Its Internal Standard Calibration Strategy for Quantitative Analysis. Anal Chem 2020; 92:7690-7698. [PMID: 32392405 DOI: 10.1021/acs.analchem.0c00633] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The present project studied the signal drift in liquid chromatography tandem mass spectrometry (LC-MS/MS) and proposed a strategy for compensating such drift. In the study, four 4-component groups were repeatedly run on different LC-MS/MS systems for over 12 h to investigate the dependence of signal drift on time and hardware systems. The 4-component groups each consisted of (1) an analyte, (2) a stable isotope labeled analyte, (3) a compound with similar structure to the analyte, and (4) a compound with dissimilar structure. All of the species showed significant signal drift, generally more than 25% over 12 h. The analyte and its stable isotope labeled analog always have the same drifting pattern including the trends and direction from one LC-MS/MS system to another. Signal drift was also found to be concentration dependent. Our experiments further proved that a conventional stable isotope labeled internal standard in LC-MS/MS quantification would not compensate the variations caused by concentration-dependent signal drift. An ideal internal standard for LC-MS/MS has both identical structure and similar concentration to the analyte. For that, we proposed a new internal standard strategy, pseudo internal standard (Pseudo IS), for LC-MS/MS quantification. Pseudo IS could effectively compensate signal drift in spite of its significant time, system, and concentration dependencies.
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Affiliation(s)
- Fulin Jiang
- Institute of Clinical Pharmacology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510080, China
| | - Qian Liu
- Institute of Clinical Pharmacology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510080, China
| | - Qiaoxi Li
- Institute of Clinical Pharmacology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510080, China
| | - Simin Zhang
- Institute of Clinical Pharmacology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510080, China
| | - Xiangyang Qu
- Institute of Clinical Pharmacology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510080, China
| | - Janshon Zhu
- Guangdong RangerBio Technologies Co., Ltd., Dongguan 523000, China
| | - Guoping Zhong
- Institute of Clinical Pharmacology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510080, China
| | - Min Huang
- Institute of Clinical Pharmacology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510080, China
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12
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Chandran J, Zheng Z, Thomas VI, Rajalakshmi C, Attygalle AB. LC-MS analysis of p-aminosalicylic acid under electrospray ionization conditions manifests a profound solvent effect. Analyst 2020; 145:5333-5344. [DOI: 10.1039/d0an00680g] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Under identical mass spectrometric conditions, chromatographic peak intensities of p-aminosalicylic acid recorded by LC-MS, using methanol as the mobile phase are drastically different from those acquired using is it acetonitrile as the eluent.
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Affiliation(s)
- Jisha Chandran
- Inter University Instrumentation Centre (IUIC)
- School of Environmental Sciences
- Mahatma Gandhi University
- Kottayam
- 686560 India
| | - Zhaoyu Zheng
- Center for Mass Spectrometry
- Department of Chemistry and Chemical Biology
- Stevens Institute of Technology
- Hoboken
- USA
| | | | | | - Athula B. Attygalle
- Center for Mass Spectrometry
- Department of Chemistry and Chemical Biology
- Stevens Institute of Technology
- Hoboken
- USA
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13
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Štícha M, Hložek T, Bursová M, Čabala R, Jelínek I. Development of a CE-MS method for the study of riociguat and metabolite M1 in pharmaceutical analysis. Electrophoresis 2019; 40:2936-2945. [PMID: 31520473 DOI: 10.1002/elps.201900181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 08/21/2019] [Accepted: 08/31/2019] [Indexed: 11/11/2022]
Abstract
Riociguat is a novel antihypertensive drug for the treatment of pulmonary hypertension. We present electrophoretic characterization, i.e. migration behavior of riociguat and metabolite M1 as support for optimized CZE/MS assay. Fundamental separation parameters, such as peak width, symmetry, and resolution are studied in a series of ammonium formate buffers within pH range 2.60-5.61. The narrow region of peak symmetry lies close to pH 4.0 for both analytes. Accordingly, the value of resolution maximizes in a background electrolyte adjusted to pH 4.10. Basic calibration parameters estimated from CZE experiments with absorption photometric and mass spectrometric detection of riociguat and metabolite M1 were evaluated. More than three orders lower LOD was achieved with high resolution mass spectrometric detection. The observed difference in the sensitivity of both detection techniques gives priority to the utilization of CZE/MS in practice. The values of dissociation constants of riociguat and metabolite M1, pKBH , were determined from CZE measurements in lithium formate and lithium acetate background electrolytes with constant ionic strength. The value of pKBH = 4.30 ± 0.02 for riociguat corresponds well to the value already presented in the literature. According to our observation, metabolite M1 behaves like a slightly stronger base with estimated pKBH = 4.40 ± 0.02.
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Affiliation(s)
- Martin Štícha
- Department of Analytical Chemistry, Faculty of Science, Charles University, Prague 2, Czech Republic
| | - Tomáš Hložek
- Department of Analytical Chemistry, Faculty of Science, Charles University, Prague 2, Czech Republic.,Institute of Forensic Medicine and Toxicology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague 2, Czech Republic
| | - Miroslava Bursová
- Department of Analytical Chemistry, Faculty of Science, Charles University, Prague 2, Czech Republic.,Institute of Forensic Medicine and Toxicology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague 2, Czech Republic
| | - Radomír Čabala
- Department of Analytical Chemistry, Faculty of Science, Charles University, Prague 2, Czech Republic.,Institute of Forensic Medicine and Toxicology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague 2, Czech Republic
| | - Ivan Jelínek
- Department of Analytical Chemistry, Faculty of Science, Charles University, Prague 2, Czech Republic
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14
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Souza AA, Vessecchi R, Castro-Gamboa I, Furlan M. Combined use of tandem mass spectrometry and computational chemistry to study 2H-chromenes from Piper aduncum. JOURNAL OF MASS SPECTROMETRY : JMS 2019; 54:634-642. [PMID: 31144377 DOI: 10.1002/jms.4378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Revised: 05/14/2019] [Accepted: 05/17/2019] [Indexed: 06/09/2023]
Abstract
Natural 2H-chromenes were isolated from the crude extract of Piper aduncum (Piperaceae) and analyzed by electrospray ionization tandem mass spectrometry (ESI-MS/MS) applying collision-induced dissociation. Density functional theory (DFT) calculations were used to explain the preferred protonation sites of the 2H-chromenes based on thermochemical parameters, including atomic charges, proton affinity, and gas-phase basicity. After identifying the nucleophilic sites, the pathways were proposed to justify the formation of the diagnostic ions under ESI-MS/MS conditions. The calculated relative energy for each pathway was in good agreement with the energy-resolved plot obtained from ESI-MS/MS data. Moreover, the 2H-chromene underwent proton attachment on the prenyl moiety via a six-membered transition state. This behavior resulted in the formation of a diagnostic ion due to 2-methylpropene loss. These studies provide novel insights into gas-phase dissociation for natural benzopyran compounds, indicating how reactivity is correlated to the intrinsic acid-base equilibrium and structural aspects, including the substitution pattern on the aromatic moiety. Therefore, these results can be applied in the identification of benzopyran derivatives in a variety of biological samples.
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Affiliation(s)
- Amauri Alves Souza
- Universidade Estadual Paulista - UNESP, Instituto de Química, Rua Professor Francisco Degni, 55, Araraquara, SP, 14800-900, Brazil
| | - Ricardo Vessecchi
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Avenida Bandeirantes, 3900, Ribeirão Preto, SP, 14040-901, Brazil
| | - Ian Castro-Gamboa
- Universidade Estadual Paulista - UNESP, Instituto de Química, Rua Professor Francisco Degni, 55, Araraquara, SP, 14800-900, Brazil
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15
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Erabelli R, Xu S, Attygalle AB. Gas-phase protomers of p-(dimethylamino)chalcone investigated by travelling-wave ion mobility mass spectrometry (TWIMS). JOURNAL OF MASS SPECTROMETRY : JMS 2018; 53:954-962. [PMID: 29989269 DOI: 10.1002/jms.4265] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Revised: 06/24/2018] [Accepted: 06/27/2018] [Indexed: 06/08/2023]
Abstract
Results from ion-mobility (IM) separation experiments demonstrate that O- and N-protomers of p-(dimethylamino)chalcone (p-DMAC) can coexist in the gas phase. The relative populations of the two protomers strongly depend on the ion-generating settings and the conditions the precursor ions experience from the point of their gas-phase inception to the time of their detection. Under relatively dry source conditions, the ratio of the gas-phase protomers generated under helium-plasma ionization (HePI) conditions is biased towards the thermodynamically favored O-protomer. However, when the humidity of the enclosed ion source was increased, the IM arrival-time distribution profile of the mass-selected protonated precursor of p-DMAC changed rapidly to one dominated by the N-protomer. Under spray-ionization conditions, the formation of the thermodynamically less favored protomer has been generally attributed to a phenomenon called kinetic trapping. Herein, we demonstrate that the population of thermodynamically less favored N-protomer can be dramatically increased simply by introducing water vapor to the HePI ion source.
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Affiliation(s)
- Ramu Erabelli
- Center for Mass Spectrometry, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, New Jersey
| | - Sihang Xu
- Center for Mass Spectrometry, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, New Jersey
| | - Athula B Attygalle
- Center for Mass Spectrometry, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, New Jersey
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16
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Xia H, Attygalle AB. Transformation of the gas-phase favored O-protomer of p-aminobenzoic acid to its unfavored N-protomer by ion activation in the presence of water vapor: An ion-mobility mass spectrometry study. JOURNAL OF MASS SPECTROMETRY : JMS 2018; 53:353-360. [PMID: 29377420 DOI: 10.1002/jms.4066] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 01/12/2018] [Accepted: 01/18/2018] [Indexed: 05/26/2023]
Abstract
An ion-mobility mass spectrometry study showed that the preferred O-protonated form of p-aminobenzoic in the gas phase can be converted to the thermodynamically less favored N-protomer by in-source collision-induced ion activation during the ion transfer process from the atmospheric region to the first vacuum region if the humidity is high in the ion source. Upon the addition of water vapor to the nitrogen gas used to promote the solid analyte to the gas phase under helium-plasma ionization conditions, the intensity of the ion-mobility arrival-time peak for the N-protomer increased dramatically. Evidently, the ion-activation process in the first vacuum region is able to provide the energy required to surmount the barrier to isomerize the O-protomer to the more energetic N-protomer. The transfer of the proton attached to the carbonyl oxygen atom of the O-protomer to the amino group takes place by a water-bridge mechanism. Apparently, the postionization transformations that take place during the transmission of ions from the atmospheric-pressure ion source to the detector, via different physical compartments of low to high vacuum, play an eminent role in determining the population ratios eventually manifested at the detector.
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Affiliation(s)
- Hanxue Xia
- Center for Mass Spectrometry, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, New Jersey, 07030, USA
| | - Athula B Attygalle
- Center for Mass Spectrometry, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, New Jersey, 07030, USA
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17
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Hines KM, Ross DH, Davidson KL, Bush MF, Xu L. Large-Scale Structural Characterization of Drug and Drug-Like Compounds by High-Throughput Ion Mobility-Mass Spectrometry. Anal Chem 2017; 89:9023-9030. [PMID: 28764324 PMCID: PMC5616088 DOI: 10.1021/acs.analchem.7b01709] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
![]()
Ion mobility-mass spectrometry (IM-MS)
can provide orthogonal information,
i.e., m/z and collision cross section
(CCS), for the identification of drugs and drug metabolites. However,
only a small number of CCS values are available for drugs, which limits
the use of CCS as an identification parameter and the assessment of
structure–function relationships of drugs using IM-MS. Here,
we report the development of a rapid workflow for the measurement
of CCS values of a large number of drug or drug-like molecules in
nitrogen on the widely available traveling wave IM-MS (TWIM-MS) platform.
Using a combination of small molecule and polypeptide CCS calibrants,
we successfully determined the nitrogen CCS values of 1425 drug or
drug-like molecules in the MicroSource Discovery Systems’ Spectrum
Collection using flow injection analysis of 384-well plates. Software
was developed to streamline data extraction, processing, and calibration.
We found that the overall drug collection covers a wide CCS range
for the same mass, suggesting a large structural diversity of these
drugs. However, individual drug classes appear to occupy a narrow
and unique space in the CCS–mass 2D spectrum, suggesting a
tight structure–function relationship for each class of drugs
with a specific target. We observed bimodal distributions for several
antibiotic species due to multiple protomers, including the known
fluoroquinolone protomers and the new finding of cephalosporin protomers.
Lastly, we demonstrated the utility of the high-throughput method
and drug CCS database by quickly and confidently confirming the active
component in a pharmaceutical product.
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Affiliation(s)
- Kelly M Hines
- Department of Medicinal Chemistry, ‡Department of Chemistry, University of Washington , Seattle, Washington 98195, United States
| | - Dylan H Ross
- Department of Medicinal Chemistry, ‡Department of Chemistry, University of Washington , Seattle, Washington 98195, United States
| | - Kimberly L Davidson
- Department of Medicinal Chemistry, ‡Department of Chemistry, University of Washington , Seattle, Washington 98195, United States
| | - Matthew F Bush
- Department of Medicinal Chemistry, ‡Department of Chemistry, University of Washington , Seattle, Washington 98195, United States
| | - Libin Xu
- Department of Medicinal Chemistry, ‡Department of Chemistry, University of Washington , Seattle, Washington 98195, United States
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18
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Attygalle AB, Xia H, Pavlov J. Influence of Ionization Source Conditions on the Gas-Phase Protomer Distribution of Anilinium and Related Cations. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:1575-1586. [PMID: 28397015 DOI: 10.1007/s13361-017-1640-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 02/23/2017] [Accepted: 02/25/2017] [Indexed: 06/07/2023]
Abstract
The gas-phase-ion generation technique and specific ion-source settings of a mass spectrometer influence heavily the protonation processes of molecules and the abundance ratio of the generated protomers. Hitherto that has been attributed primarily to the nature of the solvent and the pH. By utilizing electrospray ionization and ion-mobility mass spectrometry (IM-MS), we demonstrate, even in the seemingly trivial case of protonated aniline, that the protomer ratio strongly depends on the source conditions. Under low in-source ion activation, nearly 100% of the N-protomer of aniline is produced, and it can be subsequently converted to the C-protomer by collisional activation effected by increasing the electrical potential difference between the entrance and exit orifices of the first vacuum region. This activation and transformation process takes place even before the ion is mass-selected and subjected to IM separation. Despite the apparent simplicity of the problem, the preferred protonation site of aniline in the gas phase-the amino group or the aromatic ring-has been a topic of controversy. Our results not only provide unambiguous evidence that ring- and nitrogen-protonated aniline can coexist and be interconverted in the gas phase, but also that the ratio of the protomers depends on the internal energy of the original ion. There are many dynamic ion-transformation and fragmentation processes that take place in the different physical compartments of a Synapt G2 HDMS instrument. Such processes can dramatically change the very identity even of small ions, and therefore should be taken into account when interpreting product-ion mass spectra. Graphical Abstract ᅟ.
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Affiliation(s)
- Athula B Attygalle
- Center for Mass Spectrometry, Department of Biomedical Engineering, Chemistry, and Biological Sciences, Stevens Institute of Technology, Hoboken, NJ, 07030, USA.
| | - Hanxue Xia
- Center for Mass Spectrometry, Department of Biomedical Engineering, Chemistry, and Biological Sciences, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Julius Pavlov
- Center for Mass Spectrometry, Department of Biomedical Engineering, Chemistry, and Biological Sciences, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
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19
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Carita Correra T, Santos Fernandes A, Mota Reginato M, Colucci Ducati L, Berden G, Oomens J. Probing the geometry reorganization from solution to gas-phase in putrescine derivatives by IRMPD, 1H-NMR and theoretical calculations. Phys Chem Chem Phys 2017; 19:24330-24340. [DOI: 10.1039/c7cp04617k] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Geometry reorganization of ESI formed ions are demonstrated and explicit calculations of the solution phase are shown to be relevant.
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Affiliation(s)
- Thiago Carita Correra
- Department of Fundamental Chemistry
- Institute of Chemistry
- University of São Paulo
- São Paulo
- Brazil
| | - André Santos Fernandes
- Department of Fundamental Chemistry
- Institute of Chemistry
- University of São Paulo
- São Paulo
- Brazil
| | - Marcelo Mota Reginato
- Department of Fundamental Chemistry
- Institute of Chemistry
- University of São Paulo
- São Paulo
- Brazil
| | - Lucas Colucci Ducati
- Department of Fundamental Chemistry
- Institute of Chemistry
- University of São Paulo
- São Paulo
- Brazil
| | - Giel Berden
- Radboud University
- Institute for Molecules and Materials
- FELIX Laboratory
- 6525 ED Nijmegen
- The Netherlands
| | - Jos Oomens
- Radboud University
- Institute for Molecules and Materials
- FELIX Laboratory
- 6525 ED Nijmegen
- The Netherlands
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20
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Svahn O, Björklund E. Increased electrospray ionization intensities and expanded chromatographic possibilities for emerging contaminants using mobile phases of different pH. J Chromatogr B Analyt Technol Biomed Life Sci 2016; 1033-1034:128-137. [DOI: 10.1016/j.jchromb.2016.07.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 07/06/2016] [Indexed: 11/30/2022]
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21
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Xia H, Attygalle AB. Effect of Electrospray Ionization Source Conditions on the Tautomer Distribution of Deprotonated p-Hydroxybenzoic Acid in the Gas Phase. Anal Chem 2016; 88:6035-43. [DOI: 10.1021/acs.analchem.6b01230] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hanxue Xia
- Center for Mass Spectrometry, Department of Biomedical Engineering, Chemistry, and Biological Sciences, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
| | - Athula B. Attygalle
- Center for Mass Spectrometry, Department of Biomedical Engineering, Chemistry, and Biological Sciences, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
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22
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Chai Y, Weng G, Shen S, Sun C, Pan Y. The protonation site of para-dimethylaminobenzoic acid using atmospheric pressure ionization methods. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:668-676. [PMID: 25627246 DOI: 10.1007/s13361-014-1069-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 12/15/2014] [Accepted: 12/15/2014] [Indexed: 06/04/2023]
Abstract
The protonation site of para-dimethylaminobenzoic acid (p-DMABA) was investigated using atmospheric pressure ionization methods (ESI and APCI) coupled with collision-induced dissociation (CID), nuclear magnetic resonance (NMR), and computational chemistry. Theoretical calculations and NMR experiments indicate that the dimethyl amino group is the preferred site of protonation both in the gas phase and aqueous solution. Protonation of p-DMABA occurs at the nitrogen atom by ESI independent of the solvents and other operation conditions under typical thermodynamic control. However, APCI produces a mixture of the nitrogen- and carbonyl oxygen-protonated p-DMABA when aprotic organic solvents (acetonitrile, acetone, and tetrahydrofuran) are used, exhibiting evident kinetic characteristics of protonation. But using protic organic solvents (methanol, ethanol, and isopropanol) in APCI still leads to the formation of thermodynamically stable N-protonated p-DMABA. These structural assignments were based on the different CID behavior of the N- and O-protonated p-DMABA. The losses of methyl radical and water are the diagnostic fragmentations of the N- and O-protonated p-DMABA, respectively. In addition, the N-protonated p-DMABA is more stable than the O-protonated p-DMABA in CID revealed by energy resolved experiments and theoretical calculations.
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Affiliation(s)
- Yunfeng Chai
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, Zhejiang, People's Republic of China
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23
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Féraud G, Esteves-López N, Dedonder-Lardeux C, Jouvet C. UV spectroscopy of cold ions as a probe of the protonation site. Phys Chem Chem Phys 2015; 17:25755-60. [DOI: 10.1039/c5cp01122a] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Where does the proton go?
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Affiliation(s)
- Géraldine Féraud
- CNRS, Aix Marseille Université
- PIIM
- Physique des Interactions Ioniques et Moléculaires (UMR-7345)
- 13397 Marseille Cedex 20
- France
| | - Natalia Esteves-López
- CNRS, Aix Marseille Université
- PIIM
- Physique des Interactions Ioniques et Moléculaires (UMR-7345)
- 13397 Marseille Cedex 20
- France
| | - Claude Dedonder-Lardeux
- CNRS, Aix Marseille Université
- PIIM
- Physique des Interactions Ioniques et Moléculaires (UMR-7345)
- 13397 Marseille Cedex 20
- France
| | - Christophe Jouvet
- CNRS, Aix Marseille Université
- PIIM
- Physique des Interactions Ioniques et Moléculaires (UMR-7345)
- 13397 Marseille Cedex 20
- France
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24
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Wright P, Alex A, Harvey S, Parsons T, Pullen F. Understanding collision-induced dissociation of dofetilide: a case study in the application of density functional theory as an aid to mass spectral interpretation. Analyst 2014; 138:6869-80. [PMID: 24071718 DOI: 10.1039/c3an01103h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Fragmentation of molecules under collision-induced dissociation (CID) conditions is not well-understood. This may make interpretation of MSMS spectra difficult and limit the effectiveness of software tools intended to aid mass spectral interpretation. Density Functional Theory (DFT) has been successfully applied to explain the thermodynamics of fragmentation in the gas phase by the modelling the effect that protonation has on the bond lengths (and hence bond strengths). In this study, dofetilide and four methylated analogues were used to investigate further the potential for using DFT to understand and predict the CID fragmentation routes. The products ions present in the CID spectra of all five compounds were consistent with charge-directed fragmentation, with protonation adjacent to the cleavage site being required to initiate fragmentation. Protonation at the dissociative site may have occurred either directly or via proton migration. A correlation was observed between protonation-induced bond lengthening and the bonds which were observed to break in the CID spectra. This correlation was quantitative in that the bonds calculated to elongate to the greatest extent gave rise to the most abundant of the major product ions. Thus such quantum calculations may offer the potential for contributing to a predictive tool for aiding the accuracy and speed mass spectral interpretation by generating numerical data in the form of bond length increases to act as descriptors flagging potential bond cleavages.
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Affiliation(s)
- Patricia Wright
- School of Science, University of Greenwich, Medway Campus, Chatham, Kent, ME4 4TB, UK.
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25
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Lapthorn C, Dines TJ, Chowdhry BZ, Perkins GL, Pullen FS. Can ion mobility mass spectrometry and density functional theory help elucidate protonation sites in 'small' molecules? RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2013; 27:2399-2410. [PMID: 24097396 DOI: 10.1002/rcm.6700] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 07/28/2013] [Accepted: 07/29/2013] [Indexed: 06/02/2023]
Abstract
RATIONALE Ion mobility spectrometry-mass spectrometry (IMS-MS) offers an opportunity to combine measurements and/or calculations of the collision cross-sections and subsequent mass spectra with computational modelling in order to derive the three-dimensional structure of ions. IMS-MS has previously been reported to separate two components for the compound norfloxacin, explained by protonation on two different sites, enabling the separation of protonated isomers (protomers) using ion mobility with distinguishable tandem mass spectrometric (MS/MS) data. This study reveals further insights into the specific example of norfloxacin and wider implications for ion mobility mass spectrometry. METHODS Using a quadrupole ion mobility time-of-flight mass spectrometer, the IMS and MS/MS spectra of norfloxacin were recorded and compared with theoretical calculations using molecular modelling (density functional theory), and subsequent collision cross-section calculations using projection approximation. RESULTS A third significant component in the ion mobilogram of norfloxacin was observed under similar experimental conditions to those previously reported. The presence of the new component is convoluted by co-elution with another previously observed component. CONCLUSIONS This case demonstrates the potential of combined IMS-MS/MS with molecular modelling information for increased understanding of 'small-molecule' fragmentation pathways.
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Affiliation(s)
- Cris Lapthorn
- School of Science, University of Greenwich, Medway Campus, Chatham Maritime, ME4 4TB, UK
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26
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Chai Y, Hu N, Pan Y. Kinetic and thermodynamic control of protonation in atmospheric pressure chemical ionization. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2013; 24:1097-1101. [PMID: 23633014 DOI: 10.1007/s13361-013-0626-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 03/21/2013] [Accepted: 03/21/2013] [Indexed: 06/02/2023]
Abstract
For p-(dimethylamino)chalcone (p-DMAC), the N atom is the most basic site in the liquid phase, whereas the O atom possesses the highest proton affinity in the gas phase. A novel and interesting observation is reported that the N- and O-protonated p-DMAC can be competitively produced in atmospheric pressure chemical ionization (APCI) with the change of solvents and ionization conditions. In neat methanol or acetonitrile, the protonation is always under thermodynamic control to form the O-protonated ion. When methanol/water or acetonitrile/water was used as the solvent, the protonation is kinetically controlled to form the N-protonated ion under conditions of relatively high infusion rate and high concentration of water in the mixed solvent. The regioselectivity of protonation of p-DMAC in APCI is probably attributed to the bulky solvent cluster reagent ions (S(n)H(+)) and the analyte having different preferred protonation sites in the liquid phase and gas phase.
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Affiliation(s)
- Yunfeng Chai
- Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang, China
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27
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Guerrero A, Baer T, Chana A, González J, Dávalos JZ. Gas Phase Acidity Measurement of Local Acidic Groups in Multifunctional Species: Controlling the Binding Sites in Hydroxycinnamic Acids. J Am Chem Soc 2013; 135:9681-90. [DOI: 10.1021/ja400571r] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andres Guerrero
- Instituto
de Química Física “Rocasolano”, CSIC, C Serrano 119, Madrid, E-28006, Spain
| | - Tomas Baer
- Instituto
de Química Física “Rocasolano”, CSIC, C Serrano 119, Madrid, E-28006, Spain
| | - Antonio Chana
- Instituto
de Química Física “Rocasolano”, CSIC, C Serrano 119, Madrid, E-28006, Spain
| | - Javier González
- Instituto
de Química Física “Rocasolano”, CSIC, C Serrano 119, Madrid, E-28006, Spain
| | - Juan Z. Dávalos
- Instituto
de Química Física “Rocasolano”, CSIC, C Serrano 119, Madrid, E-28006, Spain
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28
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Bouchoux G. From the mobile proton to wandering hydride ion: mechanistic aspects of gas-phase ion chemistry. JOURNAL OF MASS SPECTROMETRY : JMS 2013; 48:505-518. [PMID: 23584944 DOI: 10.1002/jms.3204] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Revised: 03/06/2013] [Accepted: 03/06/2013] [Indexed: 06/02/2023]
Abstract
Structural characterization of molecular species by mass spectrometry supposes the knowledge of the type of ions generated and the mechanism by which they dissociate. In this context, a need for a rationalization of electrospray ionization(+)(-) mass spectra of small molecules has been recently expressed. Similarly, at the other end of the mass scale, efforts are currently made to interpret the major fragmentation processes of protonated and deprotonated peptides and their reduced forms produced in electron capture or electron transfer experiments. Most fragmentation processes of molecular and pseudo-molecular ions produced in the ion source of a mass spectrometer may be described by a combination of several key mechanistic steps: simple bond dissociation, formation of ion-neutral complex intermediates, hydrogen atom, hydride ion or proton migrations and nucleophilic attack. Selected crucial aspects of these elementary reactions, occurring inside positively charged ions, will be recalled and illustrated by examples taken in recent mass spectrometry literature. Emphasis will be given on the protonation process and its consequence in terms of structure and energetic.
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Affiliation(s)
- Guy Bouchoux
- Laboratoire des Mécanismes Réactionnels. Ecole Polytechnique. CNRS, Université Paris-sud, 91128, Palaiseau, France.
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29
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Pechan T, Gwaltney SR. Calculations of relative intensities of fragment ions in the MSMS spectra of a doubly charged penta-peptide. BMC Bioinformatics 2012; 13 Suppl 15:S13. [PMID: 23046347 PMCID: PMC3439735 DOI: 10.1186/1471-2105-13-s15-s13] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Currently, the tandem mass spectrometry (MSMS) of peptides is a dominant technique used to identify peptides and consequently proteins. The peptide fragmentation inside the mass analyzer typically offers a spectrum containing several different groups of ions. The mass to charge (m/z) values of these ions can be exactly calculated following simple rules based on the possible peptide fragmentation reactions. But the (relative) intensities of the particular ions cannot be simply predicted from the amino-acid sequence of the peptide. This study presents initial work towards developing a theoretical fundamental approach to ion intensity elucidation by utilizing quantum mechanical computations. METHODS MSMS spectra of the doubly charged GAVLK peptide were collected on electrospray ion trap mass spectrometers using low energy modes of fragmentation. Density functional theory (DFT) calculations were performed on the population of ion precursors to determine the fragment ion intensities corresponding to a Boltzmann distribution of the protonation of nitrogens in the peptide backbone amide bonds. RESULTS We were able to a) predict the y and b ions intensities order in concert with the experimental observation; b) predict relative intensities of y ions with errors not exceeding the experimental variation. CONCLUSIONS These results suggest that the GAVLK peptide fragmentation process in the ion trap mass spectrometer is predominantly driven by the thermodynamic stability of the precursor ions formed upon ionization of the sample. The computational approach presented in this manuscript successfully calculated ion intensities in the mass spectra of this doubly charged tryptic peptide, based solely on its amino acid sequence. As such, this work indicates a potential of incorporating quantum mechanical calculations into mass spectrometry based algorithms for molecular identification.
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Affiliation(s)
- Tibor Pechan
- Institute for Genomics, Biocomputing and Biotechnology, Mississippi Agricultural and Forestry Experiment Station, High Performance Computing Collaboratory, Mississippi State University, Mississippi State, MS 39762, USA.
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Bokatzian-Johnson SS, Stover ML, Dixon DA, Cassady CJ. A comparison of the effects of amide and acid groups at the C-terminus on the collision-induced dissociation of deprotonated peptides. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:1544-1557. [PMID: 22833234 DOI: 10.1007/s13361-012-0431-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 05/10/2012] [Accepted: 06/12/2012] [Indexed: 06/01/2023]
Abstract
The dissociative behavior of peptide amides and free acids was explored using low-energy collision-induced dissociation and high level computational theory. Both positive and negative ion modes were utilized, but the most profound differences were observed for the deprotonated species. Deprotonated peptide amides produce a characteristic c(m-2)(-) product ion (where m is the number of residues in the peptide) that is either absent or in low abundance in the analogous peptide acid spectrum. Peptide acids show an enhanced formation of c(m-3)(-); however, this is not generally as pronounced as c(m-2)(-) production from amides. The most notable occurrence of an amide-specific product ion is for laminin amide (YIGSR-NH(2)) and this case was investigated using several modified peptides. Mechanisms involving 6- and 9-membered ring formation were proposed, and their energetic properties were investigated using G3(MP2) molecular orbital theory calculations. For example, with C-terminal deprotonation of pentaglycine amide, formation of c(m-2)(-) and a 6-membered ring diketopiperazine neutral requires >31.6 kcal/mol, which is 26.1 kcal/mol less than the analogous process involving the peptide acid. The end group specific fragmentation of peptide amides in the negative ion mode may be useful for identifying such groups in proteomic applications.
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Campbell JL, Le Blanc JCY, Schneider BB. Probing Electrospray Ionization Dynamics Using Differential Mobility Spectrometry: The Curious Case of 4-Aminobenzoic Acid. Anal Chem 2012; 84:7857-64. [DOI: 10.1021/ac301529w] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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