1
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Wan J, Nytka M, Qian H, Vu K, Lemr K, Tureček F. Nitrile Imines as Peptide and Oligonucleotide Photo-Cross-Linkers in Gas-Phase Ions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2024; 35:344-356. [PMID: 38252626 DOI: 10.1021/jasms.3c00379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Nitrile imines produced by photodissociation of 2,5-diaryltetrazoles undergo cross-linking reactions with amide groups in peptide-tetrazole (tet-peptide) conjugates and a tet-peptide-dinucleotide complex. Tetrazole photodissociation in gas-phase ions is efficient, achieving ca. 50% conversion with 2 laser pulses at 250 nm. The formation of cross-links was detected by CID-MS3 that showed structure-significant dissociations by loss of side-chain groups and internal peptide segments. The structure and composition of cross-linking products were established by a combination of UV-vis action spectroscopy and cyclic ion mobility mass spectrometry (c-IMS). The experimental absorption bands were found to match the bands calculated for vibronic absorption spectra of nitrile imines and cross-linked hydrazone isomers. The calculated collision cross sections (CCSth) for these ions were related to the matching experimental CCSexp from multipass c-IMS measurements. Loss of N2 from tet-peptide conjugates was calculated to be a mildly endothermic reaction with ΔH0 = 80 kJ mol-1 in the gas phase. The excess energy in the photolytically formed nitrile imine is thought to drive endothermic proton transfer, followed by exothermic cyclization to a sterically accessible peptide amide group. The exothermic nitrile imine reaction with peptide amides is promoted by proton transfer and may involve an initial [3 + 2] cycloaddition followed by cleavage of the oxadiazole intermediate. Nucleophilic groups, such as cysteine thiol, did not compete with the amide cyclization. Nitrile imine cross-linking to 2'-deoxycytidylguanosine was found to be >80% efficient and highly specific in targeting guanine. The further potential for exploring nitrile-imine cross-linking for biomolecular structure analysis is discussed.
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Affiliation(s)
- Jiahao Wan
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
| | - Marianna Nytka
- Department of Analytical Chemistry, Faculty of Science, Palacky University, 17. listopadu 12, Olomouc 779 00, Czech Republic
| | - Haocheng Qian
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
| | - Kim Vu
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
| | - Karel Lemr
- Department of Analytical Chemistry, Faculty of Science, Palacky University, 17. listopadu 12, Olomouc 779 00, Czech Republic
- Institute of Microbiology of the Czech Academy of Sciences, Prague 142 20, Czech Republic
| | - František Tureček
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
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2
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Tureček F. Covalent crosslinking in gas-phase biomolecular ions. An account and perspective. Phys Chem Chem Phys 2023; 25:32292-32304. [PMID: 37990588 DOI: 10.1039/d3cp04879a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2023]
Abstract
Photochemical crosslinking in gas-phase ion complexes has been introduced as a method to study biomolecular structures and dynamics. Emphasis has been on carbene-based crosslinking induced by photodissociation of diazirine-tagged ions. The features that characterize gas-phase crosslinking include (1) complex formation in electrospray droplets that allows for library-type screening; (2) well defined stoichiometry of the complexes due to mass-selective isolation; (3) facile reaction monitoring and yield determination, and (4) post-crosslinking structure analysis by tandem mass spectrometry that has been combined with hydrogen-deuterium exchange, UV-vis action spectroscopy, and ion mobility measurements. In this account, examples are given of peptide-peptide, peptide-nucleotide, and peptide-ligand crosslinking that chiefly used carbene-based reactions. The pros and cons of gas-phase crosslinking are discussed. Nitrile-imine based crosslinking in gas-phase ions is introduced as a promising new approach to ion structure analysis that offers high efficiency and has the potential for wide ranging applications.
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Affiliation(s)
- František Tureček
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, WA 98195-1700, USA.
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3
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Liu Y, Ma C, Nováková G, Marek A, Tureček F. Charge-Tagged Nucleosides in the Gas Phase: UV-Vis Action Spectroscopy and Structures of Cytidine Cations, Dications, and Cation Radicals. J Phys Chem A 2021; 125:6096-6108. [PMID: 34240862 DOI: 10.1021/acs.jpca.1c03477] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Cytidine ribonucleosides were furnished at O5' with fixed-charge 6-trimethylammoniumhexan-1-aminecarbonyl tags and studied by UV-vis photodissociation action spectroscopy in the gas phase to probe isolated nucleobase chromophores in their neutral, protonated, and hydrogen-adduct radical forms. The action spectrum of the doubly charged cytidine conjugate showed bands at 310 and 270 nm that were assigned to the N3- and O2-protonated cytosine tautomers formed by electrospray, respectively. In contrast, cytidine conjugates coordinated to dibenzo-18-crown-6-ether (DBCE) in a noncovalent complex were found to strongly favor protonation at N3, forming a single-ion tautomer. This allowed us to form cytidine N3-H radicals by electron transfer dissociation of the complex and study their action spectra. Cytidine radicals showed only very weak absorption in the visible region of the spectrum for dipole-disallowed transitions to the low (A and B) excited states. The main bands were observed at 360, 300, and 250 nm that were assigned with the help of theoretical vibronic spectra obtained by time-dependent density functional theory calculations of multiple (>300) radical vibrational configurations. Collision-induced dissociations of cytidine radicals proceeded by major cleavage of the N1-C1' glycosidic bond leading to loss of cytosine and competitive loss of N3-hydrogen atom. These dissociations were characterized by calculations of transition-state structures and energies using combined Born-Oppenheimer molecular dynamics and DFT calculations. Overall, cytidine radicals were found to be kinetically and thermodynamically more stable than previously reported analogous adenosine and guanosine radicals.
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Affiliation(s)
- Yue Liu
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
| | - Congcong Ma
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
| | - Gabriela Nováková
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 16610 Prague 6, Czech Republic
| | - Aleš Marek
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 16610 Prague 6, Czech Republic
| | - František Tureček
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
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4
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Abdelmouleh M, Lalande M, Nicol E, Frison G, van der Rest G, Poully JC. Chemical Processes Involving 18-Crown-6-Ether in Activated Noncovalent Complexes with Protonated Peptides. Chemphyschem 2021; 22:1243-1250. [PMID: 33881793 DOI: 10.1002/cphc.202100075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 04/07/2021] [Indexed: 11/10/2022]
Abstract
These last decades, it has been widely assumed that 18-crown-6-ether (CE) plays a spectator role during the chemical processes occurring in isolated host-guest complexes between peptides or proteins and CE after activation in mass spectrometers. Our present experimental and theoretical results challenge this hypothesis by showing that CE can abstract a proton or a protonated molecule from protonated peptides after activation by collisions in argon or electron capture/transfer. Furthermore, thanks to comparison between experimental and calculated values of collision cross-sections, we demonstrate that CE can change binding site after electron transfer. We also propose detailed mechanisms for these processes.
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Affiliation(s)
- Marwa Abdelmouleh
- CIMAP UMR 6252, CEA/CNRS/ENSICAEN/Université de Caen Normandie, Bd Becquerel, 14070, Caen, France
| | - Mathieu Lalande
- CIMAP UMR 6252, CEA/CNRS/ENSICAEN/Université de Caen Normandie, Bd Becquerel, 14070, Caen, France
| | - Edith Nicol
- Laboratoire de Chimie Moléculaire, Ecole Polytech, Inst Polytech Paris, CNRS, 91128, Palaiseau, France
| | - Gilles Frison
- Laboratoire de Chimie Moléculaire, Ecole Polytech, Inst Polytech Paris, CNRS, 91128, Palaiseau, France.,Laboratoire de Chimie Théorique, Sorbonne Université and CNRS, 75005, Paris, France
| | - Guillaume van der Rest
- Institut de Chimie Physique, Université Paris Saclay, CNRS, Bâtiment 349, 91405, Orsay, France
| | - Jean-Christophe Poully
- CIMAP UMR 6252, CEA/CNRS/ENSICAEN/Université de Caen Normandie, Bd Becquerel, 14070, Caen, France
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5
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Huang SR, Nováková G, Marek A, Tureček F. The Elusive Noncanonical Isomers of Ionized 9-Methyladenine and 2′-Deoxyadenosine. J Phys Chem A 2020; 125:338-348. [DOI: 10.1021/acs.jpca.0c10293] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Shu R. Huang
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
| | - Gabriela Nováková
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
| | - Aleš Marek
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
| | - František Tureček
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
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6
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Bayat P, Lesage D, Cole RB. TUTORIAL: ION ACTIVATION IN TANDEM MASS SPECTROMETRY USING ULTRA-HIGH RESOLUTION INSTRUMENTATION. MASS SPECTROMETRY REVIEWS 2020; 39:680-702. [PMID: 32043643 DOI: 10.1002/mas.21623] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 01/23/2020] [Indexed: 05/16/2023]
Abstract
Tandem mass spectrometry involves isolation of specific precursor ions and their subsequent excitation through collision-, photon-, or electron-mediated activation techniques in order to induce unimolecular dissociation leading to formation of fragment ions. These powerful ion activation techniques, typically used in between mass selection and mass analysis steps for structural elucidation, have not only found a wide variety of analytical applications in chemistry and biology, but they have also been used to study the fundamental properties of ions in the gas phase. In this tutorial paper, a brief overview is presented of the theories that have been used to describe the activation of ions and their subsequent unimolecular dissociation. Acronyms of the presented techniques include CID, PQD, HCD, SORI, SID, BIRD, IRMPD, UVPD, EPD, ECD, EDD, ETD, and EID. The fundamental principles of these techniques are discussed in the context of their implementation on ultra-high resolution tandem mass spectrometers. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.
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Affiliation(s)
- Parisa Bayat
- Faculté des Sciences et Ingénierie, Sorbonne Université, IPCM (UMR 8232), F-75252, Paris, France
| | - Denis Lesage
- Faculté des Sciences et Ingénierie, Sorbonne Université, IPCM (UMR 8232), F-75252, Paris, France
| | - Richard B Cole
- Faculté des Sciences et Ingénierie, Sorbonne Université, IPCM (UMR 8232), F-75252, Paris, France
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7
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Huang SR, Liu Y, Tureček F. UV–vis Photodissociation Action Spectroscopy Reveals Cytosine–Guanine Hydrogen Transfer in DNA Tetranucleotide Cation Radicals upon One-Electron Reduction. J Phys Chem B 2020; 124:3505-3517. [DOI: 10.1021/acs.jpcb.0c01693] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Shu R. Huang
- Department of Chemistry, Bagley Hall, Box
351700, University of Washington, Seattle, Washington 98195-1700, United States
| | - Yue Liu
- Department of Chemistry, Bagley Hall, Box
351700, University of Washington, Seattle, Washington 98195-1700, United States
| | - František Tureček
- Department of Chemistry, Bagley Hall, Box
351700, University of Washington, Seattle, Washington 98195-1700, United States
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8
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Liu Y, Huang SR, Tureček F. Guanine–adenine interactions in DNA tetranucleotide cation radicals revealed by UV/vis photodissociation action spectroscopy and theory. Phys Chem Chem Phys 2020; 22:16831-16842. [DOI: 10.1039/d0cp02362k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Hydrogen-rich cation radicals (GATT + 2H)+˙ and (AGTT + 2H)+˙ represent oligonucleotide models of charged hydrogen atom adducts to DNA.
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Affiliation(s)
- Yue Liu
- Department of Chemistry
- University of Washington
- Seattle
- USA
| | - Shu R. Huang
- Department of Chemistry
- University of Washington
- Seattle
- USA
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9
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Dang A, Liu Y, Tureček F. UV–Vis Action Spectroscopy of Guanine, 9-Methylguanine, and Guanosine Cation Radicals in the Gas Phase. J Phys Chem A 2019; 123:3272-3284. [DOI: 10.1021/acs.jpca.9b01542] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Andy Dang
- Department of Chemistry, University of Washington, Bagley Hall,
Box 351700, Seattle, Washington 98195-1700, United States
| | - Yue Liu
- Department of Chemistry, University of Washington, Bagley Hall,
Box 351700, Seattle, Washington 98195-1700, United States
| | - František Tureček
- Department of Chemistry, University of Washington, Bagley Hall,
Box 351700, Seattle, Washington 98195-1700, United States
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10
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Huang SR, Liu Y, Tureček F. Non-covalent complexes of the peptide fragment Gly-Asn-Asn-Gln-Gln-Asn-Tyr in the gas-phase. Photodissociative cross-linking, Born–Oppenheimer molecular dynamics, and ab initio computational binding study. Phys Chem Chem Phys 2019; 21:2046-2056. [DOI: 10.1039/c8cp06893c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photodissociative cross-linking in the Gly-Asn-Asn-Gln-Gln-Asn-Tyr peptide ion complex revealed non-bonding interactions between the peptide units.
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Affiliation(s)
- Shu R. Huang
- Department of Chemistry
- University of Washington
- Seattle
- USA
| | - Yang Liu
- Department of Chemistry
- University of Washington
- Seattle
- USA
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11
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Kempkes LJ, Martens J, Berden G, Houthuijs KJ, Oomens J. Investigation of the position of the radical in z3-ions resulting from electron transfer dissociation using infrared ion spectroscopy. Faraday Discuss 2019; 217:434-452. [DOI: 10.1039/c8fd00202a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The molecular structures of six open-shell z3-ions resulting from electron transfer dissociation mass spectrometry (ETD MS) were investigated using infrared ion spectroscopy in combination with density functional theory and molecular mechanics/molecular dynamics calculations.
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Affiliation(s)
| | - Jonathan Martens
- Radboud University
- FELIX Laboratory
- 6525 ED Nijmegen
- The Netherlands
| | - Giel Berden
- Radboud University
- FELIX Laboratory
- 6525 ED Nijmegen
- The Netherlands
| | - Kas J. Houthuijs
- Radboud University
- FELIX Laboratory
- 6525 ED Nijmegen
- The Netherlands
| | - Jos Oomens
- Radboud University
- FELIX Laboratory
- 6525 ED Nijmegen
- The Netherlands
- Van’t Hoff Institute for Molecular Sciences
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12
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Kempkes LM, Martens J, Berden G, Oomens J. Spectroscopic Characterization of an Extensive Set of c-Type Peptide Fragment Ions Formed by Electron Transfer Dissociation Suggests Exclusive Formation of Amide Isomers. J Phys Chem Lett 2018; 9:6404-6411. [PMID: 30343579 PMCID: PMC6240889 DOI: 10.1021/acs.jpclett.8b02850] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Accepted: 10/18/2018] [Indexed: 06/08/2023]
Abstract
Electron attachment dissociation (electron capture dissociation (ECD) and electron transfer dissociation (ETD)) applied to gaseous multiply protonated peptides leads predominantly to backbone N-Cα bond cleavages and the formation of c- and z-type fragment ions. The mechanisms involved in the formation of these ions have been the subject of much discussion. Here, we determine the molecular structures of an extensive set of c-type ions produced by ETD using infrared ion spectroscopy. Nine c3- and c4-ions are investigated to establish their C-terminal structure as either enol-imine or amide isomers by comparison of the experimental infrared spectra with quantum-chemically predicted spectra for both structural variants. The spectra suggest that all c-ions investigated possess an amide structure; the absence of the NH bending mode at approximately 1000-1200 cm-1 serves as an important diagnostic feature.
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Affiliation(s)
- Lisanne
J. M. Kempkes
- FELIX
Laboratory, Institute for Molecules and Materials, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Jonathan Martens
- FELIX
Laboratory, Institute for Molecules and Materials, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Giel Berden
- FELIX
Laboratory, Institute for Molecules and Materials, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Jos Oomens
- FELIX
Laboratory, Institute for Molecules and Materials, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
- Van’t
Hoff Institute for Molecular Sciences, University
of Amsterdam, Science
Park 904, 1098 XH Amsterdam, The Netherlands
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13
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Lermyte F, Valkenborg D, Loo JA, Sobott F. Radical solutions: Principles and application of electron-based dissociation in mass spectrometry-based analysis of protein structure. MASS SPECTROMETRY REVIEWS 2018; 37:750-771. [PMID: 29425406 PMCID: PMC6131092 DOI: 10.1002/mas.21560] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 01/19/2018] [Accepted: 01/19/2018] [Indexed: 05/11/2023]
Abstract
In recent years, electron capture (ECD) and electron transfer dissociation (ETD) have emerged as two of the most useful methods in mass spectrometry-based protein analysis, evidenced by a considerable and growing body of literature. In large part, the interest in these methods is due to their ability to induce backbone fragmentation with very little disruption of noncovalent interactions which allows inference of information regarding higher order structure from the observed fragmentation behavior. Here, we review the evolution of electron-based dissociation methods, and pay particular attention to their application in "native" mass spectrometry, their mechanism, determinants of fragmentation behavior, and recent developments in available instrumentation. Although we focus on the two most widely used methods-ECD and ETD-we also discuss the use of other ion/electron, ion/ion, and ion/neutral fragmentation methods, useful for interrogation of a range of classes of biomolecules in positive- and negative-ion mode, and speculate about how this exciting field might evolve in the coming years.
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Affiliation(s)
- Frederik Lermyte
- Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, Antwerp, Belgium
- Centre for Proteomics, University of Antwerp, Antwerp, Belgium
- School of Engineering, University of Warwick, Coventry, United Kingdom
| | - Dirk Valkenborg
- Centre for Proteomics, University of Antwerp, Antwerp, Belgium
- Interuniversity Institute for Biostatistics and Statistical Bioinformatics, Hasselt University, Agoralaan, Diepenbeek, Belgium
- Applied Bio and Molecular Systems, Flemish Institute for Technological Research (VITO), Mol, Belgium
| | - Joseph A Loo
- Department of Biological Chemistry, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, California
- UCLA/DOE Institute for Genomics and Proteomics, University of California-Los Angeles, Los Angeles, California
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California
| | - Frank Sobott
- Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, Antwerp, Belgium
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
- School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
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14
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Imaoka N, Houferak C, Murphy MP, Nguyen HTH, Dang A, Tureček F. Spontaneous Isomerization of Peptide Cation Radicals Following Electron Transfer Dissociation Revealed by UV-Vis Photodissociation Action Spectroscopy. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:1768-1780. [PMID: 29340957 DOI: 10.1007/s13361-017-1871-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Revised: 12/06/2017] [Accepted: 12/14/2017] [Indexed: 06/07/2023]
Abstract
Peptide cation radicals of the z-type were produced by electron transfer dissociation (ETD) of peptide dications and studied by UV-Vis photodissociation (UVPD) action spectroscopy. Cation radicals containing the Asp (D), Asn (N), Glu (E), and Gln (Q) residues were found to spontaneously isomerize by hydrogen atom migrations upon ETD. Canonical N-terminal [z4 + H]+● fragment ion-radicals of the R-C●H-CONH- type, initially formed by N-Cα bond cleavage, were found to be minor components of the stable ion fraction. Vibronically broadened UV-Vis absorption spectra were calculated by time-dependent density functional theory for several [●DAAR + H]+ isomers and used to assign structures to the action spectra. The potential energy surface of [●DAAR + H]+ isomers was mapped by ab initio and density functional theory calculations that revealed multiple isomerization pathways by hydrogen atom migrations. The transition-state energies for the isomerizations were found to be lower than the dissociation thresholds, accounting for the isomerization in non-dissociating ions. The facile isomerization in [●XAAR + H]+ ions (X = D, N, E, and Q) was attributed to low-energy intermediates having the radical defect in the side chain that can promote hydrogen migration along backbone Cα positions. A similar side-chain mediated mechanism is suggested for the facile intermolecular hydrogen migration between the c- and [z + H]●-ETD fragments containing Asp, Asn, Glu, and Gln residues. Graphical Abstract ᅟ.
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Affiliation(s)
- Naruaki Imaoka
- Department of Physics, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
| | - Camille Houferak
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA, 98195-1700, USA
| | - Megan P Murphy
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA, 98195-1700, USA
| | - Huong T H Nguyen
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA, 98195-1700, USA
| | - Andy Dang
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA, 98195-1700, USA
| | - František Tureček
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA, 98195-1700, USA.
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15
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Nguyen HTH, Tureček F. Near-UV Photodissociation of Tryptic Peptide Cation Radicals. Scope and Effects of Amino Acid Residues and Radical Sites. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:1333-1344. [PMID: 28155086 DOI: 10.1007/s13361-016-1586-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 12/20/2016] [Accepted: 12/21/2016] [Indexed: 06/06/2023]
Abstract
Peptide cation-radical fragment ions of the z-type, [●AXAR+], [●AXAK+], and [●XAR+], where X = A, C, D, E, F, G, H, K, L, M, N, P, Y, and W, were generated by electron transfer dissociation of peptide dications and investigated by MS3-near-ultraviolet photodissociation (UVPD) at 355 nm. Laser-pulse dependence measurements indicated that the ion populations were homogeneous for most X residues except phenylalanine. UVPD resulted in dissociations of backbone CO─NH bonds that were accompanied by hydrogen atom transfer, producing fragment ions of the [yn]+ type. Compared with collision-induced dissociation, UVPD yielded less side-chain dissociations even for residues that are sensitive to radical-induced side-chain bond cleavages. The backbone dissociations are triggered by transitions to second (B) excited electronic states in the peptide ion R-CH●-CONH- chromophores that are resonant with the 355-nm photon energy. Electron promotion increases the polarity of the B excited states, R-CH+-C●(O-)NH-, and steers the reaction to proceed by transfer of protons from proximate acidic Cα and amide nitrogen positions. Graphical Abstract ᅟ.
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Affiliation(s)
- Huong T H Nguyen
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, WA, 98195-1700, USA
| | - František Tureček
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, WA, 98195-1700, USA.
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16
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Nguyen HTH, Andrikopoulos PC, Bím D, Rulíšek L, Dang A, Tureček F. Radical Reactions Affecting Polar Groups in Threonine Peptide Ions. J Phys Chem B 2017; 121:6557-6569. [DOI: 10.1021/acs.jpcb.7b04661] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Huong T. H. Nguyen
- Department
of Chemistry, University of Washington, Bagley Hall, Box
351700, Seattle, Washington 98195-1700, United States
| | - Prokopis C. Andrikopoulos
- Institute
of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám 2, 16610 Prague, Czech Republic
| | - Daniel Bím
- Institute
of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám 2, 16610 Prague, Czech Republic
| | - Lubomír Rulíšek
- Institute
of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám 2, 16610 Prague, Czech Republic
| | - Andy Dang
- Department
of Chemistry, University of Washington, Bagley Hall, Box
351700, Seattle, Washington 98195-1700, United States
| | - František Tureček
- Department
of Chemistry, University of Washington, Bagley Hall, Box
351700, Seattle, Washington 98195-1700, United States
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17
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Schäfer M, Peckelsen K, Paul M, Martens J, Oomens J, Berden G, Berkessel A, Meijer AJHM. Hydrogen Tunneling above Room Temperature Evidenced by Infrared Ion Spectroscopy. J Am Chem Soc 2017; 139:5779-5786. [PMID: 28282985 DOI: 10.1021/jacs.6b10348] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
While hydrogen tunneling at elevated temperatures has, for instance, often been postulated in biochemical processes, spectroscopic proof is thus far limited to cryogenic conditions, under which thermal reactivity is negligible. We report spectroscopic evidence for H-tunneling in the gas phase at temperatures around 320-350 K observed in the isomerization reaction of a hydroxycarbene into an aldehyde. The charge-tagged carbene was generated in situ in a tandem mass spectrometer by decarboxylation of oxo[4-(trimethylammonio)phenyl]acetic acid upon collision induced dissociation. All ion structures involved are characterized by infrared ion spectroscopy and quantum chemical calculations. The charge-tagged phenylhydroxycarbene undergoes a 1,2-H-shift to the corresponding aldehyde with an half-life of about 10 s, evidenced by isomer-selective two-color (IR-IR) spectroscopy. In contrast, the deuterated (OD) carbene analogue showed much reduced 1,2-D-shift reactivity with an estimated half-life of at least 200 s under the experimental conditions, and provides clear evidence for hydrogen atom tunneling in the H-isotopologue. This is the first spectroscopic confirmation of hydrogen atom tunneling governing 1,2-H-shift reactions at noncryogenic temperatures, which is of broad significance for a range of (bio)chemical processes, including enzymatic transformations and organocatalysis.
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Affiliation(s)
- Mathias Schäfer
- Department of Chemistry, Organic Chemistry, University of Cologne , Greinstraße 4, 50939 Cologne, Germany
| | - Katrin Peckelsen
- Department of Chemistry, Organic Chemistry, University of Cologne , Greinstraße 4, 50939 Cologne, Germany
| | - Mathias Paul
- Department of Chemistry, Organic Chemistry, University of Cologne , Greinstraße 4, 50939 Cologne, Germany
| | - Jonathan Martens
- Radboud University , Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands
| | - Jos Oomens
- Radboud University , Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands.,Van't Hoff Institute for Molecular Sciences, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Giel Berden
- Radboud University , Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands
| | - Albrecht Berkessel
- Department of Chemistry, Organic Chemistry, University of Cologne , Greinstraße 4, 50939 Cologne, Germany
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18
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Pepin R, Layton ED, Liu Y, Afonso C, Tureček F. Where Does the Electron Go? Stable and Metastable Peptide Cation Radicals Formed by Electron Transfer. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:164-181. [PMID: 27709510 DOI: 10.1007/s13361-016-1512-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 09/12/2016] [Accepted: 09/15/2016] [Indexed: 06/06/2023]
Abstract
Electron transfer to doubly and triply charged heptapeptide ions containing polar residues Arg, Lys, and Asp in combination with nonpolar Gly, Ala, and Pro or Leu generates stable and metastable charge-reduced ions, (M + 2H)+●, in addition to standard electron-transfer dissociation (ETD) fragment ions. The metastable (M + 2H)+● ions spontaneously dissociate upon resonant ejection from the linear ion trap, giving irregularly shaped peaks with offset m/z values. The fractions of stable and metastable (M + 2H)+● ions and their mass shifts depend on the presence of Pro-4 and Leu-4 residues in the peptides, with the Pro-4 sequences giving larger fractions of the stable ions while showing smaller mass shifts for the metastables. Conversion of the Asp and C-terminal carboxyl groups to methyl esters further lowers the charge-reduced ion stability. Collisional activation and photodissociation at 355 nm of mass-selected (M + 2H)+● results in different dissociations that give sequence specific MS3 spectra. With a single exception of charge-reduced (LKGLADR + 2H)+●, the MS3 spectra do not produce ETD sequence fragments of the c and z type. Hence, these (M + 2H)+● ions are covalent radicals, not ion-molecule complexes, undergoing dramatically different dissociations in the ground and excited electronic states. The increased stability of the Pro-4 containing (M + 2H)+● ions is attributed to radicals formed by opening of the Pro ring and undergoing further stabilization by hydrogen atom migrations. UV-VIS photodissociation action spectroscopy and time-dependent density functional theory calculations are used in a case in point study of the stable (LKGPADR + 2H)+● ion produced by ETD. In contrast to singly-reduced peptide ions, doubly reduced (M + 3H)+ ions are stable only when formed from the Pro-4 precursors and show all characteristics of even electron ions regarding no photon absorption at 355 nm or ion-molecule reactions, and exhibiting proton driven collision induced dissociations. Graphical Abstract ᅟ.
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Affiliation(s)
- Robert Pepin
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, WA, 98195-1700, USA
| | - Erik D Layton
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, WA, 98195-1700, USA
| | - Yang Liu
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, WA, 98195-1700, USA
| | - Carlos Afonso
- INSA Rouen, UNIROUEN, CNRS, COBRA, Normandie University, 76000, Rouen, France
| | - František Tureček
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, WA, 98195-1700, USA.
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19
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Asakawa D, Osaka I. High-Confidence Sequencing of Phosphopeptides by Electron Transfer Dissociation Mass Spectrometry Using Dinuclear Zinc(II) Complex. Anal Chem 2016; 88:12393-12402. [PMID: 28193068 DOI: 10.1021/acs.analchem.6b03645] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Phosphorylation is the most abundant protein modification, and tandem mass spectrometry (MS2) with electron transfer dissociation (ETD) has proven to be a promising method for phosphoproteomic applications owing to its ability to determine phosphorylation sites on proteins. However, low precursor charge states hinder the ability to obtain useful information through peptide sequencing by ETD, and the presence of acidic phosphate groups contributes to a low charge state of peptide ions. In the present report, we used a dinuclear zinc complex, (Zn2L)3+ (L = alkoxide form of 1,3-bis[bis(pyridin-2-ylmethyl)amino]propan-2-ol) for electrospray ionization (ESI), followed by ETD-MS2 analysis. Since (Zn2L)3+ selectively bound to phosphopeptide with addition of a positive charge per phosphate group, the use of (Zn2L)3+ for ESI improved the ionization yield of phosphopeptides in phosphoprotein digest. Additionally, an increase in the charge state of phosphopeptides were observed by addition of (Zn2L)3+, facilitating phosphopeptide sequencing by ETD-MS2. Since the binding between (Zn2L)3+ and the phosphate group was retained during the ETD process, a comparison between the ETD mass spectra obtained using two dinuclear zinc complex derivatives containing different zinc isotopes, namely (64Zn2L)3+ and (68Zn2L)3+, provided information about the number of phosphate groups in each fragment ion, allowing the phosphorylation site to be unambiguously determined. The details of the fragmentation processes of the (Zn2L)3+-phosphopeptide complex were investigated using a density functional theory calculation. As in the case of protonated peptides, ETD induced peptide backbone dissociation in the (Zn2L)3+-phosphopeptide complex proceeded through an aminoketyl radical intermediate.
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Affiliation(s)
- Daiki Asakawa
- National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki, 305-8568 Japan
| | - Issey Osaka
- Center for Nano Materials and Technology, Japan Advanced Institute of Science and Technology , 1-1 Asahidai, Nomi, Ishikawa, Japan
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20
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Viglino E, Lai CK, Mu X, Chu IK, Tureček F. Ground and Excited-Electronic-State Dissociations of Hydrogen-Rich and Hydrogen-Deficient Tyrosine Peptide Cation Radicals. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:1454-1467. [PMID: 27278824 DOI: 10.1007/s13361-016-1425-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 05/10/2016] [Accepted: 05/20/2016] [Indexed: 06/06/2023]
Abstract
We report a comprehensive study of collision-induced dissociation (CID) and near-UV photodissociation (UVPD) of a series of tyrosine-containing peptide cation radicals of the hydrogen-rich and hydrogen-deficient types. Stable, long-lived, hydrogen-rich peptide cation radicals, such as [AAAYR + 2H](+●) and several of its sequence and homology variants, were generated by electron transfer dissociation (ETD) of peptide-crown-ether complexes, and their CID-MS(3) dissociations were found to be dramatically different from those upon ETD of the respective peptide dications. All of the hydrogen-rich peptide cation radicals contained major (77%-94%) fractions of species having radical chromophores created by ETD that underwent photodissociation at 355 nm. Analysis of the CID and UVPD spectra pointed to arginine guanidinium radicals as the major components of the hydrogen-rich peptide cation radical population. Hydrogen-deficient peptide cation radicals were generated by intramolecular electron transfer in Cu(II)(2,2':6',2″-terpyridine) complexes and shown to contain chromophores absorbing at 355 nm and undergoing photodissociation. The CID and UVPD spectra showed major differences in fragmentation for [AAAYR](+●) that diminished as the Tyr residue was moved along the peptide chain. UVPD was found to be superior to CID in localizing Cα-radical positions in peptide cation radical intermediates. Graphical Abstract ᅟ.
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Affiliation(s)
- Emilie Viglino
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, WA, 981915-1700, USA
| | - Cheuk Kuen Lai
- Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Xiaoyan Mu
- Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Ivan K Chu
- Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, China.
| | - František Tureček
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, WA, 981915-1700, USA.
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21
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Pepin R, Petrone A, Laszlo KJ, Bush MF, Li X, Tureček F. Does Thermal Breathing Affect Collision Cross Sections of Gas-Phase Peptide Ions? An Ab Initio Molecular Dynamics Study. J Phys Chem Lett 2016; 7:2765-71. [PMID: 27389035 PMCID: PMC5032842 DOI: 10.1021/acs.jpclett.6b01187] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Ab initio molecular dynamics (AIMD) with density functional theory (DFT) was applied to explore conformational motions and collision cross sections (Ω) of folded (2) and extended (7) conformers of doubly charged peptide ions, (Ala-Ala-Leu-Arg + 2H)(2+), in the gas phase at 300 and 473 K. The experimental Ω of (Ala-Ala-Leu-Arg +2H)(2+) was measured as 149 ± 1.2 Å(2) at 298 K. Thermally distributed mean values of Ω for 2 and 7 at 300 and 473 K were only 0.8-1.1% larger than for the equilibrium 0 K structures. Long (>10 ps) trajectory calculations indicated entropy-driven conformational change of 2 to 7 that occurred at random within a ∼ 4 ps time window. The experimental Ω was found to fit the calculated population averaged values for 2 and 7, indicating a rapid conformer interconversion. Overall, thermal breathing had only a minor effect on the peptide ion collision cross sections.
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22
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Shaffer CJ, Martens J, Marek A, Oomens J, Tureček F. Photoleucine Survives Backbone Cleavage by Electron Transfer Dissociation. A Near-UV Photodissociation and Infrared Multiphoton Dissociation Action Spectroscopy Study. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:1176-1185. [PMID: 27059977 DOI: 10.1007/s13361-016-1390-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 03/15/2016] [Accepted: 03/16/2016] [Indexed: 06/05/2023]
Abstract
We report a combined experimental and computational study aimed at elucidating the structure of N-terminal fragment ions of the c type produced by electron transfer dissociation of photo-leucine (L*) peptide ions GL*GGKX. The c 4 ion from GL*GGK is found to retain an intact diazirine ring that undergoes selective photodissociation at 355 nm, followed by backbone cleavage. Infrared multiphoton dissociation action spectra point to the absence in the c 4 ion of a diazoalkane group that could be produced by thermal isomerization of vibrationally hot ions. The c 4 ion from ETD of GL*GGK is assigned an amide structure by a close match of the IRMPD action spectrum and calculated IR absorption. The energetics and kinetics of c 4 ion dissociations are discussed. Graphical Abstract ᅟ.
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Affiliation(s)
| | - Jonathan Martens
- FELIX Laboratory, Radboud University Nijmegen, Institute for Molecules and Materials, Toernooiveld 7c, 6525ED, Nijmegen, The Netherlands
| | - Aleš Marek
- Department of Chemistry, University of Washington, Seattle, WA, 98195-1700, USA
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Jos Oomens
- FELIX Laboratory, Radboud University Nijmegen, Institute for Molecules and Materials, Toernooiveld 7c, 6525ED, Nijmegen, The Netherlands
- van't Hoff Institute for Molecular Sciences, University of Amsterdam, 1098XH, Amsterdam, Science Park 908, The Netherlands
| | - František Tureček
- Department of Chemistry, University of Washington, Seattle, WA, 98195-1700, USA.
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23
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Asakawa D, De Pauw E. Difference of Electron Capture and Transfer Dissociation Mass Spectrometry on Ni(2+)-, Cu(2+)-, and Zn(2+)-Polyhistidine Complexes in the Absence of Remote Protons. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:1165-1175. [PMID: 27098412 DOI: 10.1007/s13361-016-1395-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 03/18/2016] [Accepted: 03/22/2016] [Indexed: 06/05/2023]
Abstract
Electron capture dissociation (ECD) and electron transfer dissociation (ETD) in metal-peptide complexes are dependent on the metal cation in the complex. The divalent transition metals Ni(2+), Cu(2+), and Zn(2+) were used as charge carriers to produce metal-polyhistidine complexes in the absence of remote protons, since these metal cations strongly bind to neutral histidine residues in peptides. In the case of the ECD and ETD of Cu(2+)-polyhistidine complexes, the metal cation in the complex was reduced and the recombination energy was redistributed throughout the peptide to lead a zwitterionic peptide form having a protonated histidine residue and a deprotonated amide nitrogen. The zwitterion then underwent peptide bond cleavage, producing a and b fragment ions. In contrast, ECD and ETD induced different fragmentation processes in Zn(2+)-polyhistidine complexes. Although the N-Cα bond in the Zn(2+)-polyhistidine complex was cleaved by ETD, ECD of Zn(2+)-polyhistidine induced peptide bond cleavage accompanied with hydrogen atom release. The different fragmentation modes by ECD and ETD originated from the different electronic states of the charge-reduced complexes resulting from these processes. The details of the fragmentation processes were investigated by density functional theory. Graphical Abstract ᅟ.
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Affiliation(s)
- Daiki Asakawa
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan.
| | - Edwin De Pauw
- Mass Spectrometry Laboratory, Department of Chemistry, and GIGA-Research, University of Liège, B-4000, Liège (Sart-Tilman), Belgium
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24
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Asakawa D, Yamashita A, Kawai S, Takeuchi T, Wada Y. N-Cα Bond Cleavage of Zinc-Polyhistidine Complexes in Electron Transfer Dissociation Mediated by Zwitterion Formation: Experimental Evidence and Theoretical Analysis of the Utah-Washington Model. J Phys Chem B 2016; 120:891-901. [PMID: 26673038 DOI: 10.1021/acs.jpcb.5b11118] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Electron capture dissociation (ECD) and electron transfer dissociation (ETD) of gas-phase ions are widely used for peptide/protein sequencing by mass spectrometry. To understand the general mechanism of ECD/ETD of peptides, we focused on the ETD fragmentation of metal-peptide complexes in the absence of remote protons. Since Zn(2+) strongly binds to neutral histidine residues in peptides, Zn(2+)-polyhistidine complexation does not generate any remote protons. However, in the absence of remote protons, electron transfer to the Zn(2+)-polyhistidine complex induced the N-Cα bond cleavage. The formation pathway for the ETD products was investigated by density functional theory calculations. The calculations showed that the charge-reduced zinc-peptide radical, [M + Zn](•+), can exist in the low-energy zwitterionic amide π* states, which underwent homolytic N-Cα bond dissociation. The homolytic cleavage resulted in the donation of an electron from the N-Cα bond to the nitrogen atom, producing an iminoenol c' anion. The counterpart z(•) radical contained a radical site on the α-carbon atom. The iminoenol c' anion then abstracted a proton to presumably form the more stable amide c' fragment. The current experimental and computational joint study strongly suggested that the N-Cα bond cleavage occurred through the aminoketyl radical-anion formation for Zn(2+)-polyhistidine complexes in ETD.
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Affiliation(s)
- Daiki Asakawa
- National Metrology Institute of Japan (NMIJ), Research Institute for Measurement and Analytical Instrumentation, National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba Central 2, Umezono 1-1-1, Tsukuba, Ibaraki, 305-8568, Japan
| | - Asuka Yamashita
- Department of Chemistry, Faculty of Science, Nara Women's University , Kitauoyanishi-machi, Nara, 630-8506, Japan
| | - Shikiho Kawai
- Department of Chemistry, Faculty of Science, Nara Women's University , Kitauoyanishi-machi, Nara, 630-8506, Japan
| | - Takae Takeuchi
- Department of Chemistry, Faculty of Science, Nara Women's University , Kitauoyanishi-machi, Nara, 630-8506, Japan
| | - Yoshinao Wada
- Department of Molecular Medicine, Osaka Medical Center and Research Institute for Maternal and Child Health , Murodo-cho 840, Izumi, Osaka, 594-1101, Japan
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25
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Abstract
UV photodissociation (UVPD) action spectroscopy is reported to provide a sensitive tool for the detection of radical sites in gas-phase peptide ions. UVPD action spectra of peptide cation radicals of the z-type generated by electron-transfer dissociation point to the presence of multiple structures formed as a result of spontaneous isomerizations by hydrogen atom migration. N-terminal Cα radicals are identified as the dominant components, but the content of isomers differing in the radical defect position in the backbone or side chain depends on the nature of the aromatic residue with phenylalanine being more prone to isomerization than tryptophan. These results illustrate that spontaneous hydrogen atom migrations can occur in peptide cation-radicals upon electron-transfer dissociation.
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Affiliation(s)
- Huong T H Nguyen
- Department of Chemistry, University of Washington , Bagley Hall, Box 351700, Seattle, Washington 981195-1700, United States
| | - Christopher J Shaffer
- Department of Chemistry, University of Washington , Bagley Hall, Box 351700, Seattle, Washington 981195-1700, United States
| | - Robert Pepin
- Department of Chemistry, University of Washington , Bagley Hall, Box 351700, Seattle, Washington 981195-1700, United States
| | - František Tureček
- Department of Chemistry, University of Washington , Bagley Hall, Box 351700, Seattle, Washington 981195-1700, United States
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