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Zima V, Gladwish O, Marek A, Tureček F. Nucleoside Cation Radicals: Generation, Radical-Induced Hydrogen Atom Migrations, and Ribose Ring Cleavage in the Gas Phase. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2024; 35:1594-1608. [PMID: 38842116 DOI: 10.1021/jasms.4c00198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2024]
Abstract
Nucleoside ions that were furnished on ribose with a 2'-O-acetyl radical group were generated in the gas phase by multistep collision-induced dissociation of precursor ions tagged with radical initiator groups, and their chemistry was investigated in the gas phase. 2'-O-Acetyladenosine cation radicals were found to undergo hydrogen transfer to the acetoxyl radical from the ribose ring positions that were elucidated using specific deuterium labeling of 1'-H, 2'-H, and 4'-H and in the N-H and O-H exchangeable positions, favoring 4'-H transfer. Ion structures and transition-state energies were calculated by a combination of Born-Oppenheimer molecular dynamics and density functional theory and used to obtain unimolecular rate constants for competitive hydrogen transfer and loss of the acetoxyl radical. Migrations to the acetoxyl radical of ribose hydrogens 1'-H, 2'-H, 3'-H, and 4'-H were all exothermic, but product formation was kinetically controlled. Both Rice-Ramsperger-Kassel-Marcus (RRKM) and transition-state theory (TST) calculations indicated preferential migration of 4'-H in a qualitative agreement with the deuterium labeling results. The hydrogen migrations displayed substantial isotope effects that along with quantum tunneling affected the relative rate constants and reaction branching ratios. UV-vis action spectroscopy indicated that the cation radicals from 2'-O-acetyladenosine consisted of a mixture of isomers. Radical-driven dissociations were also observed for protonated guanosine, cytosine, and thymidine conjugates. However, for those nucleoside ions and cation radicals, the dissociations were dominated by the loss of the nucleobase or formation of protonated nucleobase ions.
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Affiliation(s)
- Václav Zima
- Department of Chemistry, University of Washington, 351700 Bagley Hall, Seattle, Washington 98195-1700, United States
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 166 10 Prague, Czech Republic
| | - Owen Gladwish
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106-7078, United States
| | - Aleš Marek
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 166 10 Prague, Czech Republic
| | - František Tureček
- Department of Chemistry, University of Washington, 351700 Bagley Hall, Seattle, Washington 98195-1700, United States
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2
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Zima V, Vlk M, Wan J, Cvačka J, Tureček F. Tracking Isomerizations of High-Energy Adenine Cation Radicals by UV-Vis Action Spectroscopy and Cyclic Ion Mobility Mass Spectrometry. J Phys Chem A 2023. [PMID: 37433135 DOI: 10.1021/acs.jpca.3c03179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/13/2023]
Abstract
We report experimental and computational studies of protonated adenine C-8 σ-radicals that are presumed yet elusive reactive intermediates of oxidative damage to nucleic acids. The radicals were generated in the gas phase by the collision-induced dissociation of C-8-Br and C-8-I bonds in protonated 8-bromo- and 8-iodoadenine as well as by 8-bromo- and 8-iodo-9-methyladenine. Protonation by electrospray of 8-bromo- and 8-iodoadenine was shown by cyclic-ion mobility mass spectrometry (c-IMS) to form the N-1-H, N-9-H and N-3-H, N-7-H protomers in 85:15 and 81:19 ratios, respectively, in accordance with the equilibrium populations of these protomers in water-solvated ions that were calculated by density functional theory (DFT). Protonation of 8-halogenated 9-methyladenines yielded single N-1-H protomers, which was consistent with their thermodynamic stability. The radicals produced from the 8-bromo and 8-iodo adenine cations were characterized by UV-vis photodissociation action spectroscopy (UVPD) and c-IMS. UVPD revealed the formation of C-8 σ-radicals along with N-3-H, N-7-H-adenine π-radicals that arose as secondary products by hydrogen atom migrations. The isomers were identified by matching their action spectra against the calculated vibronic absorption spectra. Deuterium isotope effects were found to slow the isomerization and increase the population of C-8 σ-radicals. The adenine cation radicals were separated by c-IMS and identified by their collision cross sections, which were measured relative to the canonical N-9-H adenine cation radical that was cogenerated in situ as an internal standard. Ab initio CCSD(T)/CBS calculations of isomer energies showed that the adenine C-8 σ-radicals were local energy minima with relative energies at 76-79 kJ mol-1 above that of the canonical adenine cation radical. Rice-Ramsperger-Kassel-Marcus calculations of unimolecular rate constants for hydrogen and deuterium migrations resulting in exergonic isomerizations showed kinetic shifts of 10-17 kJ mol-1, stabilizing the C-8 σ-radicals. C-8 σ-radicals derived from N-1-protonated 9-methyladenine were also thermodynamically unstable and readily isomerized upon formation.
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Affiliation(s)
- Václav Zima
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Mikuláš Vlk
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 16610 Prague 6, Czech Republic
- Department of Analytical Chemistry, Faculty of Science, Charles University, 12800 Prague, Czech Republic
| | - Jiahao Wan
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Josef Cvačka
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 16610 Prague 6, Czech Republic
- Department of Analytical Chemistry, Faculty of Science, Charles University, 12800 Prague, Czech Republic
| | - František Tureček
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
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Tureček F. UV-vis spectroscopy of gas-phase ions. MASS SPECTROMETRY REVIEWS 2023; 42:206-226. [PMID: 34392556 DOI: 10.1002/mas.21726] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 06/07/2021] [Accepted: 06/08/2021] [Indexed: 06/13/2023]
Abstract
Photodissociation action spectroscopy has made a great progress in expanding investigations of gas-phase ion structures. This review deals with aspects of gas-phase ion electronic excitations that result in wavelength-dependent dissociation and light emission via fluorescence, chiefly covering the ultraviolet and visible regions of the spectrum. The principles are briefly outlined and a few examples of instrumentation are presented. The main thrust of the review is to collect and selectively present applications of UV-vis action spectroscopy to studies of stable gas-phase ion structures and combinations of spectroscopy with ion mobility, collision-induced dissociation, and ion-ion reactions leading to the generation of reactive intermediates and electronic energy transfer.
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Affiliation(s)
- František Tureček
- Department of Chemistry, University of Washington, Seattle, Washington, USA
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4
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Zima V, Liu Y, Tureček F. Radical Cascade Dissociation Pathways to Unusual Nucleobase Cation Radicals. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:1038-1047. [PMID: 35536606 DOI: 10.1021/jasms.2c00098] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We report unusual dissociations of protonated RNA nucleosides tagged with radical initiator groups at ribose 5'-O and furnished with a 2',3'-O-isopropylidene protecting group. The ions undergo collision-induced radical cascade dissociations starting at the radical initiator that break down the dioxolane ring and trigger the formation of nucleobase cations and cation radicals. The adenine cation radical that was formed by radical cascade dissociations was identified by MS5 UV-vis photodissociation action spectroscopy to be a higher-energy N-3-H tautomer of the canonical ionized nucleobase. The guanine cation radical was formed by radical cascade dissociations as the N-7-H tautomer. In contrast to adenosine and guanosine, radical cascade dissociations of the tagged ribocytidine ion produced protonated cytosine, whereas tagged ribothymidine showed yet different dissociations resulting in predominant thymine loss. Reaction mechanisms were suggested for the cascade dissociations that were based on Born-Oppenheimer molecular dynamics and density functional theory calculations that were used to map the relevant parts of the potential energy surfaces for adenosine, guanosine, and cytidine radical ions. The reported radical cascade dissociations represent a new, nonredox approach to nucleobase and nucleoside cation radicals that has the potential of being expanded to the generation of various oligonucleotide cation radicals.
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Affiliation(s)
- Václav Zima
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 981195-1700, United States
| | - Yue Liu
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 981195-1700, United States
| | - František Tureček
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 981195-1700, United States
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Pereverzev A, Roithová J. Experimental techniques and terminology in gas-phase ion spectroscopy. JOURNAL OF MASS SPECTROMETRY : JMS 2022; 57:e4826. [PMID: 35434805 PMCID: PMC9285946 DOI: 10.1002/jms.4826] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 03/24/2022] [Accepted: 03/31/2022] [Indexed: 06/01/2023]
Abstract
This perspective gives an overview of the action spectroscopy methods for measurements of electronic, vibrational, and rotational spectra of mass-selected ions in the gas phase. We classify and give a short overview of the existing experimental approaches in this field. There is currently a plethora of names used for, essentially, the same techniques. Hence within this overview, we scrutinized the notations and suggested terms to be generally used. The selection was either driven by making the name unique and straightforward or the term being the most broadly used one. We believe that a simplification and a unification of the notation in ion spectroscopy can make this field better accessible for experts outside the mass spectrometry community where the applications of gas-phase action ion spectroscopy can make a large impact.
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Affiliation(s)
| | - Jana Roithová
- Institute for Molecules and MaterialsRadboud UniversityNijmegenThe Netherlands
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6
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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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7
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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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8
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Huang SR, Dang A, Tureček F. Ground and Excited States of Gas-Phase DNA Nucleobase Cation-Radicals. A UV-vis Photodisociation Action Spectroscopy and Computational Study of Adenine and 9-Methyladenine. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:1271-1281. [PMID: 32324398 DOI: 10.1021/jasms.0c00095] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Cation radicals of adenine (A•+) and 9-methyladenine (MA•+) were generated in the gas phase by collision-induced intramolecular electron transfer in copper-terpyridine-nucleobase ternary complexes and characterized by collision-induced dissociation (CID) mass spectra and UV-vis photodissociation action spectroscopy in the 210-700 nm wavelength region. The action spectra of both A•+ and MA•+ displayed characteristic absorption bands in the near-UV and visible regions. Another tautomer of A•+ was generated as a minor product by multistep CID of protonated 9-(2-bromoethyl)adenine. Structure analysis by density functional theory and coupled-clusters ab initio calculations pointed to the canonical 9-H-tautomer Ad1•+ as the global energy minimum of adenine cation radicals. The canonical tautomer MA1•+ was also calculated to be a low-energy structure among methyladenine cation radicals. However, two new noncanonical tautomers were found to be energetically comparable to MA1•+. Vibronic absorption spectra were calculated for several tautomers of A•+ and MA•+ and benchmarked on equation-of-motion coupled-clusters excited-state calculations. Analysis of the vibronic absorption spectra of A•+ tautomers pointed to the canonical tautomer Ad1•+ as providing the best match with the action spectrum. Likewise, the canonical tautomer MA1•+ was the unequivocal best match for the MA•+ ion generated in the gas phase. According to potential-energy mapping, MA1•+ was separated from energetically favorable noncanonical cation radicals by a high-energy barrier that was calculated to be above the dissociation threshold for loss of a methyl hydrogen atom, thus preventing isomerization. Structures and energetics of all four DNA nucleobase cation radicals are compared and discussed.
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Affiliation(s)
- Shu R Huang
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
| | - 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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9
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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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10
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Dang A, Korn JA, Gladden J, Mozzone B, Tureček F. UV-Vis Photodissociation Action Spectroscopy on Thermo LTQ-XL ETD and Bruker amaZon Ion Trap Mass Spectrometers: a Practical Guide. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:1558-1564. [PMID: 31087269 DOI: 10.1007/s13361-019-02229-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 04/09/2019] [Accepted: 04/13/2019] [Indexed: 06/09/2023]
Abstract
We report automated procedures for multiple tandem mass spectra acquisition allowing UV-Vis photodissociation action spectroscopy measurements of ions and radicals. The procedures were developed for two commercial ion trap mass spectrometers and applied to collision-induced and electron-transfer dissociation tandem mass spectrometry modes of ion generation.
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Affiliation(s)
- Andy Dang
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, WA, 98195-1700, USA
| | - Joseph A Korn
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, WA, 98195-1700, USA
| | - James Gladden
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, WA, 98195-1700, USA
| | - Brandon Mozzone
- 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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11
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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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12
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Liu Y, Korn JA, Dang A, Tureček F. Hydrogen-Rich Cation Radicals of DNA Dinucleotides: Generation and Structure Elucidation by UV-Vis Action Spectroscopy. J Phys Chem B 2018; 122:9665-9680. [PMID: 30269486 DOI: 10.1021/acs.jpcb.8b07925] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Hydrogen-rich DNA dinucleotide cation radicals (dGG + 2H)+•, (dCG + 2H)+•, and (dGC + 2H)+• represent transient species comprising protonated and hydrogen atom adducted nucleobase rings that serve as models for proton and radical migrations in ionized DNA. These DNA cation radicals were generated in the gas phase by electron-transfer dissociation of dinucleotide dication-crown-ether complexes and characterized by UV-vis photodissociation action spectra, ab initio calculations of structures and relative energies, and time-dependent density functional theory calculations of UV-vis absorption spectra. Theoretical calculations indicate that (dGG + 2H)+• cation radicals formed by electron transfer underwent an exothermic conformational collapse that was accompanied by guanine ring stacking and facile internucleobase hydrogen atom transfer, forming 3'-guanine C-8-H radicals. In contrast, exothermic hydrogen transfer from the 5'-cytosine radical onto the guanine ring in (dCG + 2H)+• was kinetically hampered, resulting in the formation of a mixture of 5'-cytosine and 3'-guanine radicals. Conformational folding and nucleobase stacking were energetically unfavorable in (dGC + 2H)+• that retained its structure of a 3'-cytosine radical, as formed by one-electron reduction of the dication. Hydrogen-rich guanine (G + H)• and cytosine (C + H)• radicals were calculated to have vastly different basicities in water, as illustrated by the respective p Ka values of 20.0 and 4.6, which is pertinent to their different abilities to undergo proton-transfer reactions in solution.
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Affiliation(s)
- Yang Liu
- Department of Chemistry, Bagley Hall , University of Washington , P.O. Box 351700, Seattle , Washington 98195-1700 , United States
| | - Joseph A Korn
- Department of Chemistry, Bagley Hall , University of Washington , P.O. Box 351700, Seattle , Washington 98195-1700 , United States
| | - Andy Dang
- Department of Chemistry, Bagley Hall , University of Washington , P.O. Box 351700, Seattle , Washington 98195-1700 , United States
| | - František Tureček
- Department of Chemistry, Bagley Hall , University of Washington , P.O. Box 351700, Seattle , Washington 98195-1700 , United States
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13
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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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14
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Ranka K, Zhao N, Yu L, Stanton JF, Polfer NC. Radical Rearrangement Chemistry in Ultraviolet Photodissociation of Iodotyrosine Systems: Insights from Metastable Dissociation, Infrared Ion Spectroscopy, and Reaction Pathway Calculations. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:1791-1801. [PMID: 29845561 DOI: 10.1007/s13361-018-1959-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 03/21/2018] [Accepted: 04/01/2018] [Indexed: 06/08/2023]
Abstract
We report on the ultraviolet photodissociation (UVPD) chemistry of protonated tyrosine, iodotyrosine, and diiodotyrosine. Distonic loss of the iodine creates a high-energy radical at the aromatic ring that engages in hydrogen/proton rearrangement chemistry. Based on UVPD kinetics measurements, the appearance of this radical is coincident with the UV irradiation pulse (8 ns). Conversely, sequential UVPD product ions exhibit metastable decay on ca. 100 ns timescales. Infrared ion spectroscopy is capable of confirming putative structures of the rearrangement products as proton transfers from the imine and β-carbon hydrogens. Potential energy surfaces for the various reaction pathways indicate that the rearrangement chemistry is highly complex, compatible with a cascade of rearrangements, and that there is no preferred rearrangement pathway even in small molecular systems like these. Graphical Abstract.
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Affiliation(s)
- Karnamohit Ranka
- Quantum Theory Project, Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, USA
- Quantum Theory Project, Department of Physics, University of Florida, P.O. Box 118435, Gainesville, FL, 32611-8435, USA
| | - Ning Zhao
- Department of Chemistry and Center for Chemical Physics, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, USA
| | - Long Yu
- Department of Chemistry and Center for Chemical Physics, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, USA
| | - John F Stanton
- Quantum Theory Project, Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, USA
- Quantum Theory Project, Department of Physics, University of Florida, P.O. Box 118435, Gainesville, FL, 32611-8435, USA
| | - Nicolas C Polfer
- Department of Chemistry and Center for Chemical Physics, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, USA.
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Dang A, Nguyen HTH, Ruiz H, Piacentino E, Ryzhov V, Tureček F. Experimental Evidence for Noncanonical Thymine Cation Radicals in the Gas Phase. J Phys Chem B 2017; 122:86-97. [DOI: 10.1021/acs.jpcb.7b09872] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Andy Dang
- Department
of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
| | - Huong T. H. Nguyen
- Department
of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
| | - Heather Ruiz
- Department
of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States
| | - Elettra Piacentino
- Department
of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States
| | - Victor Ryzhov
- Department
of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States
| | - František Tureček
- Department
of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
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Korn JA, Urban J, Dang A, Nguyen HTH, Tureček F. UV-Vis Action Spectroscopy Reveals a Conformational Collapse in Hydrogen-Rich Dinucleotide Cation Radicals. J Phys Chem Lett 2017; 8:4100-4107. [PMID: 28809578 DOI: 10.1021/acs.jpclett.7b01856] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report the generation of deoxyriboadenosine dinucleotide cation radicals by gas-phase electron transfer to dinucleotide dications and their noncovalent complexes with crown ether ligands. Stable dinucleotide cation radicals of a novel hydrogen-rich type were generated and characterized by tandem mass spectrometry and UV-vis photodissociation (UVPD) action spectroscopy. Electron structure theory analysis indicated that upon electron attachment the dinucleotide dications underwent a conformational collapse followed by intramolecular proton migrations between the nucleobases to give species whose calculated UV-vis absorption spectra matched the UVPD action spectra. Hydrogen-rich cation radicals generated from chimeric riboadenosine 5'-diesters gave UVPD action spectra that pointed to novel zwitterionic structures consisting of aromatic π-electron anion radicals intercalated between stacked positively charged adenine rings. Analogies with DNA ionization are discussed.
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Affiliation(s)
- Joseph A Korn
- Department of Chemistry, University of Washington , Bagley Hall, Seattle, Washington 98195-1700, United States
| | - Jan Urban
- Metagenics, Inc. , Gig Harbor, Washington 98335-3729, United States
| | - Andy Dang
- Department of Chemistry, University of Washington , Bagley Hall, Seattle, Washington 98195-1700, United States
| | - Huong T H Nguyen
- Department of Chemistry, University of Washington , Bagley Hall, Seattle, Washington 98195-1700, United States
| | - František Tureček
- Department of Chemistry, University of Washington , Bagley Hall, Seattle, Washington 98195-1700, United States
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17
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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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18
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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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19
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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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20
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Shaffer CJ, Pepin R, Tureček F. Combining UV photodissociation action spectroscopy with electron transfer dissociation for structure analysis of gas-phase peptide cation-radicals. JOURNAL OF MASS SPECTROMETRY : JMS 2015; 50:1438-1442. [PMID: 26634979 DOI: 10.1002/jms.3717] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 09/22/2015] [Accepted: 10/09/2015] [Indexed: 06/05/2023]
Abstract
We report the first example of using ultraviolet (UV) photodissociation action spectroscopy for the investigation of gas-phase peptide cation-radicals produced by electron transfer dissociation. z-Type fragment ions (●) Gly-Gly-Lys(+), coordinated to 18-crown-6-ether (CE), are generated, selected by mass and photodissociated in the 200-400 nm region. The UVPD action spectra indicate the presence of valence-bond isomers differing in the position of the Cα radical defect, (α-Gly)-Gly-Lys(+) (CE), Gly-(α-Gly)-Lys(+) (CE) and Gly-Gly-(α-Lys(+))(CE). The isomers are readily distinguishable by UV absorption spectra obtained by time-dependent density functional theory (TD-DFT) calculations. In contrast, conformational isomers of these radical types are calculated to have similar UV spectra. UV photodissociation action spectroscopy represents a new tool for the investigation of transient intermediates of ion-electron reactions. Specifically, z-type cation radicals are shown to undergo spontaneous hydrogen atom migrations upon electron transfer dissociation.
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Affiliation(s)
- Christopher J Shaffer
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, WA, 98195-1700, USA
| | - Robert Pepin
- 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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