UV/Vis Action Spectroscopy and Structures of Tyrosine Peptide Cation Radicals in the Gas Phase

Viglino, Emilie; Shaffer, Christopher J.; Tureček, František

doi:10.1002/anie.201602604

Cited by 16 publications

(17 citation statements)

References 33 publications

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“…Based on the analysis of peptide radical chromophores [58] +• are most straightforward in that they both result in a dominant loss of the Tyr side chain. This is consistent with the Tyr-O radical structure of this ion where loss of C 7 H 6 O is the lowest energy process in CID and the Tyr-O radical is the absorbing chromophore for UVPD [43]. We cannot distinguish whether UVPD occurs from an excited electronic state or after vibronic transition to a vibrationally hot ground electronic state because both are expected to display similar reactivity.…”

Section: Discussionsupporting

confidence: 74%

“…In contrast, the loss of H does not have an analogy in CID and is likely proceeding from an excited electronic state of the ion. A previous UV photodissociation action spectroscopy study has concluded that [AAAYR] +• was a mixture of isomeric radicals [43], and thus it is possible that the observed photodissociations originated from different radical isomers.…”

Section: Discussionmentioning

confidence: 98%

“…1d). This dissociation is usually associated with the presence of a tyrosyl-O radical moiety [9,43]. However, the CID spectra do not allow us to distinguish if Tyr-O radicals were present to a different extent in the stable [M + 2H] +• cation radicals or if they were produced as reactive intermediates in the course of dissociation.…”

Section: Note On Nomenclaturementioning

confidence: 99%

“…We note that the absorption spectra of peptide cation radicals depend on the position of the C α radical and ion Figure 5. UVPD-MS 4 mass spectra of (a) [AAAG α [34,43], and elucidating this effect would require a dedicated study.…”

Section: Aar]mentioning

confidence: 99%

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Ground and Excited-Electronic-State Dissociations of Hydrogen-Rich and Hydrogen-Deficient Tyrosine Peptide Cation Radicals

Viglino

Lai

et al. 2016

J. Am. Soc. Mass Spectrom.

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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 C α -radical positions in peptide cation radical intermediates.

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Section: Discussionsupporting

confidence: 74%

Section: Discussionmentioning

confidence: 98%

Section: Note On Nomenclaturementioning

confidence: 99%

Section: Aar]mentioning

confidence: 99%

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Ground and Excited-Electronic-State Dissociations of Hydrogen-Rich and Hydrogen-Deficient Tyrosine Peptide Cation Radicals

Viglino

Lai

et al. 2016

J. Am. Soc. Mass Spectrom.

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“…Whereas UV photo-excitation (UVPD) at 193 nm results in nonspecific dissociation of many bonds in ETD fragment ions, UVPD at 355 nm has been shown to trigger backbone and side-chain bond cleavage that were specific for amino acid residues in the peptide ion [22][23][24][25][26]. When combined with action spectroscopy [9], UV-VIS photodissociation provides information on mass-resolved photodissociation channels pertinent to different excited electronic states of the ion [27,28].…”

Section: Introductionmentioning

confidence: 99%

Near-UV Photodissociation of Tryptic Peptide Cation Radicals. Scope and Effects of Amino Acid Residues and Radical Sites

Nguyen

Tureček

2017

J. Am. Soc. Mass Spectrom.

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, 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 MS 3 -nearultraviolet 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 [y n ] + type. Compared with collision-induced dissociation, UVPD yielded less sidechain 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 C α and amide nitrogen positions.

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Cytosine Radical Cations: A Gas‐Phase Study Combining IRMPD Spectroscopy, UVPD Spectroscopy, Ion–Molecule Reactions, and Theoretical Calculations

et al. 2017

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The radical cation of cytosine (Cyt ) is generated by dissociative oxidation from a ternary Cu complex in the gas phase. The radical cation is characterized by infrared multiple photon dissociation (IRMPD) spectroscopy in the fingerprint region, UV/Vis photodissociation (UVPD) spectroscopy, ion-molecule reactions, and theoretical calculations (density functional theory and ab initio). The experimental IRMPD spectrum features diagnostic bands for two enol-amino and two keto-amino tautomers of Cyt that are calculated to be among the lowest energy isomers, in agreement with a previous study. Although the UVPD action spectrum can also be matched to a combination of the four lowest energy tautomers, the presence of a nonclassical distonic radical cation cannot be ruled out. Its formation is, however, unlikely due to the high energy of this isomer and the respective ternary Cu complex. Gas-phase ion-molecule reactions showed that Cyt undergoes hydrogen-atom abstraction from 1-propanethiol, radical recombination reactions with nitric oxide, and electron transfer from dimethyl disulfide.

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UV/Vis Action Spectroscopy and Structures of Tyrosine Peptide Cation Radicals in the Gas Phase

Cited by 16 publications

References 33 publications

Ground and Excited-Electronic-State Dissociations of Hydrogen-Rich and Hydrogen-Deficient Tyrosine Peptide Cation Radicals

Ground and Excited-Electronic-State Dissociations of Hydrogen-Rich and Hydrogen-Deficient Tyrosine Peptide Cation Radicals

Near-UV Photodissociation of Tryptic Peptide Cation Radicals. Scope and Effects of Amino Acid Residues and Radical Sites

Cytosine Radical Cations: A Gas‐Phase Study Combining IRMPD Spectroscopy, UVPD Spectroscopy, Ion–Molecule Reactions, and Theoretical Calculations

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