Probing the Radical and Base Dual Properties of Peptide Sulfinyl Radicals via Mass Spectrometry

Tan, Lei; Tureček, František; Francisco, Joseph S.; Xia, Yu

doi:10.1021/jp510362p

Cited by 2 publications

(1 citation statement)

References 33 publications

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“…For example, regiospecific radical generation has been demonstrated from nitrate esters, diazo derivatives, peroxycarbamate derivatives, and diazirine rings . A variety of peptide ions with different radical sites can be formed at atmospheric pressure (AP) through ion–radical reactions . Furthermore, the formation of molecular peptide radical ions (i. e., M •+ , [M + H] •2+ , [M – 2H] •– ) can also be achieved through dissociative electron transfers of ternary metal–ligand–peptide complexes, which have been studied extensively and applied by our and other research groups …”

Section: Common Techniques For Formation Of Peptide Radical Ions In Tmentioning

confidence: 99%

Tautomerization and Dissociation of Molecular Peptide Radical Cations

Mu¹,

Song²,

Siu

et al. 2017

The Chemical Record

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Radical-mediated dissociations of peptide radical cations have intriguing unimolecular gas phase chemistry, with cleavages of almost every bond of the peptide backbone and amino acid side chains in a competitive and apparently "stochastic" manner. Challenges of unraveling mechanistic details are related to complex tautomerizations prior to dissociations. Recent conjunctions of experimental and theoretical investigations have revealed the existence of non-interconvertible isobaric tautomers with a variety of radical-site-specific initial structures, generated from dissociative electron transfer of ternary metal-ligand-peptide complexes. Their reactivity is influenced by the tautomerization barriers, perturbing the nature, location, or number of radical and charge site(s), which also determine the energetics and dynamics of the subsequent radical-mediated dissociatons. The competitive radical- and charge-induced dissociations are extremely dependent on charge density. Charge sequesting can reduce the charge densities on the peptide backbone and hence enhance the flexibility of structural rearrangement. Analysing the structures of precursors, intermediates and products has led to the discovery of many novel radical migration prior to peptide backbone and/or side chain fragmentations. Upon these successes, scientists will be able to build peptide cationic analogues/tautomers having a variety of well-defined radical sites.

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Section: Common Techniques For Formation Of Peptide Radical Ions In Tmentioning

confidence: 99%

Tautomerization and Dissociation of Molecular Peptide Radical Cations

Mu¹,

Song²,

Siu

et al. 2017

The Chemical Record

View full text Add to dashboard Cite

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Gas‐Phase Unimolecular Dissociation Reveals Dominant Base Property of Protonated Homocysteine Sulfinyl Radical Ions

Love-Nkansah

Tan

Francisco

et al. 2015

Chemistry A European J

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Homocysteine sulfinyl radical ((SO⋅) Hcy) is a reactive intermediate involved during oxidative damage of DNA in the presence of high concentrations of homocysteine (Hcy). The short lifetime of (SO⋅) Hcy makes its preparation, isolation, and characterization challenging using traditional chemical measurement tools. Herein, we demonstrate the first study on mass-selected protonated (SO⋅) Hcy ions in the gas phase by investigating its unimolecular dissociation pathways from low energy collision-induced dissociation (CID). Tandem mass spectrometry (MS/MS), stable-isotope labeling, and theoretical calculations were employed to rationalize the observed fragmentation pathways. The dominant dissociation channel of protonated (SO⋅) Hcy was a charge-directed H2 O loss from the protonated sulfinyl radical (-SO⋅) moiety, forming a thiyl radical (-S⋅), which further triggered sequential radical-directed ⋅SH loss through multiple pathways. Compared to cysteine sulfinyl radical ((SO⋅) Cys), the small structural change induced by one additional methylene group in the side chain of (SO⋅) Hcy significantly promotes its base property while reducing the radical reactivity of sulfinyl radical. This observation provides new insight into studying reactions of (SO⋅) Hcy with biomolecules, which are critical in understanding toxicity induced by high levels of Hcy in biological conditions.

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Probing the Radical and Base Dual Properties of Peptide Sulfinyl Radicals via Mass Spectrometry

Cited by 2 publications

References 33 publications

Tautomerization and Dissociation of Molecular Peptide Radical Cations

Tautomerization and Dissociation of Molecular Peptide Radical Cations

Gas‐Phase Unimolecular Dissociation Reveals Dominant Base Property of Protonated Homocysteine Sulfinyl Radical Ions

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