2012
DOI: 10.1021/jp305865q
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Perturbing Peptide Cation-Radical Electronic States by Thioxoamide Groups: Formation, Dissociations, and Energetics of Thioxopeptide Cation-Radicals

Abstract: Thioxodipeptides Gly-thio-Lys (GtK), Ala-thio-Lys (AtK), and Ala-thio-Arg (AtR) in which the amide group has been modified to a thioxoamide were made into dications by electrospray ionization and converted to cation-radicals, (GtK + 2H)(+•), (AtK + 2H)(+•), and (AtR + 2H)(+•), by electron transfer dissociation (ETD) tandem mass spectrometry using fluoranthene anion-radical as an electron donor. The common and dominant dissociation of these cation-radicals was the loss of a hydrogen atom. The dissociation produ… Show more

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Cited by 7 publications
(7 citation statements)
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“…Other functional groups that work as disruptors have been previously identified (e.g., aromatic amino acid residues furnished with NO 2 or CN substituents [56][57][58], thioxoamide groups [59], or fixed charge tags [60]). Conversely, some side-chain dissociations upon electron capture have been identified on the basis of thermochemical arguments as originating from excited electronic states accessed by electron attachment [61].…”
Section: Discussionmentioning
confidence: 99%
“…Other functional groups that work as disruptors have been previously identified (e.g., aromatic amino acid residues furnished with NO 2 or CN substituents [56][57][58], thioxoamide groups [59], or fixed charge tags [60]). Conversely, some side-chain dissociations upon electron capture have been identified on the basis of thermochemical arguments as originating from excited electronic states accessed by electron attachment [61].…”
Section: Discussionmentioning
confidence: 99%
“…ETD of Gly-thio-Lys, Ala-thio-Lys, and Ala-thio-Arg dications in which the amide group was replaced with a thioxoamide showed a complete lack of N–C α bond dissociations upon ETD . The common and dominant dissociation of these cation radicals was the loss of a hydrogen atom.…”
Section: Dissociations Of Hydrogen-rich Peptide Radicals and Cation R...mentioning
confidence: 98%
“…This discrepancy was interpreted as being due to the population upon electron transfer of low-lying excited electronic states that promoted loss of hydrogen atoms. For (Gly-thio-Lys + 2H) +• , these excited states were characterized by time-dependent density functional theory as A – C states that had large components of Rydberg-like 3s molecular orbitals at the N-terminal and lysine ammonium groups that were conducive to hydrogen atom loss …”
Section: Dissociations Of Hydrogen-rich Peptide Radicals and Cation R...mentioning
confidence: 99%
“…Factors influencing the prominent N−C α bond cleavage processes leading to c and z ions in ECD have been a major focus of these investigations. These wide ranging investigations include tagging peptides with permanent charged groups [2027], electron/hydrogen atom scavengers [2833] and modified peptide backbones [3438]. These experiments are primarily designed to monitor the initial electron capture and subsequent electronic state relaxation via internal conversion and intramolecular electron, proton and hydrogen atom transfer processes.…”
Section: Introductionmentioning
confidence: 99%