Decomposition of Protonated Threonine, Its Stereoisomers, and Its Homologues in the Gas Phase:  Evidence for Internal Backside Displacement

Serafin, Scott V.; Zhang, Kangling; Aurelio, Luigi; Hughes, and Andrew B.; Morton, Thomas Hellman

doi:10.1021/ol049700p

Cited by 22 publications

(20 citation statements)

References 15 publications

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“…One pathway (Scheme 1) leads to formation of an aziridine ring on water loss. This pathway has been shown to be operative in loss of H 2 O from protonated serine and threonine [12][13][14]. A second pathway involves (Scheme 3) formation of an oxazoline upon elimination of H 2 O.…”

Section: Discussionmentioning

confidence: 99%

“…There have been several studies concerning the mechanism of water loss from protonated serine and threonine and their derivatives. For protonated serine and threonine, it has been shown that attack of the amino group in the hydroxyl-protonated form leads to water loss and formation of a protonated three-membered aziridine ring [12][13][14]. By contrast, in N-acetyl derivatives interaction of the carboxyl group with the side-chain protonated hydroxyl group leads to formation of a protonated five-membered oxazoline ring upon loss of water [13].…”

Section: Introductionmentioning

confidence: 99%

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Pathways for Water Loss from Doubly Protonated Peptides Containing Serine or Threonine

Harrison

2011

J. Am. Soc. Mass Spectrom.

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The doubly-protonated peptides Ala-Ala-Xaa-Ala-Ala-Ala-Arg show extensive loss of H 2 O when Xaa=Ser or Thr. Using quasi-MS 3 techniques the fragmentation reactions of the [M+2H -H 2 O] +2 ions have been studied in detail. For both Ser and Thr, the [M+2H -H 2 O] +2 ions show three primary fragmentation reactions, elimination of CH 3 CH=NH, elimination of one Ala residue, and elimination of two Ala residues, in all cases forming doubly-charged products. From a study of the further fragmentation of these products, it is concluded that elimination of two Ala residues results in formation of a three-membered aziridine ring by interaction with the adjacent amide function as H 2 O is lost. The elimination of one Ala residue results in formation of a five-membered oxazoline ring through interaction with the N-terminal adjacent carbonyl function as H 2 O is lost. The elimination of CH 3 CH=NH appears to involve formation of an eight-membered ring by interaction with the remote N-terminal carbonyl function as H 2 O is lost. However, this initial structure undergoes rearrangement through interaction with the adjacent C-terminal carbonyl function prior to further fragmentation. The [MH -H 2 O] + ion of Ala-Ala-Ser-Ala-Ala-Ala also shows elimination of CH 3 CH=NH, one Ala residue and two Ala residues.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Pathways for Water Loss from Doubly Protonated Peptides Containing Serine or Threonine

Harrison

2011

J. Am. Soc. Mass Spectrom.

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“…[25,26] Thr-containing peptides usually show many special characteristics upon CID and mechanisms into their fragmentation behavior have been reported. Loss of water upon CID is common for Thrcontaining peptides and has been proposed to form an aziridine ring [27][28][29] involving C α , C β , and the nitrogen of the amino group or of the peptide bond. It was also found that in the product ion spectra of doubly charged peptides, cleavages N-terminal to Ser and Thr show slightly enhanced tendency in comparison with cleavages C-terminal to these residues.…”

Section: Introductionmentioning

confidence: 99%

Characteristic neutral loss of CH₃CHO from Thr-containing sodium-associated peptides

Wang

Wei

et al. 2015

J. Mass Spectrom.

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A characteristic neutral loss of 44 Da is observed in the MS/MS spectra of Thr-containing sodiated peptides. A combination of tandem mass spectrometry and quantum chemical calculations calculated at the B3LYP/6-311G (d, p) level of ab initio theory is used to elucidate this fragmentation pathway. The high resolution mass spectrometry data indicate this neutral loss is acetaldehyde lost from the side chain of Thr rather than CO2. The intensity of this neutral loss can be enhanced when Thr residue is far from the C-terminus and when the C-terminus is esterified as well. The mechanism of the acetaldehyde loss is proposed to adopt a McLafferty-type rearrangement reaction, which involves a proton transfer from the hydroxyl of Thr side chain to its C-terminal neighboring carbonyl oxygen inducing the cleavage of the Ca-Cβ bond. This mechanism is further supported by examining the fragmentation of a [GT(tBu)G + Na](+) peptide derivative and by comparing the product ion spectra of [M + Na-44](+) of [GTGA + Na](+) with [M + Na](+) of [GGGA + Na](+). A similar neutral loss of HCHO can also be detected in Ser-containing peptides. Our computational results reveal that the most stable [GTG + Na](+) ion is present as a tridentate charge-solvated structure and the dissociation leading to the 44 loss is dynamically and energetically favorable.

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“…The water losses from the side chain of hydroxyl group containing amino acid residues have been extensively investigated by several groups [29][30][31][32][33][34][35][36]. In line with these works, a possible mechanism for the formation of m/z 279 fragment ion from protonated b 5 ion of SGGFL-NH 2 is shown in Scheme 1.…”

Section: Resultsmentioning

confidence: 91%

Protonated Dipeptide Losses from b₅ and b₄ Ions of Side Chain Hydroxyl Group Containing Pentapeptides

Atik

Yalçın

2013

J. Am. Soc. Mass Spectrom.

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Decomposition of Protonated Threonine, Its Stereoisomers, and Its Homologues in the Gas Phase: Evidence for Internal Backside Displacement

Cited by 22 publications

References 15 publications

Pathways for Water Loss from Doubly Protonated Peptides Containing Serine or Threonine

Pathways for Water Loss from Doubly Protonated Peptides Containing Serine or Threonine

Characteristic neutral loss of CH₃CHO from Thr-containing sodium-associated peptides

Protonated Dipeptide Losses from b₅ and b₄ Ions of Side Chain Hydroxyl Group Containing Pentapeptides

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Decomposition of Protonated Threonine, Its Stereoisomers, and Its Homologues in the Gas Phase: Evidence for Internal Backside Displacement

Cited by 22 publications

References 15 publications

Pathways for Water Loss from Doubly Protonated Peptides Containing Serine or Threonine

Pathways for Water Loss from Doubly Protonated Peptides Containing Serine or Threonine

Characteristic neutral loss of CH3CHO from Thr-containing sodium-associated peptides

Protonated Dipeptide Losses from b5 and b4 Ions of Side Chain Hydroxyl Group Containing Pentapeptides

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Characteristic neutral loss of CH₃CHO from Thr-containing sodium-associated peptides

Protonated Dipeptide Losses from b₅ and b₄ Ions of Side Chain Hydroxyl Group Containing Pentapeptides