Interpretation of the characteristic fragmentation mechanisms through determining the initial ionization site by natural spin density: A study on the derivatives of tryptophan and tryptamine

Ouyang, Yongzhong; Liang, Yi‐Zeng; Li, Shuhua; Luo, Xiao Liang; Zhang, Liangxiao; Tang, Zhonghai; Wang, Qin; Xu, Xiaona

doi:10.1016/j.ijms.2009.07.004

Cited by 12 publications

(5 citation statements)

References 31 publications

(40 reference statements)

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“…DFT calculations on the positional isomers of phenoxyspirophosphoranes 4 were performed. Considering that NPA analysis could provide an explanation of bond properties and electronic properties, the charge distribution of the P─O bond was also analyzed. The results of calculations are shown in Table .…”

Section: Resultsmentioning

confidence: 99%

The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI‐MSⁿ

et al. 2018

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The fragmentation pathways of pentacoordinated phenoxyspirophosphoranes were investigated in the positive mode by electrospray ionization multistage mass spectrometry. The results demonstrate that the sodium adducts of the title compounds undergo two competitive fragmentation pathways, and the fragmentation patterns are heavily dependent on the various substituent patterns at the phenolic group. An electron-withdrawing substituent at the ortho-position always results in the removal of a corresponding phenol analogue, while cleavage by spiroring opening becomes the predominant fragmentation pathway if an electron-donating substituent is at the phenolic group. The substituent effects on the competitive fragmentation pathways were further elucidated by theoretical calculations, single crystal structure analysis, and high-resolution mass spectrometry. The results contribute to the understanding of the gas-phase fragmentation reactions and the structure identification of spirophosphorane analogues by electrospray ionization multistage mass spectrometry.

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Section: Resultsmentioning

confidence: 99%

The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI‐MSⁿ

et al. 2018

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“…[11][12][13][14][15][16][17][18][19] Recent investigations have indicated that cationic peptide radicals undergo both backbone and sidechain cleavages. 18,[20][21][22][23][24][25] Among the backbone cleavages, N-C a , [26][27][28][29] N-terminal bond amide, [30][31][32] and C a -C bond cleavages, [33][34][35] which produce [c n + 2H] + /[z n À H] + ions, [y nÀ1 + 2H] + ions, and [a n ] + / [x n + H] + ions, respectively, have been observed; known side-chain reactions include C a -C b and C b -C g bond cleavages. [30][31][32][35][36][37][38] The nomenclature used here for describing product ions is the recently proposed 'all-explicit' system.…”

Section: Introductionmentioning

confidence: 99%

Nucleophilic substitution by amide nitrogen in the aromatic rings of [z_n− H]˙⁺ions; the structures of the [b₂− H − 17]˙⁺and [c₁− 17]⁺ions

Lau

Lai

et al. 2016

Phys. Chem. Chem. Phys.

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Peptide radical cations that contain an aromatic amino acid residue cleave to give [zn - H]˙⁺ ions with [b2 - H - 17]˙⁺ and [c1 - 17](+) ions, the dominant products in the dissociation of [zn - H]˙⁺, also present in lower abundance in the CID spectra. Isotopic labeling in the aromatic ring of [Yπ˙GG](+) establishes that in the formation of [b2 - H - 17]˙⁺ ions a hydrogen from the δ-position of the Y residue is lost, indicating that nucleophilic substitution on the aromatic ring has occurred. A preliminary DFT investigation of nine plausible structures for the [c1 - 17](+) ion derived from [Y(π)˙GG](+) shows that two structures resulting from attack on the aromatic ring by oxygen and nitrogen atoms from the peptide backbone have significantly better energies than other isomers. A detailed study of [Y(π)˙GG](+) using two density functionals, B3LYP and M06-2X, with a 6-31++G(d,p) basis set gives a higher barrier for attack on the aromatic ring of the [zn - H]˙⁺ ion by nitrogen than by the carbonyl oxygen. However, subsequent rearrangements involving proton transfers are much higher in energy for the oxygen-substituted isomer leading to the conclusion that the [c1 - 17](+) ions are the products of nucleophilic attack by nitrogen, protonated 2,7-dihydroxyquinoline ions. The [b2 - H - 17]˙⁺ ions are formed by loss of glycine from the same intermediates involved in the formation of the [c1 - 17](+) ions.

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“…Figure 4 shows a possible alternative path for loss of methyl group for compound 6, locating the initial positive charge on another atom. There are in the MS literature several papers in which theoretical calculations -including semi-empirical methods -are helpful to explain and better understand the ways of fragmentation [for example, see [45], [46], [47], [48], [49], [50]). Therefore in a first step we conducted a preliminary and exploratory study using B3LYP/6-31G(d) calculations in order to compare the neutral compounds with their corresponding molecular ions.…”

Section: Introductionmentioning

confidence: 99%

Mass spectrometry and theoretical calculations about the loss of methyl radical from methoxilated coumarins

Borkowski

Cecati

Suvire

et al. 2015

Journal of Molecular Structure

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Interpretation of the characteristic fragmentation mechanisms through determining the initial ionization site by natural spin density: A study on the derivatives of tryptophan and tryptamine

Cited by 12 publications

References 31 publications

The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI‐MSⁿ

The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI‐MSⁿ

Nucleophilic substitution by amide nitrogen in the aromatic rings of [z_n− H]˙⁺ions; the structures of the [b₂− H − 17]˙⁺and [c₁− 17]⁺ions

Mass spectrometry and theoretical calculations about the loss of methyl radical from methoxilated coumarins

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Interpretation of the characteristic fragmentation mechanisms through determining the initial ionization site by natural spin density: A study on the derivatives of tryptophan and tryptamine

Cited by 12 publications

References 31 publications

The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI‐MSn

The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI‐MSn

Nucleophilic substitution by amide nitrogen in the aromatic rings of [zn− H]˙+ions; the structures of the [b2− H − 17]˙+and [c1− 17]+ions

Mass spectrometry and theoretical calculations about the loss of methyl radical from methoxilated coumarins

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Product

Resources

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The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI‐MSⁿ

The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI‐MSⁿ

Nucleophilic substitution by amide nitrogen in the aromatic rings of [z_n− H]˙⁺ions; the structures of the [b₂− H − 17]˙⁺and [c₁− 17]⁺ions