Theoretical study of through-space and through-bond electron transfer within positively charged peptides in the gas phase

Sobczyk, Monika; Neff, Diane; Simons, Jack

doi:10.1016/j.ijms.2007.10.003

Cited by 34 publications

(31 citation statements)

References 37 publications

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“…[30] Simons et al have also examined theoretically the process by which electrons can be transferred either through bond or through space to an anti-bonding amide bond orbital from relatively low-lying Rydberg orbitals of a charged site of peptide side chain. [31,32,33] The peptide charge state is relevant to the ECD/ETD mechanism in that it is associated with differences in the cation recombination energy, the electronic structures of precursor and product ions, the electrostatic field in the ions for the initially captured or transferred electrons, the higher order structure of peptide ions, the kinetic stabilities of the products, etc. For example, cation charge state for a given polypeptide ion is known to have significant effects on the dissociation of peptides ions in both ECD and ETD experiments in terms of dissociation patterns, sequence coverage, etc.…”

Section: Introductionmentioning

confidence: 99%

Electron transfer dissociation: Effects of cation charge state on product partitioning in ion/ion electron transfer to multiply protonated polypeptides

Liu

McLuckey

2012

International Journal of Mass Spectrometry

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The effect of cation charge state on product partitioning in the gas-phase ion/ion electron transfer reactions of multiply protonated tryptic peptides, model peptides, and relatively large peptides with singly charged radical anions has been examined. In particular, partitioning into various competing channels, such as proton transfer (PT) versus electron transfer (ET), electron transfer with subsequent dissociation (ETD) versus electron transfer with no dissociation (ET,noD), and fragmentation of backbone bonds versus fragmentation of side chains, was measured quantitatively as a function of peptide charge state to allow insights to be drawn about the fundamental aspects of ion/ion reactions that lead to ETD. The ET channel increases relative to the PT channel, ETD increases relative to ET,noD, and fragmentation at backbone bonds increases relative to side-chain cleavages as cation charge state increases. The increase in ET versus PT with charge state is consistent with a Landau-Zener based curve-crossing model. An optimum charge state for ET is predicted by the model for the ground state-to-ground state reaction. However, when the population of excited product ion states is considered, it is possible that a decrease in ET efficiency as charge state increases will not be observed due to the possibility of the population of excited electronic states of the products. Several factors can contribute to the increase in ETD versus ET,noD and backbone cleavage versus side-chain losses. These factors include an increase in reaction exothermicity and charge state dependent differences in precursor and product ion structures, stabilities, and sites of protonation.

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Section: Introductionmentioning

confidence: 99%

Electron transfer dissociation: Effects of cation charge state on product partitioning in ion/ion electron transfer to multiply protonated polypeptides

Liu

McLuckey

2012

International Journal of Mass Spectrometry

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“…5 In contrast with vibrational activation methods in tandem mass spectrometry where formation of b or y ions 6 via cleavage of the peptide bonds is the most effective fragmentation pathway of positive multiply charged peptides, reaction of these species with electrons leads to the generation of mainly cЈ and z · ions in which the peptide bonds remain intact, while neighboring N -C ␣ bonds break. The mechanism of this complementary decay reaction in charged peptides has been a subject of many experimental and theoretical investigations, 7 where one of the main challenges was the difficulties associated with determining the internal energy of the breakdown products.…”

Section: Introductionmentioning

confidence: 99%

Fragmentation of peptide negative molecular ions induced by resonance electron capture

Vasil’ev

Figard

Morré

et al. 2009

The Journal of Chemical Physics

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A simple robust method to study resonance gas-phase reactions between neutral peptides of low volatility and free electrons has been designed and implemented. Resonance electron capture ͑REC͒ experiments were performed by several neutral model peptides and two naturally occurring peptides. The assignment of negative ions ͑NIs͒ formed in these gas-phase reactions was based on high mass-resolving power experiments. From these accurate mass measurements, it was concluded that fragment NIs formed by low ͑1-2 eV͒ energy REC are of the same types as those observed in electron capture/transfer dissociation, where the positive charge is a factor. The main feature resulting from these REC experiments by peptides is the occurrence of z n − 1 ions, which are invariably of the highest abundances in the negative ion mass spectra of larger peptides. ͓M-H͔ − NIs presumably the carboxylate anion structure dominate the REC spectra of smaller peptides. There was no evidence for the occurrence of the complementary reaction, i.e., the formations of c n + 1 ions. Instead, c n ions arose without hydrogen/proton transfer albeit with lower abundances than that observed for z n − 1 ions. Only the amide forms of small peptides showed more abundant ion peaks for the c n ions than for the z n − 1 ions. The mechanisms for the N -C ␣ bond cleavage are discussed.

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“…Moreover, it can be also used to understand radical-driven fragmentation mechanisms for gas-phase peptide occurring in electron capture dissociation (ECD) [28], electron transfer dissociation (ETD) [29], or low-energy CID of peptide radical cations [31,32].…”

Section: Resultsmentioning

confidence: 99%

“…Determining the initial ionization site is a key step for predicting the preferred fragmentation pathways so as to unravel the mechanisms of the fragmentation reaction in detail, which must be defined at first in the mass spectra interpretation not only for small molecules [15,16], but also for gas-phase peptides [28][29][30][31][32]. In general, the most favorable initial ionization site could be evaluated by comparison with the approximate IEs for the functional groups in the molecule, based on the IEs of appropriate model compounds [15,16].…”

Section: Compared With Ionization Energy For Determination Of Initialmentioning

confidence: 99%

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

Ouyang¹,

Liang²,

Li³

et al. 2009

International Journal of Mass Spectrometry

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Theoretical study of through-space and through-bond electron transfer within positively charged peptides in the gas phase

Cited by 34 publications

References 37 publications

Electron transfer dissociation: Effects of cation charge state on product partitioning in ion/ion electron transfer to multiply protonated polypeptides

Electron transfer dissociation: Effects of cation charge state on product partitioning in ion/ion electron transfer to multiply protonated polypeptides

Fragmentation of peptide negative molecular ions induced by resonance electron capture

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

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