Through-space and through-bond electron transfer within positively charged peptides in the gas phase

Neff, Diane; Sobczyk, Monika; Simons, Jack

doi:10.1016/j.ijms.2008.04.012

Cited by 23 publications

(22 citation statements)

References 41 publications

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“…Alternatively, electrons evolve from higher to lower Rydberg orbitals with eventual intramolecular electron transfer to amide antibonding orbitals, which leads to the backbone dissociation of the ion. [32,33] The probability for either electron capture or transfer to amide antibonding orbitals is therefore expected to be dependent upon charge state for a given polypeptide ion. If the antibonding orbitals are less likely to be populated due to a low Coulomb field, the electrons will more likely remain localized at the protonation sites leading to greater side-chain loss.…”

Section: Resultsmentioning

confidence: 99%

“…[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%

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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: Resultsmentioning

confidence: 99%

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 question of which states are accessed upon electron attachment has been recently addressed by Simons and coworkers [71][72][73], who presented a semiquantitative model of intramolecular electron transfer according to LandauZenner theory. Their model was built on an interaction of ammonium Rydberg 3s and higher ns orbitals with a σ* orbital of a remote disulfide bond or a π* orbital of a remote amide group.…”

Section: Electronic States and Dipolar Field Effectsmentioning

confidence: 99%

“…Their model was built on an interaction of ammonium Rydberg 3s and higher ns orbitals with a σ* orbital of a remote disulfide bond or a π* orbital of a remote amide group. According to the analysis of the spatial extent of ammonium 3s, 4s and 5s orbitals, Simons and coworkers estimated the ranges of best overlap of the Rydberg and amide π* orbitals and used them as a measure of the coupling H 12 terms for electron hopping between the pertinent potential energy surfaces [71]. We now attempt to apply this analysis to ion 2a 2+ , which has an extended structure that separates the amide groups in space and also with regard to their distance from the N-terminal ammonium.…”

Section: Electronic States and Dipolar Field Effectsmentioning

confidence: 99%

Dipole-Guided Electron Capture Causes Abnormal Dissociations of Phosphorylated Pentapeptides

Moss

Chung

Wyer

et al. 2011

J. Am. Soc. Mass Spectrom.

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Electron transfer and capture mass spectra of a series of doubly charged ions that were phosphorylated pentapeptides of a tryptic type (pS,A,A,A,R) showed conspicuous differences in dissociations of charge-reduced ions. Electron transfer from both gaseous cesium atoms at 100 keV kinetic energies and fluoranthene anion radicals in an ion trap resulted in the loss of a hydrogen atom, ammonia, and backbone cleavages forming complete series of sequence z ions. Elimination of phosphoric acid was negligible. In contrast, capture of lowenergy electrons by doubly charged ions in a Penning ion trap induced loss of a hydrogen atom followed by elimination of phosphoric acid as the dominant dissociation channel. Backbone dissociations of charge-reduced ions also occurred but were accompanied by extensive fragmentation of the primary products. z-Ions that were terminated with a deaminated phosphoserine radical competitively eliminated phosphoric acid and H 2 PO 4 radicals. A mechanism is proposed for this novel dissociation on the basis of a computational analysis of reaction pathways and transition states. Electronic structure theory calculations in combination with extensive molecular dynamics mapping of the potential energy surface provided structures for the precursor phosphopeptide dications. Electron attachment produces a multitude of low lying electronic states in charge-reduced ions that determine their reactivity in backbone dissociations and H-atom loss. The predominant loss of H atoms in ECD is explained by a distortion of the Rydberg orbital space by the strong dipolar field of the peptide dication framework. The dipolar field steers the incoming electron to preferentially attach to the positively charged arginine side chain to form guanidinium radicals and trigger their dissociations.

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“…The ion-electron pair then undergoes a cascade of nonadiabatic transitions to lower Rydberg and valence orbitals that represent excited electronic states of the charge-reduced peptide cation-radical. 43,44) Figure 4 shows molecular orbitals for a few low-energy excited states in the charge-reduced cation-radical of pentapeptide AApSAR that were calculated by time-dependent density functional theory. The common feature of the valence excited states is that their energies form a very dense manifold containing many (10-15) electronic states within 1 eV of the ground electronic state.…”

Section: Exd Mechanismsmentioning

confidence: 99%

Renaissance of Cation-Radicals in Mass Spectrometry

Tureček

2013

Mass Spectrometry

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This brief overview addresses the topic that was presented in the Thomson Medal Award session at the 19th International Mass Spectrometry Conference in Kyoto, Japan. Mass spectrometry of cation-radicals has enjoyed a remarkable renaissance thanks to the development of new methods for electron attachment to multiply charged peptide ions. The charge-reduced ions that are odd-electron species exhibit interesting reactivity that is useful for peptide and protein sequencing. The paper briefly reviews the fundamental aspects of the formation, energetics, and backbone dissociations of peptide cation-radicals.

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Through-space and through-bond electron transfer within positively charged peptides in the gas phase

Cited by 23 publications

References 41 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

Dipole-Guided Electron Capture Causes Abnormal Dissociations of Phosphorylated Pentapeptides

Renaissance of Cation-Radicals in Mass Spectrometry

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