Dissociative recombination cross section and branching ratios of protonated dimethyl disulfide and <i>N</i>-methylacetamide

Al-Khalili, A.; Thomas, Richard; Ehlerding, Anneli; Hellberg, F.; Geppert, Wolf D.; Zhaunerchyk, V.; Ugglas, M. af; Larsson, Mats; Uggerud, Einar; Vedde, John; Adlhart, Christian; Semaniak, J.; Kaminska, M.; Zubarev, Roman A.; Kjeldsen, Frank; Andersson, Patrik; Österdahl, Fabian; Bednarska, Violetta; Paál, A.

doi:10.1063/1.1782772

Cited by 19 publications

(14 citation statements)

References 23 publications

(30 reference statements)

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“…Experiments performed on this instrument indicate that the energy W. A. DONALD AND E. R. WILLIAMS deposited upon EC does not depend on the cathode voltage or the trapping potentials of the FT-ICR cell over a very wide range of experimental conditions [45]. The cross-sections for ion-electron recombination, as measured in ion storage rings, increases rapidly as the relative kinetic energy between the ion and electron approaches zero [60][61][62][63][64]. In our experiments, although there is a wide spread of electron kinetic energies, it is the electrons for which the relative kinetic energy between the ion and electron is essentially zero that should be captured most efficiently [45].…”

Section: Hydrated Ion Nanocalorimetry Measurementsmentioning

confidence: 99%

Gas-phase electrochemistry: Measuring absolute potentials and investigating ion and electron hydration

Donald

Williams

2011

Pure and Applied Chemistry

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In solution, half-cell potentials and ion solvation energies (or enthalpies) are measured relative to other values, thus establishing ladders of thermochemical values that are referenced to the potential of the standard hydrogen electrode (SHE) and the proton hydration energy (or enthalpy), respectively, which are both arbitrarily assigned a value of 0. In this focused review article, we describe three routes for obtaining absolute solution-phase halfcell potentials using ion nanocalorimetry, in which the energy resulting from electron capture (EC) by large hydrated ions in the gas phase are obtained from the number of water molecules lost from the reduced precursor cluster, which was developed by the Williams group at the University of California, Berkeley. Recent ion nanocalorimetry methods for investigating ion and electron hydration and for obtaining the absolute hydration enthalpy of the electron are discussed. From these methods, an absolute electrochemical scale and ion solvation scale can be established from experimental measurements without any models.

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Section: Hydrated Ion Nanocalorimetry Measurementsmentioning

confidence: 99%

Gas-phase electrochemistry: Measuring absolute potentials and investigating ion and electron hydration

Donald

Williams

2011

Pure and Applied Chemistry

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“…The conformational dynamics of multiply protonated peptides and proteins also contributes to uncertainties in identification of a particular charged site associated with the capture dynamics of an electron in high- n Rydberg states and the specification of the eventual site of electron localization in the cation radical. To circumvent these problems, relatively simple model systems have been investigated with high level quantum mechanical calculations 35,39. The amide-I vibration (C=O stretching mode) dynamics was also examined as a simple model of the vibrational energy propagation in α-helix fragmentation upon ECD and ETD 40…”

Section: Introductionmentioning

confidence: 99%

Probing the Mechanism of Electron Capture and Electron Transfer Dissociation Using Tags with Variable Electron Affinity

et al. 2009

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Electron capture dissociation (ECD) and electron transfer dissociation (ETD) of doubly protonated electron affinity (EA)-tuned peptides were studied to further illuminate the mechanism of these processes. The model peptide FQpSEEQQQTEDELQDK, containing a phosphoserine residue, was converted to EA-tuned peptides via β-elimination and Michael addition of various thiol compounds. These include propanyl, benzyl, 4-cyanobenzyl, perfluorobenzyl, 3,5-dicyanobenzyl, 3-nitrobenzyl and 3,5-dinitrobenzyl structural moieties, having a range of EA from -1.15 to 1.65 eV, excluding the propanyl group. Typical ECD or ETD backbone fragmentations are completely inhibited in peptides with substituent tags having EA over 1.00 eV, which are referred to as electron predators in this work. Nearly identical rates of electron capture by the dications substituted by the benzyl (EA = -1.15 eV) and 3-nitrobenzyl (EA = 1.00 eV) moieties are observed, which indicates the similarity of electron capture cross sections for the two derivatized peptides. This observation leads to the inference that electron capture kinetics are governed by the long range electron-dication interaction and are not affected by side chain derivatives with positive EA. Once an electron is captured to high-n Rydberg states, however, through-space or through-bond electron transfer to the EA-tuning tags or low-n Rydberg states via potential curve crossing occurs in competition with transfer to the amide π* orbital. The energetics of these processes are evaluated using time-dependent density functional theory with a series of reduced model systems. The intramolecular electron transfer process is modulated by structure-dependent hydrogen bonds and is heavily affected by the presence and type of electron withdrawing groups in the EA-tuning tag. The anion radicals formed by electron predators have high proton affinities (approximately 1400 kJ/mol for the 3-nitrobenzyl anion radical) in comparison to other basic sites in the model peptide dication, facilitating exothermic proton transfer from one of the two sites of protonation. This interrupts the normal sequence of events in ECD or ETD leading to backbone fragmentation by forming a stable radical intermediate. The implications which these results have for previously proposed ECD and ETD mechanisms are discussed.

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“…A direct mechanism has been suggested in which electron capture at C OH ϩ is accompanied by cleavage of the NOC␣ bond. Uggerud and coworkers [25,26] have shown theoretically and experimentally that both hydrogen transfer and direct processes play a role in ECD. Recently, Syrstad and Tureček [27] have proposed a mechanism for ECD that explains the low selectivity of NOC␣ cleavage and applies equally to peptide ions whose charge carriers are not protons.…”

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Investigation of the presence of b ions in electron capture dissociation mass spectra

Cooper

2005

J. Am. Soc. Mass Spectrom.

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Previously, we have indicated (Cooper, H.J., et al. Int. J. Mass Spectrom., 2003, 228, 723-728) that electron capture dissociation (ECD) of the doubly protonated peptides, Leu 4 -Sar-Leu 3 -Lys-OH, Leu 4 -Ala-Leu 3 -Lys-OH, Gly 4 -Sar-Gly 3 -Lys-NH 2 , and Gly 3 -Pro-Sar-Gly 3 -Lys-NH 2 , results in abundant b ions, which derive from fragmentation of backbone amide bonds, a nonstandard fragmentation channel in ECD. The instrumental conditions were such that the possibility that collision-induced dissociation processes were contributing to the observed spectra was eliminated. In a separate study (Fung, Y.M.E., et al. Eur. J. Mass Spectrom., 2004, 10, 449 -457. ECD of peptides Arg-(Gly) n -Xxx-(Gly) n -Arg, where Xxx is the amino acid of interest, did not result in b ions. The variation in ECD observed for strikingly similar peptides suggests that the nature of the charge carrier (Arg or Lys) is instrumental in governing the fragmentation channels. Here, we describe the ECD behavior of a suite of model peptides designed such that the nature and position of the charge carrier could be probed. The results suggest that the presence of b ions in ECD spectra is a consequence of both charge carrier and peptide structure. The mechanism by which ECD of NOC␣ bonds in peptides and proteins occurs has been a matter of considerable debate [1, 5, 14 -23]. One proposed mechanism [1] involves capture of an electron by a charged site in the ion, for example, a protonated lysine or arginine residue, followed by H· transfer to (or recapture by) an amide carbonyl resulting in an aminoketyl radical. The radical subsequently dissociates via cleavage of the NOC␣ bond. Originally, it was suggested that c/z· fragment ion formation proceeded faster than vibrational energy redistribution, and that the process was nonergodic [1]. Recent work by Tureček suggests that NOC␣ bond dissociation is particularly facile in thermalized radicals and radical cations, that is, nonergodicity does not apply [21]. McLafferty and coworkers [24] showed that infrared multiphoton dissociation of thermalized [M ϩ 12H] 11ϩ· ions results in the dominant loss of H· atoms in marked contrast to the c/z ions produced following electron capture by [M ϩ 12H] 12ϩ ions to form [M ϩ 12H] 11ϩ· radical ions. These researchers concluded that ECD was nonergodic and the mechanism involves electron capture in a high-n Rydberg state followed by cooling to a dissociative electronic state. A direct mechanism has been suggested in which electron capture at C OH ϩ is accompanied by cleavage of the NOC␣ bond. Uggerud and coworkers [25,26] have shown theoretically and experimentally that both hydrogen transfer and direct processes play a role in ECD. Recently, Syrstad and Tureček [27] have proposed a mechanism for ECD that explains the low selectivity of NOC␣ cleavage and applies equally to peptide ions whose charge carriers are not protons. Either electron capture in a ground electronic state results in hydrogen atom transfer from the ammonium group to the amide carbonyl ...

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Dissociative recombination cross section and branching ratios of protonated dimethyl disulfide and N-methylacetamide

Cited by 19 publications

References 23 publications

Gas-phase electrochemistry: Measuring absolute potentials and investigating ion and electron hydration

Gas-phase electrochemistry: Measuring absolute potentials and investigating ion and electron hydration

Probing the Mechanism of Electron Capture and Electron Transfer Dissociation Using Tags with Variable Electron Affinity

Investigation of the presence of b ions in electron capture dissociation mass spectra

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