Nondissociative Electron Capture by Disulfide Bonds

Carles, Sophie; Lecomte, Frédéric; Schermann, J. P.; Desfrançois, C.; Xu, Shou‐Jun; Nilles, J. Michael; Bowen, Kit H.; Bergès, Jacqueline; Houée-Levin⊥, Chantal

doi:10.1021/jp0040603

Cited by 48 publications

(58 citation statements)

References 23 publications

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“…This leads to a substantial increase of the X™X bond length and eventual fragmentation along this bond favored by the repulsion of the (Se™Se)* anti-bonding HOMO. In agreement with this, it is experimentally estimated that low energy electron capture in disulfides lowers the S™S bond dissociation energy by about 40% [14].…”

Section: Eiϫ Ionizationsupporting

confidence: 58%

Interpretation of alkyl diselenide and selenosulfenate mass spectra

Meija

Beck

Caruso

2004

J. Am. Soc. Mass Spectrom.

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The mass spectral fragmentation of aliphatic diselenides and selenosulfenates is analyzed to gain a better understanding of the behavior of these species. The main fragmentation pathways of these species include the fragmentation along the Se™C bond, fragmentation along the Se™Se or Se™S bonds and intra-molecular rearrangements. In general, negative ionization favors the fragmentation along the Se™Se or Se™S bonds while positive ionization leads to stable molecular ions. Density functional theory calculations of bond dissociation energies and molecular orbital analysis was undertaken to explain the observed trends in molecular fragmentation. Besides the analysis of molecular fragmentation, a phenomenon of molecular association in negative electron impact and positive chemical ionization conditions was observed and investigated using a high resolution time-of-flight mass spectrometer. Molecular association that occurs during the ionization of species includes the formation of symmetrical diselenides from asymmetrical selenosulfenates and formation of alkylseleno adducts from the corresponding diselenides. For species which is hard to resolve by mass analysis, such as isobars of CHSe, CH 2 Se, and CH 3 Se, the isotope pattern superimposition procedure was applied to define the overlapping clusters. nterest in selenium species has recently increased because of their anti-oxidative and anti-carcinogenic properties. As a result, speciation of selenium metabolites in the environment has been undertaken by many research groups to gain more understanding about bio-transformations and the occurrence of the various selenium compounds. Inductively coupled plasma mass spectrometry (ICP-MS) is usually utilized for efficient detection and screening of the various selenium species at ultra-trace levels; however, the ultimate identification necessitates characterization by molecular mass spectrometry [1].Volatile selenium species are of interest as the end terminal in Se metabolism, and are emitted by plants as a means of self-detoxification [2]. Additionally, diselenides and selenosulfenates are red.-ox. active species and account for the anti-oxidative action of selenium [3]. Despite the interest in the selenium volatiles, very few reports are devoted to the investigation of mass spectral fragmentation of heavier dichalcogenidesdiselenides (R-SeSe-R) and selenosulfenates (R-SeS-R). Early mass spectrometric studies of organic selenium compounds were undertaken by Rebane [4 -6] and recently by Prabhakar et al. [7]. However, diselenides and selenosulfenates were not a subject of interest in either of the studies.In this study we analyzed the mass spectral fragmentation of methyl-, ethyl-and ethylmethyl-diselenides and selenosulfenates to gain a better understanding of the behavior of these species. In order to explain the fragmentation behavior of diselenides and selenosulfenates, density functional theory calculations were performed to obtain the bond dissociation energies and molecular orbital information. Experimental Reagen...

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Section: Eiϫ Ionizationsupporting

confidence: 58%

Interpretation of alkyl diselenide and selenosulfenate mass spectra

Meija

Beck

Caruso

2004

J. Am. Soc. Mass Spectrom.

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“…The only attempt to study the nondissociative electron capture by the species which mimic the disulfide-bridged cystine containing one S-S bond is that reported by Carles et al and investigating the nondissociative electron capture by a series of saturated disulfides given by the R-S-S-R formula (where R stands for CH 3 , C 2 H 5 , and C 3 H 7 ). 9 The neutral model systems RS-SR were examined using Rydberg electron-transfer spectroscopy (RETS), negative ion photoelectron spectroscopy, and computational techniques (MP2 and DFT methods). It has been shown that the saturated disulfides form stable anions but do not capture thermal (nearly zero energy) electrons when isolated.…”

Section: Introductionmentioning

confidence: 99%

Excess Electron Attachment to Disulfide-Bridged l,l-Cystine. An ab Initio Study

2004

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The possibility of excess electron binding to cystine (consisting of two L-cysteine molecules linked via a disulfide bridge) in the gas-phase was studied at the second-order Møller-Plesset perturbation theory (MP2) level using the 6-31+G**+6(sp) basis sets. Several geometrically stable conformers and tautomers were found on the potential energy surfaces (PES) of both the neutral and anionic species. The most stable neutral isomer has proven to (i) involve two canonical rather than zwitterionic cysteine monomers, (ii) possess no inter-monomer hydrogen bonds, and (iii) exhibit an extended structure due to the presence of four intramonomer hydrogen bonds. It has also been found that most neutral isomers are capable of excess electron binding to form geometrically and electronically stable anions of dipole-bound nature. The electron binding energies for these anions span a wide region of 0.0004-0.947 eV (depending on the neutral parent molecule). In addition, several cystine-based anions were found at geometries where the neutral species are not stable. The latter anions gain stability from their large electron binding energies (they bind an excess electron by 0.488-1.975 eV).

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“…There has been a large number of studies aiming at providing a detailed knowledge of disulfide RAs (structure, formation and stability), either on disulfide-containing models [9] or proteinic systems. Two main factors capable of tuning disulfide adiabatic electron affinity (AEA) have been delineated: they appear to be of geometric (ring strain [10,11]) or electrostatic nature, with motifs such as peptide mutation in -Cys-(Xxx) n -Cys-loops [11], proximal positively charged residues [12,13], and N-terminal a-helix [14].…”

Section: Introductionmentioning

confidence: 99%

“…This potential role has never been explored to date. In the present Letter, we analyze the effect of microhydration on AEA of disulfide bond using dimethyldisulfide (DMDS) as prototypical system [9,10,17].…”

Section: Introductionmentioning

confidence: 99%