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Effective yield curves of negative ions with m/z 28 (A), 26 (B), 17 (C), and 16 (D) from serine as functions of electron energy.
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Cited By (since 1996):10, Export Date: 29 November 2013, Source: Scopus, CODEN: JPCAF, doi: 10.1021/jp906636b, PubMed ID: 20043683, Language of Original Document: English, Correspondence Address: Matejčík, Š.; Department of Experimental Physics, Comenius University Bratislava, Mlynská Dolina F2, 84248, Bratislava, Slovakia; email: matejcik@fmph.uni...
Context in source publication
Context 1
... Mauracher et al. 23 and Sulzer et al. 31 using a double focusing instrument with high mass resolving power reported on accurate mass measurements of some of the ions. Bearing in mind these accurate mass measurements, negative ions with m/z 26 from serine (Table 1; Figure 9) can be interpreted as C 2 H 2 -(high energies) and CN -(low energies), whereas negative ions with m/z 17 and m/z 16 can be attributed, respectively, to OH - and O -or NH 2 -. The ion signal at m/z 28 we are not able to assign unequivocally. ...
Citations
... They can be due to formation of VFRs via coupling of a DBS with a valence σ * anion state that initiates H atom tunneling through the potential barrier formed by avoided crossing between these states [25]. The same mechanism is attributed to dehydrogenation of several amino acids via the DEA [78,79]. However, in the present case the position of the lowest π * 1 resonance matches well the observed maxima of the [M−H] − DEA signals (m/z = 67 for II and III, m/z = 66 for IV, and m/z = 81 for VI, as shown in Figs. ...
Low-energy (0–15 eV) resonance electron attachment to a series of five-membered heterocyclic rings (isoxazole, imidazole, pyrazole, pyrrole, 1-methyl-, and 2-methylimidazole) is studied under gas-phase conditions by means of electron transmission spectroscopy and dissociative electron attachment spectroscopy (DEAS). Experimental spectral features are assigned on the basis of Hartree-Fock and density functional theory calculations. Sharp features, with a width of less than 0.1 eV, observed in the electron transmission spectra of imidazole, pyrazole, and pyrrole close to 0.45 eV, i.e., well below the energy of their lowest-lying π* shape resonances detected at 1.90, 1.87, and 2.33 eV, respectively, are associated with formation of negative ion states bound by long-range electron-molecule interactions. Effective range theory calculations which include both dipolar and polarization interactions support this interpretation. In addition to the general observation of cleavage of the N–H bond at incident electron energies close to 2 eV, elimination of as many as three hydrogen atoms from the molecular negative ions is detected at higher energies by DEAS with the only exception of methylated imidazoles. This complex process is associated with ring opening and formation of diatomic hydrogen as one of the neutral fragments, as indicated by the calculations to satisfy the energetic requirements. The present results are of importance for understanding the basic mechanisms of damages caused in living tissues by high-energy radiations.
... Одно из таких свойств проявляется в интенсивной фрагментации короткоживущих молекулярных ОИ аминокислот с выбросом атома водорода СООН-группы в низкоэнергетической области. Пик ионов [M−H] − в диапазоне энергии 1−3 eV является основным в массспектрах аминокислот [28][29][30][31][32][33][34][35], а относительная интенсивность пиков других ионов не превышает 10%. Другое свойство аминокислот проявляется в перегруппировочных реакциях с участием Н-атома СООН-группы с выбросом частиц NH • 2 и NH 3 (и, возможно, с выбросом бокового заместителя в фенилаланине, тирозине, триптофане -наши неопубликованные данные) в указанной области энергии. ...
... In the recent years, several investigations have employed soft ionization techniques, such as matrix‐assisted laser desorption ionization (MALDI) [104][105][106][107], electrospray ionization (ESI) [108, 109], and collision‐induced dissociation (CID) [110][111][112][113][114], to study the ionization and fragmentation of different amino acids and small peptides in the gas phase. Gas‐phase investigations of LEE‐induced damage to protein subunits have been reported for the amino acids alanine [115], tyrosine [116], glycine [117, 118], proline [119, 120], cysteine [121], and serine [122,123], as well as small peptides, such as dialanine [124] and amino acid esters [125]. For all cases, the anion yield functions (i.e., ion yields measured as a function of electron energy) exhibited localized maxima at energies below 15 eV, indicating the formation of TMAs. ...
... For all cases, the anion yield functions (i.e., ion yields measured as a function of electron energy) exhibited localized maxima at energies below 15 eV, indicating the formation of TMAs. It has been established that no intact parent anion is observable on mass spectrometric timescales after capture of a free electron, and that the most probable reaction corresponds to the loss of a hydrogen atom from a carboxyl group to form for a molecule " M, " the dehydro‐ genated anion (M–H)‾ at energies of around 1.5 eV [120, 123, 126, 127]. Early DEA studies ascribed this process to initial electron attachment into a π* orbital of the (C=O) bond in the COOH group, which couples to the repulsive σ* (O–H) orbital [118]. ...
This chapter focuses on the fundamental processes that govern interactions of low‐energy (1–30 eV) electrons with biological systems. These interactions have been investigated in the gas phase and within complex arrangements in the condensed phase. They often lead to the formation of transient molecular anions (TMAs), and their decay by autoionization or dissociation accompanied by bond dissociation. The damage caused to biomolecules via TMAs is emphasized in all sections. Such damage, which depends on a large number of factors, including electron energy, molecular environment, and type of biomolecule, and its physical and chemical interactions with radiosensitizing agents are extensively discussed. A majority of recent findings resulting from experimental and theoretical endeavors are presented. They encompass broad research areas to elucidate important roles of TMAs in irradiated biological systems, from the molecular level to nanoscale cellular dimensions. Fundamental aspects of TMA formation are stressed in this chapter, but many practical applications in a variety of radiation‐related fields such as radiobiology and radiotherapy are addressed.
Applying this technique, Bald and coworkers compared the absolute strand break cross sections of different 13‐mer oligonucleotide sequences (i.e., 5'‐TT(XTX)3TT, with X = A, C, or G) to evaluate the role of the different DNA nucleobases in DNA strand breakage. They also studied the sensitizing effect of incorporation of 5‐bromouracil (BrU) by comparing the absolute strand break cross sections for the sequences 5'‐TT(XBrUX)3TT, with X = A, C, or G. The observed trend in the absolute strand break cross sections agrees qualitatively with the previous HPLC studies investigating the fragmentation of oligonucleotide trimers of the sequence TXT, with X = A, C, G, irradiated with 10 eV electrons [83]. Additionally, the cross sections measured with this method are comparable in magnitude with the cross sections for strand breaks in different plasmid DNA molecules induced by 1–10 eV electrons, as determined by agarose gel electrophoresis [84, 85]. The DNA nanoarray technique thus bridges the gap between very large genomic double‐stranded DNA and very short oligonucleotides, and enables the detailed investigation of sequence‐dependent processes in DNA radiation damage. Further experimental and theoretical studies are carried out covering a broad range of electron energies and DNA sequences to elucidate the most relevant damage mechanisms [86].
... The fragmentation of serine has previously been studied using electron attachment 13,14 (isolated and clustered serine) and X-ray irradiation (condensed phase serine). 15 To our knowledge, this is the first study on fragmentation of isolated core-ionized serine in the gas phase. ...
Photofragmentation pathways of doubly ionized serine molecules are investigated and compared with those of cysteine. The main motivation for the study is to investigate if an atomic substitution within the same group of elements, namely replacing sulfur (in cysteine) with oxygen (in serine), causes a major change in the C 1s core ionization induced dissociation pattern in the molecules of otherwise identical structure. The results show that in serine there is a single completely dominant fragmentation channel producing the (CNH2-4+, COH1-3+), pairs, whereas in cysteine there are also many other fragmentation channels. The employed experimental method was the photoelectron-photoion-photoion coincidence (PEPIPICO) technique combined with synchrotron radiation tuned to ionize desired core levels. Molecular dynamics calculations were also carried out in order to extract information on the fragmentation and the neutral final fragments.
... The loss of an H atom driven by electrons with low energy (nearly 1 eV) is a reaction common to many biologically relevant molecules, including DNA nucleobases [1][2][3][4][5], organic acids [6,7] and amino acids [8][9][10][11][12][13][14]. More generally, low-energy electron (LEE)-driven reactions are considered to be important initial and decisive steps in the molecular description of radiation damage to biological systems. ...
... These experiments initiated much activity towards a detailed investigation of the interaction of LEEs with biomolecular systems including the building blocks of DNA, organic acids and amino acids. From gas phase experiments, it was found that all the nucleobases (thymine, adenine, cytosine, guanine-aminobutanoic acid-aminobutanoic acid-aminobutanoic acid and uracil) [1][2][3][4][5], organic acids [6,7] and also amino acids [8][9][10][11][12][13][14] exhibit a low-energy decomposition reaction triggered by electrons at subexcitation energies (nearly 1 eV), namely dissociative electron attachment (DEA) leading to the loss of a neutral hydrogen atom: ...
... In the simplest organic molecule containing a carboxyl group, formic acid (HCOOH), isotope labeling experiments using HCOOD and DCOOH have in fact shown that H loss exclusively occurs at the OH site [7], which turned out to be the case also for small amino acids [8][9][10][11][12][13][14]. In a theoretical study [22], H loss from formic acid (HCOOH) has been attributed to initial electron attachment into the COOH π * MO, followed by out-of-plane distortions, thereby coupling the π * MO, to the σ * MO, ultimately generating HCOO − + H. ...
The mechanism of a hydrogen loss reaction upon dissociative electron attachment to organic acids and amino acids has been a matter of controversy. In this study, we investigate this process for three isomers of aminobutanoic acid and the deuterated analogue of the α isomer (αAD) in the electron energy range 0–2.5 eV. We implement the resonant
R-matrix theory, applying a one-dimensional model involving electron capture into the σ*(OH) orbital which reproduces convincingly the conspicuous features of the experimental cross sections, i.e. the pronounced cusps at the vibrational excitation threshold, the substantially different shapes of the three constitutional isomers and the characteristic differences between αA and its isotopologue αAD.
In this Topical Review we survey the current state of the art in the study of low energy electron collisions with biologically relevant molecules and molecular clusters. We briefly describe the methods and techniques used in the investigation of these processes and summarise the results obtained so far for DNA constituents and their model compounds, amino acids, peptides and other biomolecules. The applications of the data obtained is briefly described as well as future required developments.
Dipeptide molecules are good model systems for investigation of resonant reactions of low-energy electrons with proteins. The present work is devoted to the study of the processes of formation and fragmentation of negative ions in aliphatic dipeptides glycyl-glycine and glycyl-alanine. The metastable decays of negative ions were detected in these objects, and have been investigated with the aim of clarification of the mechanisms of fragmentation.
The effective yield curves for negative ions as functions of electron energy were obtained using a magnetic sector mass spectrometer rebuilt for generation and detection of negative ions. For analysis of the observed metastable decays statistical and thermochemical approaches have been used.
The ions structures, the enthalpies of formation of neutral and charged particles, and the rate constants of dissociative reactions have been found.
Comparison of the experimental results with theoretical data leads to the conclusion that metastable ion decay proceeds with minimal structural changes avoiding complicated rearrangements and isomerization processes.
