Fragmentation of Neutral Amino Acids and Small Peptides by Intense, Femtosecond Laser Pulses

Duffy, Martin; Kelly, Orla; Calvert, C. R.; King, R. B.; Belshaw, Louise; Kelly, Thomas J.; Costello, J. T.; Timson, David J.; Bryan, William A.; Kierspel, Thomas; Turcu, I. C. E.; Cacho, Céphise; Springate, E.; Williams, Ian D.; Greenwood, J. B.

doi:10.1007/s13361-013-0653-6

Cited by 9 publications

(10 citation statements)

References 58 publications

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“…78 In the case of negative ion formation, five fragment anions were obtained in the course of the present studies. Like for all other studied aromatic (as well as aliphatic) amino acids so far, no molecular anion was observed within the detection limit of the apparatus, which indicates that the temporary negative ion undergoes fast spontaneous emission of the excess electron or dissociation into sta- result is in agreement with the previous studies of the His mass spectrum based on the laser-induced acoustic desorption technique, 53,54 which is a gentle method to transfer neutral molecule into the gas phase. The only volatile thermal decomposition product of His detected in the present mass spectrum is carbon dioxide, which was straightforward to identify in the electron energy scans due its wellknown ionisation energy and resonance energies.…”

supporting

confidence: 89%

“…and Duffy et al,54 ie, by this comparison, it may be concluded that the major fragment ion peaks at m/z 54, 81, 82, and 110 arise from ionisation of intact His.Yet in contrast, Wilson et al assigned the ion yield at m/z 82 to result from ionisation of thermal decomposition products,31 where thermal decomposition was already operational at the His sample temperature of 100°C; however, we note that they produced gas-phase His by particle evaporation. Interestingly, they also observed a peak at m/z 111, which was about 1.5 times more abundant than m/z 110.…”

mentioning

confidence: 60%

“…We note that electron 53 and photon 54 ionisation studies with His were also carried by means of a more gentle sublimation method, respectively. Both studies employed laser-induced acoustic desorption (LIAD) of the His sample, where thermal decomposition should not play a considerable role.…”

Section: Quantum Chemical Calculationsmentioning

confidence: 99%

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Positive and negative ions of the amino acid histidine formed in low‐energy electron collisions

et al. 2019

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Histidine is an aromatic amino acid crucial for the biological functioning of proteins and enzymes. When biological matter is exposed to ionising radiation, highly energetic particles interact with the surrounding tissue which leads to efficient formation of low‐energy electrons. In the present study, the interaction of low‐energy electrons with gas‐phase histidine is studied at a molecular level in order to extend the knowledge of electron‐induced reactions with amino acids. We report both on the formation of positive ions formed by electron ionisation and negative ions induced by electron attachment. The experimental data were complemented by quantum chemical calculations. Specifically, the free energies for possible fragmentation reactions were derived for the τ and the π tautomer of histidine to get insight into the structures of the formed ions and the corresponding neutrals. We report the experimental ionisation energy of (8.48 ± 0.03) eV for histidine which is in good agreement with the calculated vertical ionisation energy. In the case of negative ions, the dehydrogenated parent anion is the anion with the highest mass observed upon dissociative electron attachment. The comparison of experimental and computational results was also performed in view of a possible thermal decomposition of histidine during the experiments, since the sample was sublimated in the experiment by resistive heating of an oven. Overall, the present study demonstrates the effects of electrons as secondary particles in the chemical degradation of histidine. The reactions induced by those electrons differ when comparing positive and negative ion formation. While for negative ions, simple bond cleav ages prevail, the observed fragment cations exhibit partly restructuring of the molecule during the dissociation process.

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confidence: 89%

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confidence: 60%

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Positive and negative ions of the amino acid histidine formed in low‐energy electron collisions

et al. 2019

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“…As was reported before for ionization of pure camphor samples near 400 nm 24 , parent ion fragmentation can be easily induced by increasing the laser fluence although, noting the invariance of mass-selected photoelectron spectra (PES) of various ionic fragments, it was concluded that fragmentation was induced after photoionization of the neutral molecule. Hence, in principle, the laser fluence could be adjusted to obtain further structural identification from the fragmentation fingerprint 31 32 , and furthermore, the wavelength could be varied to achieve more selective ionization of preferred mixture components.…”

Section: Resultsmentioning

confidence: 99%

Enantiomer-specific analysis of multi-component mixtures by correlated electron imaging–ion mass spectrometry

Fanood¹,

Ram

Lehmann

et al. 2015

Nat Commun

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Simultaneous, enantiomer-specific identification of chiral molecules in multi-component mixtures is extremely challenging. Many established techniques for single-component analysis fail to provide selectivity in multi-component mixtures and lack sensitivity for dilute samples. Here we show how enantiomers may be differentiated by mass-selected photoelectron circular dichroism using an electron–ion coincidence imaging spectrometer. As proof of concept, vapours containing ∼1% of two chiral monoterpene molecules, limonene and camphor, are irradiated by a circularly polarized femtosecond laser, resulting in multiphoton near-threshold ionization with little molecular fragmentation. Large chiral asymmetries (2–4%) are observed in the mass-tagged photoelectron angular distributions. These asymmetries switch sign according to the handedness (R- or S-) of the enantiomer in the mixture and scale with enantiomeric excess of a component. The results demonstrate that mass spectrometric identification of mixtures of chiral molecules and quantitative determination of enantiomeric excess can be achieved in a table-top instrument.

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“…However, it has been shown that high-power and ultra-short femtosecond laser pulses (kilohertz repetition rates) can provide a rather effective universal ionisation source. 4,56,59,60 The intense electric field of the pulse leads to very rapid dissociative ionisation rather than generation of an excited state of the neutral molecule. The resulting fragmentation can be similar to that of electron impact.…”

Section: Universal Ionisationmentioning

confidence: 99%

Account: An Introduction to Velocity-Map Imaging Mass Spectrometry (VMImMS)

Bull

Lee

Gardiner

et al. 2014

Eur J Mass Spectrom (Chichester)

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This account introduces a new variant of time-of-flight mass spectrometry, termed velocity-map imaging mass spectrometry (VMImMS).While the ion abundances recorded in conventional ToF-MS measurements are highly useful for molecular quantification and structure determination, the final parent and fragment ion yields are largely blind to the dynamics of the processes in which the ions were formed inside the mass spectrometer. By recording the velocity distribution of each ion in tandem with the mass spectrum, not only can the details of the dissociative ionisation dynamics be unravelled, but the extra dimensions of information can be used for enhanced molecular fingerprinting, separating contributions from ions with identical mass-to-charge ratio and resolving components within mixtures, to name but a few examples. Measuring ion-velocity distributions within a mass spectrometry measurement is not new, but incorporating imaging techniques developed within the reaction dynamics community provides vastly improved velocity resolution for all ions simultaneously in a single-stage instrument. This account provides an introduction to VMImMS, outlines the fundamental instrumentation and detector requirements and the challenges associated with developing the method further, and details proof-of-concept work from our laboratory on a number of potential applications of the technique.

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Fragmentation of Neutral Amino Acids and Small Peptides by Intense, Femtosecond Laser Pulses

Cited by 9 publications

References 58 publications

Positive and negative ions of the amino acid histidine formed in low‐energy electron collisions

Positive and negative ions of the amino acid histidine formed in low‐energy electron collisions

Enantiomer-specific analysis of multi-component mixtures by correlated electron imaging–ion mass spectrometry

Account: An Introduction to Velocity-Map Imaging Mass Spectrometry (VMImMS)

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