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1.
Phys Chem Chem Phys ; 22(10): 5785-5796, 2020 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-32105280

RESUMO

The laboratory study of prebiotic molecules interacting with solar wind ions is important to understand their role in the emergence of life in the complex context of the astrochemistry of circumstellar environments. In this work, we present the first study of the interaction of hydantoin (C3N2O2H4, 100 a.m.u.) with solar wind minority multi-charged ions: O6+ at 30 keV and He2+ at 8 keV. The fragmentation mass spectra as well as correlation maps resulting from the interaction are presented and discussed in this paper. Prompt and delayed dissociations from metastable states of the ionized molecule have been observed and the corresponding lifetimes measured. Experimental results are completed by quantum Density Functional Theory (DFT) calculations for energies, structures and dynamics (Internal Reaction Coordinates and Dynamic Reaction Coordinates) of the molecule for its different reachable charge states and the major observed fragmentation pathways. These calculations show that the molecule can only support two charges before spontaneously dissociating in agreement with the experimental observations. Calculations also demonstrate that hydantoin's ring opens after double ionization of the molecule which may enhance its reactivity in the background of biological molecule formation in a cirmcumstellar environment. For the major experimentally observed fragmentations (like 44 a.m.u./56 a.m.u. dissociation), Internal Reaction Coordinate (IRC) calculations were performed pointing out for example the important role of hydrogen transfer in the fragmentation processes.

2.
Rev Sci Instrum ; 90(8): 083306, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31472612

RESUMO

The performance of a newly built omega type electrostatic analyzer designed to act as an in-line charge-state purification system for ions in the kiloelectronvolt energy range is reported. The analyzer consists of a set of four consecutive electrostatic 140° concentric cylindrical electrodes enclosed by Matsuda electrodes. This setup was recently tested and validated using O5+, Ar9+, and Xe20+ ion beams at an energy of 14 qkeV at the ARIBE facility. A resolving power of 10.5 and a transmission of 100% of the desired charge state are measured allowing a good purification of incoming ion beams with charge states up to 10+ and a fairly good purification for charge states at least up to 20+. In comparison with other in-line solutions such as the Wien filter, our system has the advantage of being purely electrostatic and therefore lacking common drawbacks as, for example, hysteresis.

3.
Clin Biochem ; 69: 1-7, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31022391

RESUMO

Artificial intelligence (AI) and data science are rapidly developing in healthcare, as is their translation into laboratory medicine. Our review article presents an overview of the data science domain while discussing the reasons for its emergence. We also present several perspectives of its applications in clinical laboratories, along with potential ethical challenges related to AI and data science.


Assuntos
Inteligência Artificial , Ciência de Dados , Aprendizado de Máquina , Ciência de Laboratório Médico , Big Data , Humanos
4.
Phys Chem Chem Phys ; 20(35): 22841-22848, 2018 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-30151535

RESUMO

The fragmentation of glycine (NH2CH2COOH) has been studied by photoelectron-photoion coincidence, PEPICO, experiments at 60 eV photon energy. Glycine practically fragments at the ionization threshold, with the charge being on the H2NCH2+ moiety, due to ejection of an electron from the nitrogen lone pair of the highest occupied molecular orbital. To observe the formation of the complementary cation COOH+ further energy is needed. The flexibility with respect to rotation about the C-C, C-N and C-O bonds makes glycine exist in the gas phase in several conformers of both Cs and C1 point group symmetry in the neutral as well as ion states. The ionization can lead to stabilization of some conformations, rearrangements and, last but not least, H migration between the two moieties. The results of these experiments prove the sensitivity of PEPICO to pin point all these processes.

5.
Rev Sci Instrum ; 89(4): 043104, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29716322

RESUMO

In the present paper, we describe a new home-built crossed-beam apparatus devoted to ion-induced ionization and fragmentation of isolated biologically relevant molecular systems. The biomolecular ions are produced by an electrospray ionization source, mass-over-charge selected, accumulated in a 3D ion trap, and then guided to the extraction region of an orthogonal time-of-flight mass spectrometer. Here, the target molecular ions interact with a keV atomic ion beam produced by an electron cyclotron resonance ion source. Cationic products from the collision are detected on a position sensitive detector and analyzed by time-of-flight mass spectrometry. A detailed description of the operation of the setup is given, and early results from irradiation of a protonated pentapeptide (leucine-enkephalin) by a 7 keV He+ ion beam are presented as a proof-of-principle.


Assuntos
Espectrometria de Massas por Ionização por Electrospray/instrumentação , Espectrometria de Massas em Tandem/instrumentação , Elétrons , Encefalina Leucina/química , Desenho de Equipamento , Gases/química , Hélio/química , Íons/química , Cinética , Estudo de Prova de Conceito
6.
Phys Chem Chem Phys ; 20(22): 15052-15060, 2018 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-29790511

RESUMO

Ionization, fragmentation and molecular growth have been studied in collisions of 22.5 keV He2+- or 3 keV Ar+-projectiles with pure loosely bound clusters of coronene (C24H12) molecules or with loosely bound mixed C60-C24H12 clusters by using mass spectrometry. The heavier and slower Ar+ projectiles induce prompt knockout-fragmentation - C- and/or H-losses - from individual molecules and highly efficient secondary molecular growth reactions before the clusters disintegrate on picosecond timescales. The lighter and faster He2+ projectiles have a higher charge and the main reactions are then ionization by ions that are not penetrating the clusters. This leads mostly to cluster fragmentation without molecular growth. However, here penetrating collisions may also lead to molecular growth but to a much smaller extent than with 3 keV Ar+. Here we present fragmentation and molecular growth mass distributions with 1 mass unit resolution, which reveals that the same numbers of C- and H-atoms often participate in the formation and breaking of covalent bonds inside the clusters. We find that masses close to those with integer numbers of intact coronene molecules, or with integer numbers of both intact coronene and C60 molecules, are formed where often one or several H-atoms are missing or have been added on. We also find that super-hydrogenated coronene is formed inside the clusters.

7.
Phys Chem Chem Phys ; 19(30): 19665-19672, 2017 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-28503696

RESUMO

We report on studies of collisions between 3 keV Ar+ projectile ions and neutral targets of isolated 1,3-butadiene (C4H6) molecules and cold, loosely bound clusters of these molecules. We identify molecular growth processes within the molecular clusters that appears to be driven by knockout processes and that could result in the formation of (aromatic) ring structures. These types of reactions are not unique to specific projectile ions and target molecules, but will occur whenever atoms or ions with suitable masses and kinetic energies collide with aggregates of matter, such as carbonaceous grains in the interstellar medium or aerosol nanoparticles in the atmosphere.

8.
Phys Chem Chem Phys ; 19(30): 19609-19618, 2017 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-28393947

RESUMO

We present a combined experimental and theoretical study of the fragmentation of multiply-charged γ-aminobutyric acid molecules (GABAz+, z = 2, 3) in the gas phase. The combination of ab initio molecular dynamics simulations with multiple-coincidence mass spectrometry techniques allows us to observe and identify doubly-charged fragments in coincidence with another charged moiety. The present results indicate that double and triple electron capture lead to the formation of doubly-charged reactive nitrogen and oxygen species (RNS and ROS) with different probabilities due to the different charge localisation and fragmentation behaviour of GABA2+ and GABA3+. The MD simulations unravel the fast (femtosecond) formation of large doubly charged species, observed on the experimental microsecond timescale. The excess of positive charge is stabilised by the presence of cyclic X-member (X = 3-5) ring structures. 5-Member cyclic molecules can sequentially evaporate neutral moieties, such as H2, H2O and CO2, leading to smaller doubly charged fragments as those observed in the experiments.


Assuntos
Argônio/química , Ácido gama-Aminobutírico/química , Elétrons , Gases/química , Íons/química , Simulação de Dinâmica Molecular , Teoria Quântica , Espécies Reativas de Nitrogênio/química , Espécies Reativas de Oxigênio/química , Espectrometria de Massas por Ionização por Electrospray
9.
Phys Chem Chem Phys ; 18(25): 16721-9, 2016 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-27271080

RESUMO

The fragmentation of uracil molecules and pure and nano-hydrated uracil clusters by (12)C(4+) ion impact is investigated. This work focuses on the fragmentation behavior of complex systems and the effect of the environment. On the one hand, it is found that the environment in the form of surrounding uracil or water molecules has a significant influence on the fragmentation dynamics, providing an overall 'protective' effect, while on the other hand we observe the opening of specific fragmentation channels. In particular, we report on the first observation of a series of hydrated fragments. This indicates a strong interaction between uracil and water molecules, holding the water clusters bound to the observed molecular fragments.

10.
J Phys Chem Lett ; 6(9): 1536-42, 2015 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-26263308

RESUMO

The present work combines experimental and theoretical studies of the collision between keV ion projectiles and clusters of pyrene, one of the simplest polycyclic aromatic hydrocarbons (PAHs). Intracluster growth processes induced by ion collisions lead to the formation of a wide range of new molecules with masses larger than that of the pyrene molecule. The efficiency of these processes is found to strongly depend on the mass and velocity of the incoming projectile. Classical molecular dynamics simulations of the entire collision process-from the ion impact (nuclear scattering) to the formation of new molecular species-reproduce the essential features of the measured molecular growth process and also yield estimates of the related absolute cross sections. More elaborate density functional tight binding calculations yield the same growth products as the classical simulations. The present results could be relevant to understand the physical chemistry of the PAH-rich upper atmosphere of Saturn's moon Titan.

11.
J Phys Chem A ; 119(37): 9581-9, 2015 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-26243533

RESUMO

We present a combined experimental and theoretical study of the ionization of N-acetylglycine molecules by 48 keV O(6+) ions. We focus on the single ionization channel of this interaction. In addition to the prompt fragmentation of the N-acetylglycine cation, we also observe the formation of metastable parent ions with lifetimes in the microsecond range. On the basis of density functional theory calculations, we assign these metastable ions to the diol tautomer of N-acetylglycine. In comparison with the simple amino acids, the tautomerization rate is higher because of the presence of the peptide bond. The study of a simple biologically relevant molecule containing a peptide bond allows us to demonstrate how increasing the complexity of the structure influences the behavior of the ionized molecule.


Assuntos
Glicina/análogos & derivados , Fragmentos de Peptídeos/química , Teoria Quântica , Cátions , Glicina/química , Modelos Químicos , Estrutura Molecular
12.
Phys Chem Chem Phys ; 17(26): 16767-78, 2015 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-26035826

RESUMO

We present a combined experimental and theoretical study of the fragmentation of doubly positively charged ß-alanine molecules in the gas phase. The dissociation of the produced dicationic molecules, induced by low-energy ion collisions, is analysed by coincidence mass spectrometric techniques; the coupling with ab initio molecular dynamics simulations allows rationalisation of the experimental observations. The present strategy gives deeper insights into the chemical mechanisms of multiply charged amino acids in the gas phase. In the case of the ß-alanine dication, in addition to the expected Coulomb explosion and hydrogen migration processes, we have found evidence of hydroxyl-group migration, which leads to unusual fragmentation products, such as hydroxymethyl cation, and is necessary to explain some of the observed dominant channels.


Assuntos
Gases/química , Hidróxidos/química , beta-Alanina/química , Cátions/química , Simulação de Dinâmica Molecular
13.
Chemistry ; 18(30): 9321-32, 2012 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-22733693

RESUMO

Fragmentation of the γ-aminobutyric acid molecule (GABA, NH(2)(CH(2))(3)COOH) following collisions with slow O(6+) ions (v≈0.3 a.u.) was studied in the gas phase by a combined experimental and theoretical approach. In the experiments, a multicoincidence detection method was used to deduce the charge state of the GABA molecule before fragmentation. This is essential to unambiguously unravel the different fragmentation pathways. It was found that the molecular cations resulting from the collisions hardly survive the interaction and that the main dissociation channels correspond to formation of NH(2)CH(2)(+), HCNH(+), CH(2)CH(2)(+), and COOH(+) fragments. State-of-the-art quantum chemistry calculations allow different fragmentation mechanisms to be proposed from analysis of the relevant minima and transition states on the computed potential-energy surface. For example, the weak contribution at [M-18](+), where M is the mass of the parent ion, can be interpreted as resulting from H(2)O loss that follows molecular folding of the long carbon chain of the amino acid.

14.
Chemphyschem ; 12(5): 930-6, 2011 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-21370376

RESUMO

In general, radiation-induced fragmentation of small amino acids is governed by the cleavage of the C-C(α) bond. We present results obtained with 300 keV Xe(20+) ions that allow molecules (glycine and valine) to be ionised at large distances without appreciable energy transfer. Also in the present case, the C-C(α) bond turns out to be the weakest link and hence its scission is the dominant fragmentation channel. Intact ionised molecules are observed with very low intensities. When the molecules are embedded in a cluster of amino acids, a protective effect of the environment is observed. The fragmentation pattern changes: the C-C(α) bond becomes more protected and stable amino acid cations are observed as fragments of the molecular clusters. Evidently, the molecular cluster acts as a "buffer" for the excess energy, capable of rapidly redistributing excess energy and charge.


Assuntos
Glicina/química , Íons/química , Valina/química , Transferência de Energia , Ligações de Hidrogênio , Espectrometria de Massas
15.
Artigo em Inglês | MEDLINE | ID: mdl-19940334

RESUMO

In this work, we have subjected protonated nucleobases MH(+) (M = guanine, adenine, thymine, uracil and cytosine) to a range of experiments that involve high-energy (50 keV) collision induced dissociation and electron capture induced dissociation. In the latter case, both neutralisation reionisation and charge reversal were done. For the collision induced dissociation experiments, the ions interacted with O(2). In neutral reionisation, caesium atoms were used as the target gas and the protonated nucleobases captured electrons to give neutrals. These were reionised to cations a microsecond later in collisions with O(2). In choosing Cs as the target gas, we have assured that the first electron transfer process is favourable (by about 0.1-0.8 eV depending on the base). In the case of protonated adenine, charge reversal experiments (two Cs collisions) were also carried out, with the results corroborating those from the neutralisation reionisation experiments. We find that while collisional excitation of protonated nucleobases in O(2) may lead to hydrogen loss with limited probabilities, this channel becomes dominant for electron capture events. Indeed, when sampling reionised neutrals on a microsecond timescale, we see that the ratio between MH(+) and M(+) is 0.2-0.4 when one electron is captured from Cs. There are differences in these ratios between the bases but no obvious correlation with recombination energies was found.

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