Search

International audience; The Annonaceous acetogenin annonacin is an environmental neurotoxin identified in the pulp of several fruits of the Annonaceae family, whose consumption was linked to the occurrence of sporadic atypical Parkinsonism with dementia. A method for its quantification in Rat brain homogenates by UPLC-MS/MS in selected reaction monitoring (SRM) mode was developed and validated. This method was applied to the quantitation of annonacin in Rat brain after intravenous (0.5 mg/kg) and oral (10 mg/kg, 100 mg/kg) administration.

Studies of the chemical composition of organs using mass spectrometry imaging become an important issue to better understand the mechanisms involved in various diseases. Biologists not only focus on the detection and characterization of compounds of interest but also on the reliability of the method. Time-of-flight secondary ion mass spectrometry (TOF-SIMS), which is already known to offer an excellent repeatability in material sciences, is also a method of choice for the detection and mapping of small molecules in biological samples. Ions corresponding to different types of lipids such as the fatty acid chains, cholesterol and vitamin E were studied in gyrus dentatus and cortex of rat brain sections. The analysis of the repeatability of the data was conducted, and a global coefficient of variation of about 10% was found. It thus confirms that TOF-SIMS studies can be considered as an accurate analytical method for the study of biological samples.

International audience; The application of mass spectrometry imaging (MS imaging) is rapidly growing with a constantly increasing number of different instrumental systems and software tools. The data format imzML was developed to allow the flexible and efficient exchange of MS imaging data between different instruments and data analysis software. imzML data is divided in two files which are linked by a universally unique identifier (UUID). Experimental details are stored in an XML file which is based on the HUPO-PSI format mzML. Information is provided in the form of a 'controlled vocabulary' (CV) in order to unequivocally describe the parameters and to avoid redundancy in nomenclature. Mass spectral data are stored in a binary file in order to allow efficient storage. imzML is supported by a growing number of software tools. Users will be no longer limited to proprietary software, but are able to use the processing software best suited for a specific question or application. MS imaging data from different instruments can be converted to imzML and displayed with identical parameters in one software package for easier comparison. All technical details necessary to implement imzML and additional background information is available at www.imzml.org. This article is part of a Special Issue entitled: Imaging Mass Spectrometry: A User's Guide to a New Technique for Biological and Biomedical Research.

Numerous African art objects collected in the course of colonial or ethnological expeditions during the 20th century are partially or completely covered with a so-called “patina”. These patinas have been formed during religious and ritual ceremonies, where different substances have been spread out at the surface of the objects. The anthropomorphic statuettes from the Dogon culture are well-known examples of this kind of practice. A better understanding of the chemical composition of these patinas could explain details of the ceremonial practices realized throughout the centuries. An important challenge is to extract unequivocal information about the original constituents of these patinas, and the techniques used for their application on ritual objects. The Dogon statuary can be divided into three periods. The oldest one, before 1350 A.D., is called the Tellem period, according to the name of the people who lived in this area before the arrival of the Dogon. The most recent, after 1650 A.D., is the Dogon period. These two periods are separated by an intermediary period, where the attribution to the Tellem or to the Dogon cultures is difficult. During our study, we have worked on the patina of 12 Dogon artifacts from these three different periods. In this paper, we present the results obtained for two representative objects, one of the Tellem period and one of the Dogon period. The aim is to access the chemical composition of the patinas and to see if they can be compared to ethnological reports, as is often done in the literature on ethnological studies. Chemical imaging techniques, based on the combination of microscopy and spectroscopy, are well suited to study both the composition and the spatial organization of heterogeneous complex mixtures of organic and inorganic matter. Time-of-flight secondary ion mass spectrometry (ToF-SIMS), followed by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDS), and synchrotron radiation-based Fourier transform infrared microscopy (SR-μFTIR) have been applied to non-destructive analyses of micro-samples of the patinas of several Dogon statuettes. A very careful preparation, using ultramicrotomy on embedded samples, allowed us to perform successively all these measurements on a single fragment. Comparison and superposition of the different chemical images lead us to identify minerals (clays, quartz and calcium carbonate), and different organic products (proteins, starch, lipids), as well as to map their spatial distribution. The patina of the most recent statuettes presents a stratigraphy which can be related to successive uses of the objects for ritual purposes, and the results are in agreement with the ethnological reports. For the Tellem objects, the significant quantity of minerals and the lack of stratigraphy suggest that the patina was deposited according to a different recipe. This difference suggests the existence of a diversity of rituals that are more extensive than that described by the ethnologists.

The capabilities of time of flight secondary ion mass spectrometry (TOF-SIMS) have been recently greatly improved with the arrival in this field of polyatomic ion sources. This technique is now able to map at the micron scale intact organic molecules in a range of a thousand Daltons or more, at the surface of tissue samples. Nevertheless, this remains a surface analysis technique, and three-dimensional information on the molecular composition of the sample could not be obtained due to the damage undergone by the organic molecules during their irradiation. The situation changed slightly with the low damage and low penetration depth of the C60 fullerene ion beams. Recent promising studies have shown the possibility of organic molecular depth profiling using this kind of beams onto model samples. This possibility has been tried out directly onto a rat brain tissue section, which is the most commonly used biological tissue model in TOF-SIMS imaging method developments. The tissue surface has been sputtered with a 10 keV energy fullerene ion beam, and surface analyses were done with a 25 keV Bi3+ ion beam at regular time intervals. The total depth which was analysed was more than two microns, with total primary ion doses of more than 1016 ions cm−2. Although not in contradiction with results previously published but with much lower doses, it is found that the molecular damage remains too large, thus making molecular imaging very difficult. In addition, most of the lipids, which are usually the main observable molecules in TOF-SIMS, are concentrated close to the sample surface in the first hundreds of nanometers.

Heavy gold cluster beams are accelerated to high energy (hundreds of keV/atom) and break up when going through a thin foil. The energy and angular distributions of the constituents are then measured and very well reproduced by a SRIM code calculation, which takes into account atomic interactions only. These distributions do not depend on the number of constituents in the cluster and are found to be the same as those of single gold atoms at the same velocity, in the studied energy range.

Resume L’essor de techniques innovantes en spectrometrie de masse, notamment dans le domaine de l’imagerie, nous a conduits a evaluer les potentialites des deux techniques actuellement disponibles : la spectrometrie de masse par filtrage d’ions secondaires (SIMS) et la desorption/ionization par laser assistee par matrice (MALDI). A titre d’illustration, des coupes de biopsies cutanees issues de patients affectes par la maladie de Fabry et de patients temoins ont ete analysees. Au cours de cette pathologie, deux glycosphingolipides physiologiques s’accumulent par defaut de catabolisme : le globotriaosylceramide (Gb3) et le digalactosylceramide (Ga2). La capacite des techniques a localiser les zones d’accumulation au niveau de coupes tissulaires et la possibilite d’identifier par les spectres de masse, les structures des lipides accumules ont ete evaluees. Les resultats ont montre la complementarite de ces techniques: — la spectrometrie de masse par filtrage d’ions secondaires a permis de localiser precisement les zones d’accumulation puisque des resolutions spatiales a l’echelle du micron ont ete obtenues ; — la desorption/ionisation par laser assistee par matrice a permis d’obtenir un signal suffisamment intense pour identifier ces structures par leurs masses moleculaires.

Recently published experiments have shown very large metal sputtering yields under bombardment by keV to MeV energy gold clusters. Analytical models or molecular dynamic simulations do not reproduce or predict the experimental yield variations as a function of the projectile number of constituents or energy. The recent literature existing on this subject provides useful concepts and some of them have guided the semi-empirical model reported here. Based on the energy deposited within a certain depth, and modulated above a critical energy density, a good agreement between the model and the experimental data is achieved.

A 1 MeV / n 127Iq+ beam of the Tandem accelerator at Orsay, France, has been used to study the dependence of hydrogen ion emission on the charge state of the incident primary ions. The samples investigated were bare gold and carbon foils and a 150 nm glycine film vacuum-evaporated on an Au foil. The measurements were performed at a vacuum pressure of about 10−7 mbar; the sample surfaces were covered by a contamination layer. The linear time-of-flight instrument used was equipped with two acceleration grids and a position sensitive stop detector, in order to measure the initial velocity components and the angle of emission for each detected ion. The results were axial, radial and total energy distributions and angular distributions for the hydrogen ions H+, H2+, H3+ and axial energy distributions for H−, all measured at constant beam energy for the charge states 17+, 20+, 26+, 30+ or 32+ under an angle of incidence of 55° against the surface normal. The angular distributions of all ions were asymmetric relative to the surface normal, for the glycine target more than for the bare metals. The mean energies increase slightly with the charge state, the increase was in the order of 0.5–2% per charge state. The change of the mean emission angle had negative as well as positive values in the order of 0–0.2° per charge state. Comparing glycine and metal targets, the angular distributions obtained with the metals seemed to be wider around the main direction of emission. A few suggestions about possible desorption/ionization processes are given.

C60 molecules accelerated to MeV energies (20 MeV) have been used to induce the desorption-ionization of large biomolecules from solid samples. For a sample consisting of trypsin molecules, the secondary molecular ion emission yield is about two orders of magnitude larger than with MeV atomic ions. This is a consequence of the very high energy density deposited in solids by 20 MeV C60 projectiles that gives rise to a large amount of matter ejected after each impact. Although time-of-flight mass spectra can be recorded within a few seconds, it is more the acquisition of knowledge on mechanistic aspects, in comparison with other particle-induced desorption methods, which is the objective of obtaining these first results with energetic fullerenes.

Bi 2 Sr 2 Ca 1 Cu 2 O 8 + δ and YBa 2 Cu 3 O 7 − δ thin films were irradiated by 23 MeV C 60 and 24 MeV Au 5 cluster ions from a tandem accelerator. The defect production of the C 60 cluster ions in Bi 2 Sr 2 Ca 1 Cu 2 O 8 + δ exceeds that of 238 U ions with an energy of 2.7 GeV. The analysis of the mechanism underlying the defect production leads to different conclusions: (i) for C 60 clusters we find independence of nuclear and electronic contributions to the defect production as in the case of atomic projectiles, (ii) for Au 5 cluster ions this independence has lost it's validity. A possible interpretation of the Au 5 results is that nuclear defects are annealed by the electronic energy loss. The size of the effective damage radii obtained for the Bi 2 Sr 2 Ca 1 Cu 2 O 8 + δ film may indicate that continuous tracks are formed in this film via the C 60 and Au 5 irradiation.

It is shown that polyatomic ions at high energy (MeV) are able to emit large size cluster ions with a high yield when they bombard solid surfaces. Results on sputtering of clusters ejected from inorganic and organic targets as well as sputtering of C x − clusters from carbon foils are presented. Gold cluster Au n , carbon cluster C n and C 60 in the energy range from 2 to 20 MeV were used as projectiles.

Silicon samples have been irradiated with cluster ions, 16.2 MeV Au4 and 23 MeV C60, from the Orsay tandem accelerator in France. After the irradiation, Schottky diodes are formed and the samples are studied with deep level transient spectroscopy. Majority carrier spectra of bombarded n-type silicon are dominated by the single charge state of the divacancy (EC − ET = 0.42 eV). Measured depth distributions of the divacancy suggest that the peak of elastic energy deposition appears at the same depth for Au4 ions as for monoatomic gold ions with one fourth of the energy. For C60 clusters the measured peak is closer to the surface than the peak of the vacancy distribution calculated with TRIM. Comparison with vacancy distributions also shows that the deep tail of the divacancy defect distribution is extended to greater depths. The interpretation is that divacancies are created not only by direct collisions, but also by diffusion and pairing of two single vacancies.

The radiation damage tracks on the surface of muscovite mica due to single 78.2 MeV 127I ions from the Uppsala EN tandem accelerator have been studied using tapping mode scanning force microscopy (TM-SFM). Conically-shaped hillocks having nearly circular bases were observed on a sample irradiated at normal incidence. Samples irradiated at grazing angles of incidence displayed wider and taller hillocks, and each hillock was accompanied by a raised tail over the bulk ion track. First SFM results are also presented from a study of radiation damage features on mica and single crystals of L-valine induced by single 23 MeV C60 ions from the Orsay tandem accelerator. Brief comments are made on the scaling laws that could link results obtained with atomic and cluster ions.

Gold clusters Au n with n ⩽ 5 and masses m ⩽ 985 u have been accelerated to MeV energies with the tandem accelerators at Orsay and Erlangen. Singly charged negative cluster ions were obtained from a conventional sputter ion source and accelerated between ground potential at the entrance of the accelerator and the terminal (in the middle) at several MV. In a gas channel positioned in the terminal they lose one or several electrons and become neutral or positively charged clusters, respectively. The ions are then accelerated towards the exit of the tandem accelerator. Identification of Au + n clusters is achieved by measuring the time-of-flight of the clusters.

For the first time fullerene ions have been accelerated to high energy (4–36 MeV). Negative ions of C − 60 were produced in an ion source with a Cs gun and injected into a tandem accelerator. The change of charge from negative to positive was achieved by collisions with N 2 molecules in a gas cell at the high voltage terminal before the second acceleration step. To identify the accelerated molecular ions, the injected beam was pulsed, and time-of-flight measurements combined with energy measurements allowed mass and charge assignments.

The high intensity of solar radiation, obtained with the Odeillo solar furnace facilities, is used to vaporize graphite in rarefied inert gas atmosphere. We show that the soot obtained contains C 60 , C 70 and other heavier fullerenes. We discuss the possibility of increasing the evaporation rate of graphite and the yield of soot with this technique.

Measurement of the H+ secondary ion yield from the surface of solid targets has been used to probe the charge state of fast heavy-ion projectiles at the target surface. Results have been obtained for ion beams of 32S, 40Ar and 84Kr at ≃ 1 MeV/u, and between 0.5 and 1.5 MeV/u for 127I. Increases in the charge state after passage through carbon and Au foils are clearly observed for 84Kr and 127I. The variation of charge state as a function of the thickness of matter traversed is compared with calculated values.

This paper describes an original method to study the influence of the projectile charge state on secondary ion emission from a solid surface. We show also that hydrogen ion emission from carbon is strongly dependent on the incident charge state. The present results confirm the former experiment at low energy in which Ar 1+ ' to Ar 11+ at 18 keV were used as projectiles [S. Della-Negra et al., Phys. Rev. Lett. 60 (1988) 148].