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Breeding and engineering of biofortified crops will benefit from a better understanding of bottlenecks controlling micronutrient loading within the seeds. However, few studies have addressed the changes in micronutrient concentrations, localization, and speciation occurring over time. Therefore, we studied spatial patterns of zinc and iron accumulation during grain development in two barley lines with contrasting grain zinc concentrations. Microparticle-induced-X-ray emission and laser ablation-inductively coupled plasma mass spectrometry were used to determine tissue-specific accumulation of zinc, iron, phosphorus, and sulfur. Differences in zinc accumulation between the lines were most evident in the endosperm and aleurone. A gradual decrease in zinc concentrations from the aleurone to the underlying endosperm was observed, while iron and phosphorus concentrations decreased sharply. Iron co-localized with phosphorus in the aleurone, whereas zinc co-localized with sulfur in the sub-aleurone. We hypothesize that differences in grain zinc are largely explained by the endosperm storage capacity. Engineering attempts should be targeted accordingly.

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is a gluten-free pseudo-cereal crop with a grain nutrient profile that makes it an excellent alternative foodstuff. The distribution of calcium (Ca), magnesium (Mg), phosphorus (P) and sulphur (S) was investigated by micro-PIXE (particle induced X-ray emission) to resolve allocation and concentration of the elements in nine distinct grain tissues. Magnesium, P and S were preferentially allocated to the cotyledons and the embryonic axis (both inner and outer tissues), and Ca was predominant in the pericarp where two Ca-rich layers were observed. Allocation of P and S to aleurone suggests that this layer of cells, although not as prominent as in cereal grain, is rich in phytate and proteins. Quantitative information on spatial distribution of mineral elements in the edible grain may be useful in the technological processing of the grain and particularly in reducing the amount of mineral-element loss during milling.

Human hair absorbs numerous biomolecules from the body during its growth. This can act as a fingerprint to determine substance intake of an individual, which can be useful in forensic studies. The cocaine concentration profile along the growth axis of hair indicates the time evolution of the metabolic incorporation of cocaine usage. It could be either assessed by chemical extraction and further analysis of hair bundels, or by direct single hair fibre analysis with mass spectroscopy imaging (MSI). Within this work, we analyzed the cocaine distribution in individual hair samples using MeV-SIMS. Unlike conventional surface analysis methods, we demonstrate high yields of nonfragmented molecular ions from the surface of biological materials, resulting in high chemical sensitivity and non-destructive characterisation. Hair samples were prepared by longitudinally cutting along the axis of growth, leaving half-cylindrical shape to access the interior structure of the hair by the probing ion beam, and attached to the silicon wafer. A focused 5.8 MeV 35Cl6+ beam was scanned across the intact, chemically pristine hair structure. A non-fragmented protonated [M+ H]+ cocaine molecular peak at m/z = 304 was detected and localized along the cross-section of the hair. Its intensity exhibits strong fluctuations along the direction of the hair’s growth, with pronounced peaks as narrow as 50 micrometres, corresponding to a metabolic incorporation time of approx. three hours.

International audience; Secondary ion mass spectrometry (SIMS), based on primary ions within the MeV energy domain, also known as MeV-SIMS, is a subject of increasing scientific interest. The main drive for the interest in the development of MeV-SIMS is the ability to desorb high yields of large non-fragmented organic molecular ions from the sample surface. This makes MeV-SIMS particulary useful in imaging of biological tissues.Imaging methods based on scanning a focused primary ion beam are associated with demanding focusing of the heavy energetic ions. As an alternative, stigmatic imaging mode has been studied here, applying point-to-point imaging characteristics of secondary ions in the linear Time-Of-Flight mass spectrometer. In stigmatic imaging approaches, spatial resolution is independent of the focussed spot size of the ionising primary ion beam, but instead dependant on the ability of the ion optics to project an image of the ion distributions removed from the surface onto a position sensitive ion detector.

Halophytes are able to tolerate relatively high concentrations of hazardous metals in a growing substrate, what makes them suitable candidates for phytoremediation of metal-contaminated soils. In this work, we aimed to study the physiological responses of the halophyte Sesuvium portulacastrum L. to Ni, with main focus on Ni localization, compartmentation and ligand environment, to decipher Ni tolerance and toxicity mechanisms. Seedlings were grown in hydroponic nutrient solution containing 0, 25, 50 and 100 μM Ni as NiCl2 for 3 weeks. Ni localization in leaves was assessed by micro-proton-induced X-ray emission (micro-PIXE). Ni ligand environment was studied by Ni K-edge X-ray absorption near edge structure (XANES). In addition, Ni-soluble, weakly bound/exchangeable and insoluble leaf tissue fractions were determined by sequential extraction. Results show that S. portulacastrum is able to tolerate up to ~ 500 μg g−1 dry weight (DW) of Ni in the shoots without significant growth reduction. At higher Ni concentrations (> 50 μM Ni in nutrient solution), chloroses were observed due to the accumulation of Ni in photosynthetically active chlorenchyma as revealed by micro-PIXE. Water storage tissue represented the main pool for Ni storage. Incorporation of Ni into Ca-oxalate crystals was also observed in some specimens, conferring tolerance to high leaf Ni concentrations. The majority of Ni (> 70%) was found in soluble tissue fraction. Ni K XANES revealed Ni bound mainly to O- (55%) and N-ligands (45%). Ni toxicity at higher Ni levels was associated with Ni binding to amino groups of proteins in cytosol of chlorenchyma and increased level of lipid peroxidation. Proline levels also increased at high Ni exposures and were associated with Ni-induced oxidative stress and alteration of water regime.

Breeding and engineering of biofortified crops will benefit from a better understanding of bottlenecks controlling micronutrient loading within the seeds. However, few studies have addressed the changes in micronutrient concentrations, localization, and speciation occurring over time. Therefore, we studied spatial patterns of zinc and iron accumulation during grain development in two barley lines with contrasting grain zinc concentrations. Microparticle-induced-X-ray emission and laser ablation-inductively coupled plasma mass spectrometry were used to determine tissue-specific accumulation of zinc, iron, phosphorus, and sulfur. Differences in zinc accumulation between the lines were most evident in the endosperm and aleurone. A gradual decrease in zinc concentrations from the aleurone to the underlying endosperm was observed, while iron and phosphorus concentrations decreased sharply. Iron co-localized with phosphorus in the aleurone, whereas zinc co-localized with sulfur in the sub-aleurone. We hypothesize that differences in grain zinc are largely explained by the endosperm storage capacity. Engineering attempts should be targeted accordingly.

MeV-SIMS is an emerging mass spectrometry imaging method that employs fast, heavy ions to desorb secondary molecules from the analyzed sample. High yields and low fragmentation rates of large molecules, associated with the dominating electronic sputtering process, make it particularly useful in biomedical research, where insight into the distribution of organic molecules is vital. Both yield and fragmentation of desorbed molecules in MeV-SIMS rely on characteristics of the primary ion but may also be impaired by poor instrumental settings. After utilizing secondary ion optics in the linear mass spectrometer at the micro-analytical center of the Jožef Stefan Institute, we demonstrate very efficient detection of secondary ions. As a result, the secondary ion yield, using such settings, solely depends on the species and the characteristics of the primary ion. In order to analyze the yield dependence on the primary ion energy, and the corresponding stopping power within the electronic excitation regime, we used a continuous electron multiplier detector to measure the primary ion current during each measurement of the mass spectra. Secondary ion yield as a function of the primary ion energy and charge is presented as well as fragmentation rates of organic molecules arginine and leu-enkephalin. Other influential instrumental drawbacks are also studied, and their effect on the results is discussed.

In Parkinson’s disease, the depletion of iron-rich dopaminergic neurons in nigrosome 1 of the substantia nigra precedes motor symptoms by two decades. Monitoring this neuronal depletion, at an early disease stage, is needed for early diagnosis. Magnetic resonance imaging (MRI) is particularly suitable for this task due to its sensitivity to iron. However, the exact mechanisms of MRI contrast in nigrosome 1 are not well understood, hindering the development of powerful biomarkers. We demonstrate that the dominant contribution to the effective transverse MRI relaxation rate in nigrosome 1 originates from iron accumulated in dopaminergic neurons. We link quantitatively to the product of cell density and local iron concentration in dopaminergic neurons, combining quantitative 3D iron histology, biophysical modeling, and quantitative MRI on post mortem brain tissue. It is now theoretically possible to monitor dopaminergic neuron depletion, in vivo, as an early diagnostic tool for Parkinson’s disease.

Element profile signatures of needle tissues differentiated four tissues: epidermis (main contributor: calcium), endodermis (main contributors: magnesium, sulphur and manganese), mesophyll (main contributor: potassium), and transfusion parenchyma (main contributor: zinc). Distribution of elements in cross-sections of Scots pine (Pinus sylvestris L.) needles was investigated using micro-proton-induced X-ray emission. Tissue-specific distributions of magnesium (Mg), sulphur (S), calcium (Ca), phosphorus (P), potassium (K), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), aluminium (Al) and silicon (Si) were resolved in a quantitative manner. Distribution maps and tissue-specific concentrations revealed the largest concentration of Ca in epidermis, of Mg, S and Mn in endodermis, of K in mesophyll and phloem and of Zn in transfusion parenchyma. Phosphorus, Cl, Fe, Al and Si did not exhibit apparent tissue-specific distribution. Inverse allocation of P and Ca was observed, a likely mechanism to prevent their precipitation. Taking the area of tissues into account, relative element distribution calculations indicated that mesophyll contained the majority of the elements studied, except Ca, which predominated in the epidermis (79% of total Ca concentration) and Mn, which predominated in the endodermis (40% of total Mn concentration). When considering a complete element profile of a particular tissue, four clusters were differentiated, which generally supported single-element observations. The first cluster differentiated mesophyll, xylem, phloem, transfusion tracheids and Strasburger cells with predominance of K, the second cluster differentiated epidermis on the basis of Ca, the third cluster differentiated endodermis with contributions from Mg, S and Mn, and the fourth cluster differentiated transfusion parenchyma with contribution from Zn. Information on tissue-specific-element allocations will complement structural and functional knowledge of needle tissues and advance our understanding of element/nutrient transfers in Scots pine.

The performance of a nuclear microprobe is dominantly determined by the brightness of the injected ion beam. At Jožef Stefan Institute (JSI), negative hydrogen ion beams are created in a multicusp ion source and injected into a 2 MV tandetron accelerator. The output characteristics of the multicusp ion source were tuned in order to obtain matching proton beam intensities for the ion accelerator and for the object slits as well. For the optimal focusing of the proton beam in a high-current mode (I > 100 pA) to the sub-micrometer dimensions, dedicated thin nanostructures with sharp edges have been manufactured. Set of nanostructures was micromachined by focused ion beam (FIB) at film reference material, produced by Institute for Reference Materials and Measurements (IRMM) and constituted of 57 μg/cm 2 of titanium on vitreous carbon substrate. The proton beam profiles were measured by beam scans across the nanostructures over long measuring times, indicating eventual slow drifts of the sample from a reference beam direction. Overall, proton beam dimensions of 600 nm were obtained, demonstrating appropriate stability for micro-PIXE (micro-Particle Induced X-ray Emission) at sub-micrometer resolution for elemental analysis of biological tissue samples prepared in a freeze-dried state or in a frozen-hydrated state. The resulting performance required for micro-PIXE analysis in a high current mode with a 3 MeV proton beam is presented.

Imaging Mass Spectroscopy (IMS) is a unique research tool providing localization and identification of a wide range of biomolecules as essential data to understand biochemical processes in living organisms. Secondary Ion Mass Spectrometry with high-energy heavy ions (MeV-SIMS) is emerging as a promising IMS technique for chemical imaging of biological tissue.We measured the molecular mass spatial distributions in leaves of khat (Catha edulis). Khat is a natural drug plant, native to eastern Africa and the Arabian Peninsula. In these countries, fresh leaves are being chewed by significant part of population. It was reported that 80% of the adult population in Yemen chew the khat leaves. The main stimulating effects of khat are induced by a monoamine alkaloid called cathinone. During leaf ageing, cathinone is further metabolised to cathine and norephedrine. Earlier studies identified the alkaloids in khat, however little is known on their spatial distribution, reflecting the biosynthesis and accumulation in the tissue.Chemical mapping of alkaloids on cross-sections of khat leaves by MeV-SIMS was done at JSI by a pulsed 5.8 MeV Cl-35(6+) beam, focused to a diameter of 15 mu m, using a linear time-of-flight (TOF) spectrometer with a mass resolution of 500. In addition, measurements of MeV-SIMS mass spectra were performed at Kyoto University by a continuous broad beam of 6 MeV Cu-63(4+) ions at an orthogonal TOF spectrometer with a high mass resolution of 11,000. Sections of leaves were analysed and mass spectra obtained at both MeV-SIMS setups were compared. Tissue-level distributions of detected alkaloids are presented and discussed. (C) 2017 Elsevier B.V. All rights reserved.

A new parallel beam wavelength dispersive X-ray emission spectrometer for high energy resolution PIXE analysis using focused proton microbeam has been constructed and installed at the microprobe of the J. Stefan Institute. Polycapillary X-ray optics is used to enhance the solid angle of X-ray collection and to transform collected proton-induced X-rays into quasi parallel beam which is analyzed using diffraction on a flat crystal. The spectrometer is installed in a vacuum chamber and operates in the 2–10 keV energy range. The main characteristics and operational properties are presented together with the results of first characterization measurements. Finally, two selected experimental examples are given illustrating the capabilities of the spectrometer in PIXE analysis and fundamental research in atomic physics.

Additional file 1 Fig. S1. Growth of Brassica oleracea accessions (C6 and F103) cultivated hydroponically for 2 weeks in solutions containing 0.025 mM P (Low P) and 0.25 mM P (High P). Fig. S2. Root (a), shoot (b) and plant (c) phosphorus (P) content of two Brassica oleracea accessions (C6 and F103) grown hydroponically for 2 weeks in solutions containing 0.025 mM P (Low P; LP) and 0.25 mM P (High P; HP). Data are means (n = 5–6) and standard errors. Asterisks indicate statistically significant differences (two-way analysis of variance followed by Holm-Sidak post hoc test at P

Lead (Pb) ranks among the most problematic environmental pollutants. Background contamination of soils is nearly ubiquitous, yet plant Pb accumulation is barely understood. In a survey covering 165 European populations of the metallophyte Arabidopsis halleri, several field samples had indicated Pb hyperaccumulation, offering a chance to dissect plant Pb accumulation. Accumulation of Pb was analysed in A. halleri individuals from contrasting habitats under controlled conditions to rule out aerial deposition as a source of apparent Pb accumulation. Several elemental imaging techniques were employed to study the spatial distribution and ligand environment of Pb. Regardless of genetic background, A. halleri individuals showed higher shoot Pb accumulation than A. thaliana. However, dose-response curves revealed indicator rather than hyperaccumulator behaviour. Xylem sap data and elemental imaging unequivocally demonstrated the in planta mobility of Pb. Highest Pb concentrations were found in epidermal and vascular tissues. Distribution of Pb was distinct from that of the hyperaccumulated metal zinc. Most Pb was bound by oxygen ligands in bidentate coordination. A. halleri accumulates Pb whenever soil conditions render Pb phytoavailable. Considerable Pb accumulation under such circumstances, even in leaves of A. thaliana, strongly suggests that Pb can enter food webs and may pose a food safety risk.

Symmetrical protein cages have evolved to fulfil diverse roles in nature, including compartmentalization and cargo delivery(1), and have inspired synthetic biologists to create novel protein assemblies via the precise manipulation of protein-protein interfaces. Despite the impressive array of protein cages produced in the laboratory, the design of inducible assemblies remains challenging(2,3). Here we demonstrate an ultra-stable artificial protein cage, the assembly and disassembly of which can be controlled by metal coordination at the protein-protein interfaces. The addition of a gold (I)-triphenylphosphine compound to a cysteine-substituted, 11-mer protein ring triggers supramolecular self-assembly, which generates monodisperse cage structures with masses greater than 2 MDa. The geometry of these structures is based on the Archimedean snub cube and is, to our knowledge, unprecedented. Cryo-electron microscopy confirms that the assemblies are held together by 120 S-Au(i)-S staples between the protein oligomers, and exist in two chiral forms. The cage shows extreme chemical and thermal stability, yet it readily disassembles upon exposure to reducing agents. As well as gold, mercury(II) is also found to enable formation of the protein cage. This work establishes an approach for linking protein components into robust, higher-order structures, and expands the design space available for supramolecular assemblies to include previously unexplored geometries.

Graphical abstract, Highlights • Soil-plant physico-chemical properties may determine regional elemental profiles. • Pore interconnectivity and distribution varied between regional beans. • Multidimensional data promising for advising coffee qualitative characteristics., The physico-elemental profiles of commercially attained and roasted organic coffee beans from Ethiopia, Colombia, Honduras, and Mexico were compared using light microscopy, X-ray micro-computed tomography, and external beam particle induced X-ray emission. External beam PIXE analysis detected P, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, Br, Rb, and Sr in samples. Linear discriminant analysis showed that there was no strong association between elemental data and production region, whilst a heatmap combined with hierarchical clustering showed that soil-plant physico-chemical properties may influence regional elemental signatures. Physical trait data showed that Mexican coffee beans weighed significantly more than beans from other regions, whilst Honduras beans had the highest width. X-ray micro-computed tomography qualitative data showed heterogeneous microstructural features within and between beans representing different regions. In conclusion, such multi-dimensional analysis may present a promising tool in assessing the nutritional content and qualitative characteristics of food products such as coffee.

MeV-SIMS is an emerging mass spectrometry imaging method, which utilizes fast, heavy ions to desorb secondary molecules. High yields and low fragmentation rates of large molecules, associated with the electronic sputtering process, make it particularly useful in biomedical research, where insight into distribution of organic molecules is needed. Since the implementation of MeV-SIMS in to the micro-beam line at the tandem accelerator of Jožef Stefan Institute, MeV-SIMS provided some valuable observations on the distribution of biomolecules in plant tissue, as discussed by Jencic et al. (Nucl. Inst. Methods Phys. Res. B. 371, 205-210, 2016; Nucl. Inst. Methods Phys. Res. B. 404, 140-145, 2017). However, limited focusing ability of the chlorine ion beam only allowed imaging at the tissue level. In order to surpass shortcomings of the existing method, we introduced a new approach, where we employ a continuous, low-current primary beam. In this mode, we bombard thin samples with a steady chlorine ion flux of approx. 5000 ions/s. After desorbing molecules, chlorine ions penetrate through the thinly cut sample and trigger the time-of-flight "start" signal on a continuous electron multiplier detector, positioned behind the sample. Such bombardment is more effective than previously used pulsing-beam mode, which demanded several orders of magnitude higher primary ion beam currents. Sub-micrometer focusing of low-current primary ion beam allows imaging of biological tissue on a subcellular scale. Simultaneously, new time-of-flight acquisition approach also improves mass resolution by a factor of 5. Within the article, we compare the performance of both methods and demonstrate the application of continuous mode on biological tissue. We also describe the thin sample preparation protocol, necessary for measurements with low primary ion currents.

The aim of this paper is to review principles and potential application of micro-proton induced X-ray emission (micro-PIXE), synchrotron-based micro-X-ray fluorescence (micro-XRF) and inductively coupled plasma-mass spectrometry (ICP-MS) hyphenated with pulsed laser ablation (LA) for analysing plants and plant materials to elucidate feature of constituensts of nutritional value. These are required in order to develop novel high-quality functional and other food products in view of the variability of properties of plant tissues and products.

Genetic biofortification requires knowledge on natural variation and the underlying mechanisms of micronutrient accumulation. We therefore studied diversity in grain micronutrient concentrations and spatial distribution in barley (Hordeum vulgare), a genetically tractable model cereal and an important crop with widespread cultivation. We assembled a diverse collection of barley cultivars and landraces and analysed grain micronutrient profiles in genebank material and after three independent cultivations. Lines with contrasting grain zinc (Zn) accumulation were selected for in-depth analysis of micronutrient distribution within the grain by micro-proton-induced X-ray emission (μ-PIXE). Also, we addressed association with grain cadmium (Cd) accumulation. The analysis of > 120 lines revealed substantial variation, especially in grain Zn concentrations. A large fraction of this variation is due to genetic differences. Grain dissection and μ-PIXE analysis of contrasting lines showed that differences in grain Zn accumulation apply to all parts of the grain including the endosperm. Cd concentrations exceeded the Codex Alimentarius threshold in most of the representative barley lines after cultivation in a Cd-contaminated agricultural soil. Two important conclusions for biofortification are: first, high-Zn grains contain more Zn also in the consumed parts of the grain; and second, higher micronutrient concentrations are strongly associated with higher Cd accumulation.

To broaden our analytical capabilities with molecular imaging in addition to the existing elemental imaging with micro-PIXE, a linear Time-Of-Flight mass spectrometer for MeV Secondary Ion Mass Spectrometry (MeV-SIMS) was constructed and added to the existing nuclear microprobe at the Jožef Stefan Institute. We measured absolute molecular yields and damage cross-section of reference materials, without significant alteration of the fragile biological samples during the duration of measurements in the mapping mode. We explored the analytical capability of the MeV-SIMS technique for chemical mapping of the plant tissue of medicinal cannabis leaves. A series of hand-cut plant tissue slices were prepared by standard shock-freezing and freeze-drying protocol and deposited on the Si wafer. We show the measured MeV-SIMS spectra showing a series of peaks in the mass area of cannabinoids, as well as their corresponding maps. The indicated molecular distributions at masses of 345.5 u and 359.4 u may be attributed to the protonated THCA and THCA-C4 acids, and show enhancement in the areas with opened trichome morphology.

As sessile organisms, plants must constantly adapt to environmental changes. Plant performance is related to availability of light, water, and mineral nutrients, which is especially important in agricultural systems, where minerals are removed from the fields at harvest. Mineral nutrients are also essential for the normal functioning of animal and human body. Since plants are world’s primary producers representing the basis for animal and human diet, it is of extreme importance that they contain sufficient amounts of mineral nutrients and low amounts of antinutrients and noxious elements. To maintain homeostasis with optimal cell functioning and integrity, proper allocation of elements at organ, tissue, cellular, and subcellular level is essential. Studies of element localization are therefore crucial to uncover the mechanisms of element transport and accumulation, toxicity, and tolerance. In the last two decades, a remarkable progress has been made in the development and application of different 2D imaging techniques in complex biological systems, especially with regard to improved lateral resolution and sensitivity as well as sample preparation. In this chapter, the latest development and applications of focused beam techniques like microparticle-induced X-ray emission (μ-PIXE), micro-X-ray fluorescence spectrometry (μ-XRF), and laser ablation inductively coupled plasma-mass spectrometry (LA-ICPMS) in imaging the distributions of major and trace elements in plants are presented. These techniques are unique in providing in situ information and, with appropriate sample preparation, provide results true to biological condition of the living plants. For example the methods for sampling and sample preparation can in conjunction with measurement conditions compromise the element distribution: critical consideration is therefore required when reporting “in vivo” elemental distribution and concentration.

MeV-SIMS is an emerging mass spectrometry imaging method that employs fast, heavy ions to desorb secondary molecules from the analyzed sample. High yields and low fragmentation rates of large molec...

Halophytes are able to tolerate relatively high concentrations of hazardous metals in a growing substrate, what makes them suitable candidates for phytoremediation of metal-contaminated soils. In this work, we aimed to study the physiological responses of the halophyte Sesuvium portulacastrum L. to Ni, with main focus on Ni localization, compartmentation and ligand environment, to decipher Ni tolerance and toxicity mechanisms. Seedlings were grown in hydroponic nutrient solution containing 0, 25, 50 and 100 μM Ni as NiCl

Sesuvium portulacastrum, a halophyte with high tolerance to heavy metals like Cd, Pb and Ni is considered for phytoremediation of metal contaminated saline soils. The tolerance to a selected metal ion could, by hypothesis, be stimulated through in vitro adaptation and regeneration of the plant. Seedlings obtained by in vitro micro-propagation, were exposed to 0, 25 and 50 μM Ni, as NiCl2, in agar-based medium for 30 days. Growth parameters, plant water content, the concentration of photosynthetic pigments, proline and malondialdehyde (MDA) concentrations were determined. Nickel and nutrients distribution in leaves was studied by micro-Proton-Induced-X-ray-Emission (μ-PIXE). The results showed that Ni was mainly accumulated in vascular bundles, next in water storage tissues and chlorenchyma. Ni concentrations in chlorenchyma increased with increasing Ni in culturing medium, in direct relation to decrease of photosynthetic pigments and increase of oxidative stress. As compared to control plants, Ni induced substantial increase in MDA and proline accumulation. Plants exposed to 50 μM Ni accumulated up to 650 μg g−1 of Ni in the shoots, exhibiting chlorosis and necrosis and a drastically reduced plant growth. Perturbations in uptake and distribution of nutrients were observed, inducing mineral deficiency, probably through membrane leakage. The mineral nutrient disturbances induced by Ni could be highly implicated in the restriction of S. portulacastrum development under the acute 50 μM Ni level.

Summary Gomphrena claussenii is a recently described zinc (Zn)- and cadmium (Cd)-hypertolerant Amaranthaceae species displaying a metal bioindicator Zn/Cd accumulation response. We investigated the Zn and Cd distribution in stem and leaf tissues of G. claussenii at the cellular level, and determined metabolite profiles to investigate metabolite involvement in Zn and Cd sequestration. Gomphrena claussenii plants exposed to high Zn and Cd supply were analysed by scanning electron microscopy with energy-dispersive X-ray (SEM-EDX) and micro-proton-induced X-ray emission (micro-PIXE). In addition, gas chromatography-time of flight-mass spectrometry (GC-TOF-MS) was used to determine metabolite profiles on high Zn and Cd exposure. Stem and leaf tissues of G. claussenii plants exposed to control and high Cd conditions showed the abundant presence of calcium oxalate (CaOx) crystals, but on high Zn exposure, their abundance was strongly reduced. Ca and Cd co-localized to the CaOx crystals in Cd-exposed plants. Citrate, malate and oxalate levels were all higher in shoot tissues of metal-exposed plants, with oxalate levels induced 2.6-fold on Zn exposure and 6.4-fold on Cd exposure. Sequestration of Cd in vacuolar CaOx crystals of G. claussenii is found to be a novel mechanism to deal with Cd accumulation and tolerance.

The analysis of biological samples in frozen-hydrated state with micro-PIXE technique at Jožef Stefan Institute (JSI) nuclear microprobe has matured to a point that enables us to measure and examine frozen tissue samples routinely as a standard research method. Cryotome-cut slice of frozen-hydrated biological sample is mounted between two thin foils and positioned on the sample holder. The temperature of the cold stage in the measuring chamber is kept below 130 K throughout the insertion of the samples and the proton beam exposure. Matrix composition of frozen-hydrated tissue is consisted mostly of ice. Sample deterioration during proton beam exposure is monitored during the experiment, as both Elastic Backscattering Spectrometry (EBS) and Scanning Transmission Ion Microscopy (STIM) in on–off axis geometry are recorded together with the events in two PIXE detectors and backscattered ions from the chopper in a single list-mode file. The aim of this experiment was to determine differences and similarities between two kinds of biological sample preparation techniques for micro-PIXE analysis, namely freeze-drying and frozen-hydrated sample preparation in order to evaluate the improvements in the elemental localisation of the latter technique if any. In the presented work, a standard micro-PIXE configuration for tissue mapping at JSI was used with five detection systems operating in parallel, with proton beam cross section of 1.0 × 1.0 μm 2 and a beam current of 100 pA. The comparison of the resulting elemental distributions measured at the biological tissue prepared in the frozen-hydrated and in the freeze-dried state revealed differences in elemental distribution of particular elements at the cellular level due to the morphology alteration in particular tissue compartments induced either by water removal in the lyophilisation process or by unsatisfactory preparation of samples for cutting and mounting during the shock-freezing phase of sample preparation.

Soil contamination by toxic metals is a major environmental problem. These pollutants, contained in anthropogenic wastes, cannot be biodegraded and accumulate in soils and transported to human through the consumption of contaminated aliments or smoking. Several recent researchers showed that these elements are able to generate many diseases as cancer and renal or kidney dysfunctions.

Background Phosphorus (P) deficiency limits crop production worldwide. Crops differ in their ability to acquire and utilise the P available. The aim of this study was to determine root traits (root exudates, root system architecture (RSA), tissue-specific allocation of P, and gene expression in roots) that (a) play a role in P-use efficiency and (b) contribute to large shoot zinc (Zn) concentration in Brassica oleracea. Results Two B. oleracea accessions (var. sabellica C6, a kale, and var. italica F103, a broccoli) were grown in a hydroponic system or in a high-throughput-root phenotyping (HTRP) system where they received Low P (0.025 mM) or High P (0.25 mM) supply for 2 weeks. In hydroponics, root and shoot P and Zn concentrations were measured, root exudates were profiled using both Fourier-Transform-Infrared spectroscopy and gas-chromatography-mass spectrometry and previously published RNAseq data from roots was re-examined. In HTRP experiments, RSA (main and lateral root number and lateral root length) was assessed and the tissue-specific distribution of P was determined using micro-particle-induced-X-ray emission. The C6 accession had greater root and shoot biomass than the F103 accession, but the latter had a larger shoot P concentration than the C6 accession, regardless of the P supply in the hydroponic system. The F103 accession had a larger shoot Zn concentration than the C6 accession in the High P treatment. Although the F103 accession had a larger number of lateral roots, which were also longer than in the C6 accession, the C6 accession released a larger quantity and number of polar compounds than the F103 accession. A larger number of P-responsive genes were found in the Low P treatment in roots of the F103 accession than in roots of the C6 accession. Expression of genes linked with “phosphate starvation” was up-regulated, while those linked with iron homeostasis were down-regulated in the Low P treatment. Conclusions The results illustrate large within-species variability in root acclimatory responses to P supply in the composition of root exudates, RSA and gene expression, but not in P distribution in root cross sections, enabling P sufficiency in the two B. oleracea accessions studied.

During tea preparation mineral elements are extracted from the dried leaves of tea (Camellia sinensis (L.) Kuntze) plants into the solution. Micro-particle induced X-ray emission was employed to investigate the spatial distribution of magnesium (Mg), calcium (Ca) and manganese (Mn) in the young and old leaves of tea plants grown in the absence and presence of aluminium (Al) in the substrate. Results revealed that in tea leaves the largest concentrations of Mg occurred in the epidermis, of Ca in oxalate crystals and of Mn in epidermis and oxalate crystals; there was a leaf-age effect on tissue-specific concentrations of Mg, Ca and Mn with all tissues of old leaves containing larger concentrations of Mg, Ca and Mn than young leaves; supplementation of substrate with Al reduced concentrations of Mg, Ca and Mn in the old leaves, and a link between the distribution of Mg, Ca and Mn in the tea leaves with the extraction efficiencies of these elements into the tea was possible. We conclude that old leaves of tea plants cultivated under conditions of low Al availability will have the largest concentrations of Mg, Ca and Mn and may represent most acceptable ingredient for the preparation of tea.

Jožef Stefan Institute recently commissioned a high brightness H − ion beam injection system for its existing tandem accelerator facility. Custom developed by High Voltage Engineering Europa, the multicusp ion source has been tuned to deliver at the entrance of the Tandetron™ accelerator H − ion beams with a measured brightness of 17.1 A m −2 rad −2 eV −1 at 170 μA, equivalent to an energy normalized beam emittance of 0.767 π mm mrad MeV 1/2 . Upgrading the accelerator facility with the new injection system provides two main advantages. First, the high brightness of the new ion source enables the reduction of object slit aperture and the reduction of acceptance angle at the nuclear microprobe, resulting in a reduced beam size at selected beam intensity, which significantly improves the probe resolution for micro-PIXE applications. Secondly, the upgrade strongly enhances the accelerator up-time since H and He beams are produced by independent ion sources, introducing a constant availability of 3 He beam for fusion-related research with NRA. The ion beam particle losses and ion beam emittance growth imply that the aforementioned beam brightness is reduced by transport through the ion optical system. To obtain quantitative information on the available brightness at the high-energy side of the accelerator, the proton beam brightness is determined in the nuclear microprobe beamline. Based on the experience obtained during the first months of operation for micro-PIXE applications, further necessary steps are indicated to obtain optimal coupling of the new ion source with the accelerator to increase the normalized high-energy proton beam brightness at the JSI microprobe, currently at 14 A m −2 rad −2 eV −1 , with the output current at 18% of its available maximum.

Wheat and its related genotypes show distinct distribution patterns for mineral nutrients in maternal and filial tissues in grains. X-ray-based imaging techniques are very informative to identify genotypes with contrasting tissue-specific localization of different elements. This can help in the selection of suitable genotypes for nutritional improvement of food grain crops. Understanding mineral localization in cereal grains is important for their nutritional improvement. Spatial distribution of mineral nutrients (Mg, P, S, K, Ca, Fe, Zn, Mn and Cu) was investigated between and within the maternal and filial tissues in grains of two wheat cultivars (Triticum aestivum Cv. WH291 and WL711), a landrace (T. aestivum L. IITR26) and a related wild species Aegilops kotschyi, using micro-proton-induced X-ray emission (µ-PIXE) and micro-X-ray fluorescence (µ-XRF). Aleurone and scutellum were major storage tissues for macro (P, K, Ca and Mg) as well as micro (Fe, Zn, Cu and Mn) nutrients. Distinct elemental distribution patterns were observed in each of the four genotypes. A. kotschyi, the wild relative of wheat and the landrace, T. aestivum L. IITR26, accumulated more Zn and Fe in scutellum and aleurone than the cultivated wheat varieties, WH291 and WL711. The landrace IITR26, accumulated far more S in grains, Mn in scutellum, aleurone and embryo region, Ca and Cu in aleurone and scutellum, and Mg, K and P in scutellum than the other genotypes. Unlike wheat, lower Mn and higher Fe, Cu and Zn concentrations were noticed in the pigment strand of A. kotschyi. Multivariate statistical analysis, performed on mineral distribution in major grain tissues (aleurone, scutellum, endosperm and embryo region) resolved the four genotypes into distinct clusters.

Cadmium and zinc share many similar physiochemical properties, but their compartmentation, complexation and impact on other mineral element distribution in plant tissues may drastically differ. In this study, we address the impact of 10μm Cd or 50μm Zn treatments on ion distribution in leaves of a metallicolous population of the non-hyperaccumulating species Zygophyllum fabago at tissue and cell level, and the consequences on the plant response through a combined physiological, proteomic and metabolite approach. Micro-proton-induced X-ray emission and laser ablation inductively coupled mass spectrometry analyses indicated hot spots of Cd concentrations in the vicinity of vascular bundles in response to Cd treatment, essentially bound to S-containing compounds as revealed by extended X-ray absorption fine structure and non-protein thiol compounds analyses. A preferential accumulation of Zn occurred in vascular bundle and spongy mesophyll in response to Zn treatment, and was mainly bound to O/N-ligands. Leaf proteomics and physiological status evidenced a protection of photosynthetically active tissues and the maintenance of cell turgor through specific distribution and complexation of toxic ions, reallocation of some essential elements, synthesis of proteins involved in photosynthetic apparatus or C-metabolism, and metabolite synthesis with some specificities regarding the considered heavy metal treatment. © 2013 John Wiley & Sons Ltd.

Elemental concentrations in micro-PIXE (Particle Induced X-ray Emission) maps of elements in biological tissue slices have been determined using auxiliary information on the sample matrix composition from EBS (Elastic Backscattering Spectroscopy) and STIM (Scanning Transmission Ion Microscopy). The thin sample approximation may be used for evaluating micro-PIXE data in cases, where X-ray absorption in the sample can be neglected and the mass of elements in a selected area can be estimated. The resulting sensitivity amounts to an impressive 10−12 g of the selected elements. Two cases are presented as examples. In the first, we determined the total mass of gold nanoparticles internalized by human monocyte-derived dendritic cells (MDDC). In the second, an inventory of the mass of elements in the micro-particulate material adsorbed at the wall of the lorica of the microzooplankton species Tintinnopsis radix has been created.

Recently we completed a construction of a cryostat at Jožef Stefan Institute (JSI) nuclear microprobe enabling us to analyze various types of biological samples in frozen hydrated state using micro-PIXE/STIM/RBS. Sample load-lock system was added to our existing setup to enable us to quickly insert a sample holder with frozen hydrated tissue samples onto a cold goniometer head cooled with liquid nitrogen inside the measuring chamber. Cryotome-cut slices of frozen hydrated plant samples were mounted between two thin silicon nitride foils and then attached to the sample holder. Sufficient thermal contact between silicon nitride foils and sample holder must be achieved, as well as between the sample holder and the cold goniometer head inside the measuring chamber to prevent melting of the samples. Matrix composition of frozen hydrated tissue is consisted mostly of ice. Thinning of the sample as well as water evaporation during high vacuum and proton beam exposure was inspected by the measurements with RBS and STIM method simultaneously with micro-PIXE. For first measuring attempts a standard micro-PIXE configuration for tissue mapping was used with proton beam cross section of 1.2 × 1.2 μm 2 and a beam current of 100 pA. The temperature of the cold goniometer head was kept below 130 K throughout the entire proton beam exposure. First measurements of thin plant tissue samples in frozen hydrated state show minute sample degradation during the 10 h period of micro-PIXE measurements.

Diverse physiological, biochemical and morphological adaptations enable plants to survive in extreme saline environments where osmotic and ionic stresses limit growth and development. Halophytes are salt-tolerant plants that can withstand extraordinarily high levels of Na and Cl in their leaves. The tissue and cellular distribution patterns of salt ions can be linked to the underlying mechanisms of salt tolerance. Application of fast, reliable, multi-elemental and quantitative techniques such as micro-proton-induced X-ray emission (micro-PIXE) will significantly contribute to and accelerate studies of plant salt tolerance, especially as micro-PIXE also provides spatially resolved quantitative data for light elements, such as Na and Mg. The spatial concentration distributions of Na, Mg, Cl, K, P and S in leaves of four halophytes (Bassia indica, Atriplex prostrata, Spartina maritima and Limonium angustifolium) were determined using micro-PIXE, to study the salt-tolerance strategies of the selected halophytes. Different distribution patterns of the studied elements were seen in the leaves; however, in all four of these plant species, Na was excluded from photosynthetically active chlorophyl tissues. With the exception of L. angustifolium, Cl, P and S contents (representing chloride, phosphate and sulphate ionic forms, respectively) did not ensure charge balance in the leaves, which suggests other anionic compounds, such as nitrate and organic anions, have crucial roles in maintaining electroneutrality in these halophytes. By increasing soil salinisation worldwide, the possibility to reliably complement spatial distributions of Na, Mg, Cl, K, P and S with plant structural morphology will contribute significantly to our understanding of plant tolerance mechanisms at the tissue and cell levels. In addition, these kinds of studies are of particular value for designing crop plants with high salt tolerance and for the development of phytoremediation technologies.

Iron insufficiency is a worldwide problem in human diets. In cereals like wheat, the bran layer of the grains is an important source of iron. However, the dietary availability of iron in wheat flour is limited due to the loss of the iron-rich bran during milling and processing and the presence of anti-nutrients like phytic acid that keep iron strongly chelated in the grain. The present study investigated the localization of iron and phosphorus in grain tissues of wheat genotypes with contrasting grain iron content using synchrotron-based micro-X-ray fluorescence (micro-XRF) and micro-proton-induced X-ray emission (micro-PIXE). X-ray absorption near-edge spectroscopy (XANES) was employed to determine the proportion of divalent and trivalent forms of Fe in the grains. It revealed the abundance of oxygen, phosphorus, and sulphur in the local chemical environment of Fe in grains, as Fe-O-P-R and Fe-O-S-R coordination. Contrasting differences were noticed in tissue-specific relative localization of Fe, P, and S among the different genotypes, suggesting a possible effect of localization pattern on iron bioavailability. The current study reports the shift in iron distribution from maternal to filial tissues of grains during the evolution of wheat from its wild relatives to the present-day cultivated varieties, and thus suggests the value of detailed physical localization studies in varietal improvement programmes for food crops.

We demonstrate the stereo-PIXE method by measurement of surface topography of the relief details on 1€ coin. Two X-ray elemental maps were simultaneously recorded by two X-ray detectors positioned at the left and the right side of the proton microbeam. The asymmetry of the yields in the pixels of the two X-ray maps occurs due to different photon attenuation on the exit travel path of the characteristic X-rays from the point of emission through the sample into the X-ray detectors. In order to calibrate the inclination angle with respect to the X-ray asymmetry, a flat inclined surface model was at first applied for the sample in which the matrix composition and the depth elemental concentration profile is known. After that, the yield asymmetry in each image pixel was transferred into corresponding local inclination angle using calculated dependence of the asymmetry on the surface inclination. Finally, the quantitative topography profile was revealed by integrating the local inclination angle over the lateral displacement of the probing beam.

With a model invertebrate animal, we have assessed the fate of magnetic nanoparticles in biologically relevant media, i.e., digestive juices. The toxic potential and the internalization of such nanoparticles by nontarget cells were also examined. The aim of this study was to provide experimental evidence on the formation of Co2+, Fe2+, and Fe3+ ions from CoFe2O4 nanoparticles in the digestive juices of a model organism. Standard toxicological parameters were assessed. Cell membrane stability was tested with a modified method for measurement of its quality. Proton-induced X-ray emission and low energy synchrotron radiation X-ray fluorescence were used to study internalization and distribution of Co and Fe. Co2+ ions were found to be more toxic than nanoparticles. We confirmed that Co2+ ions accumulate in the hepatopancreas, but Fen+ ions or CoFe2O4 nanoparticles are not retained in vivo. A model biological system with a terrestrial isopod is suited to studies of the potential dissolution of ions and other ...

Understanding the uptake, accumulation and distribution of toxic elements in plants is crucial to the design of effective phytoremediation strategies, especially in the case of complex multi-element pollution. Using micro-proton induced X-ray emission, the spatial distribution of Na, Mg, Al, Si, P, S, Cl, K, Ca, Mn, Fe, Zn, As, Br, Rb, Sr, Cd and Pb have been quantitatively resolved in roots and rhizomes of an obligate wetland plant species, Typha latifolia, treated with a mixture of 100 μM each of As, Cd and Pb, together. The highest concentrations of As, Cd and Pb were found in the roots of the T. latifolia, with tissue-specific distributions. The As was detected in the root rhizodermis, and in the rhizome the majority of the As was within the vascular tissues, which indicates the high mobility of As within T. latifolia. The Cd was detected in the root exodermis, and in the vascular bundle and epidermis of the rhizome. The highest Pb concentrations were detected in the root rhizodermis and exodermis, and in the epidermis of the rhizome. These data represent an essential step in the resolution of fundamental questions in plant ionomics.

In this paper, we present the use of focused MeV ion beams to study the distribution of deuterium (D), boron (B) and nitrogen (N) on tungsten (W) samples exposed in the divertor region of the ASDEX Upgrade tokamak during 15N-seeded L-mode discharges in deuterium and during non-seeded H-mode discharges in helium. In both experiment samples of various surface roughness were exposed and analyzed: W coatings on milled or polished graphite substrates and bulk W samples, ranging from the roughest (milled) to the smoothest (bulk W), to study the effects of surface roughness on deposition profiles of D, B and N. In the case of samples from the 15N experiment, we found that D, N and B are distributed quite homogeneously over the sample on the micrometer scale with some small variation inside the analysed area. The surface densities show strong variations in the poloidal direction, with maximum values slightly above the strike point. The amounts of the retained (D, B, N) were strongly correlated with the surface roughness of the samples, being the highest on the rough samples. Samples originating from the He campaign showed inhomogeneous distribution of impurities with a distinct micro-scale structure, which is most pronounced on pre-damaged W samples, where a rough fuzz-like surface is created during the exposure in the GLADIS machine. We observe a distinct difference in behavior of deposited B profiles from both experiments with higher retention of B in the He experiment.