Characterization of selenium speciation in selenium-enriched button mushrooms (Agaricus bisporus) and selenized yeasts (dietary supplement) using X-ray absorption near-edge structure (XANES) spectroscopy.

Selenium is an essential trace element for which dietary intake is not sufficient in many parts of the world such as in Europe. Yeast and mushrooms may accumulate considerable amounts of selenium, but the chemical form in mushrooms has not been elucidated yet. Thus, we determined the selenium speciation of selenium-enriched button mushrooms in comparison to that of selenized yeast via Se K-edge XANES spectroscopy. Quantitative analysis of the XANES spectra revealed that the selenium in selenized yeast is mainly present as seleno-methionine but that in selenium-enriched button mushrooms, it is present predominantly as Se-methyl-l-selenocysteine. As this form is highly bioavailable and directly enters the selenium metabolic pool, selenium-enriched mushrooms may be a good food choice to improve selenium intake.

The interaction of copper ions with Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli: an X-ray absorption near-edge structure (XANES) spectroscopy study.

The antimicrobial properties of copper ions have been known for a long time. However, the exact mechanism of action of the transition metal on microorganisms has long been unclear. X-ray absorption near-edge structure (XANES) spectroscopy at the Cu K edge allows the determination of copper speciation in Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa that have been treated with Cu(II) and Cu(I) solutions. The death/inactivation of the bacteria was observed using plate counting and light microscopy. The Cu K-XANES spectra of the two Gram-negative bacteria are different than those of the Gram-positive strain. The results clearly show that the Cu+-S bond contributes to the antibacterial activity of copper, as in the case of silver. The detailed evaluation of the differentiated absorption spectra shows that Cu+ (not Cu2+) is the dominant ion that binds to the bacteria. Because Cu+ is not the most common copper ion, copper is not as effective an antibacterial agent as silver, whose common valency is actually + 1. Any reaction of copper with phosphorus from the bacteria can be excluded after the evaluation of the absorption spectra.

In Situ Investigations of Laser-Generated Ligand-Free Platinum Nanoparticles by X-ray Absorption Spectroscopy: How Does the Immediate Environment Influence the Particle Surface?

Pulsed laser ablation in liquid (PLAL) has proven its usefulness as a nanoparticle (NP) synthesis method alternative to traditional chemical reduction methods, where the absence of any molecular ligands or residual reactants makes laser-generated nanoparticles ideal reference materials for charge-transfer experiments. We synthesized additive-free platinum nanoparticles by PLAL and in-situ characterized their interaction with H2O, sodium phosphate buffer, and sodium citrate as well as a TiO2 support by X-ray absorption fine structure (XAFS), i.e., X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). Differences in the white-line intensity among the colloidal particles in the three liquids indicate that the respective NP-solvent interaction varies in strength. The ions added ex situ diffuse through the particles' electric double layer and interact electrostatically with the Stern plane. Consequently, these ions weaken the interaction of the functional OH groups that are bound to the partially oxidized platinum surfaces and cause their partial reduction. Comparing XAFS spectra of laser-generated Pt NPs in citrate with wet-chemically synthesized ones (both ligand-covered) indicates different types of Pt-O bonds: a Pt(IV)O2 type in the case of wet-chemical NPs and a Pt(II)O type in the case of laser-generated NPs. A comparison of unsupported laser-generated platinum NPs in H2O with TiO2-supported ones shows no white-line intensity differences and also an identical number of Pt-O bonds in both cases. This suggests that in the deposition process at least part of the double-layer coating stays intact and that the ligand-free Pt particle properties are preserved in the TiO2-supported Pt particles, relevant for heterogeneous catalysis.

Site-selective high-resolution X-ray absorption spectroscopy and high-resolution X-ray emission spectroscopy of cobalt nanoparticles.

The special (macroscopic) properties of nanoparticles are mainly due to their large surface-to-volume ratio. Thus, the separate characterization of geometric and electronic properties of surface and bulk would be favorable for a better understanding of the properties of nanoparticles. Because of the chemical sensitivity of X-ray fluorescence lines, in particular those involving higher lying electronic states, high-resolution fluorescence-detected X-ray absorption spectra (HRFD-XAS) offer these opportunities. In this study, three types of wet-chemically synthesized Co nanoparticles, ∼6 nm in diameter with varying thicknesses of a protective shell, were investigated at the ID26 beamline of the European Synchrotron Radiation Facility. HRFD-XAS spectra at the Co K-edge, that is, X-ray absorption near-edge structure (HRFD-XANES) and extended X-ray absorption fine structure (HRFD-EXAFS) spectra, were recorded via detection of the Kß1,3 fluorescence at specific energies. As these spectra are only partly site-selective due to a strong overlap of the emission lines, a numerical procedure was applied based on a least-squares fitting procedure, realized by singular value decomposition. The detailed analysis of the obtained site-selective spectra, regarding chemical composition and crystallographic phase, using measured and simulated FEFF9-based reference spectra, showed that the metallic core had mainly hexagonal close-packed structure with lattice constants matching bulk Co; the spectra for the shell could be satisfactorily fitted by a mixture of CoO and CoCO3; however, with an obvious need for at least a third compound. To obtain additional information about ligands attached to Co, valence-to-core X-ray emission spectra (VTC-XES) using the Kß2,5 and the satellite structure Kß″ and VTC-XANES spectra thereof were also recorded, by which the former results are confirmed. Further on, FEFF simulations indicate that a Co-N compound is a very likely candidate for the third component. The presented results clearly show that VTC-XES and HRFD-XAS are suitable tools for the detailed specification of the core and the surface of nanoparticles, in particular upon realizing "real" site-selectivity for XANES and EXAFS with a general strategy applicable to a wide range of systems.

X-ray absorption near-edge structure (XANES) spectroscopy study of the interaction of silver ions with Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli.

Silver ions are widely used as antibacterial agents, but the basic molecular mechanism of this effect is still poorly understood. X-ray absorption near-edge structure (XANES) spectroscopy at the Ag LIII, S K, and P K edges reveals the chemical forms of silver in Staphylococcus aureus and Escherichia coli (Ag(+) treated). The Ag LIII-edge XANES spectra of the bacteria are all slightly different and very different from the spectra of silver ions (silver nitrate and silver acetate), which confirms that a reaction occurs. Death or inactivation of bacteria was observed by plate counting and light microscopy. Silver bonding to sulfhydryl groups (Ag-S) in cysteine and Ag-N or Ag-O bonding in histidine, alanine, and DL-aspartic acid was detected by using synthesized silver-amino acids. Significantly lower silver-cysteine content, coupled with higher silver-histidine content, in Gram-positive S. aureus and Listeria monocytogenes cells indicates that the peptidoglycan multilayer could be buffering the biocidal effect of silver on Gram-positive bacteria, at least in part. Bonding of silver to phosphate groups was not detected. Interaction with DNA or proteins can occur through Ag-N bonding. The formation of silver-cysteine can be confirmed for both bacterial cell types, which supports the hypothesis that enzyme-catalyzed reactions and the electron transport chain within the cell are disrupted.

Lead uptake in diverse plant families: a study applying X-ray absorption near edge spectroscopy.

The chemical environment of lead in roots and leaves of plants from four different plant families and a lichen from a former lead mining site in the Eifel Mountains in Germany was determined by Pb L3-edge XANES measurements using solid reference compounds and also aqueous solutions of different ionic strength simulating the plant environment. Pb(2+) ions in the plants were found to have two major coordinations, one with nine oxygen atoms in the first coordination shell similar to outer-sphere complexation and a second coordination with just three oxygen atoms similar to inner-sphere complexation. This can be interpreted assuming that lead is sorbed on the surface of cell walls depending on the concentration of lead in the soil solution. Pb L3-edge XANES spectra of dried and fresh plant samples are very similar because sorption does not change with removal of water but only because of the initial ionic strength. No bonding to biologically important groups (-S, - N) or precipitation (-PO4) was found.

Time-resolved XAS (Bonn-SUT-SLRI) beamline at SLRI.

An energy-dispersive X-ray absorption spectroscopy beamline has been constructed at the Synchrotron Light Research Institute, Thailand. The beamline was designed to utilize the synchrotron radiation with photon energies between 2400 and 8000 eV. The horizontal focusing of the bent crystal in the energy-dispersive monochromator offers a small polychromatic focal spot of 1 mm at the sample position. By employing an energy-dispersive scheme, the whole X-ray absorption near-edge structure (XANES) can be obtained simultaneously using a position-sensitive detector with a fastest readout speed of 25 ms. The short data collection time opens a new opportunity for time-resolved X-ray absorption spectroscopy (XAS) experiments such as studies of changes of the electronic structures or the local coordination environments of an atom during a change in thermodynamic conditions. For this purpose, an in situ cell was designed and fabricated for the beamline. Thermal oxidation of TiO(2) was chosen as an in situ experiment example. The structural change of TiO(2) as a function of temperatures was monitored from the change in the measured XAS spectra. The obtained Ti K-edge XANES spectra clearly show the formation of an anatase phase when the temperature was raised to 673 K.

The speciation of soluble sulphur compounds in bacterial culture fluids by X-ray absorption near edge structure spectroscopy.

Over the last decade X-ray absorption near edge structure (XANES) spectroscopy has been used in an increasing number of microbiological studies. In addition to other applications it has served as a valuable tool for the investigation of the sulphur globules deposited intra- or extracellularly by certain photo- and chemotrophic sulphur-oxidizing (Sox) bacteria. For XANES measurements, these deposits can easily be concentrated by filtration or sedimentation through centrifugation. However, during oxidative metabolism of reduced sulphur compounds, such as sulphide or thiosulphate, sulphur deposits are not the only intermediates formed. Soluble intermediates such as sulphite may also be produced and released into the medium. In this study, we explored the potential of XANES spectroscopy for the detection and speciation of sulphur compounds in culture supernatants of the phototrophic purple sulphur bacterium Allochromatium vinosum. More specifically, we investigated A. vinosum DeltasoxY, a strain with an in frame deletion of the soxY gene. This gene encodes an essential component of the thiosulphate-oxidizing Sox enzyme complex. Improved sample preparation techniques developed for the DeltasoxY strain allowed for the first time not only the qualitative but also the quantitative analysis of bacterial culture supernatants by XANES spectroscopy. The results thus obtained verified and supplemented conventional HPLC analysis of soluble sulphur compounds. Sulphite and also oxidized organic sulphur compounds were shown by XANES spectroscopy to be present, some of which were not seen when standard HPLC protocols were used.

Unexpected extracellular and intracellular sulfur species during growth of Allochromatium vinosum with reduced sulfur compounds.

Before its uptake and oxidation by purple sulfur bacteria, elemental sulfur probably first has to be mobilized. To obtain more insight into this mobilization process in the phototrophic purple sulfur bacterium Allochromatium vinosum, we used HPLC analysis and X-ray absorption near-edge structure (XANES) spectroscopy for the detection and identification of sulfur compounds in culture supernatants and bacterial cells. We intended to identify soluble sulfur compounds that specifically occur during growth on elemental sulfur, and therefore compared spectra of cultures grown on sulfur with those of cultures grown on sulfide or thiosulfate. While various unexpected oxidized organic sulfur species (sulfones, C-SO(2)-C, and sulfonates, C-SO(3)(-)) were observed via XANES spectroscopy in the supernatants, we obtained evidence for the presence of monosulfane sulfonic acids inside the bacterial cells by HPLC analysis. The concentrations of the latter compounds showed a tight correlation with the content of intracellular sulfur, reaching their maximum when sulfur began to be oxidized. None of the detected sulfur compounds appeared to be a specific soluble intermediate or product of elemental sulfur mobilization. It therefore seems unlikely that mobilization of elemental sulfur by purple sulfur bacteria involves excretion of soluble sulfur-containing substances that would be able to act on substrate distant from the cells.

Microfluidic synthesis of nanomaterials.

An overview of the current information and analyses on the microfluidic synthesis of different types of nanomaterial, including metallic and silica nanoparticles and quantum dots, is presented. Control of particle size, size distribution, and crystal structure of nanomaterials are examined in terms of the special features of microfluidic reactors.

Glutaric acid as a spacer facilitates improved intracellular uptake of LHRH-SPION into human breast cancer cells.

Superparamagnetic iron oxide nanoparticles (SPIONs) bound directly to luteinizing hormone releasing hormone (LHRH) have shown high efficiency for intracellular uptake to breast cancer cells, MDA-MB-435S.luc. We demonstrate in this communication that inclusion of a small spacer molecule such as glutaric acid (Glu) in between SPION and LHRH increases further receptor mediated intracellular uptake. LHRH-bound SPIONs with and without the spacer molecule were nontoxic.

Utilization of solid "elemental" sulfur by the phototrophic purple sulfur bacterium Allochromatium vinosum: a sulfur K-edge X-ray absorption spectroscopy study.

The purple sulfur bacterium Allochromatium vinosum can use elemental sulfur as an electron donor for anoxygenic photosynthesis. The elemental sulfur is taken up, transformed into intracellular sulfur globules and oxidized to sulfate. Commercially available "elemental" sulfur usually consists of the two species cyclo-octasulfur and polymeric sulfur. The authors investigated whether only one sulfur species is used or at least preferred when Alc. vinosum takes up elemental sulfur and forms globules. To this end, Alc. vinosum was cultivated photolithoautotrophically with two types of elemental sulfur that differed in their cyclo-octasulfur : polymeric sulfur ratio, as well as with pure polymeric sulfur. Sulfur speciation was analysed using X-ray absorption spectroscopy, and sulfate contents were determined by HPLC to quantify the amount of elemental sulfur being taken up and oxidized by Alc. vinosum. The results show that Alc. vinosum uses only the polymeric sulfur (sulfur chain) fraction of elemental sulfur and is probably unable to take up and form sulfur globules from cyclo-octasulfur. Furthermore, direct cell-sulfur contact appears to be necessary for uptake of elemental sulfur by Alc. vinosum.

Speciation of sulfur from filamentous microbial mats from sulfidic cave springs using X-ray absorption near-edge spectroscopy.

Most transformations within the sulfur cycle are controlled by the biosphere, and deciphering the abiotic and biotic nature and turnover of sulfur is critical to understand the geochemical and ecological changes that have occurred throughout the Earth's history. Here, synchrotron radiation-based sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy is used to examine sulfur speciation in natural microbial mats from two aphotic (cave) settings. Habitat geochemistry, microbial community compositions, and sulfur isotope systematics were also evaluated. Microorganisms associated with sulfur metabolism dominated the mats, including members of the Epsilonproteobacteria and Gammaproteobacteria. These groups have not been examined previously by sulfur K-edge XANES. All of the mats consisted of elemental sulfur, with greater contributions of cyclo-octasulfur (S8) compared with polymeric sulfur (Smicro). While this could be a biological fingerprint for some bacteria, the signature may also indicate preferential oxidation of Smicro and S8 accumulation. Higher sulfate content correlated to less S8 in the presence of Epsilonproteobacteria. Sulfur isotope compositions confirmed that sulfur content and sulfur speciation may not correlate to microbial metabolic processes in natural samples, thereby complicating the interpretation of modern and ancient sulfur records.

LHRH-conjugated magnetic iron oxide nanoparticles for detection of breast cancer metastases.

Targeted delivery of superparamagnetic iron oxide nanoparticles (SPIONs) could facilitate their accumulation in metastatic cancer cells in peripheral tissues, lymph nodes and bones and enhance the sensitivity of magnetic resonance imaging (MRI). The specificities of luteinizing hormone releasing hormone (LHRH) and luteinizing hormone/chorionic gonadotropin (LH/CG)- bound SPIONs were tested in human breast cancer cells in vitro and were found to be dependent on the receptor expression of the target cells, the time of incubation and showed saturation kinetics. In incubations with MDA-MB-435S.luc cells, the highest iron accumulation was 452.6 pg Fe/cell with LHRH-SPIONs, 203.6 pg Fe/cell with beta-CG-SPIONs and 51.3 pg Fe/cell with SPIONs. Incubations at 4 degrees C resulted in 1.1 pg Fe/cell. Co-incubation with the same ligands (betaCG or LHRH) decreased the iron accumulation in each case. LHRH-SPIONs were poorly incorporated by macrophages. Tumors and metastatic cells from breast cancer xenografts were targeted in vivo in a nude mouse model. LHRH-SPION specifically accumulated in cells of human breast cancer xenografts. The amount of LHRH-SPION in the lungs was directly dependent on the number of metastatic cells and amounted to 77.8 pg Fe/metastastic cell. In contrast, unconjugated SPIONs accumulated in the liver, showed poor affinity to the tumor, and were not detectable in metastatic lesions in the lungs. LHRH-SPION accumulated in the cytosolic compartment of the target cells and formed clusters. LHRH-SPIONs did not accumulate in livers of normal mice. In conclusion, LHRH conjugated SPIONs may serve as a contrast agent for MR imaging in vivo and increase the sensitivity for the detection of metastases and disseminated cells in lymph nodes, bones and peripheral organs.

Functionalization of gold and glass surfaces with magnetic nanoparticles using biomolecular interactions.

Advances in nanotechnology have enabled the production and characterization of magnetic particles with nanometer-sized features that can be functionalized with biological recognition elements for numerous applications in biotechnology. In the present study, the synthesis of and interactions between self-assembled monolayers (SAMs) on gold and glass surfaces and functionalized magnetic nanoparticles have been characterized. Immobilization of 10-15 nm streptavidin-functionalized nanoparticles to biotinylated gold and glass surfaces was achieved by the strong interactions between biotin and streptavidin. Fluorescent streptavidin-functionalized nanoparticles, biotinylated surfaces, and combinations of the two were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and electron and fluorescent microscopy to confirm that little or no functionalization occurred in nonbiotinylated regions of the gold and glass surfaces compared to the biotinylated sites. Together these techniques have potential use in studying the modification and behavior of functionalized nanoparticles on surfaces in biosensing and other applications.

Sub-cellular accumulation of magnetic nanoparticles in breast tumors and metastases.

In this study, the sub-cellular accumulation of superparamagnetic iron oxide nanoparticles (SPIONs) in breast tumors and peripheral organs were investigated. MNPs were conjugated with luteinizing hormone releasing hormone (LHRH), whose receptors are expressed by most types of breast cancer cells. After the nanoparticles were injected into female nude mice bearing MDA-MB-435S.luc tumors, the mice were sacrificed to collect tumors and peripheral organs for biological and TEM analyses. LHRH conjugated SPIONs (LHRH- SPIONs) were found to accumulate in cancer cells, mainly in the primary tumors and the metastatic lungs, where they aggregated to form clusters. In contrast, most of the unconjugated SPIONs were collected in the liver cells. The results suggest that LHRH- SPIONs can be used to target cancer cells in the primary breast tumors and the lung metastases. TEM is also shown to be a useful tool for the studies of sub-cellular distributions of SPIONs in tumors and tissues.

Influence of mycotoxin producing fungi (Fusarium, Aspergillus, Penicillium) on gluten proteins during suboptimal storage of wheat after harvest and competitive interactions between field and storage fungi.

Cereals contaminated by Aspergillus spp., Penicillium spp., and Fusarium spp. and their mycotoxins, for example, ochratoxin A (OTA) and deoxynivalenol (DON), are not only a risk to human and animal health but can also show poor technological properties and baking quality. The influence of these genera on the sulfur speciation of low molecular weight (LMW) subunits of glutenin was characterized by investigating suboptimally stored wheat samples in situ by X-ray absorption near edge structure (XANES) spectroscopy and baking tests. Field fungi of the genus Fusarium have hardly any influence on both the sulfur speciation of wheat gluten proteins and the baking properties, whereas storage fungi of the genera Aspergillus and Penicillium have a direct influence. An increased amount of sulfur in sulfonic acid state was found, which is not available for thiol/disulfide exchange reactions in the gluten network, and thus leads to a considerably reduced baking volume. From changes of the composition of the mould flora during suboptimal storage of wheat and from the mycotoxin contents, it can be concluded that microbial competitive interactions play an important role in the development of the mould flora and the mycotoxin concentrations during (suboptimal) storage of wheat.

Investigations into sulfobetaine-stabilized Cu nanoparticle formation: toward development of a microfluidic synthesis.

The mechanistic aspects of the formation of sulfobetaine-stabilized copper nanoparticles were investigated by using in situ XANES (X-ray absorption near edge structure), UV-vis spectroscopy, and reaction calorimetry. The tetracoordinated sulfobetaine-Cu(II) complex was reduced to a stable sulfobetaine-Cu(I) complex prior to the formation of sulfobetaine-stabilized copper nanoparticles. The stability of the Cu(I) complex was found to be sensitive to the concentration of the sulfobetaine stabilizer and the addition rate of the reducing agent. It appears to exist primarily as a linear complex. A tetracoordinated Cu(I) complex as an intermediate has also been postulated. Based on the understanding from these investigations, a microfluidic process for copper nanoparticle synthesis was designed by using sulfobetaine-Cu(I) complex as the starting material. When compared with the copper nanoparticles synthesized by a conventional batch process, the microfluidic reactor process provided particles with a smaller size and narrower size distribution. The copper nanoparticles from the microreactor process could also be more easily purified and the particles were relatively stable in air. Both XRD and SAED indicated that the Cu nanoparticles synthesized have fcc structure.

Synthesis of palladium nanoparticles using a continuous flow polymeric micro reactor.

A continuous flow polymeric micro reactor, fabricated using a negative photo resist SU-8 on a 10 x 10 cm PEEK (polyetheretherketone) substrate by standard UV lithography, was utilized to synthesize palladium nanoparticles. The nanoparticles were characterized by Transmission Electron Microscopy, Selected Area Electron Diffraction and X-ray Diffraction. The Pd nanoparticles synthesized in the micro reactor were found to have a narrower size distribution when compared with those obtained by the conventional batch process.

Efficacy of lytic peptide-bound magnetite nanoparticles in destroying breast cancer cells.

A 23-amino-acid synthetic lytic peptide (Hecate) was covalently linked to magnetite nanoparticles and the lytic peptide-bound nanoparticles were characterized by X-ray absorption near-edge structure spectroscopy, transmission electron microscopy, and electron diffraction. Investigation of magnetic properties with a superconducting quantum interference device (SQUID) magnetometer has shown a reduction in the saturation magnetization (Ms) of magnetite nanoparticles after binding with lytic peptide. An in vitro cell culture assay with breast cancer cell lines MDA-MB-435S revealed that the lytic peptide-bound magnetite nanoparticles were therapeutically active.