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X‐ray emission spectroscopy in a point‐to‐point focusing geometry using instruments that employ more than one analyzer crystal poses challenges with respect to mechanical design and performance. This work discusses various options for positioning the components and provides the formulas for calculating their relative placement. Ray‐tracing calculations were used to determine the geometrical contributions to the energy broadening including the source volume as given by the beam footprint on the sample. The alignment of the instrument is described and examples are given for the performance. [ABSTRACT FROM AUTHOR]

The design and first results of a large‐solid‐angle X‐ray emission spectrometer that is optimized for energies between 1.5 keV and 5.5 keV are presented. The spectrometer is based on an array of 11 cylindrically bent Johansson crystal analyzers arranged in a non‐dispersive Rowland circle geometry. The smallest achievable energy bandwidth is smaller than the core hole lifetime broadening of the absorption edges in this energy range. Energy scanning is achieved using an innovative design, maintaining the Rowland circle conditions for all crystals with only four motor motions. The entire spectrometer is encased in a high‐vacuum chamber that allocates a liquid helium cryostat and provides sufficient space for in situ cells and operando catalysis reactors. [ABSTRACT FROM AUTHOR]

In Rhodospirillum rubrum, the maturation of carbon monoxide dehydrogenase (CODH) requires three nickel chaperones, namely RrCooC, RrCooT and RrCooJ. Recently, the biophysical characterisation of the RrCooT homodimer and the X‐ray structure of its apo form revealed the existence of a solvent‐exposed NiII‐binding site at the dimer interface, involving the strictly conserved Cys2. Here, a multifaceted approach that used NMR and X‐ray absorption spectroscopies, complemented with structural bio‐modelling methodologies, was used to characterise the binding mode of NiII in RrCooT. This study suggests that NiII adopts a square‐planar geometry through a N2S2 coordinating environment that comprises the two thiolate and amidate groups of both Cys2 residues at the dimer interface. The existence of a diamagnetic mononuclear NiII centre with bis‐amidate/bis‐thiolate ligands, coordinated by a single‐cysteine motif, is unprecedented in biology and raises the question of its role in the activation of CODH at the molecular level. [ABSTRACT FROM AUTHOR]

Of all divalent metals, mercury (HgII) has the highest affinity for metallothioneins. HgII is considered to be enclosed in the α and β domains as tetrahedral α‐type Hg4Cys11‐12 and β‐type Hg3Cys9 clusters similar to CdII and ZnII. However, neither the four‐fold coordination of Hg nor the existence of Hg–Hg atomic pairs have ever been demonstrated, and the HgII partitioning among the two protein domains is unknown. Using high energy‐resolution XANES spectroscopy, MP2 geometry optimization, and biochemical analysis, evidence for the coexistence of two‐coordinate Hg‐thiolate complex and four‐coordinate Hg‐thiolate cluster with a metacinnabar‐type (β‐HgS) structure in the α domain of separate metallothionein molecules from blue mussel under in vivo exposure is provided. The findings suggest that the CXXC claw setting of thiolate donors, which only exists in the α domain, acts as a nucleation center for the polynuclear complex and that the five CXC motifs from this domain serve as the cluster‐forming motifs. Oligomerization is driven by metallophilic Hg⋅⋅⋅Hg interactions. Our results provide clues as to why Hg has higher affinity for the α than the β domain. More generally, this work provides a foundation for understanding how metallothioneins mediate mercury detoxification in the cell under in vivo conditions. Mercury binding to metallothionein under in vivo exposition is unknown. HR‐XANES spectroscopy identifies two mercury‐thiolate complexes in the α domains of separate MT molecules. One is mononuclear and modeled as a bis‐six‐membered ring chelate through two axial sulfur atoms and two equatorial peptide oxygens from a CXXC (single‐letter amino acid code, where X can be any amino acid) motif. The other complex is polynuclear with a metacinnabar‐type (β‐HgS) core bound to the CXC motifs. The CXXC motif acts as a nucleation center for the Hg clusters. [ABSTRACT FROM AUTHOR]

The nanoscale distribution of magnetic anisotropies is measured in core@shell MnFe2O4@CoFe2O4 7.0 nm particles using a combination of element selective magnetic spectroscopies with different probing depths. As this picture is not accessible by any other technique, emergent magnetic properties are revealed. The coercive field is not constant in a whole nanospinel. The very thin (0.5 nm) CoFe2O4 hard shell imposes a strong magnetic anisotropy to the otherwise very soft MnFe2O4 core: a large gradient in coercivity is measured inside the MnFe2O4 core with lower values close to the interface region, while the inner core presents a substantial coercive field (0.54 T) and a very high remnant magnetization (90% of the magnetization at saturation). [ABSTRACT FROM AUTHOR]

The study of the speciation of highly diluted elements by X-ray absorption spectroscopy (XAS) is extremely challenging, especially in environmental biogeochemistry sciences. Here we present an innovative synchrotron spectroscopy technique: high-energy resolution fluorescence detected XAS (HERFD-XAS). With this approach, measurement of the XAS signal in fluorescence mode using a crystal analyzer spectrometer with a ~1-eV energy resolution helps to overcome restrictions on sample concentrations that can be typically measured with a solid-state detector. We briefly describe the method, from both an instrumental and spectroscopic point of view, and emphasize the effects of energy resolution on the XAS measurements. We then illustrate the positive impact of this technique in terms of detection limit with two examples dealing with Ce in ecologically relevant organisms and with Hg species in natural environments. The sharp and well-marked features of the HERFD-X-ray absorption near-edge structure spectra obtained enable us to determine unambiguously and with greater precision the speciation of the probed elements. This is a major technological advance, with strong benefits for the study of highly diluted elements using XAS. It also opens new possibilities to explore the speciation of a target chemical element at natural concentration levels, which is critical in the fields of environmental and biogeochemistry sciences. [ABSTRACT FROM AUTHOR]

Combined high-resolution fluorescence detection X-ray absorption near-edge spectroscopy, X-ray diffraction, and X-ray emission spectroscopy have been employed under operando conditions to obtain detailed new insight into the nature of the Mo species on zeolite ZSM-5 during methane dehydroaromatization. The results show that isolated Mo-oxo species present after calcination are converted by CH4 into metastable MoC xO y species, which are primarily responsible for C2Hx/C3Hx formation. Further carburization leads to MoC3 clusters, whose presence coincides with benzene formation. Both sintering of MoC3 and accumulation of large hydrocarbons on the external surface, evidenced by fluorescence-lifetime imaging microscopy, are principally responsible for the decrease in catalytic performance. These results show the importance of controlling Mo speciation to achieve the desired product formation, which has important implications for realizing the impact of CH4 as a source for platform chemicals. [ABSTRACT FROM AUTHOR]

Blue mussel, a widely distributed filter‐feeder mollusk often used as a sentinel organism for marine pollutants, copes with metal toxicity by overexpressing metallothionein, represented as wicked enchantments on the frontispiece. Two mercury‐thiolate complexes were identified in metallothionein in response to in vivo Hg exposure using high energy‐resolution XANES spectroscopy. One is mononuclear and modeled as a bis‐six‐membered ring chelate through two axial sulfur atoms and two equatorial peptide oxygens from a CXXC motif. The other complex is polynuclear with a metacinnabar‐type (β‐HgS) core bound to the CXC motifs. We propose that the CXXC motif, only present in the α‐domain, acts as a nucleation center for the Hg clusters via metallophilic Hg‐Hg interactions. Results from this research provide a molecular understanding for the higher mercury affinity of the α than the β domain, and provide a foundation for understanding how metallothionein mediates the detoxification of toxic metals in the cell under in vivo conditions. For more details, see the Full Paper by A. Manceau et al. on page 997 ff. [ABSTRACT FROM AUTHOR]

Die Überführung von Methan …… in C2‐ bis C6‐Kohlenwasserstoffe könnte eine wertvolle Alternative zu Öl als Quelle für Plattformchemikalien sein. A. M. Beale, B. M. Weckhuysen et al. wenden in ihrer Zuschrift auf S. 5301 ff. eine Kombination aus Operando‐Röntgentechniken und bildgebender Fluoreszenzlebenszeit‐Mikroskopie auf den Mo‐ZSM‐5‐Zeolithen an, um zu verstehen, wie die Mo‐Position sich während der katalytischen Umwandlung von Methan verändert und wie dies die Reaktionsprodukte beeinflusst. [ABSTRACT FROM AUTHOR]