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Abstract: Energy dispersive EXAFS (EDE), using a Laue monochromator on ID24 of the ESRF, and multiple ion monitoring mass spectrometry have been used to monitor the structure and function of alumina-supported rhodium and palladium catalysts within a microreactor. Metallic 5%-Rh/Al2O3 was preformed in situ by hydrogen reduction, and shown to react rapidly with NO at room temperature yielding an oxidised phase. In order for this material to catalyse the reduction of NO by H2 (to N2), it was shown that the metallic phase must be reformed. The ""light-off"" temperature at which the metallic phase was formed and catalysis commenced varied with NO : H2 stoichiometry, this temperature lowering in more reducing conditions. N2O formation was concomitant with the conversion from the oxidised to the metallic phase. The EDE configuration allowed the simultaneous monitoring of structure at both the rhodium and palladium K-edges. Incorporation of a 20% palladium mole fraction into 5%-Rh-Pd/Al2O3 protected rhodium from oxidation and also reduced the light-off temperature, and this is reflected in low coordination number values for the composite Pd to Rh/Pd shell. This favours palladium being preferentially on the surface of the nanoparticles. At higher temperatures there are changes in coordination numbers than imply a redistribution of metal sites under catalytic conditions. Future plans to include infrared spectroscopy as a third simultaneous technique will be outlined.

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Abstract: The non-linear beam dynamics have been investigated for the non-zero dispersion lattice of the Diamond storage ring. Effects in realistic lattice configuration, where coupling errors and engineering aperture limitations are considered, have been studied here. Frequency Map Analysis together with 6D tracking allows identification of the limiting resonances as well as the loss locations and calculation of the influence of non-linear longitudinal motion on the Touschek lifetime. The sensitivity of the lattice to these effects suggests the identification of a better working point for the machine.

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Abstract: Diamond is a 3 GeV synchrotron light source under construction at the Rutherford Appleton Laboratory in Oxfordshire (UK)[1]. The accelerator complex consists of a 100 MeV linac, a full-energy booster and a 3 GeV storage ring with 22 straight sections available for insertion devices. Installation of all three accelerators has begun and linac commissioning is due to start in summer 2005. This paper will give an overview of the status of the installation and the progress in accelerator physics studies. The Diamond facility is expected to be operational for users in 2007.

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Abstract: Polarized fluorescence spectra were recorded in the vicinity of the Se and Br K edges on crystals of the selenated protein aldose reductase in complex with a brominated inhibitor molecule. The X-ray absorption, refraction and resonant scattering tensors as a function of X-ray energy were derived from these data. Substantial dichroism and anisotropy of resonant scattering were observed in these crystals. It is predicted that these effects are present in many resonant scattering experiments in macromolecular crystallography and are likely to affect the diffraction data. As a consequence, the anomalous phasing signal in single- or multi-wavelength anomalous diffraction experiments can be optimized simply by choosing a judicious orientation of the crystal with respect to the polarization direction of the incident X-ray beam. A simple procedure is presented to achieve this, prior to any knowledge about the selenium sites.

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Abstract: NGFI-B is a ligand-independent orphan nuclear receptor of the NR4A subfamily that displays important functional differences with its homolog Nurr1. In particular, the NGFI-B ligand-binding domain (LBD) exhibits only modest activity in cell lines in which the Nurr1 LBD strongly activates transcription. To gain insight into the structural basis for the distinct activation potentials, we determined the crystal structure of the NGFI-B LBD at 2.4-Å resolution. Superimposition with the Nurr1 LBD revealed a significant shift of the position of helix 12, potentially caused by conservative amino acids exchanges in helix 3 or helix 12. Replacement of the helix 11–12 region of Nurr1 with that of NGFI-B dramatically reduces the transcriptional activity of the Nurr1 LBD. Similarly, mutation of Met414 in helix 3 to leucine or of Leu591 in helix 12 to isoleucine (the corresponding residues found in NGFI-B) significantly affects Nurr1 transactivation. In comparison, swapping the helix 11–12 region of Nurr1 into NGFI-B results in a modest increase of activity. These observations reveal a high sensitivity of LBD activity to changes that influence helix 12 positioning. Furthermore, mutation of hydrophobic surface residues in the helix 11–12 region (outside the canonical co-activator surface constituted by helices 3, 4, and 12) severely affects Nurr1 transactivation. Together, our data suggest that a novel co-regulator surface that includes helix 11 and a specifically positioned helix 12 determine the cell type-dependent activities of the NGFI-B and the Nurr1 LBD.