The platinum hexahalides have an octahedral arrangement of six halogen atoms bound to a Pt centre, thus having an octahedral shape that could prove to be useful in interpreting poor electron-density maps. In a detailed characterization, PtI6 chemically transformed to a square-planar PtI3 complex bound to the Nδ atom of His15 of HEWL was also observed, which was not observed for PtBr6 or PtCl6.
Abstract. Multi heavy atom cluster compounds like K 2 PtBr 6 offer a way forward to solve, de novo, unknown protein structures by powder diffraction involving dispersive (measured at two X-ray wavelengths) and isomorphous intensity differences as a complement to micro-crystallography or by using both approaches in combination. Towards this end, using the ESRF high resolution synchrotron X-ray powder diffraction beamline ID31, we have recorded high quality protein powder diffractograms at the platinum LIII and bromine K absorption edges, as well as reference wavelengths, for K 2 PtBr 6 bound to lysozyme. These experiments were conducted at 80K to protect the sample against X-radiation damage as much as possible and also to fix the K 2 PtBr 6 bound state, which seemed to show instability at room temperature. With multiple powder pattern analysis we extracted intensities and showed the PtBr 6 bound in lysozyme using 'omit electron density maps'. In addition the wavelength dispersive Fourier around the Br K edge shows up the bromine signal at PtBr 6 binding site 1 in one of the six samples tested. To better understand the chemical properties of this heavy atom compound we have elucidated the detailed binding behaviour using single crystal analyses with time-resolved freeze quenching after soak times of 10, 90 and 170 minutes. Whilst the quick soaking of 10 to 30 minutes, used at ESRF ID31 shows clear binding, there is increasing binding strength with increasing soak time. Thus, these time-resolved analytical chemistry results show that further heavy atom signal optimizations are possible. Prospects for extending our approach to the yet larger isomorphous and wavelength dispersive signal case of Ta 6 Br 12 bound to lysozyme are also described.
A proton-conducting coordination polymer of anionic one-dimensional (1D) chains of Zn phosphate and protonated imidazole with the formula of [Zn(HPO)(HPO)](ImH) has been used as a novel supercapacitor material in aqueous electrolytes. This material stores charges via a proton-hopping mechanism.
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