No abstract

No abstract

The bis(catecholamide) α,αЈ-bis(2,3-dihydroxybenzoylamino)-m-xylene (H 4 L 3 ) has been synthesized and characterised. It is an analogue of the naturally occurring siderophore azotochelin and structurally related to an approved enterobactin model. Two dioxomolybdenum() complexes of it have been synthesized, namely a di-and a mono-nuclear one. Variable-temperature proton NMR studies of the initially obtained dinuclear compound revealed that three kinetic processes are operative in Me 2 SO solution: geometrical isomerisation at lower temperatures, and inversion of configuration concomitant with dissociation into the monomer at higher temperatures. In contrast, the mononuclear complex obtained in this way isomerises and inverts almost simultaneously at 343-353 K. The crystal structure of Na 2 [MoO 2 L 3 ] confirmed the mononuclear nature of the complex and revealed that the cis, cis, cis geometrical isomer is adopted in the solid state.

No abstract

We have studied the molybdenum K-edge X-ray absorption spectra of Mo bound in the Mo-binding proteins Mop from Haemophilus influenzae, ModG from Azotobacter vinelandii and the Escherichia coli ModE transcriptional regulatory protein, and compared them with the absorption spectra of A. vinelandii ModA and monomeric molybdate. Pre-edge and extended fine structure data indicate that the Mo-binding proteins with molbindin-like domains bind tetrahedral molybdate with a Mo-O distance of 1.76 A. The molbindin subunits or sub-domains represent a novel protein fold that is used by proteins with distinct functions to bind molybdate in the cytoplasm. The high specificity of the proteins for molybdenum does not depend on a change of coordination number or geometry.