Halogens in seaweeds : Biological and Environmental Significance

Acknowledgments: We are grateful to the Kuwait Institute for Scientific Research (KISR) for PhD 1129 funding for Hanan Al-Adilah and to the European Commission for a Marie Curie International In- 1130 coming Fellowship (Horizon 2020 Research and Innovation Programme of the European Union un- 1131 der the Marie Skłodowska-Curie grant agreement No 839151) to Puja Kumari. We would equally 1132 like to thank the UK Natural Environment Research Council for their support to FCK (program 1133 Oceans 2025 – WP 4.5 and grants NE/D521522/1 and NE/J023094/1) and LJC (grant NE/N009983/1). 1134 This work also received support from the Marine Alliance for Science and Technology for Scotland 1135 pooling initiative. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and 1136 contributing institutions. MCF, FCK and HAA thank the Lorentz Center (funded by the Netherlands 1137 Organization for Scientific Research, NWO, and the University of Leiden) for the organization of 1138 the workshop ‘IODINE: Biogeochemical Cycle of Iodine and Human Health’ (Oct. 4-6, 2017) which 1139 partly inspired this review. LJC acknowledges funding from the European Research Council (ERC) 1140 under the European Union’s Horizon 2020 programme (project O3-SML; grant agreement no. 1141 833290).Peer reviewedPublisher PD

Emission of volatile halogenated compounds, speciation and localization of bromine and iodine in the brown algal genome model Ectocarpus siliculosus

This study explores key features of bromine and iodine metabolism in the filamentous brown alga and genomics model Ectocarpus siliculosus. Both elements are accumulated in Ectocarpus, albeit at much lower concentration factors (2-3 orders of magnitude for iodine, and < 1 order of magnitude for bromine) than e.g. in the kelp Laminaria digitata. Iodide competitively reduces the accumulation of bromide. Both iodide and bromide are accumulated in the cell wall (apoplast) of Ectocarpus, with minor amounts of bromine also detectable in the cytosol. Ectocarpus emits a range of volatile halogenated compounds, the most prominent of which by far is methyl iodide. Interestingly, biosynthesis of this compound cannot be accounted for by vanadium haloperoxidase since the latter have not been found to catalyze direct halogenation of an unactivated methyl group or hydrocarbon so a methyl halide transferase-type production mechanism is proposed

Trace analysis in water-alcohol mixtures by continuous p-H-2 hyperpolarization at high magnetic field

Contains fulltext : 192300.pdf (Publisher’s version ) (Open Access

Monitoring Heterogeneously Catalyzed Hydrogenation Reactions at Elevated Pressures Using In-Line Flow NMR

Contains fulltext : 209509.pdf (publisher's version ) (Open Access

Self-assembly of porphyrin hexamers via bidentate metal-ligand coordination

The supramolecular assembly of metal-porphyrin hexamers with bidentate ligands in chloroform solutions is demonstrated by UV/Vis and H-1 NMR-titrations, and Small Angle Neutron Scattering (SANS) experiments. Titrations of zinc porphyrin hexamer Zn1 with 1,4-diazabicyclo[2,2,2]octane (DABCO) revealed that at a DABCO/Zn1 molar ratio of 3, intermolecular sandwich complexes are formed, which can be considered as circular-shaped porphyrin ladders. These supramolecular complexes further aggregate into larger polymeric stacks, as a result of a combination of cooperativity effects, - stacking interactions, and chelate effects. The presence of rodlike assemblies in solution, formed by assembly of Zn1 and DABCO, is confirmed by SANS-experiments. Using a model for cylindrical assemblies, curve fitting calculations reveal that rods with an average length of 26 nm and a radius of 30-35 angstrom were formed, corresponding to columnar stacks of approximately 30 hexamer molecules. In contrast, the metal-free hexamer H(2)1 did not form extended assemblies due to the absence of coordinative intermolecular interactions

Distorted octahedral coordination of tungstate in a subfamily of specific binding proteins

Bacteria and archaea import molybdenum andtungsten from the environment in the form of theoxyanions molybdate (MoO42-) and tungstate (WO42-).These substrates are captured by an external, high-affinitybinding protein, and delivered to ATP binding cassettetransporters, which move them across the cell membrane.We have recently reported a crystal structure of themolybdate/tungstate binding protein ModA/WtpA fromArchaeoglobus fulgidus, which revealed an octahedrallycoordinated central metal atom. By contrast, the previouslydetermined structures of three bacterial homologs showedtetracoordinate molybdenum and tungsten atoms in theirbinding pockets. Until then, coordination numbers abovefour had only been found for molybdenum/tungsten inmetalloenzymes where these metal atoms are part of thecatalytic cofactors and coordinated by mostly non-oxygenligands. We now report a high-resolution structure ofA. fulgidus ModA/WtpA, as well as crystal structures offour additional homologs, all bound to tungstate. Thesecrystal structures match X-ray absorption spectroscopymeasurements from soluble, tungstate-bound protein, andreveal the details of the distorted octahedral coordination.Our results demonstrate that the distorted octahedralgeometry is not an exclusive feature of the A. fulgidusprotein, and suggest distinct binding modes of the bindingproteins from archaea and bacteria