Comparison of the impact of ships to size-segregated particle concentrations in two harbour cities of northern Adriatic Sea.

Detailed information on in-harbour shipping contribution to size segregated particles in coastal cities are scarce, especially in the busy Mediterranean basin. This poses issues for human exposure and air quality in urban harbour agglomerates, where only criteria pollutants (i.e. PM10 and/or PM2.5) are usually monitored. In this work, particle number and mass size distributions, in a large size range (0.01-31 µm), were obtained in two coastal cities of northern Adriatic Sea: Venice (Italy) and Rijeka (Croatia). Three size ranges were investigated: nanoparticles (diameter D < 0.25 µm); fine particles (0.25 1 µm). Absolute concentrations were larger in Venice for all size ranges showing, using analysis of daily trends, a large influence of local meteorology and boundary-layer dynamics. Contribution of road transport was larger (in relative terms) in Rijeka compared to Venice. The highest contributions of shipping were in Venice, mainly because of the larger ship traffic. Maximum impact was on nanoparticles 7.4% (Venice) and 1.8% (Rijeka), the minimum was on fine range 1.9% (Venice) and <0.2% (Rijeka) and intermediate values were found in the coarse fraction 1.8% (Venice) and 0.5% (Rijeka). Contribution of shipping to mass concentration was not distinguishable from uncertainty in Rijeka (<0.2% for PM1, PM2.5, and PM10) and was about 2% in Venice. Relative contributions as function of particles size show remarkable similitudes: a maximum for nanoparticles, a quick decrease and a successive secondary maximum (2-3 times lower than the first) in the fine range. For larger diameters, the relative contributions reach a minimum at 1-1.5 µm and there is a successive increase in the coarse range. Size distributions showed a not negligible contribution of harbour emissions to nanoparticle and fine particle number concentrations, compared to PM2.5 or PM10, indicating them as a better metric to monitor shipping impacts compared to mass concentrations (PM2.5 or PM10).

Crystal structure of a eukaryotic (pea seedling) copper-containing amine oxidase at 2.2 A resolution.

BACKGROUND: Copper-containing amine oxidases catalyze the oxidative deamination of primary amines to aldehydes, in a reaction that requires free radicals. These enzymes are important in many biological processes, including cell differentiation and growth, would healing, detoxification and signalling. The catalytic reaction requires a redox cofactor, topa quinone (TPQ), which is derived by post-translational modification of an invariant tyrosine residue. Both the biogenesis of the TPQ cofactor and the reaction catalyzed by the enzyme require the presence of a copper atom at the active site. The crystal structure of a prokaryotic copper amine oxidase from E. coli (ECAO) has recently been reported. RESULTS: The first structure of a eukaryotic (pea seedling) amine oxidase (PSAO) has been solved and refined at 2.2 A resolution. The crystallographic phases were derived from a single phosphotungstic acid derivative. The positions of the tungsten atoms in the W12 clusters were obtained by molecular replacement using E. coli amine oxidase as a search model. The methodology avoided bias from the search model, and provides an essentially independent view of a eukaryotic amine oxidase. The PSAO molecule is a homodimer; each subunit has three domains. The active site of each subunit lies near an edge of the beta-sandwich of the largest domain, but is not accessible from the solvent. The essential active-site copper atom is coordinated by three histidine side chains and two water molecules in an approximately square-pyramidal arrangement. All the atoms of the TPQ cofactor are unambiguously defined, the shortest distance to the copper atom being approximately 6 A. CONCLUSIONS: There is considerable structural homology between PSAO and ECAO. A combination of evidence from both structures indicates that the TPQ side chain is sufficiently flexible to permit the aromatic grouf to rotate about the Cbeta-Cgamma bond, and to move between bonding and non-bonding positions with respect to the Cu atom. Conformational flexibility is also required at the surface of the molecule to allow the substrates access to the active site, which is inaccessible to solvent, as expected for an enzyme that uses radical chemistry.

Purification, crystallization and preliminary X-ray crystal structure analysis of copper amine oxidase from Arthrobacter globoformis.

beta-Phenylethylamine oxidase from the Gram-positive bacterium Arthrobacter globoformis has been crystallized as three crystal forms. Two belong to space group C2 and one to space group P2(1)2(1)2(1), respectively. The unit-cell volumes are consistent with one infunit of 70 644 Da per asymmetric unit for the two monoclinic forms, and with two infunits per asymmetric unit for the orthorhombic crystals. Three-dimensional intensity data have been recorded to 2.8A resolution for one of the monoclinic crystal forms and to 3A, resolution for the orthorhombic crystal form.