Maurizio Passaponti

Carbonic anhydrase inhibitors: guaiacol and catechol derivatives effectively inhibit certain human carbonic anhydrase isoenzymes (hCA I, II, IX and XII)

Abstract Carbonic anhydrases (CAs) are widespread metalloenzymes in higher vertebrates including humans. A series of phenolic compounds, including guaiacol, 4-methylguaiacol, 4-propylguaiacol, eugenol, isoeugenol, vanillin, syringaldehyde, catechol, 3-methyl catechol, 4-methyl catechol and 3-methoxy catechol were investigated for their inhibition of all the catalytically active mammalian isozymes of the Zn2+-containing CA (EC 4.2.1.1). All the phenolic compounds effectively inhibited human carbonic anhydrase isoenzymes (hCA I, II, IX and XII), with Kis in the range of 2.20–515.98 μM. The various isozymes showed diverse inhibition profiles. Among the tested phenolic derivatives, compounds 4-methyl catechol and 3-methoxy catechol showed potent activity as inhibitors of the tumour-associated transmembrane isoforms (hCA IX and XII) in the submicromolar range, with high selectivity. The results obtained from this research may lead to the design of more effective carbonic anhydrase isoenzyme inhibitors (CAIs) based on such phenolic compound scaffolds.

The amphipod Talitrus saltator as a bioindicator of human trampling on sandy beaches

The present paper assesses the use of the supralittoral amphipod Talitrus saltator as a bioindicator of the effects of human trampling on the supralittoral sandy band. Samplings in delimited areas were carried out at sites subjected to different human impact. The results showed a strong negative correlation between the number of swimmers and the sandhopper population density, while there was no clear relationship between sandhopper abundance and the other factors considered: granulometry, compactness and organic carbon content of the sand, and trace metal contents in the sand and sandhoppers. A field test of trampling conducted in a confined space showed its direct negative effect on sandhopper survival. However, trace metal analysis confirmed the ability of T. saltator to bioaccumulate some elements (Hg, Zn, Cu, Cd). Our study demonstrates that T. saltator is a good bioindicator of human impact in the supralittoral zone of sandy shores.

Composition of supralittoral sediments bacterial communities in a Mediterranean island

Marine coasts represent highly dynamic ecosystems, with sandy beaches being one of the most heterogeneous. Despite the key importance of sandy beaches as transition ecosystems between sea and land, very few studies on the microbiological composition of beach sediments have been performed. To provide a first description of microbial composition of supralittoral sediments, we investigated the composition of bacterial communities of three sandy beaches, at Favignana Island, Italy, using metagenetic approaches (Terminal-Restriction Fragment Length Polymorphism, sequencing of 16S rRNA genes by Illumina-Solexa technology, functional genes detection, and quantitative Real-Time PCR). Results showed that the investigated beaches are harboring a rich bacterial diversity, mainly composed by members of classes Alphaproteobacteria, Gammaproteobacteria, Flavobacteria and Actinobacteria. The metagenetic analysis showed profiles of decreasing beta diversity and increasing richness, as well as a differentiation of communities, along the sea-to-land axis. In particular, members of Firmicutes and Proteobacteria displayed contrasting profiles of relative abundance (to decrease and to increase, respectively) along the sea-to-land axis of the beach. Finally, a search for the presence of genes related to the nitrogen and carbon biogeochemical cycle (nifH, nosZ, pmoA/amoA) detected the presence of ammonia monoxygenase sequences (amoA) only, suggesting the presence of bacterial ammonia oxidation to some extent, probably due to members of Nitrospira, but with the lack of nitrogen fixation and denitrification.

Heat treated carbon supported iron(II)phthalocyanine oxygen reduction catalysts: elucidation of the structure–activity relationship using X-ray absorption spectroscopy

This paper focuses on studying the influence of the heat treatment on the structure and activity of carbon supported Fe(ii)phthalocyanine (FePc/C) oxygen reduction reaction (ORR) catalysts under alkaline conditions. The FePc macrocycle was deposited onto ketjen black carbon and heated treated for 2 hours under inert atmosphere (Ar) at different temperatures (400, 500, 600, 700, 800, 900 and 1000 °C). The atomic structure of Fe in each sample has been determined by XAS and correlated to the activity and ORR mechanisms determined in electrochemical half cells and in a complete H2/O2 anion exchange membrane fuel cells (AEM-FC). The results show that the samples prepared at 600 and 700 °C have the highest electrochemical catalytic activity for the ORR, consistent with the findings that the FeN4 active sites are thermally stable up to 700 °C, confirmed by both XANES linear combination fittings and EXAFS fittings. Upon annealing at temperatures above 800 °C, the FeN4 structure partially decomposes to small iron nanoparticles. The transition from the FeN4 structure to metallic Fe results in a significant loss in ORR activity and an increase in the production of undesirable HO2- during catalysis.

An XRPD and EPR spectroscopy study of microcrystalline calcite bioprecipitated by Bacillus subtilis

We report in this study the first XRPD and EPR spectroscopy characterisation of a biogenic calcite, obtained from the activity of the bacterium Bacillus subtilis. Microcrystalline calcite powders obtained from bacterial culture in a suitable precipitation liquid medium were analysed without further manipulation. Both techniques reveal unusual parameters, closely related to the biological source of the mineral, i.e., to the bioprecipitation process and in particular to the organic matrix observed inside calcite. In detail, XRPD analysis revealed that bacterial calcite has slightly higher c/a lattice parameters ratio than abiotic calcite. This correlation was already noticed in microcrystalline calcite samples grown by bio-mineralisation processes, but it had never been previously verified for bacterial biocalcites. EPR spectroscopy evidenced an anomalously large value of W6, a parameter that can be linked to occupation by different chemical species in the next nearest neighbouring sites. This parameter allows to clearly distinguish bacterial and abiotic calcite. This latter achievement was obtained after having reduced the parameters space into an unbiased Euclidean one, through an isometric log-ratio transformation. We conclude that this approach enables the coupled use of XRPD and EPR for identifying the traces of bacterial activity in fossil carbonate deposits.

Investigations on the Electrochemical Atomic Layer Growth of Bi2Se3 and the Surface Limited Deposition of Bismuth at the Silver Electrode

The Electrochemical Atomic Layer Deposition (E-ALD) technique is used for the deposition of ultrathin films of bismuth (Bi) compounds. Exploiting the E-ALD, it was possible to obtain highly controlled nanostructured depositions as needed, for the application of these materials for novel electronics (topological insulators), thermoelectrics and opto-electronics applications. Electrochemical studies have been conducted to determine the Underpotential Deposition (UPD) of Bi on selenium (Se) to obtain the Bi2Se3 compound on the Ag (111) electrode. Verifying the composition with X-ray Photoelectron Spectroscopy (XPS) showed that, after the first monolayer, the deposition of Se stopped. Thicker deposits were synthesized exploiting a time-controlled deposition of massive Se. We then investigated the optimal conditions to deposit a single monolayer of metallic Bi directly on the Ag.

MWCNTs-Supported Pd(II) Complexes with High Catalytic Efficiency in Oxygen Reduction Reaction in Alkaline Media

We report here the remarkable catalytic efficiency observed for two Pd(II) azamacrocyclic complexes supported on multiwalled carbon nanotubes (MWCNTs) toward oxygen reduction reactions. Beyond a main (>90%) 4e- process and an onset potential close to or better than those of commercial Pt electrodes, the MWCNTs functionalization strategy, aimed at chemically defined Pd(II)-based catalytic centers, allowed the half-cell to exceed the proton-exchange-membrane fuel-cell reference/target mass activity efficiency set by the U.S. Department of Energy for 2020 (440 mA/mgPGM at 0.9 V vs reversible hydrogen electrode).