Chemistry

New diorganopnicogen(III) compounds of type [CH 3 OCH 2 CH 2 N(CH 2 C 6 H 4) 2 ]ML (M ¼ Sb, L ¼ ONO 2 (3), OSO 2 CF 3 (4); M ¼ Bi, L ¼ ONO 2 (5), OSO 2 CF 3 (6), OSO 2 C 6 H 4 (CHCH 2)-4 (7) based on a heterocyclic butterfly-like tetrahydro-dibenzo[c,f][1,5]azastibocine/azabismocine skeleton were prepared by ligand exchange reactions between [CH 3 OCH 2 CH 2 N(CH 2 C 6 H 4) 2 ]MX (M ¼ Sb, X ¼ Cl (1); M ¼ Bi, X ¼ Br (2) and the appropriate silver salt. The new compounds 1 and 3e7 were structurally characterized by NMR and IR spectroscopy. For compounds 5, 7‧CHCl 3 and the hydrolysis product [{CH 3 OCH 2 CH 2 N(CH 2 C 6 H 4) 2 } BiOH 2 ][CF 3 SO 3 ] (6h) the crystal and molecular structures were determined by single-crystal X-ray diffraction. Strong transannular N/Bi interactions accompanied by strong MeO/Bi intramolecular interactions result in hypercoordinated species: 14-Bi-6 in 5, with a unisobidentate ONO 2 ligand, and 12-Bi-5 in the cation of 6h and in 7‧CHCl 3 , with a monodentate OSO 2 C 6 H 4 (CHCH 2)-4 ligand. The molecules are associated in dimeric units by Bi/p arene interactions (approx. 3.50 Å). Weak H/O (in 5), H/p arene (in 7‧CHCl 3), H/p arene, H/O and H/F (in 6h) intermolecular interactions contribute to supramolecular networks in all three compounds.

A simple method to synthesize copper, nickel and Cu-Ni nanotubes in alumina membrane by direct electrochemical deposition technique is presented. This work is divided into three main parts: elaboration of the nanostructured metals supported on Cu and Ni electroconductive support; SEM-EDX characterization of nanodeposits; electrochemical characterization of the nanostructured electrodes; Cu and Cu-Ni nanostructures were obtained by deposition through an alumina membrane (AAO) that is later dissolved. The diameter of the nanorods deposited on Cu foil is about 40-150 nanometres, which is in good agreement with the AAO membrane pore size used in the electrolysis process. The nanorods were found to be vertically aligned; their collapsing was observed with the height deposited, at high current densities. These nanostructure electrodes exhibit a high electrocatalytic activity both for oxygen reduction and carbon dioxide electroreduction to formic acid. Faradic efficiency up to 50% was obtained on (Ni-Cu) nano

Biosorption of cadmium ions from synthetic aqueous solution using popular Romanian fir tree sawdust (Abies Alba) as biosorbent, was investigated in this work. Prior to its utilization the considered biomass was washed, dried and sieved without further chemical treatments. The biosorbent was characterized using humidity, density and elemental analysis determinations and FTIR. FTIR analysis indicated that, on the biomass surface hydroxyl and carboxyl groups are presented. The effect of different biosorption parameters was studied. Higher biomass quantity, neutral pH, slightly elevated temperature and high cadmium ions concentration are all favouring the biosorption process. Equilibrium (Langmuir and Freundlich isotherm), kinetics and thermodynamics of the considered biosorption process were discussed in details. Equilibrium was best described by the Langmuir isotherm, while the kinetic of the process was best described by the pseudo-second-order model, suggesting monolayer coverage and a chemisorption process. Thermodynamic parameters showed that cadmium biosorption process on fir tree sawdust is an endothermic process. Zn 2+ and Ca 2+ from the binding sites of certain enzymes. Over the past 10 years, extensive research has been carried out to identified new and economically priced adsorbent for cadmium ions removal/preconcentration such as different types of algae, 12-16 yeast biomass, 17,18 rice husk, 19 mushrooms, 20 orange peels, 21 papaya wood, 22 pine bark, 23 aquatic moss, 24,25 tea waste 26 and various types of sawdust. As we know, the sawdust is a solid by-product abundant, inexpensive and not enough exploited material, obtained from mechanical wood processing, which can be used as biosorbent for removing different heavy metals, cadmium (II) in particular, from aqueous waste solutions. The adsorption of heavy metals by these types of materials might be attributed to their lignin, cellulose and hemicellulose, which have proteins, carbohydrates and polyphenolic compounds with carboxyl, hydroxyl, sulphate, phosphate and amino groups that can bind metal ions. Abies Alba fir is a common tree from some forest areas in Transylvania (Romania). These trees are the main source in the local wood industry and their sawdust could be a good candidate as a green and economic alternative for Cd (II) removal from wastewater. The sawdust was evaluated without any chemical pretreatment.

The present study investigates the biosorption of cadmium ions from aqueous solution onto unmodified, ultrasound and microwave treated cells of Saccharomyces cerevisiae. FTIR analysis was conducted to characterize the biosorbent. Equilibrium and kinetic studies of unmodified RBW (residual brewery waste) cell yeast and DSM 1333 (pure strain) were conducted by considering the effect of initial cadmium ions concentration. Results showed that the ultrasound and microwave treatments decrease the heavy metal uptake compared with the unmodified biomass. Langmuir and Freundlich isotherm models on both unmodified yeast cell types were used to analyze the equilibrium data. It was found that the Langmuir isotherm and pseudo-second-order kinetics models describe better the cadmium ions removal process.

Two dimesitylboryl-functionalized fluorene derivatives are synthesized and characterized. They show deep blue fluorescence in both solution and film states, with narrow spectral profiles and excellent solidstate emission efficiencies up to 94%. Due to the presence of the boron atoms, both luminophors possess low-lying LUMO energy levels as revealed by theoretical calculation. They can function as both light emitter and electron transporter in organic light-emitting diodes. A device fabricated from one of the new luminophors radiates deep blue light with a maximum emission at 432 nm (CIE ¼ 0.179, 0.128), and affords a maximum luminance of 10,320 cd m À2 , and a peak efficiency of 3.4 cd A À1 .

High-resolution crystal structures of Desulfovibrio vulgaris nigerythrin (DvNgr), a member of the rubrerythrin (Rbr) family, demonstrate an approximately 2-Å movement of one iron (Fe1) of the diiron site from a carboxylate to a histidine ligand upon conversion of the mixed-valent ([Fe2(II),Fe1(III)]) to diferrous states, even at cryogenic temperatures. This Glu↔His ligand “toggling” of one iron, which also occurs in DvRbr, thus, appears to be a characteristic feature of Rbr-type diiron sites. Unique features of DvNgr revealed by these structures include redox-induced flipping of a peptide carbonyl that reversibly forms a hydrogen bond to the histidine ligand to Fe1 of the diiron site, an intra-subunit proximal orientation of the rubredoxin-(Rub)-like and diiron domains, and an electron transfer pathway consisting of six covalent and two hydrogen bonds connecting the Rub-like iron with Fe2 of the diiron site. This pathway can account for DvNgr’s relatively rapid peroxidase turnover. The characteristic combination of iron sites together with the redox-dependent iron toggling between protein ligands can account for the selectivity of Rbrs for hydrogen peroxide over dioxygen.

The methyl-accepting chemotaxis protein, DcrH, from the anaerobic sulfate-reducing bacterium, DesulfoVibrio Vulgaris (Hildenborough), has a hemerythrin-like domain, DcrH-Hr, at its C terminus. DcrH-Hr was previously shown to contain a diiron site that binds O 2 , suggesting an O 2 -sensing function. X-ray crystal structures of diferric (met-), azido-diferric (azidomet-), and diferrous (deoxy-) DcrH-Hr reveal a "substrate tunnel" distinct from that in invertebrate hemerythrins. This tunnel is proposed to facilitate the rapid autoxidation of oxy-DcrH-Hr and suggests that sensing is triggered by O 2 binding and subsequent oxidation of the diferrous active site. The N-terminal loop of DcrH-Hr is highly ordered in both met-and azidomet-DcrH-Hr but is disordered in deoxy-DcrH-Hr. These redox-dependent conformational differences presumably transduce the sensory signal of DcrH-Hr to the neighboring methylation domain in the fulllength receptor. Given the putative cytoplasmic localization of its Hr-like O 2 -sensing domain, DcrH is proposed to serve a role in negative aerotaxis (anaerotaxis). D. Vulgaris DcrH hemerythrin-like domain; Hr, hemerythrin; myoHr, monomeric Hr present in invertebrate muscle tissue; met-DcrH-Hr, form containing a diferric site; azidomet-DcrH-Hr, form containing the azide adduct of the diferric site; deoxy-DcrH-Hr, form containing a diferrous site; MCP, methyl-chemotaxis protein; MAD, multiple anomalous dispersion.

A few members of a widespread class of bacterial and archaeal flavo-diiron proteins, dubbed FprAs, have been shown to function as either oxidases (dioxygen reductases) or scavenging nitric oxide reductases, but the questions of which of these functions dominates in vivo for a given FprA and whether all FprAs function as oxidases or nitric oxide reductases remain to be clarified. To address these questions, an FprA has been characterized from the anaerobic sulfate-reducing bacterium DesulfoVibrio Vulgaris. The gene encoding this D. Vulgaris FprA lies downstream of an operon encoding superoxide reductase and rubredoxin, consistent with an O 2 -scavenging oxidase function for this FprA. The recombinant D.

A reliable procedure is proposed for assigning the electronic structures for large biologically-relevant systems, where the size of the model confines one to the use of density functional theory (DFT) methods, and where the risk of over-interpreting DFT-derived molecular orbitals and spin densities still exists. The proposed approach focuses on the use of the only DFT-derived parameter that is unanimously recognized to be reliable: the geometry. We examine DFT-derived O-O bond lengths in formally ferrous-dioxygen models, and compare them to bond lengths in free, non metal-bound, dioxygen, superoxide and peroxide moieties. Likewise, we compare the N-O bond lengths within ferrous-nitrosyl {FeNO} 7 models, with the same parameter in free NO + , NO Å , and HNO species. This allows a calibrated, straightforward way of assigning the electronic structure in systems where electromerism makes detailed single-reference molecular orbital analysis unreliable.

Myoglobin (Mb) from gastropod mollusc Aplysia limacina shows only 20% sequence homology to the prototype sperm whale Mb but exhibits a typical Mb fold and can reversibly bind oxygen. An intriguing feature of aplysia Mb is that it lacks the distal histidine and displays a ligand stabilisation based on an arginine. Here we report the reaction of aplysia metMb with hydrogen peroxide studied by optical and electron paramagnetic resonance (EPR) spectroscopies. Two electron oxidation of the protein by H 2 O 2 results in formation of two intermediates typical for this class of reactions, the oxoferryl haem state and a globin-bound free radical. An unusual characteristic of the aplysia Mb reaction is formation, prior to haem oxidation, of an optically distinct compound with an EPR spectrum typical of the low spin Fe 3+ haem state. This compound is interpreted as the complex between H 2 O 2 and the ferric haem state (Compound 0), formed prior to cleavage of the dioxygen bond. We conclude that H 2 O 2 is singly deprotonated in Compound 0 which can thus be notated as [Fe 3+ --OOH]. A new low spin ferric haem state has been observed over the period of Compound 0 decay, and hypotheses have been formulated as to its identity and role. The location of the protein bound radical observed in aplysia Mb is discussed in light of the fact that the protein does not have any tyrosine residues, the most common site of free radical formation in the haem protein/peroxide systems. All intermediates of the reaction are kinetically characterised. Pagina 2 di 15 file:///Users/Serena/Desktop/doc/lav/APLYSIA/Reaction%20of%20A…h%20hydrogen%20peroxide%20(DOI-%2010.1039-b615770j).webarchive limacina Mb, Protein Data Bank structure file 1MBA. 2 B, Physeter catodon Mb, PDB structure file 1BZ6. 45