Elizabeta Tratar Pirc

Biotic and abiotic processes contribute to successful anaerobic degradation of cyanide by UASB reactor biomass treating brewery waste water.

In contrast to the general aerobic detoxification of industrial effluents containing cyanide, anaerobic cyanide degradation is not well understood, including the microbial communities involved. To address this knowledge gap, this study measured anaerobic cyanide degradation and the rearrangements in bacterial and archaeal microbial communities in an upflow anaerobic sludge blanket (UASB) reactor biomass treating brewery waste water using bio-methane potential assays, molecular profiling, sequencing and microarray approaches. Successful biogas formation and cyanide removal without inhibition were observed at cyanide concentrations up to 5 mg l(-1). At 8.5 mg l(-1) cyanide, there was a 22 day lag phase in microbial activity, but subsequent methane production rates were equivalent to when 5 mg l(-1) was used. The higher cumulative methane production in cyanide-amended samples indicated that part of the biogas was derived from cyanide degradation. Anaerobic degradation of cyanide using autoclaved UASB biomass proceeded at a rate more than two times lower than when UASB biomass was not autoclaved, indicating that anaerobic cyanide degradation was in fact a combination of simultaneous abiotic and biotic processes. Phylogenetic analyses of bacterial and archaeal 16S rRNA genes for the first time identified and linked the bacterial phylum Firmicutes and the archaeal genus Methanosarcina sp. as important microbial groups involved in cyanide degradation. Methanogenic activity of unadapted granulated biomass was detected at higher cyanide concentrations than reported previously for the unadapted suspended biomass, making the aggregated structure and predominantly hydrogenotrophic nature of methanogenic community important features in cyanide degradation. The combination of brewery waste water and cyanide substrate was thus shown to be of high interest for industrial level anaerobic cyanide degradation.

Copper(II) ion binding to cellular prion protein.

Prion diseases are fatal neurodegenerative diseases thought to arise from the post-translational conversion of normal cellular prion protein to a scrapie isoform. Experimental data suggest a role for copper(II) ions in the process. An ab initio QM/MM approach and available experimental data were combined in order to identify and evaluate three potential copper(II) ion binding sites in the C-terminal portion of the normal cellular prion protein. Our results suggest that copper(II) ion binds to His 187 but not to His 140 and His 177 of the binding site in the cellular prion protein.

Preparation and characterisation of copper(II) hyaluronate

Amorphous copper complexes of the general composition Cu(C14H20O11N)2 x xH2O have been prepared with high- and low-molecular-weight hyaluronic acid (HA). Optimal conditions for preparation are obtained at pH values from 5.0 to 5.5, with a molar ratio of HA versus Cu2+ of 1:1, and at a mass concentration of 5 and 10 mg/mL for high- (Mw = 1.8 x 10(6) Da) and low-molecular-weight sodium hyaluronate (Mw = 2 x 10(5) Da), respectively. The coordination polyhedron of the copper ion has been elucidated by EXAFS and XANES spectroscopy. Copper atoms are octahedrally coordinated in both cases with four equatorial Cu-O bond lengths of 1.95 A, and two axial Cu-O bonds of 2.46 A. Visible spectra of acidic aqueous solution suggest that substitution of axial oxygens by NH groups occurs at pH 6.5 or higher. If the pH value of the copper(II) hyaluronate solution increases above 6.5, the coordination of copper(II) changes. It is very likely that the N atom coming from the acetamido group enters into the coordination sphere of the copper(II) ion.

Synthesis, structure, antioxidant and SOD-mimetic activity of [Cu(xanthurenate)(nicotinamide)(H2O)] complexes

This study reports the synthesis of novel mixed ligand complexes of copper(II) with the xanthurenate anion (Xan2−) and nicotinamide ligand (NA): [Cu(Xan)(NA)(H2O)]·H2O and [Cu(Xan)(NA)(H2O)]·3H2O. The compounds were characterized by single crystal X-ray diffraction, IR spectroscopy, and thermal analysis. The first coordination sphere of copper(II) in [Cu(Xan)(NA)(H2O)] consists of a water molecule, a nicotinamide ligand coordinated via the pyridine nitrogen and a xanthurenate dianion coordinated in a tridentate manner via carboxylate oxygen, nitrogen, and phenolate oxygen. The five donor atoms define a distorted square pyramid whose apex is occupied by the aqua ligand. The antioxidant activities of the compounds were investigated by the 2,2-diphenyl-1-picrylhydrazyl scavenging method, which showed that the IC50 values for both compounds are higher than for related [Cu(Xan)(H2O)2] complex. The title compounds also exhibit superoxide dismutase mimetic activity.Graphical abstract

Supramolecular framework of a dinuclear cadmium complex with a dianion of xanthurenic acid [Cd2(Xan)2(H2O)4]

Reaction of the sodium salt of xanthurenic acid (8-hydroxy-4-oxo-1H-quinoline-2-carboxylic acid, H2Xan) with cadmium(II) cations in aqueous solution leads to the formation of the dinuclear complex [Cd2(Xan)2(H2O)4]. The structure of this compound was studied by single-crystal X-ray diffraction, IR spectroscopy, and via thermal and elemental analysis. The [Cd2(Xan)2(H2O)4] complex consists of two cadmium(II) ions bridged by a pair of carboxylate oxygen atoms from two Xan2− ligands. The coordination environments of the two metal atoms are similar—each consists of two Xan2− ligands and two aqua ligands. Each metal ion is in a pentagonal pyramidal coordination environment, which is highly unusual. An intricate pattern of hydrogen bonds links the molecules in the complex into a three-dimensional structure.Graphical abstract

Aerobic and anaerobic biodegradation potential of leachate from old active landfill

AbstractA common problem of biological treatment of landfill leachates is high toxicity and low biodegradability. Leachates from old landfills do not exhibit high toxicity and if the landfill is still filled by waste, they may contain sufficient amounts of biodegradable organic matter. With the aim of evaluating biotreatability of leachates from old, but active landfill, aerobic and anaerobic degradation assessment procedures were carried out. Investigated leachates showed low toxicity to aerobic and anaerobic micro-organisms. During biodegradability tests, anaerobic biological treatment did not lead to measurable production of biogas. Leachates were well degraded under aerobic condition in ready (66%) and inherent (78%) biodegradability tests, while simulation test in pilot sequencing batch reactor showed that leachates can be successfully treated, mixed with sewage up to 10% v/v.

A Computational Study of Calcium(II) and Copper(II) Ion Binding to the Hyaluronate Molecule

The hyaluronate molecule is a negatively charged polysaccharide that performs a plethora of physiological functions in many cell tissues depending on its conformation. In the present paper, molecular modeling at three levels of theory and two basis sets was used to gain a deeper insight in the complex molecular structure of calcium(II) and copper(II) hyaluronate. Simulation results were compared with the experimental data (EXAFS or X-ray). It was found that B3LYP does not properly reproduce the experimental data while the HF and M06 methods do. Simulation data confirm that the N-acetyl group of the N-acetylglucosamine residue does not participate in the coordination bonding to the calcium(II) or copper(II) ion, as evident from the experimental data.