Coordinated cations in dipicolinato complexes of divalent metal ions

Several salts of alkali, alkaline earth metal and organic ammonium cations of a complex anion [ML₂]²⁻ {Where L = dipicolinato dianion, M = copper(II), nickel(II) and zinc(II)} are prepared. The coordination effect of [ML₂]²⁻ with the cations such as sodium, potassium, calcium, magnesium, and organic cations namely diammonium cation of 1,5-pentanediamine, diammonium cation of 1,8-octyldiamine, mono ammonium cation of 4-aminobenzylamine are studied by determining their X-ray crystal structures. Depending on the nature of cations, four different types of structures are obtained. When calcium is the cation a polymeric structure with calcium ions bridging the [ML₂]²⁻ is observed. The salts having sodium and potassium cations form polymeric chain like structures by oxo and aqua bridges. In the case of magnesium, the hydrated form of magnesium cations coordinates to [ML₂]²⁻. The organic ammonium salts of [ML₂]²⁻ have the structural features of conventional ionic complexes. These salts easily exchange cations. The organic ammonium salts of [ML₂]²⁻ decomposes to give the corresponding metal oxides at relatively low temperature range 300-450 °C.     

Similar structural feature observed in the crystal packing of [Ni(dmit)2] salts of geometrical isomer of methoxycarbonyl pyridinium

The crystal structures of the C-H?O hydrogen-bonded, 1:1 complex salts of with [Ni(dmit)₂]⁻ 2MMP, 3MMP and 4MMP (ortho-, meta-, and para-methoxycarbonyl N-methyl-pyridinium, respectively) cations with have been investigated. All complex salts formed non-segregated stacks with the anions being sandwiched between layers or dimers of cations. Within these salts, the arrangement of the counter cations are structurally modulated by two weak intermolecular hydrogen bonds between the hydrogen of the pyridinium ring, methyl group or one of the two and the CO group of the cations. The alignment of Ni(dmit)₂ molecules is found to be mainly governed by the attached position of methoxycarbonyl group. Powders of (2MMP)[Ni(dmit)₂], (3MMP)[Ni(dmit)₂] and (4MMP)[Ni(dmit)₂] salts exhibited room temperature conductivities of 4.33 × 10⁻¹⁰, 1.80 × 10⁻⁶ and 5.60 × 10⁻⁶ S cm⁻¹, respectively.     

BEDT-TTF salts of the unsymmetrical [M(tfadt)2] dithiolene complexes (M = Ni, Au; tfadt = S2C2(CN)(CF3))

Two closely related 1:1 salts are obtained upon electrocrystallization of BEDT-TTF (BEDT-TTF: bis(ethylenedithio)tetrathiafulvalene) in the presence of the isosteric [M(tfadt)₂]⁻ dithiolene complexes (tfadt: 1-trifluoromethyl-2-cyano-1,2-dithiolato), which essentially differ by their spin state, S = 0 in [Au(tfadt)₂]⁻, S = 1/2 in [Ni(tfadt)₂]⁻. In both [BEDT-TTF][M(tfadt)₂] salts, the BEDT-TTF radical cations form chains with a strong lateral overlap and strong antiferromagnetic interactions while the paramagnetic anions in the nickel-containing salt [BEDT-TTF][Ni(tfadt)₂] are essentially non-interacting. The structural differences between the nickel and gold complexes are analyzed and discussed.     

Dynamics of microbial community for X-3B wastewater decolorization coping with high-salt and metal ions conditions

In this study, decolorization of Reactive Brilliant Red X-3B wastewater by the biological process coping with high salinity and metal ions conditions was investigated, and 16S rDNA based fingerprint technique was used to investigate microbial population dynamics. Results of sequencing batch tests showed that the microbial community could keep efficient with high concentration of dye (1100 mg L⁻¹), salt (150 g L⁻¹ NaCl) and some metal ions such as Mg²⁺, Ca²⁺ (1–10 mmol L⁻¹) and Pb²⁺ (1 mmol L⁻¹). 16S rDNA-based molecular analysis techniques demonstrated that the microbial community shifted during the acclimatization process affected by salt or metal ions. Some stains similar to Bacillus, Sedimentibacter, Pseudomonas, Clostridiales, Streptomyces and some uncultured clones acted for the dynamic succession, supposed as potential decolorization bacteria. This study provided insights on the decolorization capability and the population dynamic shifts during decolorization process of azo dye wastewater coping with salt and metal ions.     

TTF charge transfer salts containing cyanometallate anions [M(phen)(CN)4] (M = Cr or Fe; phen = 1,10-phenanthroline)

Two new charge transfer salts of TTF with the counter anions [M(phen)(CN)₄]⁻ (phen = 1,10-phenanthroline, M = Cr (I) and Fe (II)) are described. The structures consist of alternating stacks of dimerised TTF⁺ cations and [M(phen)(CN)₄]⁻ anions and they are linked together by many short S?S contacts and hydrogen bonds. Within the organic stack, two dimerised TTF⁺ cations are arranged in a slipped face-to-face mode with short intra-dimer and long inter-dimer S?S distances. Strong antiferromagnetic exchange was found in the TTF⁺ dimers. Conductivity measurements show that compound I is a semiconductor.     

Aerial and underwater carbon metabolism of a Zostera noltii seagrass bed in the Banc d’Arguin, Mauritania

Community respiration and primary production were measured in a dense intertidal Zostera noltii bed on the Banc d’Arguin, Mauritania (West Africa) under aerial and submerged conditions. Metabolism was studied in situ in dark and transparent benthic chambers. CO₂ fluxes in the air were measured over a series of short-term incubations (3 min) using an infrared gas analyzer. Dissolved inorganic carbon fluxes were calculated from concentration changes during one-hour underwater incubations. Air and underwater irradiance levels were measured every minute throughout the experiments. Carbon respiration was lower in the air (2.2 mmol m⁻² h⁻¹) than underwater (5.0 mmol m⁻² h⁻¹); similarly, a production-irradiance model fitted to the data indicated that gross maximal photosynthetic rate was markedly lower during emergence (6.0 mmol C m⁻² h⁻¹) than under water (42.7 mmol C m⁻² h⁻¹). The δ¹³C values observed in shoots indicated a decrease in atmospheric CO₂ contribution, compared to dissolved inorganic carbon, in Z. noltii metabolism along a depth gradient within a single location. As the seagrass bed remains under a thin layer of water at low tide at the studied site, the large difference in primary production can be mainly attributed to photosynthesis inhibition by high pH and oxygen concentration, as well as to the negative feedback of self-shading by seagrass leaves during emersion. The observed differences in respiration can be explained by the oxygen deficit at night during low tide near the sediment surface, a deficit that is consistent with the abundance of anoxia-tolerant species.     

Use of a cubane-type Mo3CoS4 molecular cluster as paramagnetic unit in the synthesis of hybrid charge-transfer salts

Selective substitution of the chlorine atom coordinated to cobalt in the paramagnetic Mo₃(CoCl)S₄(dmpe)₃Cl₃ (dmpe = 1,2-bis(dimethylphosphanyl) ethane) complex with a S = 1/2 ground state has been achieved by iodine oxidation to afford the also paramagnetic [Mo₃(CoI)S₄(dmpe)₃Cl₃]I ([1]I) salt with a S = 1 ground state in almost quantitative yield. Replacement of chorine by iodine has no significant effect on the structural and electrochemical properties of the Mo₃CoS₄ system. Metathesis of the [1]I salt with the paramagnetic nickel anionic dithiolate [Ni(mnt)₂]⁻ (mnt = maleonitrilodithiolate) affords [1]₂[Ni(mnt)₂]. The stoichiometry evidenced by X-ray analysis reveals that reduction of the [Ni(mnt)₂]⁻ radical to the corresponding diamagnetic closed shell [Ni(mnt)₂]²⁻ dianion, presumably via dismutation, has occurred during the metathesis process. The crystal structure of [1]₂[Ni(mnt)₂] consists of [Ni(mnt)₂]²⁻ dianions sandwiched by two cluster 1⁺ cations which yield {1⁺·[Ni(mnt)₂]²⁻·1⁺} subunits arranged along the crystallographic c axis. Magnetic susceptibility measurements for [1]₂[Ni(mnt)₂] show a χT product of 0.99 emu K/mol largely unchanged in the 10-300 K range. This behavior agrees with the presence of an S = 1 cluster 1⁺ cation while the Ni(mnt)₂ moiety does not contribute to the paramagnetism of the sample.     

Hofmeister effects on activity and stability of alkaline phosphatase

We have studied the effects on alkaline phosphatase of adding high concentrations (normally 1.0 M) of simple salts. It is necessary to allow for significant effects of salts on the extinction coefficient of the reaction product, and on the apparent pH of the buffer. Both activity and stability of the enzyme correlate well with the Hofmeister series in terms of the salt's kosmotropic/chaotropic properties, which are assessed by the Jones–Dole viscosity B coefficients (B₊ for cations and B₋ for anions). The catalytic activity or V_max/K_m of the enzyme showed a bell-shaped relationship with the (B₋ − B₊) values of the salts present, being optimal with salts (such as NaCl, KCl, and KNO₃) where the anion and cation have similar kosmotropic/chaotropic properties. This effect is believed to be enzyme-specific and relates to the impact of both cations and anions on the enzyme's surface pH, active site, and catalytic mechanism. Anions play a more predominant role than cations in affecting enzyme stability. The rate of irreversible thermal inactivation is strongly reduced by addition of kosmotropic anions like SO₄²⁻ (half-life increased from 8 to 580 min at 60 °C). This effect is general and the mechanism probably involves the ability of the ions to affect the water solvation layer around the enzyme molecule and to interact with both the surface and internal structure of the enzyme.     

SOS1 gene overexpression increased salt tolerance in transgenic tobacco by maintaining a higher K(+)/Na(+) ratio

Crop productivity is greatly affected by soil salinity, so improvement in salinity tolerance of crops is a major objective of many studies. We overexpressed the Arabidopsis thaliana SOS1 gene, which encodes a plasma membrane Na⁺/H⁺ antiporter, in tobacco (Nicotiana tabacum cv. Xanthi-nc). Compared with nontransgenic plants, seeds from transgenic tobacco had better germination under 120 mM (mmol L⁻¹) NaCl stress; chlorophyll loss in the transgenic seedlings treated with 360 mM NaCl was less; transgenic tobacco showed superior growth after irrigation with NaCl solutions; and transgenic seedlings with 150 mM NaCl stress accumulated less Na⁺ and more K⁺. In addition, roots of SOS1-overexpressing seedlings lost less K⁺ instantaneously in response to 50 mM NaCl than control plants. These results showed that the A. thaliana SOS1 gene potentially can improve the salt tolerance of other plant species.     

Electrochemical monitoring of chlorhexidine digluconate effect on polyelectrolyte immobilized bacteria and kinetic cell adhesion

The electrochemical impedance spectroscopy (EIS) technique has been used as a sensitive method to explore the effect of antibacterial molecules on immobilized bacteria and biofilm formation. In this work, we describe the electrochemical spectroscopy as a powerful method to monitor the effect of Chlorhexidine Digluconate (CHX-Dg) on polyelectrolyte immobilized Escherichia coli K12 MG1655 and the kinetics of cell adhesion on gold electrodes. The experimental impedance data were modelised with a Zview program to find the best equivalent electrical circuit and analyse its parameter's properties. Polyelectrolyte multilayer formation on the electrode surface and bacteria immobilization greatly increased the electron-transfer resistance (R_et) and reduced the constant phase element (CPE_dl). The effect of CHX-Dg was studied in a 0.5 × 10⁻⁴ mmol l⁻¹ to 0.5 mmol l⁻¹ range. The relation between the evolution of R_et and CHX-Dg concentration was found to be negatively correlated. When CHX-Dg was added, the electrochemical monitoring of the bacterial kinetic adhesion showed that the electrode's capacity (C_P) variation remained stable, demonstrating that the addition of CHX-Dg in the broth inhibited bacterial adhesion.     

Hemolymph ion regulation and kinetic characteristics of the gill (Na⁺, K⁺)-ATPase in the hermit crab Clibanarius vittatus (Decapoda, Anomura) acclimated to high salinity

We examine hemolymph ion regulation and the kinetic properties of a gill microsomal (Na⁺, K⁺)-ATPase from the intertidal hermit crab, Clibanarius vittatus, acclimated to 45‰ salinity for 10 days. Hemolymph osmolality is hypo-regulated (1102.5 ± 22.1 mOsm kg⁻¹ H₂O) at 45‰ but elevated compared to fresh-caught crabs (801.0 ± 40.1 mOsm kg⁻¹ H₂O). Hemolymph [Na⁺] (323.0 ± 2.5 mmol L⁻¹) and [Mg²⁺] (34.6 ± 1.0 mmol L⁻¹) are hypo-regulated while [Ca²⁺] (22.5 ± 0.7 mmol L⁻¹) is hyper-regulated; [K⁺] is hyper-regulated in fresh-caught crabs (17.4 ± 0.5 mmol L⁻¹) but hypo-regulated (6.2 ± 0.7 mmol L⁻¹) at 45‰. Protein expression patterns are altered in the 45‰-acclimated crabs, although Western blot analyses reveal just a single immunoreactive band, suggesting a single (Na⁺, K⁺)-ATPase α-subunit isoform, distributed in different density membrane fractions. A high-affinity (Vm = 46.5 ± 3.5 U mg⁻¹; K_0.5 = 7.07 ± 0.01 μmol L⁻¹) and a low-affinity ATP binding site (Vm = 108.1 ± 2.5 U mg⁻¹; K_0.5 = 0.11 ± 0.3 mmol L⁻¹), both obeying cooperative kinetics, were disclosed. Modulation of (Na⁺, K⁺)-ATPase activity by Mg²⁺, K⁺ and NH₄⁺ also exhibits site-site interactions, but modulation by Na⁺ shows Michaelis-Menten kinetics. (Na⁺, K⁺)-ATPase activity is synergistically stimulated up to 45% by NH₄⁺ plus K⁺. Enzyme catalytic efficiency for variable [K⁺] and fixed [NH₄⁺] is 10-fold greater than for variable [NH₄⁺] and fixed [K⁺]. Ouabain inhibited ≈80% of total ATPase activity (K_I = 464.7 ± 23.2 μmol L⁻¹), suggesting that ATPases other than (Na⁺, K⁺)-ATPase are present. While (Na⁺, K⁺)-ATPase activities are similar in fresh-caught (around 142 nmol Pi min⁻¹ mg⁻¹) and 45‰-acclimated crabs (around 154 nmol Pi min⁻¹ mg⁻¹), ATP affinity decreases 110-fold and Na⁺ and K⁺ affinities increase 2-3-fold in 45‰-acclimated crabs.     

Electrochemical and spectroscopic studies on electron-transfer reaction between novel water-soluble tetrazolium salts and a superoxide ion

The electrochemical behavior of water-soluble tetrazoliums (WST) has been studied by cyclic voltammetry. WST was reduced in a two-step process. The first reduction peak at −0.20 V versus Ag/AgCl corresponds to one-electron reduction reaction and is independent of pH. The second reduction peak at −0.47 V corresponds to one-electron/one-proton process. Since the first reduction peak potential is more positive than the formal potential of O₂/O₂ ⁻ redox couple, WST can be reduced by O₂ ⁻. A possible mechanism is proposed for the reduction of WST dyes by O₂ ⁻. Their reduced forms, which are called formazan, exhibited the absorbance maxima in the range of 435-537 nm with large molar extinction coefficients ((1-2) × 10⁴ M⁻¹ cm⁻¹). The electron-transfer reactions between O₂ ⁻ and WST dyes were quantitatively examined by stopped-flow spectroscopy using KO₂/DMSO as O₂ ⁻ generating system and the second-order rate constants of the order of 10⁴ M⁻¹ s⁻¹ were obtained. These values are comparable to that obtained for the conventional nitroblue tetrazolium (NBT).     

Hexachlororhenate(IV) salts of organic radical cations

The ionic salts (p-rad)₂[ReCl₆] (1) and (m-rad)₂[ReCl₆] (2) (p/m-rad = 2-(4/3-N-methylpyridinium)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl-3-N-oxide) have been prepared and their crystal structures determined by single-crystal X-ray diffraction. The nitronyl nitroxide cations in compound 1 show a layered disposition, whereas the [ReCl₆]²⁻ units are placed between these layers. The nitronyl nitroxide cations in compound 2 adopt an hexagonal array but they do not result in layers. Bulk magnetic properties of 1 and 2 have been investigated in the temperature range 2-300 K. Both compounds show weak but significant intermolecular antiferromagnetic interactions.     

Sorption of phosphate onto giant reed based adsorbent: FTIR, Raman spectrum analysis and dynamic sorption/desorption properties in filter bed

A sorption process for the removal of phosphate was evaluated under various conditions using a filter bed packed with giant reed (GR) based adsorbent. FTIR spectrum measurement validated the existence of grafted amine groups in the adsorbent and Raman spectrum displayed the characteristic peaks of different forms of phosphate. The column sorption capacity of the adsorbent for phosphate was 54.67 mg g⁻¹ in comparison with the raw GR of 0.863 mg g⁻¹. Influent pH demonstrated an essential effect on the performance of the filter bed as compared to other influent conditions (flow rates and influent concentrations) and the optimal pH was selected at 5.0-10.0. Eluents of HCl, NaOH and NaCl solutions with concentrations of 0.01-0.1 mol l⁻¹ showed the excellent capacities for desorption of phosphate from the adsorbent, and their elution processes could be finished in 90 min.     

Growth, reproductive and photosynthetic responses to copper in the yellow-horned poppy, Glaucium flavum Crantz.

Glaucium flavum Crantz. is found in an anthropized coastal grassland at the joint estuary of the Tinto and Odiel rivers (SW Spain), growing under the influence of high levels of copper contamination derived from nearby petrochemical industries, with no obvious adverse affects on the performance of the plant. In addition, this species exhibits a series of ecological characteristics which may render it appropriate for use in the phytoremediation of contaminated areas. Nonetheless, the response of G. flavum to elevated copper concentrations has not been studied. A greenhouse experiment was conducted to investigate the effects of a range of Cu concentrations (0 to 47 mmol l⁻¹) on the growth, reproduction and photosynthetic performance of G. flavum, by measuring relative growth rate, fruit and seed production, chlorophyll fluorescence parameters, gas exchange and photosynthetic pigment concentrations. We also determined total copper, nitrogen, phosphorous, sulphur, calcium and magnesium concentrations. G. flavum survived with concentrations of up to 730 mg Cu kg⁻¹ DW in the leaves, when treated with 30 mmol Cu l⁻¹ (2000 mg l⁻¹). Quantum efficiency of PSII, net photosynthesis rate, as well as leaf Ca and Mg concentrations were all negatively affected by Cu concentrations greater than 9 mmol l⁻¹ in the nutrient solution. Our results indicate that the reduction in photosynthetic performance may be attributed to the adverse effect of excess Cu on the photosynthetic apparatus of the plant, both directly, via a decrease in pigment concentrations, and indirectly, via interference of Cu with Ca ions of PSII. Growth and seed production were only slightly affected by leaf tissue concentrations as high as 230 mg Cu kg⁻¹ dry mass, which suggests that this species could play an important role in phytoremediation of Cu-contaminated soils.     

Anaerobic degradation of tetrachlorobisphenol-A in river sediment

This study investigated the anaerobic degradation of tetrachlorobisphenol-A (TCBPA) in sediment samples collected at three sites along the Erren River in southern Taiwan. TCBPA anaerobic degradation half-lives (t_1/2) in the sediment were 12.6, 16.9 and 21.7 d at concentrations of 50, 100, and 250 ??g g⁻¹, respectively. TCBPA (50 ??g g⁻¹) anaerobic degradation half-lives (t_1/2) in the sediment were 10.1, 11.8, 11.0, 11.6, 10.8, 9.1, 8.5, 18.2, 19.3, and 16.1 d by the addition of yeast extract (5 mg l⁻¹), cellulose (0.96 mg l⁻¹), sodium chloride (1%), brij 30 (130 mg l⁻¹), brij 35 (43 mg l⁻¹), rhamnolipid (55 ??M), surfactin (91 ??M), phthalic esters (2 mg l⁻¹), nonylphenol (2 mg l⁻¹), and heavy metals (2 mg l⁻¹), respectively. The degradation rate of TCBPA was enhanced by the addition of yeast extract, cellulose, sodium chloride, brij 30, brij 35, rhamnolipid, or surfactin. However, it was inhibited by the addition of phthalic esters, nonylphenol, or heavy metals. Also noted was the presence of dichlorobisphenol-A and bisphenol-A, two intermediate products resulting from the anaerobic degradation of TCBPA accumulated in the sediments.     

Formation and structural chemistry of the unusual cyanide-bridged dinuclear species [Ru2(NN)2(CN)7] (NN = 2,2′-bipyridine or 1,10-phenanthroline)

Crystallisation of simple cyanoruthenate complex anions [Ru(NN)(CN)₄]²⁻ (NN = 2,2′-bipyridine or 1,10-phenanthroline) in the presence of Lewis-acidic cations such as Ln(III) or guanidinium cations results, in addition to the expected [Ru(NN)(CN)₄]²⁻ salts, in the formation of small amounts of salts of the dinuclear species [Ru₂(NN)₂(CN)₇]³⁻. These cyanide-bridged anions have arisen from the combination of two monomer units [Ru(NN)(CN)₄]²⁻ following the loss of one cyanide, presumably as HCN. The crystal structures of [Nd(H₂O)_5.5][Ru₂(bipy)₂(CN)₇] · 11H₂O and [Pr(H₂O)₆][Ru₂(phen)₂(CN)₇] · 9H₂O show that the cyanoruthenate anions form Ru-CN-Ln bridges to the Ln(III) cations, resulting in infinite coordination polymers consisting of fused Ru₂Ln₂(μ-CN)₄ squares and Ru₄Ln₂(μ-CN)₆ hexagons, which alternate to form a one-dimensional chain. In [CH₆N₃]₃[Ru₂(bipy)₂(CN)₇] · 2H₂O in contrast the discrete complex anions are involved in an extensive network of hydrogen-bonding involving terminal cyanide ligands, water molecules, and guanidinium cations. In the [Ru₂(NN)₂(CN)₇]³⁻ anions themselves the two NN ligands are approximately eclipsed, lying on the same side of the central Ru-CN-Ru axis, such that their peripheries are in close contact. Consequently, when NN = 4,4′-^tBu₂-2,2′-bipyridine the steric bulk of the t-butyl groups prevents the formation of the dinuclear anions, and the only product is the simple salt of the monomer, [CH₆N₃]₂[Ru(^tBu₂bipy)(CN)₄] · 2H₂O. We demonstrated by electrospray mass spectrometry that the dinuclear by-product [Ru₂(phen)₂(CN)₇]³⁻ could be formed in significant amounts during the synthesis of monomeric [Ru(phen)(CN)₄]²⁻ if the reaction time was too long or the medium too acidic. In the solid state the luminescence properties of [Ru₂(bipy)₂(CN)₇]³⁻ (as its guanidinium salt) are comparable to those of monomeric [Ru(bipy)(CN)₄]²⁻, with a ³MLCT emission at 581 nm.     

Assessment of olive-mill wastewater as a growth medium for lipase production by Candida cylindracea in bench-top reactor

Olive-mill wastewater (OMW) was investigated for its suitability to serve as a medium for lipase production by Candida cylindracea NRRL Y-17506. The OMW that best supported enzyme production was characterized by low COD and low total sugars content. In shake flask batch cultures, OMW supplementation with 2.4 g l⁻¹ NH₄Cl and 3 g l⁻¹ olive oil led to an enzyme activity of about 10 U ml⁻¹. The addition of glucose or malt extract and supplements containing organic N (e.g., peptone, yeast extract) either depressed or did not affect the enzyme production. Further experiments were then performed in a 3-l stirred tank reactor to assess the impact of medium pH and stirring speed on the yeast enzyme activity. The lipase activity was low (1.8 U ml⁻¹) when the pH was held constant at 6.5, significantly increased (18.7 U ml⁻¹) with uncontrolled pH and was maximum (20.4 U ml⁻¹) when the pH was let free to vary below 6.5. A stirring regime, that varied depending on the dissolved oxygen concentration in the medium, both prevented the occurrence of anoxic conditions during the exponential growth phase and enabled good lipase production (i.e., 21.6 U ml⁻¹) and mean volumetric productivity (i.e., 123.5 U l⁻¹ h⁻¹).     

Influence of NaCl and Na2SO4 on the kinetics and dye decolorization ability of crude laccase from Ganoderma lucidum

In a solid state medium using yellow passion fruit waste as substrate, the basidiomycete Ganoderma lucidum produced a laccase as the main ligninolytic enzyme. This crude enzyme presented Michaelian behavior with both substrates tested, namely 3-ethylbenzthiazoline-6-sulphonic acid (ABTS) and the anthraquinone dye remazol brilliant blue R (RBBR). The K_M’s for these substrates were, respectively, 0.232 × 10⁻³ and 0.602 × 10⁻³ M. The actions of NaCl and Na₂SO₄, two important salts usually found in textile wastewaters, were investigated. The enzyme was inhibited by NaCl, but not by Na₂SO₄. Inhibition by NaCl was of the mixed type with two different inhibition constants. The enzyme was able to completely decolorize RBBR in the presence of 1.0 M Na₂SO₄ and 50% decolorization was found in the presence of 0.1 M NaCl. Such properties certainly make the enzyme a good agent for textile dye effluent treatment considering the fact that wastewaters of this industry usually contain high concentrations of NaCl and Na₂SO₄.     

Searching for switchable molecular conductors: Salts of [M(dcbdt)2] (M = Ni, Au) anions with [Fe(sal2-trien)] and [Fe(phen)3]

Salts of [Fe^III(sal₂-trien)]⁺and [Fe^II(phen)₃]²⁺ cations and M[(dcbdt)₂]⁻ anions with M = Ni and Au (dcbdt = dicyanobenzenedithiolate) with formula [Fe(sal₂-trien)] [M(dcbdt)₂] and [Fe(phen)₃] [M(dcbdt)₂]₂ were obtained and characterized by single X-ray diffraction and magnetic measurements. None of these salts shows a clear spin crossover behaviour and their magnetic properties are due essentially to the cations in a high spin S = 5/2 and low spin states for the Fe^III and Fe^II salts respectively. The magnetic Ni sublattices in both compounds appear to have a negligible direct contribution to the magnetization but enhance the AF interactions in the cation sublattice.