Fluidized-bed denitrification for mine waters. Part I: low pH and temperature operation

Mining often leads to nitrate and metal contamination of groundwater and water bodies. Denitrification of acidic water was investigated in two up-flow fluidized-bed reactors (FBR) and using batch assays. Bacterial communities were enriched on ethanol plus nitrate in the FBRs. Initially, the effects of temperature, low-pH and ethanol/nitrate on denitrification were revealed. Batch assays showed that pH 4.8 was inhibitory to denitrification, whereas FBR characteristics permitted denitrification even at feed pH of 2.5 and at 7–8 °C. Nitrate and ethanol were removed and the feed pH was neutralized, provided that ethanol was supplied in excess to nitrate. Subsequently, Fe(II) and Cu impact on denitrification was investigated within batch tests at pH 7. Iron supplementation up to 100 mg/L resulted in iron oxidation and soluble concentrations ranging from 0.4 to 1.6 mg/L that stimulated denitrification. On the contrary, 0.7 mg/L of soluble Cu significantly slowed denitrification down resulting in about 45 % of inhibition in the first 8 h. Polymerase chain reaction—denaturant gradient gel electrophoresis demonstrated the co-existence of different denitrifying microbial consortia in FBRs. Dechloromonas denitrificans and Hydrogenophaga caeni were present in both FBRs and mainly responsible for nitrate reduction.     

Searching for allosteric effects via QSAR. Part II

Allosteric interactions have in the past been established by means of X-ray crystallography or careful study of a single molecule at a variety of concentrations. Here we report a method for using QSAR to establish a change in reaction mechanism by establishing an inversion point. That is, as polarizability of a member of a congeneric set of compounds is increased (as measured by CMR), activity at first decreases until, at the inversion, activity turns around and increases. Out of 23 examples, 14 have inversion points of 10+/-1. This includes a wide variety of receptors such as thrombin, 5-HT, dopamine, and tyrosine kinase acting with a variety of ligands.     

Paramagnetic NMR investigations of Co(II) and Ni(II) amicyanin

 The paramagnetic ¹H NMR spectra of the Co(II) and Ni(II) substituted forms of the type 1 blue copper protein (cupredoxin) amicyanin have been assigned. This is the first such analysis of a cupredoxin, which has a distorted tetrahedral active site with the ligands provided by two histidines, a cysteine and a methionine. The isotropic shifts of the resonances in these spectra are compared with those of Co(II) and Ni(II) azurin. A number of interesting similarities and differences are found. The coordination of the metal by the two equatorial histidine ligands is very similar in both proteins. The interaction between the introduced metal and the thiolate sulfur of the equatorial cysteine ligand is enhanced in the amicyanin derivatives. Resonances belonging to the weak axial methionine ligand exhibit much larger shifts in the amicyanin derivatives, indicative of shorter M(II)-S(Met) distances. The presence of shorter axial M(II)-S(Met) and equatorial M(II)-S(Cys) distances in both Co(II) and Ni(II) amicyanin is ascribed to the absence of a second axially interacting amino acid at the active site of this cupredoxin. Received: 2 February 1999 / Accepted: 19 May 1999     

Interaction of metal ions with humic-like models. Part VII. Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes of 2,5-dihydroxybenzoic acid

Complexes of formula M(2,5-DHB)₂4H₂O (M = Mn, Co, Ni, Zn, Cu and Cd; 2,5-DHB = 2,5-dihydroxybenzoate) were prepared and characterized by means of infrared and electronic spectroscopy, and by electron spin resonance. For the Zn complex the crystal and molecular structure was also determined by single-crystal X-ray diffraction analysis. The crystal is orthorhombic, space group Pbca (No. 61), with a = 18.503(4), b = 13.536(3), c = 6.900(2) Å, and Z = 4. The final refinement used 877 reflections and gave a residual R value of 0.041. The complex has slightly compressed octahedral coordination, with the zinc atom bound to two monodentate carboxylate groups lying in trans positions and four water molecules. X-ray data and infrared spectra show the Mn, Co, Ni, Zn and Cd complexes to be isostructural with the Zn compound. The electronic, infrared and ESR spectra of the copper(II) complex are consistent with a CuO_4? based chromophore involving two water molecules and two monodentate carboxylate groups in the metal plane, and long axial contacts.     

Spectral properties of Co(II)- and Ni(II)-activated rabbit muscle pyruvate kinase.

Stoichiometry, kinetics, and optical properties of rabbit muscle pyruvate kinase activated with Co(II), Ni(II), Mg(II), and Mn(II) were studied. The stoichiometry of metal binding to enzyme was found to be 4 metal ions per tetrameric enzyme for Co(II) and Ni(II) by carrying out circular dichroic titrations. Cu(II) and Fe(II) were inactive. Ca(II) and Zn(II) were not activating, and were inhibitory with respect to all of the active cations. The temperature dependence of the optimal velocity is similar for all activating metals. The pH rate profiles suggest that there are two classes of enzyme activation by metal ions. Mg(II) and Mn(II) are quite similar to each other while Co(II) and Ni(II) are different from them but similar to each other. Absorption, natural, and magnetic CD in the visible region were used to probe the environment of the activating divalent cation in Ni(II)- and Co(II)-activated pyruvate kinase and their complexes with substrates and inhibitors...     

Pathophysiology and therapy for haemoglobinopathies. Part II: thalassaemias

Thalassaemias result from mutations of the globin genes that cause reduced or absent haemoglobin production and thus interfere with the critical function of oxygen delivery. They represent the most common single-gene disorders, with 4.83% of the world population carrying globin gene variants. Reduced or absent alpha-globin (alpha-thalassaemia) or beta-globin (beta-thalassaemia) leads to anaemia and multifaceted clinical syndromes. In this second of two reviews on the pathophysiology of haemoglobinopathies, we describe the clinical features, pathophysiology and molecular basis of alpha- and beta-thalassaemias. We then discuss current targeted therapies, including the new oral iron chelators, which, along with chronic transfusions, constitute the mainstay of symptomatic therapy for the majority of patients. Finally, we describe potentially curative therapies, such as bone marrow transplant, and discuss some of the outstanding research studies and questions, including the upcoming field of gene therapy for beta-thalassaemia. An accompanying article on haemoglobinopathies (Part I) focuses on sickle cell disease.     

Cardiovascular effects of nerve growth factor: An analytical review. Part II

The features of NGF’s influence on the functional activity of the cardiovascular system and the signaling pathways by which activated NGF TrkA and p75 ^ntr receptors regulate the functional state of endothelial and vascular smooth muscle cells and cardiomyocytes are discussed. In addition, the theoretical prospects of agonists and antagonists of TrkA and p75 ^ntr receptors for the treatment of heart and vascular disorders are considered.     

Modification of cellulosic fibers by UV-irradiation. Part II: After treatments effects

This work presents the comparative study on the dyeing behavior of cellulose fibers in alkaline solutions and under the influence of UV radiation. The cellulosic fabrics were pretreated followed by conventional mercerization technique or treatment with UV irradiation. For different time duration the reorganization of cellulose fibers by swelling treatments in alkaline solutions results in numerous structural modifications, causing changes of their accessibility and/or reactivity. The results revealed that the swelling of the cellulosic fibers depends on type of pre-treatment, dose of the radiation and the concentration of alkaline solution used. SEM analysis confirmed that UV irradiation of the cellulosic fibers leads to a higher swelling in comparison with any concentration of NaOH treatment. In comparison of both the treatments, the mercerized cellulosic fibers have shown better tear and tensile strength as compared to the untreated and UV irradiated one. There is adverse effect of UV radiation on the mechanical properties of UV radiation. Moreover, no loss in weight was observed after exposing the cellulose fabrics surface to UV radiation.     

Cyclam cored luminescent dendrimers as ligands for Co(II), Ni(II) and Cu(II) ions

We have investigated the photophysical properties of two dendrimers containing a cyclam core decorated with 4 naphthyl units (G0), 12 dimethoxybenzene and 16 naphthyl units (G2). These dendrimers show fluorescence bands that can be assigned to naphthyl localized excited states (λ_max = 337 nm), naphthyl-amine exciplexes (λ_max = 470 nm) and, for G2, naphthyl excimers (λ_max ca. 400 nm). Cyclam is a very good ligand for transition metal ions and we have investigated complex formation between these dendritic ligands and Ni(II), Co(II) and Cu(II), added as nitrate salts. This process can be monitored by the strong changes, both in shape and intensity, observed in the emission spectra of these dendrimers. Complexation with Cu(II) causes not only changes in the relative intensities of the fluorescence bands, but also the appearance of a new absorption band in the near UV spectral region. An analysis of the titration curves has allowed us to obtain clear evidence for the formation of not only 1:1 species, but also 1:2 metal to ligand species. G2 shows a clear preference, compared to G0, in forming complexes with a 1:2 metal-to-ligand stoichiometry, although it possesses very bulky dendrons appended to the cyclam central unit.     

Metal-ion environment in solid Mn(II), Co(II) and Ni(II) hyaluronates

Amorphous powders and films of some metal hyaluronate complexes of general composition (C14H20O11N)2 x xH2O (M = Mn2+, Ni2+ and Co2+) have been prepared at pH 5.5-6.0. The coordination geometry around the metal ions has been analyzed by EXAFS (extended X-ray absorption fine structure) and FTIR spectroscopy. Mn2+, Ni2+, and Co2+ ions are coordinated to carboxylate oxygen atoms and water molecules. The process of local geometry formation round the metal ions is sensitive to sample preparation.     

Cyanoscorpionates: Co(II), Mn(II), and Ni(II) complexes coordinated only through the cyano group

New complexes have been synthesized of scorpionate ligands with cyano substituents in the 4-positions of the pyrazoles and tert-butyl substituents in the 3-positions of the pyrazoles. Reaction of Co²⁺, Mn²⁺, and Ni(cyclam)²⁺ (cyclam = 1,4,8,11-tetraazacyclotetradecane) with Tp^t-Bu,4CN in a 1:2 ratio produced new octahedral metal complexes of the form (Tp^t-Bu,4CN)₂ML₄ (L₄ = (H₂O)₄, (H₂O)₂(MeOH)₂, or cyclam). Unlike the sandwich complexes previously isolated with Tp^Ph,4CN, the crystal structures showed none of the pyrazole nitrogen atoms coordinated to the metal. Rather, the metal is coordinated to one CN nitrogen atom from each ligand, with two Tp anions coordinated trans to each other around the metal center. This leaves the Tp pyrazole nitrogen atoms open for another metal to coordinate, which could to lead to heterometallic complexes, new coordination polymers, as well as the framework for supramolecular complexes.     

Auricular reconstruction for microtia: Part II. Surgical techniques

Reconstruction of the microtic ear represents one of the most demanding challenges in reconstructive surgery. In this review the two most commonly used techniques for ear reconstruction, the Brent and Nagata techniques, are addressed in detail. Unique to this endeavor, the originator of each technique has been allowed to submit representative case material and to address the pros and cons of the other's technique. What follows is a detailed, insightful overview of microtia reconstruction, as a state of the art. The review then details commonly encountered problems in ear reconstruction and pertinent technical points. Finally, a glimpse into the future is offered with an accounting of the advances made in tissue engineering as this technology applies to auricular reconstruction.     

Competitive Immunochemical Determination of Antigens Using Conjugates Containing Co(II) and Ni(II)

A new variant of competitive heterogeneous immunoassay for certain proteinaceous antigens has been developed. The assay is based on the use of the target protein conjugated with Co(II) or Ni(II) ions and immobilized antibodies. The effect of catalytic hydrogen release allows quantitation of the metal ion labels by voltammetry at the final step of the assay. The conjugates have been characterized by spectrophotometry, voltammetry, atomic adsorption spectrometry, and nuclear magnetic relaxation. Based on the use of the conjugate RNase–diethylenetriaminepentaacetic acid–Co(II) (10 : 4 : 4), a competitive immunoassay for RNase has been developed, detecting the target protein in the range 2 × 10^–2–2 × 10^–4 mg/ml.     

Precision rhinoplasty. Part II: Prediction

This retrospective study was undertaken to investigate the soft-tissue response rate to the skeletal and soft-tissue alterations following a rhinoplasty. Ninety-eight patients, 80 females and 18 males, with a mean follow-up of 13 months, were included in this study. The tracings of the outline of preoperative cephaloxerograms and life-size photographs were superimposed on the postoperative ones, and the differences were measured and confirmed with measurements of intraoperative resected segments. The soft-tissue response to skeletal alterations was measured in seven different zones. Zone 1 (nasion) and zone 7 (nasal spine area) had the lowest mean response rate of approximately 25 percent. Zone 2 (proximal bridge) and zone 3 (midbridge) had a 60 percent response rate. Zone 4 (supratip area) had a 43 percent response, zone 5 had a 41 percent response, and zone 6 had a 40 percent response rate. There were statistically significant differences among the response rates of thick, medium, and thin noses. Age was an important factor in zones 1, 4, 5, 6, and 7. The patient's sex did not influence the soft-tissue response rate to skeletal alterations. The soft-tissue response in relation to the alar base narrowing was about 52 percent. This study reveals a predictable soft-tissue response to skeletal alterations on all zones except zone 7 (nasal spine area).     

X-ray crystal and molecular structures of the Ni(II) and Co(II) complexes of 2'-deoxyguanosine-5'-monophosphate.

The structures of [Ni(5′-dGMP)(H₂O)₅] and [Co(5′-dGMP)(H₂O)₅] have been solved by single-crystal x-ray diffraction techniques. Their common geometry consists of a metal ion octahedrally coordinated to the N₇ atom of guanine and five water ligands. The phosphate group of the nucleotide is hydrogenbonded to two of the coordinated water molecules.     

Ammonium regulation inSaccharopolyspora erythraea. Part II: Regulatory effects under different nutritional conditions

Summary Non-limiting nutritional conditions revealed a growth-associated erythromycin production with ammonium sulfate while the relation was growth-dissociated for ammonium nitrate. Feeding experiments suggested that the residual nitrate level might be the key regulatory element. A nitrate-induced glutamine synthetase pathway was postulated according to the nature and initial concentration of the ammonium salt.     

Chemical cleavage of plasmid DNA by Cu(II), Ni(II) and Co(III) desferal complexes.

It is demonstrated that the Cu(II), Co(III) and Ni(II) complexes of a siderophore chelating drug desferal cleave DNA, in contrast to the corresponding Fe(II) complex which does not bring about DNA scission. Hydroxy radical scavengers inhibit the cleavage reaction.