Novel atmospheric scorodite synthesis by oxidation of ferrous sulfate solution. Part I

A new atmospheric scorodite synthesis process was investigated. A large size and good crystalline scorodite was precipitated at 95 °C even in a short time of 1 to 7 h when ferrous ions were oxidized by oxygen gas in the presence of As(V) ion with concentrations as high as 50 g/L As in sulfuric acid solution. The key point of the process is the ferrous state of iron in solution and the oxidation of ferrous ions during the scorodite precipitation. This scorodite has a particle size of 15 μm with approximately 10% moisture content (wet base) even under atmospheric conditions. The arsenic content was about 30% by mass. The results of the leach test are very desirable. The process can be applied to a primary smelter which produces copper, zinc, lead and other secondary materials.     

A seven-gene locus for synthesis of phenazine-1-carboxylic acid by Pseudomonas fluorescens 2-79

Pseudomonas fluorescens 2-79 produces the broad-spectrum antibiotic phenazine-1-carboxylic acid (PCA), which is active against a variety of fungal root pathogens. In this study, seven genes designated phzABCDEFG that are sufficient for synthesis of PCA were localized within a 6.8-kb BglII-XbaI fragment from the phenazine biosynthesis locus of strain 2-79. Polypeptides corresponding to all phz genes were identified by analysis of recombinant plasmids in a T7 promoter/polymerase expression system. Products of the phzC, phzD, and phzE genes have similarities to enzymes of shikimic acid and chorismic acid metabolism and, together with PhzF, are absolutely necessary for PCA production. PhzG is similar to pyridoxamine-5'-phosphate oxidases and probably is a source of cofactor for the PCA-synthesizing enzyme(s). Products of the phzA and phzB genes are highly homologous to each other and may be involved in stabilization of a putative PCA-synthesizing multienzyme complex. Two new genes, phzX and phzY, that are homologous to phzA and phzB, respectively, were cloned and sequenced from P. aureofaciens 30-84, which produces PCA, 2-hydroxyphenazine-1-carboxylic acid, and 2-hydroxyphenazine. Based on functional analysis of the phz genes from strains 2-79 and 30-84, we postulate that different species of fluorescent pseudomonads have similar genetic systems that confer the ability to synthesize PCA.     

Novel atmospheric scorodite synthesis by oxidation of ferrous sulfate solution. Part II. Effect of temperature and air

We have previously reported a novel method for producing stable scorodite (FeAsO₄·2H₂O) under atmospheric conditions in which ferrous sulfate was oxidized by oxygen in the presence of high concentrations of arsenic(V). This work examines the effects of reaction temperature (95, 70, 50 °C) and the oxidizing agent (air, pure oxygen gas) to optimize scorodite formation in a practical process. Crystalline scorodite of low solubility could be prepared at 70 °C within only 7 h using either oxygen or air sparging and small particles were even formed at 50 °C using air oxidation.     

An efficient approach to the synthesis of 1,3-diaryl-1,2,3,4-[4H]-tetrahydronaphthalene-2-carboxylic acids

Oligosaccharide recognition is a major means of bacterial-host cell attachment. Bacterial-host receptor binding can subvert host signaling pathways to cause pathology. In addition, pathogenic bacteria can utilize more than one recognition system to bind host cells. Recent studies of Helicobacter pylori illustrate both these points. Together with this redundancy in recognition, the importance of multivalent sugar binding has become apparent. Multivalent sugar receptor analogs have been used to both prevent and detach adherent bacteria. Several new chemical technologies for the generation of bioactive glycopolymers have been developed and may be successfully adapted to address both these issues.     

Research on heterocyclic compounds, Part 40. 2-Phenylimidazo[1,2-a]pyridine-3-carboxylic acid derivatives: synthesis and antiinflammatory activity

A series of 2-phenylimidazo[1,2-a]pyridine-3-carboxylic esters, acids, and amides were synthesized and pharmacologically tested in order to evaluate their antiinflammatory and analgesic activity and their ulcerogenic action on the gastro-intestinal tract. The most active member of this series of compounds was found to be 6-methyl-2-phenylimidazo[1,2-a]pyridine-3-carboxylic acid (5c).     

7-(2-Aminomethyl-1-azetidinyl)-4-oxoquinoline-3-carboxylic acids as potent antibacterial agents: design, synthesis, and antibacterial activity

2-Aminomethyl-1-azetidinyl, -1-pyrrolidinyl, and -1-piperidinyl groups were designed as novel C-7 substituents for potential antibacterial quinolone agents. Of the three substituents, the 2-aminomethyl-1-azetidinyl group (compound 12a) was found to be the most favorable for enhancing the activity of the 6,8-difluoroquinoline molecule 12. Therefore the 2-aminomethyl-1-azetidinyl group was introduced into a variety of quinolines (giving 24-26a, and 28a) and naphthyridines (giving 31a and 32a). Through optical resolution of 1-benzylazetidine-2-carboxamide (19) and chiral synthesis of its R-isomer, both enantiomers of 2-aminomethyl-1-azetidinyl quinolines 12a and 24-26a were also prepared. The most active of all the compounds was 5-amino-6,8-difluoroquinoline (R)-26a. The activity of (R)-26a was more potent than those of the corresponding 1-piperazinyl derivative (3) and sparfloxacin (1), and was comparable to those of the corresponding 3-amino-1-pyrrolidinyl (4), 3-aminomethyl-1-pyrrolidinyl (5), and 3-amino-1-azetidinyl (6) derivatives.     

Mass spectroscopic analysis of a novel enzymatic reaction. Oxidative decarboxylation of the lantibiotic precursor peptide EpiA catalyzed by the flavoprotein EpiD

The epidermin biosynthetic reaction between the flavoprotein EpiD and the precursor peptide EpiA was investigated by reversed-phase chromatography and ion spray mass spectrometry. Several products with molecular masses 46 and 104 Da less than that of EpiA were observed; these results were confirmed by using an MBP-EpiD fusion protein as enzyme and the mutant peptides EpiAR-1Q and K-EpiA as substrates. The reaction was inhibited by Zn2+ ions. Modifications were localized in the C-terminal fragment of EpiA as shown by factor Xa cleavage of the products followed by mass spectrometry analysis. In addition, EpiD reacted with the precursor peptides and with proepidermin, indicating that the leader peptide is not necessary for the recognition of EpiA by EpiD. Sequence analysis of modified proepidermin revealed that at least the amino acids Ile(+1)-Tyr+20 are unmodified. The observed decrease in mass of 46 Da and the modification at the C terminus of EpiA is in agreement with the proposed enzymatic function of EpiD, the oxidative decarboxylation of the precursor peptide. In addition, the increased absorbance at 260 nm of the modified peptides indicates the presence of a thioenol group in the C-terminal proepidermin.     

AM1 theoretical study, synthesis and biological evaluation of some benzofuran analogues of anti-inflammatory arylalkanoic acids

To evaluate different methods for strain differentiation, 10 isolates of Aspergillus terreus from Germany and two epidemiologically unrelated strains were investigated. The sources of the isolates were patients with cystic fibrosis (4), immunosuppression (2), otitis externa (2), sinusitis (1) and endocarditis (1). Environmental isolates were obtained from a contaminated cell culture and from soil. The isolates did not differ in their macroscopic and microscopic morphology, in their protein patterns analysed by SDS-PAGE and in their susceptibility to amphotericin B and itraconazole. The RFLP analysis of total genomic DNA digested by EcoRI resulted in patterns that were too faint for interpretation. However, after hybridisation of the digested DNA with a short DNA probe of repetitive sequence, six different patterns were found. Based on the patterns of the randomly amplified polymorphic DNA (RAPD) with three primers, nine different genotypes were discriminate. RAPD patterns discriminated the epidemiologically unrelated reference strains (endocarditis isolate from Thailand, soil isolate from the USA) and the isolates from Germany. It is concluded that, in contrast to the phenotypic methods, the analysis of RAPD patterns is useful for strain differentiation of A. terreus.     

Microarc oxidation of light constructional alloys: Part 1. Main notions on the microarc oxidation of light constructional alloys

The method of microarc oxidation of materials is described and its advantages over the anodization conventionally used to obtain protective coatings on the surface of light aluminum and constructional alloys are shown; the main notions of the mechanism of this process in the understanding of the authors of this article are presented.     

Leaching of waste battery paste components. Part 1: Lead citrate synthesis from PbO and PbO2

In this study, as part of developing a new process which can avoid smelting and electro-winning, citric acid based reagents in aqueous media were reacted with PbO and PbO₂. These two oxides are important components in the spent lead-acid battery paste and together account for up to 50% of the paste by weight. PbSO₄, the main component in a spent battery paste accounting for the remaining 50%, is dealt with in Part 2 in a separate paper. Reaction between PbO and C₆H₈O₇·H₂O or PbO₂ with a mixture of C₆H₈O₇·H₂O and H₂O₂ yielded lead citrate, Pb(C₆H₆O₇)·H₂O, which was characterised by XRD, SEM and FT-IR analysis. Optimal synthesis conditions were determined by investigating the effect of time, temperature, concentration, and the starting Pb oxide/water ratio. The optimal condition for leaching a mol of PbO at room temperature (20 °C) was found to be: 1 mol of (C₆H₈O₇)·H₂O solution; 1/3 as the starting PbO/water ratio and 15 min of reaction time. Pure citrate product, Pb(C₆H₆O₇)·H₂O was rapidly crystallized from the solution, in the leaching process. Leaching of PbO₂ required the use of a mild reducing agent. For each mole of PbO₂, the optimum condition at 20 °C was found to be: a solution containing 4 mol of C₆H₈O₇·H₂O and 2 mol of H₂O₂; 1/5 as the starting solid PbO₂/water ratio; and 60 min of reaction time. The product, as with PbO, was pure Pb(C₆H₆O₇)·H₂O compound. The remaining lead content of the filtrate solution was 0.017% and 1% corresponding to recoveries of 99.98% and 99% of lead as citrate, after the leaching/crystallization/filtration process with PbO and PbO₂, respectively. Asymmetric stretching vibrations between 1599 and 1662 cm^? 1, whereas symmetric vibrations between 1520 and 1327 cm^? 1 for lead citrate synthesised from PbO and asymmetric stretching vibrations between 1600 and 1642 cm^? 1 as well as symmetric vibrations between 1517 and 1326 cm^? 1 for the product obtained from PbO₂ revealed the strong IR adsorptions associated with a carboxylate structure. XRD data was identical to the well documented crystalline Pb(C₆H₆O₇)·H₂O compound from both the oxides. SEM revealed the formation of plate/sheet like morphologies. The difference in the column size of the Pb(C₆H₆O₇)·H₂O formed from the two lead oxides can be related to difference in the rate of the respective reactions.     

Oxysterols and TBARS are among the LDL oxidation products which enhance thromboxane A2 synthesis by platelets

In this study, we compared the effects of normal LDL (nLDL) and oxidized LDL (oxLDL) on thromboxane (TXA2) release by platelets triggered by low concentration of thrombin, and we determined which component of oxLDL is responsible for that activation. After oxidation of LDL with copper sulfate, the small molecular weight fraction (< 10 kDa) which was high in TBARS was removed; using Amicon Centriprep-10 concentrator membrane. More than 67% of TBARS in the oxLDL preparation was found in solution while the remaining was covalently attached to the oxLDL particles. OxLDL contained significantly higher levels of oxysterols and TBARS than the nLDL. Platelets preincubated with low concentrations of oxLDL (33-132 micrograms protein/mL) produced significantly higher TXA2 than platelets preincubated with equivalent concentrations of nLDL when triggered with thrombin. Platelets treated with oxLDL also contained significantly higher levels of oxysterols than platelets treated with nLDL. Platelets preincubated with pure cholestanetriol (10 micrograms/mL) contained a high level of cholestanetriol in the membrane, and TXA2 release was significantly increased in these platelets compared to the control platelets. The TBARS in solution also was very potent in enhancing TXA2 release by thrombin-treated platelets. These results indicate that oxysterols and the free TBARS either in solution or covalently attached to the oxLDL particles are partly responsible for the stimulatory effect of oxLDL on TXA2 release by platelets. The present study also showed that this enhancement of TXA2 release was due to activation of phospholipase A2 and to the increase of arachidonic acid liberation from the platelet phospholipids.     

Upsetting of a cylindrical blank by conical and flat dies. Part 1

The plastic flows of metal for the light stages in the upsetting of a cylindrical blank by conical and flat dies are considered. The position of the flows division is established at the boundary of two free surfaces at the end of the blank: the internal (conical) surface; and the external (lateral) surface. We may identify phenomenological aspects of the upsetting of a cylindrical blank by conical and flat dies: the direction of the displaced-metal flows; the curvature of the trajectory; the transition from sections that have no contact with the tool to end sections of the blank’s surface; the alternating rotation of the primary axes of the coordinate-grid cells; and the deformational rotation and shear near the end. The deformation due to the conical and flat dies is found to be superior to that associated with decrease in the contact friction and with the conversion of braking frictional forces to active forces. The theoretical conclusions are based on analysis of the same coordinate grid within the billet on the basis of nine photographs in step-by-step upsetting.     

Probing the initial stage of synthesis of Al2O3/Al composites by directed oxidation of Al-Mg alloys

In the directed oxidation of Al-Mg alloys, the amount of MgO that forms in the initial stage prior to the incubation period affects the rate of oxidation of Al to Al₂O₃ in the composite growth stage. The mechanism of formation of MgO and the duration of the initial stage were investigated experimentally and theoretically. The variables studied were total pressure in the reaction chamber, partial pressure of oxygen, and the nature of the diluent gas which affects the diffusion coefficients of magnesium vapor and oxygen in the gas phase. The oxidation rate in the initial stage was proportional to both the oxygen partial pressure and the diffusivity of oxygen. The duration of the initial stage decreased with the increase in oxygen pressure. To understand the role of magnesium evaporation in the oxidation behavior of the alloy, the velocity, temperature, and concentration fields in the gas phase were simulated numerically. The calculated concentration profiles of magnesium vapor and oxygen as a function of time were consistent with the experimentally measured oxidation rates and confirm reaction-enhanced gaseous diffusion-limited vaporization of magnesium in the initial stage of oxidation of Al-Mg alloys. The region where the magnesium vapor is oxidized in the gas phase moved progressively closer to the alloy surface during the initial stage of oxidation. The end of the initial stage and the start of the incubation period corresponded to the arrival of the oxygen front close to the surface when the spinel formation occurred.     

Structure--activity relationships in cephalosporins prepared from penicillins. 1. 7beta-Acylamino derivatives of 3-benzyl- and 3-(3-pyridylmethyl)ceph-3-em-4-carboxylic acids

tert-Butyl 7beta-aminoceph-3-em-4-carboxylates carrying either benzyl or 3-pyridylmethyl substituents at position 3 have been prepared by a multistep modification of the penicillin nucleus. Acylation of either amine, followed by deprotection, gave a range of new cephalosporins. The relationship between structure and antibacterial activity is discussed. D-Phenylglycine proved to be a preferred side chain in both series.     

ATP synthesis by the F0F1 ATP synthase from thermophilic Bacillus PS3 reconstituted into liposomes with bacteriorhodopsin. 2. Relationships between proton motive force and ATP synthesis

The correlation between the rate of ATP synthesis and light-induced proton flux was investigated in proteoliposomes reconstituted with bacteriorhodopsin and ATP synthase from thermophilic Bacillus PS3. By variation of the actinic light intensity it was found that ATP synthase activity depended in a sigmoidal manner on the amplitude of the transmembrane light-induced pH gradient. Maximal rates of ATP synthesis (up to to 200 nmol ATP x min(-1) x mg protein (-1) were obtained at saturating light intensities under a steady-state pH gradient of about pH 1.25. It was demonstrated that this was the maximal deltapH attainable at 40 degrees C in reconstituted proteoliposomes, due to the feedback inhibition of bacteriorhodopsin by the proton gradient it generates. In the absence of valinomycin, a small but significant transmembrane electrical potential could develop at 40 degrees C, contributing to an increase in the rate of ATP synthesis. The H+/ATP stoichiometry was measured at the static-head (equilibrium) conditions from the ratio of the phosphate potential to the size of the light-induced pH gradient and a value of about four was obtained under the maximal electrochemical proton gradient. Increasing the amount of bacteriorhodopsin in the proteoliposomes at a constant F0F1 concentration led to a large increase in the rate of ATP synthesis whereas the magnitude of delta pH remained the same or, at very high bacteriorhodopsin levels, decreased. Consequently the H+/ATP stoichiometry was found to increase significantly with increasing bacteriorhodopsin content. Reconstitutions with mixtures of native and impaired bacteriorhodopsin (Asp96-->Asn mutated bacteriorhodopsin) further demonstrated that this increase in the coupling efficiency could not be related to protein-protein interactions but rather to bacteriorhodopsin donating H+ to the ATP synthase. Increasing the amount of negatively charged phospholipids in the proteoliposomes also increased the coupling efficiency between bacteriorhodopsin and ATP synthase at a constant transmembrane pH gradient. Similar results were obtained with chloroplast ATP synthase. Furthermore, ATP synthase activities induced by delta pH/delta psi transitions were independent of bacteriorhodopsin or anionic lipid levels. These observations were interpreted as indicating that, in bacteriorhodopsin/ATP synthase, proteoliposomes, a localized pathway for coupling light-driven H+ transport by bacteriorhodopsin to ATP synthesis by F0F1 might exist under specific experimental conditions.     

Free amino acids and peptides in the muscles of 1- and 2-day-old cadavers

High-voltage electrophoresis and the analytic procedure combination of high-voltage electrophoresis--paper chromatography were used for the analysis of protein-free extracts of muscle tissue in one-- to two--day old corpses. The protein-free extracts from both types of tissue specimen were found to contain also peptides in addition to free amino acids. The amino acids composition of isolated fractions is not mutually comparable. There were also differences as regards peptides. In the two--day corpse a new peptide appeared in the acid part and disappeared in the weak base part. The changes suggest that not only proteolysis but also peptidolysis are in progress on the second post-mortem day.     

Fatty acids as natural uncouplers preventing generation of O2.- and H2O2 by mitochondria in the resting state

Both natural (laurate) and artificial (m-chlorocarbonylcyanide phenylhydrazone; CCCP) uncouplers strongly inhibit O2.- and H2O2 formation by rat heart mitochondria oxidizing succinate. Carboxyatractylate, an ATP/ADP antiporter inhibitor, abolishes the laurate inhibition, the CCCP inhibition being unaffected. Atractylate partially releases the inhibition by laurate and decelerates the releasing effect of carboxyatractylate. GDP is much less effective than carboxyatractylate in releasing the laurate inhibition of reactive oxygen species (ROS) formation. Micromolar laurate concentrations arresting the ROS formation cause strong inhibition of reverse electron transfer from succinate to NAD+, whereas State 4 respiration and the transmembrane electric potential difference (delta psi) level are affected only slightly. It is suggested that (i) free fatty acids operate as natural 'mild uncouplers' preventing the transmembrane electrochemical H+ potential difference (delta muH+) from being above a threshold critical for ROS formation by complex I and, to a lesser degree, by complex III of the respiratory chain, and (ii) it is the ATP/ADP-antiporter, rather than uncoupling protein 2, that is mainly involved in this antioxidant mechanism of heart muscle mitochondria.