Composition of rocks, minerals, water, and gases from uplift areas of the Central Atlantic

Original geological, geophysical, lithological, mineralogical data on uplifts of the Central Atlantic are given in the book based on materials of Cruise 1 of the R/V Akademik Nikolaj Strakhov. Geological and geophysical studies include description of the obtained material and analysis of structural and morphological elements of the ocean floor. Results of lithological, petrochemical and geochemical studies were extremely innovative and develop a conceptual model. The latter include studies of petrochemical evolution of tholeiitic alkaline plate volcanism, large-scale hydrothermal transformation of basement rocks - palygorskitization, phosphatization and ferromanganese mineralization. Showing imposition Superposition of hydrogenic alteration on hydrothermally altered rocks and its role in Cenozoic history of sedimentation is shown.

Coordinate regulation of Bacillus subtilis peroxide stress genes by hydrogen peroxide and metal ions.

The Bacillus subtilis mrgA gene encodes an abundant DNA-binding protein that protects cells against the lethal effects of H2O2. Transcription of mrgA is induced by H2O2 or by entry into stationary phase when manganese and iron levels are low. We have selected for strains derepressed for transcription of mrgA in the presence of Mn(II). The resulting cis-acting mutants define an operator site just upstream of the mrgA promoter. Similar sequences flank the promoters for the catalase gene, katA, and the heme biosynthesis operon, hemAXCDBL. Like mrgA, transcription of the katA and hem genes is repressed by Mn(II), which thereby potentiates the killing action of H2O2. We identified two classes of trans-acting mutants derepressed for mrgA transcription in the presence of Mn(II): some exhibit a coordinate derepression of MrgA, catalase, heme biosynthesis, and alkyl hydroperoxide reductase and are H2O2 resistant, while others have reduced catalase activity and are H2O2 sensitive. These data indicate that the peroxide stress response of B. subtilis is regulated by a repressor that senses both metal ion levels and H2O2.

Espécies polinucleares de cobre e ferro com catalisadores de oxidação e modelos de sítios ativos

Diferentes complexos de cobre(II), contendo ligantes do tipo base de Schiff e um grupamento imidazólico, com interesse bioinorgânico, catalítico e como novos materiais, foram preparados na forma de sais perclorato, nitrato ou cloreto e caracterizados através de diferentes técnicas espectroscópicas (UV/Vis, IR, EPR, Raman) e espectrometria de massa Tandem (ESI-MS/MS), além de análise elementar, condutividade molar e medidas de propriedades magnéticas. Alguns destes compostos, obtidos como cristais adequados, tiveram suas estruturas determinadas por cristalografia de raios-X. As espécies di- e polinucleares contendo pontes cloreto, mostraram desdobramentos das hiperfinas nos espectros de EPR, relacionados à presença do equilíbrio com a respectiva espécie mononuclear, devido à labilidade dos íons cloretos, dependendo do contra-íon e do tipo de solvente utilizado. Adicionalmente, em solução alcalina, estes compostos estão em equilíbrio com as correspondentes espécies polinucleares, onde os centros de cobre estão ligados através de um ligante imidazolato. Em meio alcalino, estes compostos polinucleares contendo ponte imidazolato foram também isolados e caracterizados por diferentes técnicas espectroscópicas e magnéticas. Através da variação estrutural e também do ligante-ponte foi possível modular o fenômeno da interação magnética entre os íons de cobre em estruturas correlatas di- e polinucleares. Os respectivos parâmetros magnéticos foram obtidos com ajuste das curvas experimentais de XM vs T, correlacionando-se muito bem com a geometria, ângulos e distâncias de ligação entre os íons, quando comparado com outros complexos similares descritos na literatura. Posteriormente, estudaram-se os fatores relacionados com a reatividade de todas essas espécies como catalisadores na oxidação de substratos de interesse (fenóis e aminas), através da variação do tamanho da cavidade nas estruturas cíclicas ou de variações no ligante coordenado ao redor do íon metálico. Vários deles se mostraram bons miméticos de tirosinases e catecol oxidases. Um novo complexo-modelo da citocromo c oxidase (CcO), utilizando a protoporfirina IX condensada ao quelato N,N,-bis[2-(1,2-metilbenzimidazolil)etil]amino e ao resíduo de glicil-L-histidina, foi sintetizado e caracterizado através de diferentes técnicas espectroscópicas, especialmente EPR. A adição de H2O2 ao sistema completamente oxidado, FeIII/CuII, a -55°C, ou o borbulhamento de oxigênio molecular a uma solução do complexo na sua forma reduzida, FeII/CuI, saturada de CO, resultou na formação de adutos com O2, de baixo spin, estáveis a baixas temperaturas.

Reactions of fac-[PtMe2(OMe)(H2O)3]+ with halide ions: effect of halide trans effect on methoxide hydrolysis

A solution of fac-[PtMe2(OMe)(H2O)(3)](+) (1) in aqueous perchloric acid underwent very slow hydrolysis of the Pt-OMe bond, over many, weeks. When chloride was added to a solution of 1, two interconverting isomers of [PtMe2(OMe)Cl(H2O)(2)] (with chloride trans to methyl) were formed, and with excess chloride, [PtMe2(OMe)Cl-2(H2O)](-) (both chloride ligands trans to methyl). This solution was stable at ambient temperature, but on heating, methanol was formed and [PtMe2Cl2(H2O)(2)] (both chloride ligands cis to methyl) was produced in the solution. It is proposed that this reaction proceeds via an intermediate complex with chloride bound trans to methoxide. Concentration gave solid [{PtMe2Cl2}n], whose identity was confirmed by conversion to [PtMe(2)Cl(2)py(2)] (pyridine, py, trans to methyl). With bromide and iodide, methoxide hydrolysis occurred at ambient temperature, more slowly with bromide than with iodide, to form solid [{PtMe2X2}(n)] without significant concentrations of [PtMe2X2(H2O)(2)] formed as an intermediate. The greater tendency for Pt-OMe bond to hydrolyse trans to halide compared with 1 was ascribed to the higher trans effect of the halide ligand compared with that of water. (C) 2003 Elsevier Science B.V. All rights reserved.

Defenses against oxidative stress in Neisseria gonorrhoeae and Neisseria meningitidis: Distinctive systems for different lifestyles

Defenses against oxidative stress are crucial for the survival of the pathogens Neisseria meningitidis and Neisseria gonorrhoeae. An Mn(II) uptake system is involved in manganese (Mn)-dependent resistance to superoxide radicals in N. gonorrhoeae. Here, we show that accumulation of Mn also confers resistance to hydrogen peroxide killing via a catalase-independent mechanism. An mntC mutant of N. meningitidis is susceptible to oxidative killing, but supplementation of growth media with Mn does not enhance the organism's resistance to oxidative killing. N. meningitidis is able to grow in the presence of millimolar levels of Mn ion, in contrast to N. gonorrhoeae, whose growth is retarded at Mn concentrations >100 mumol/L, indicating that Mn homeostasis in the 2 species is probably quite different. N. meningitidis superoxide dismutase B plays a role in protection against oxidative killing. However, a sodC mutant of N. meningitidis is no more sensitive to oxidative killing than is the wild type. A cytochrome c peroxidase (Ccp) is present in N. gonorrhoeae but not in N. meningitidis. Investigations of a ccp mutant revealed a role for Ccp in protection against hydrogen peroxide killing. These differences in oxidative defenses in the pathogenic Neisseria are most likely a result of their localization in different ecological niches.

Metal Clips Induce Folding of a Short Unstructured Peptide into an a-Helix via Turn Conformations in Water. Kinetic versus Thermodynamic Products

Short peptides corresponding to two to four a-helical turns of proteins are not thermodynamically stable helices in water. Unstructured octapeptide Ac-His1*-Ala2-Ala3-His4*-His5*-Glu6-Leu7-His8*-NH2 (1) reacts with two [Pd ((NH2)-N-15(CH2)(2) (NH2)-N-15)(NO3)(2)] in water to form a kinetically stable intermediate, [{Pden}(2)-{(1,4)(5,8)-peptide}](2), in which two 19-membered metallocyclic rings stabilize two peptide turns. Slow subsequent folding to a thermodynamically more stable two-turn a-helix drives the equilibrium to [{Pden}(2)-{(1,5)(4,8)-peptide}] (3), featuring two 22-membered rings. This transformation from unstructured peptide via turns to an a-helix suggests that metal clips might be useful probes for investigating peptide folding.

Electronic energy-transfer rate constants for geometrical isomers of a bichromophoric macrocyclic complex

The rate of electronic energy transfer (EET) between a naphthalene donor and an anthracene acceptor in [ZnL3]-(ClO4)(2) and [ZnL4](ClO4)(2) was determined by time-resolved fluorescence measurements, where L 3 and L 4 are the geometrical isomers of 6-[(anthracen-9-ylmethyl)amino]-trans-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-13-amine (L-2), substituted with either a naphthalen-1-ylmethyl or naphthalen-2-ylmethyl donor, respectively. The energy transfer rate constant, k(EET), was determined to be (0.92 +/- 0.02) x 10(9) s(-1) for the naphthalen-1-ylmethyl-substituted isomer, while that for the naphthalen-2-ylmethyl-substituted isomer is somewhat faster, with k(EET) = (1.31 +/- 0.01) x 10(9) s(-1). The solid-state structure of [(ZnLCl)-Cl-3]ClO4 has been determined, and using molecular modeling calculations, the likely distributions of solution conformations in CH3CN have been evaluated for both complexes. The calculated conformational distributions in the common trans-III N-based isomeric form gave Forster EET rate constants that account for the differences observed and are in excellent agreement with the experimental values. It is shown that the full range of conformers must be considered to accurately reproduce the observed EET kinetics.

Influence of lattice interactions on the jahn-teller distortion of the [Cu(H2O)(6)](2+) ion: Dependence of the crystal structure of K-2[Cu(H2O)(6)](SO4)(2x)(SeO4)(2-2x) upon the sulfate/selenate ratio

The temperature dependence of the structure of the mixed-anion Tutton salt K-2[Cu(H2O)(6)](SO4)(2x)(SeO4)(2-2x) has been determined for crystals with 0, 17, 25, 68, 78, and 100% sulfate over the temperature range of 85-320 K. In every case, the [Cu(H2O)(6)](2+) ion adopts a tetragonally elongated coordination geometry with an orthorhombic distortion. However, for the compounds with 0, 17, and 25% sulfate, the long and intermediate bonds occur on a different pair of water molecules from those with 68, 78, and 100% sulfate. A thermal equilibrium between the two forms is observed for each crystal, with this developing more readily as the proportions of the two counterions become more similar. Attempts to prepare a crystal with approximately equal amounts of sulfate and selenate were unsuccessful. The temperature dependence of the bond lengths has been analyzed using a model in which the Jahn-Teller potential surface of the [Cu(H2O)(6)](2+) ion is perturbed by a lattice-strain interaction. The magnitude and sign of the orthorhombic component of this strain interaction depends on the proportion of sulfate to selenate. Significant deviations from Boltzmann statistics are observed for those crystals exhibiting a large temperature dependence of the average bond lengths, and this may be explained by cooperative interactions between neighboring complexes.

Polyamines from polyols - Pathways to azamacrocycles with hydroxymethyl pendent groups

Several pathways to macromonocylic polyamine ligands with pendent hydroxymethyl substituents have been explored. The new ligands have all been characterised by single-crystal, X-ray structure determinations on their complexes with Co(III) (one case) and Cu(II). As in some related systems, four-membered ring species, here oxetanes rather than azetidines, appear to be involved as reaction intermediates and can be quite readily isolated, providing reactants of potential for the construction of even more complicated multidentate ligands. (C) 2005 Elsevier Ltd. All rights reserved.

Oxidation of organic compounds in molten salts

The objective of this research was to investigate the oxidation of organic compounds in molten alkali metal hydroxides containing manganates. It has been shown that controlled oxidation can be readily achieved with high specificity to give products in high yield with very short reaction times. The concurrent changes in the melt were monitored using a vibrating platinum indicator electrode with a quazi-reference electrode which was successfully developed for use in molten (Na-K)OH eutectic at 523K. Henry's Law constants for water in the molten eutectic system (Na-K)OH have been measured and used to calculate the water concentration in the melt. The electrochemistry of manganates in molten (Na-K)OH eutectic at 523K has been studied using the vibrating platinum electrode, and the existence of the species Mn(II), Mn(II!), Mn(IV), Mn(V) and Mn(VI) in such melts has been investigated at various water concentrations. The half-wave potentials of the voltammetric waves were measured versus the cathodic limit of the melt. The stability of Mn(V) or Mn(VI) in the melt was achieved by varying the water concentration. A range of organic chemicals has been passed through molten (Na-K)OH at 523K and the reactions of these chemicals with the melt have been studied. The same organics were then passed through molten (Na-K)OH containing stabilized Mn(V) or Mn{VI) without violent reaction. Methanol, allyl alcohol, propane 1, 2 diol, I-heptene and acetone were oxidized by Mn(V) and Mn(VI). Ethanol was only oxidized by Mn(VI), isopropanol and benzyl alcohol were only oxidized by Mn(V). Npropanol, butanol, 2 methyl propan-2-ol, n-hexane, n-heptane toluene and cyclohexane were unchanged by both Mn(V) and Mn(VI). Detailed experiments have been performed on the reactions of ethanol, iso-propanol and methanol in molten (Na-K)OH containing stabilized Mrt(V) or Mn(VI), and reaction mechanisms have been postulated. Ethanol and iso-propanol were oxidized to acetaldehyde and acetone respectively with a potential for useful chemical process. The oxidation of methanol could be developed as a basis for an industrial methanol disposal process.

Transition metal ion coordination in hydrophilic polymer membranes

The research described within this thesis is concerned with the investigation of transition metal ion complexation within hydrophilic copolymer membranes. The membranes are copolymers of 4-methyl-4'-vinyl-2,2'-bipyridine, the 2-hydroxyethyl ester of 4,4'- dicarboxy-2,2'-bipyridine & bis-(5-vinylsalicylidene)ethylenediamine with 2-hydroxyethyl methacrylate. The effect of the polymer matrix on the formation and properties of transition metal iron complexes has been studied, specifically Cr(III) & Fe(II) salts for the bipyridyl- based copolymer membranes and Co(II), Ni(II) & Cu(II) salts for the salenH2- based copolymer membranes. The concomitant effect of complex formation on the properties of the polymer matrix have also been studied, e.g. on mechanical strength. A detailed body of work into the kinetics and thermodynamics for the formation of Cu(II) complexes in the salenH2- based copolymer membranes has been performed. The rate of complex formation is found to be very slow while the value of K for the equilibrium of complex formation is found to be unexpectedly small and shows a slight anion dependence. These phenomena are explained in terms of the effects of the heterogeneous phase provided by the polymer matrix. The transport of Cr(III) ions across uncomplexed and Cr(III)-pre-complexed bipyridyl-based membranes has been studied. In both cases, no Cr(III) coordination occurs within the time-scale of an experiment. Pre-complexation of the membrane does not lead to a change in the rate of permeation of Cr(III) ions. The transport of Co(II), Ni(II) & Cu(II) ions across salenH2- based membranes shows that there is no detectable lag-time in transport of the ions, despite independent evidence that complex formation within the membranes does occur. Finally, the synthesis of a number of functionalised ligands is described. Although they were found to be non-polymerisable by the methods employed in this research, they remain interesting ligands which provide a startmg pomt for further functionalisation.

The structural and electrochemical consequences of hydrogenating Copper N2S2 Schiff base macrocycles

A series of cis and trans tetradentate copper macrocyclic complexes, of ring size fourteen - sixteen, which employ amine and thioether donor groups are reported. Apart from 5,6,15,16-bisbenzo-8,13-diaza-1,4-dithia-cyclohexadecane copper(I) (cis-[Cu(H4NbuSen)]+) all of the complexes are obtained in the copper(II) form. Crystallographic analysis shows that the copper(II) complexes all adopt a distorted planar geometry around the copper. In contrast, cis-[Cu(H4NbuSen)]+ is found to adopt a distorted tetrahedral geometry. The complexes were subjected to electrochemical analysis in water and acetonitrile. The effect of the solvent, positions of the donor atoms (cis/trans) on E1/2 is discussed as is the comparison of the electrochemical behaviour of these complexes with their parent Schiff base macrocycles.

Transition metal ion co-ordination in hydrophilic polymer membrane

This thesis is concerned with the investigation of transition metal (TM) ion complexation with hydrophilic membranes composed of copolymers of 4-vinyl pyridine & 4-methyl-4'vinyl- 2,2'-bipyridine with 2-hydroxyethyl methacrylate. The Cu(II), CoCII) & Fe(II) complexes with these coordinating membranes were characterised by a variety of techniques, in order to assess the effect of the polymer on the properties of the complex, and vice versa. A detailed programme of work was instigated into the kinetics of formation for the polymer-bound tris(bipyridyl) iron(II) complex; the rate and extent of complex formation was found to be anion-dependent. This is explained in terms of the influence of the anion on the transport properties and water content of the membrane, the controlling factor in the development of the tris-complex being the equilibrium concentration of Fe(II) in the gel matrix. A series of transport studies were performed with a view to the potential application of complexing hydrogel membranes for aqueous TM ion separations. A number of salts were studied individually and shown to possess a range of permeabilities; the degree of interaction between particular metal-ion:ligand combinations is given by the lag-time observed before steady-state permeation is achieved. However, when two TM salts that individually display different transport properties were studied in combination, they showed similar lag-times & permeabilities, characteristic of the more strongly coordinating metal ion. This 'anti-selective' nature thus renders the membrane systems unsuitable for TM ion separations. Finally, attempts were made to synthesise and immobilise a series of N ,0-donor macrocyclic ligands into hydrogel membranes. Although the functionalisation reactions failed, limited transport data was obtained from membranes in which the ligands were physically entrapped within the polymer matrix.

Développement et caractérisation de dérivés dipyrrométhène pour des applications dans le domaine du photovoltaïque

Ce projet de recherche mené en collaboration industrielle avec St-Jean Photochimie Inc. / PCAS Canada vise le développement et la caractérisation de dérivés dipyrrométhène pour des applications dans le domaine du photovoltaïque. La quête du récoltage des photons se situant dans le proche-infrarouge a été au centre des modifications structurales explorées afin d’augmenter l’efficacité de conversion des cellules solaires de type organique et à pigments photosensibles. Trois familles de composés intégrant le motif dipyrrométhène ont été synthétisées et caractérisées du point de vue spectroscopique, électrochimique, structural ainsi que par modélisation moléculaire afin d’établir des relations structures-propriétés. La première famille comporte six azadipyrrométhènes au potentiel de coordination tétradentate sur des centres métalliques. Le développement d’une nouvelle voie synthétique asymétrique combinée à l’utilisation d’une voie symétrique classique ont permis d’obtenir l’ensemble des combinaisons de substituants possibles sur les aryles proximaux incluant les noyaux 2-hydroxyphényle, 2-méthoxyphényle et 2- pyridyle. La modulation du maximum d’absorption dans le rouge a pu être faite entre 598 et 619 nm. De même, la présence de groupements méthoxyle ou hydroxyle augmente l’absorption dans le violet (~410 nm) tel que démontré par modélisation. La caractérisation électrochimique a montré que les dérivés tétradentates étaient en général moins stables aux processus redox que leur contre-parti bidentate. La deuxième famille comporte dix dérivés BODIPY fusionnés de façon asymétrique en position [b]. L’aryle proximal a été modifié de façon systématique afin de mieux comprendre l’impact des substituents riches en électron et de la fusion de cycles aromatiques. De plus, ces dérivés ont été mis en relation avec une vaste série de composés analogues. Les résultats empiriques ont montré que les propriétés optoélectroniques de la plateforme sont régies par le degré de communication électronique entre l’aryle proximal, le pyrrole sur lequel il est attaché et le noyau indolique adjacent à ce dernier. Les maximums d’absorption dans le rouge sont modulables entre 547 et 628 nm et la fluorescence des composés se situe dans le proche- infrarouge. L’un des composé s’est révélé souhaitable pour une utilisation en photovoltaïque ainsi qu’à titre de sonde à pH. La troisième famille comporte cinq complexes neutres de RuII basés sur des polypyridines et portant un ligand azadipyrrométhène cyclométalé. Les composés ont montré une forte absorption de photons dans la région de 600 à 800 nm (rouge à proche- infrarouge) et qui a pu être étendue au-delà de 1100 nm dans le cas des dérivés portant un ligand terpyridine. L’analyse des propriétés optoélectroniques de façon empirique et théorique a montré un impact significatif de la cyclométalation et ouvert la voie pour leur étude en tant que photosensibilisateurs en OPV et en DSSC. La capacité d’un des complexes à photo-injecter un électron dans la bande de conduction du semi-conducteur TiO2 a été démontré en collaboration avec le groupe du Pr Gerald J. Meyer à University of North Carolina at Chapel Hill, premier pas vers une utilisation dans les cellules solaires à pigments photosensibles. La stabilité des complexes en solution s’est toutefois avérée problématique et des pistes de solutions sont suggérées basées sur les connaissances acquises dans le cadre de cette thèse.