The genus Gluconobacter is industrially important due to the ability to accomplish unusual and almost complete oxidation reactions (bioconversions) and to contaminate high sugar content products. Following preliminary evidence that some strains of Gluconobacter were resistant to cadmium, and realizing that cadmium resistance among gram-negative organisms is often encoded by an operon which also encodes cobalt and zinc resistance via an efflux mechanism, 10 strains of Gluconobacter were tested for heavy-metal resistance. Three of the 10 representative strains appeared to be resistant to cadmium chloride, and two were also resistant to cobalt- and zinc chloride. These strains, as well as two cadmium-sensitive strains were analyzed using PCR and sequencing to establish gene homology with Ralstonia eutropha, the most frequently studied Gram-negative bacterium exhibiting cadmium resistance. Amplification of two genes from the czc operon, known to encode cadmium, cobalt and zinc resistance in Ralstonia, was attempted in the three resistant and two sensitive strains of Gluconobacter. The gene, czcA, thought to encode the main pump protein of the efflux mechanism, was found in all Gluconobacter strains tested. However, amplification of a regulatory gene czcD, thought to sense the extracellular metal ion concentration, was not possible in the Gluconobacter strains tested. The PCR products were sequenced and analyzed for homology to the czc operon in Ralstonia. From the data gathered, it appears as though some strains of Gluconobacter contain at least a portion of the czc operon , encoding cadmium, cobalt and zinc resistance in Ralstonia eutropha. / Master of Science

One of the most important additives in High Speed Steels (HSS) is cobalt, mainly for its effect on the hot properties. Based on statistic data about the increased price of cobalt and its negative effect on human health, an ethical and financial barrier in the steel industry have occurred. In order to solve the problem, it is of great importance to examine the future cobalt price and accessibility, as well as examine the possibility of finding alternative substitutes to cobalt. The purpose of this project was therefore to examine alternatives to cobalt as an alloying element in HSS. A qualitative literature study was performed by analyzing the economy of cobalt, studying the main reasons for cobalts tendency to improve the hot properties of the steel and finding alternative elements to replace, or at least reduce, cobalt in HSS without degrading the hot properties. Cobalt is used both in the chemical and metallurgical business. But the demand of cobalt is largely driven by chemical purposes with the focus on its rechargeable battery applications. The analysis shows that there is nothing pointing at a significant decrease of the price of cobalt. Lithium ion batteries stands for about 50% of current cobalt supply, which is why the price has surged the recent years. The market for electric vehicles and rechargeable batteries has skyrocketed. To decrease the price of cobalt, a substitute for cobalt in rechargeable batteries would need to be found, which is not very likely for the time being. The effect of cobalt in HSS is mainly on the red hardness and tempering resistance. Cobalt increases the bonding strength in the steel matrix and changes the microstructure of the finer secondary carbides. Also the growth rate and coalescence rate of the carbides decreases. This causes the red hardness and the tempering resistance to increase. To replace cobalt, several alternative alloying elements have been researched. Among the most promising are niobium, nitrogen and aluminium, where niobium were found to be of most interest, due to the broad support of relevant articles in the field of powder metallurgical processing. The positive effect of niobium could be regarded as three-fold. The first contribution is the refinement of grain size and homogeneity of the primary carbides, which increases the overall hardness. The second effect is that the addition of niobium shifts the phase equilibria in such a way that the precipitation of primary carbides mainly will be in the form of hard and stable NbC. The majority of the other alloying elements will hence be precipitated as secondary carbides during tempering. The final effect is an increase in secondary hardness, as a consequence of the large amounts of vanadium and smaller amounts of niobium that is being precipitated during tempering to the secondary carbides. This enables a high matrix hardening potential in the optimal state of tempering.

Photodynamic therapy (PDT) is a non-invasive treatment of cancer with an advantage of having localized photo-activation of the drug at the targeted tumor cells leaving the healthy cells unaffected by the photo-toxicity of the PDT agent. Organic molecules and 4d/5d metal complexes have been extensively studied for their DNA cleavage activity and photo-cytotoxicity in UV and/or visible light. The photoactivity of the current PDT drugs is due to reactive singlet oxygen species. To address the hypoxic nature within neoplasia and to get a realistic scenario to build model and potent PDT agents, attempts have been made in this thesis work to design and synthesize new cobalt and copper complexes having a variety of ancillary ligands and planar phenanthroline bases showing efficient visible light-induced anaerobic plasmid DNA cleavage activity. The disulfide and thiol compounds are known to generate thyil radical in anaerobic medium in presence of some electron donating solvent. To exploit this chemistry of the sulfur anion radical as a reactive species damaging DNA under light irradiation, we have prepared copper(II) complexes of bis(2-hydroxybenzylamino-ethyl)disulfide and D-penicillaminedisulfide and characterized. The complexes are moderate binders to calf thymus DNA and exhibit plasmid DNA cleavage activity in red light. Near-IR light-induced double-strand DNA cleavage activity is observed for the complexes having 3,3' -dithiodipropionic acid and phenanthroline bases. These complexes show lethal double strand breaks in SC DNA responsible for the inhibition in DNA repair mechanism in the cells thus becoming potent candidates as transcription inhibitors. The work has been extended to achieve better visible light-induced plasmid DNA cleavage activity and UV light-induced photocytotoxicity using a more bio-compatible metal ion, viz. cobalt(II) with the same ligand system and enhancement in the photocytotoxicity is observed. To investigate the role of the disulfide ancillary ligands, complexes of salicylideneaminothiophenol bound to the copper(II) are prepared and the complexes show significant plasmid DNA cleavage activity in red light. Finally, ternary cobalt(III) phenanthroline base complexes are prepared to study their DNA cleavage activity in red light and photo-cytotoxicity in UV light. The complexes show efficient plasmid DNA cleavage activity in red light, significant cytotoxicity in UV light, low dark cytotoxicity, and protein (BSA, lysozyme) cleavage activity in UV light. The mechanistic aspects of the photo-induced DNA and protein cleavage activity of the complexes have been studied. A dual involvement of the charge transfer and d-d band is observed in the photosensitization process leading to generation of reactive oxygen species. In summary, the thesis work presents cobalt and copper complexes having thiolate and disulfide moieties that are designed and synthesized as new photodynamic therapeutic agents showing anaerobic DNA cleavage activity in red light and photocytotoxicity. The present study opens up new strategies for designing and developing cobalt and copper based photosensitizers for their potential photochemotherapeutic applications under hypoxic reaction conditions. References: Lahiri, D. et al., J Chern. Sci, 2010, 122, 321-333; Inorg. Chern., 2009, 48, 339-349; Dalton Trans. 2010,39,1807-1816; Polyhedron, 2010, 29, 2417-2425.