To study the role of YDL100c during the growth of Saccharomyces cerevisiae in the presence of oxidant, the wild type strain (WT) and YDL100c disrupted strain (KO) were grown at 30oC for 6 hr after adding 0.25 mM of tert-butyl hydroperoxide (t-BOOH). The cells of both strains were assayed for the expression of anti-oxidant system, trehalose accumulation, intracellular molecular oxidation level, membrane lipid peroxidation, and glutathione (GSH) content. The results show that growth of KO is slower than that of WT and the cause of growth delay is the cell death. The data also show that the molecular oxidation level is lower but the lipid peroxidation of membrane is higher in KO compared with WT in the presence of t-BOOH, indicating that ROS do cause the damage on membrane. Further, analysis of the expression of cellular defense-related genes show that expressions of GSH1, CTT1, TPS1, TSL1, and NTH1 in KO are lower than in WT, but expressions of SOD1, TRR1 and TRX1 have no difference, demonstrating that the deletion of YDL100c in S. cerevisiae affects the general and specific stress response when grown in the presence of t-BOOH. In general, the decrease in CTT1 expression is not consistent with the catalase activity assay, however, decreased expressions of GSH1 and genes involved in trehalose metabolism are consistent with the decreased GSH content and increased trehalose accumulation in KO compared with WT. Therefore, the cause of KO cell death in the presence of t-BOOH is most likely related to the decrease in cellular GSH level and trehalose accumulation.

A atividade catalítica de clusters trigonais de acetato de rutênio e porfirinas supramoleculares contendo quatro unidades de clusters periféricos ou complexos de bis(bipiridina)rutênio, na oxidação de substratos orgânicos por iodosil-benzeno ou terc-butil-hidroperóxido, é abordada nesta tese. Foram feitos estudos cinéticos para elucidar o mecanismo de catálise, com especial destaque para duas espécies supramoleculares isoméricas representadas por Mn(3-TRPyP) ou Mn(4-TRPyP), nos quais os complexos de bis(bipiridina)(cloro)rutênio se coordenam à tetrapiridilporfirina através das posições meta ou para da ponte piridínica, respectivamente. Além da maior seletividade proporcionada pelos catalisadores supramoleculares, a substituição do íon cloreto pela água nos complexos periféricos de rutênio, intensificou a atividade catalítica, gerando novos sítios ativos, do tipo Ru(IV)=O. Também foram estudados clusters trinucleares de rutênio, altamente reativos, no estado Ru(III)Ru(IV)Ru(IV)=O. Estes foram gerados eletroquimicamente em solução aquosa, apresentando pronunciada atividade catalítica na oxidação do alcool benzílico. Finalmente, uma espécie dimérica de cluster, ainda inédita, com ponte oxo, foi caracterizada e investigada do ponto de vista catalítico. / The catalytic activity of trinuclear ruthenium clusters and supramolecular tetrapyridylporphyrins containing four peripheral cluster units or bis(bipyridine)ruthenium complexes, in the oxidation of organic substrates by iodosylbenzene or tert-butil-hydroperoxide, is dealt with in this thesis. Kinetic studies were performed in order to elucidate the mechanisms of catalysis involving two isomeric species denoted Mn(3-TRPyP) or Mn(4-TRPyP), in which the bis(bipyridine)(chloro)ruthenium complexes are bound to the tetrapyridylporphyrin center, at the meta or para positions of the pyridine bridge, respectively. In addition to the improved selectivity by such supramolecular catalysts, the substitution of the chloride ion by water in the peripheral ruthenium complexes, greatly enhanced their catalytic activity by generating new Ru(IV)=O reactive sites. Highly reactive trinuclear ruthenium clusters of the type Ru(III)Ru(IV)Ru(IV)=O were also generated electrochemically in aqueous solution, exhibiting pronounced catalytic activity in the oxidation of benzyl alcohol. Finally, a novel dimeric oxo-bridged cluster species was characterized, and its role in catalysis investigated.

A atividade catalítica de clusters trigonais de acetato de rutênio e porfirinas supramoleculares contendo quatro unidades de clusters periféricos ou complexos de bis(bipiridina)rutênio, na oxidação de substratos orgânicos por iodosil-benzeno ou terc-butil-hidroperóxido, é abordada nesta tese. Foram feitos estudos cinéticos para elucidar o mecanismo de catálise, com especial destaque para duas espécies supramoleculares isoméricas representadas por Mn(3-TRPyP) ou Mn(4-TRPyP), nos quais os complexos de bis(bipiridina)(cloro)rutênio se coordenam à tetrapiridilporfirina através das posições meta ou para da ponte piridínica, respectivamente. Além da maior seletividade proporcionada pelos catalisadores supramoleculares, a substituição do íon cloreto pela água nos complexos periféricos de rutênio, intensificou a atividade catalítica, gerando novos sítios ativos, do tipo Ru(IV)=O. Também foram estudados clusters trinucleares de rutênio, altamente reativos, no estado Ru(III)Ru(IV)Ru(IV)=O. Estes foram gerados eletroquimicamente em solução aquosa, apresentando pronunciada atividade catalítica na oxidação do alcool benzílico. Finalmente, uma espécie dimérica de cluster, ainda inédita, com ponte oxo, foi caracterizada e investigada do ponto de vista catalítico. / The catalytic activity of trinuclear ruthenium clusters and supramolecular tetrapyridylporphyrins containing four peripheral cluster units or bis(bipyridine)ruthenium complexes, in the oxidation of organic substrates by iodosylbenzene or tert-butil-hydroperoxide, is dealt with in this thesis. Kinetic studies were performed in order to elucidate the mechanisms of catalysis involving two isomeric species denoted Mn(3-TRPyP) or Mn(4-TRPyP), in which the bis(bipyridine)(chloro)ruthenium complexes are bound to the tetrapyridylporphyrin center, at the meta or para positions of the pyridine bridge, respectively. In addition to the improved selectivity by such supramolecular catalysts, the substitution of the chloride ion by water in the peripheral ruthenium complexes, greatly enhanced their catalytic activity by generating new Ru(IV)=O reactive sites. Highly reactive trinuclear ruthenium clusters of the type Ru(III)Ru(IV)Ru(IV)=O were also generated electrochemically in aqueous solution, exhibiting pronounced catalytic activity in the oxidation of benzyl alcohol. Finally, a novel dimeric oxo-bridged cluster species was characterized, and its role in catalysis investigated.