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Every year millions of tons of lignin, a complex biopolymer present in plants that naturally contains aromatic subunits, are produced as a by-product of industries like the food sector and paper sector. Until now it has been considered as a waste but proper valorisation through optimized depolymerization techniques would allow to recover of high-added value fine chemicals and bulk commodities. Vanadium(V) triphenolamine complexes (VO-TPA), developed and studied in the group of Giulia Licini (University of Padova, IT), are of interest in this context as they are efficient catalysts for the oxidative cleavage of carbon-carbon bonds typical of those present in lignin. However, the mechanism of this reaction had not yet been elucidated and the catalysts have exclusively been used in organic solvents. This Thesis is a contribution to the further development of these catalysts and takes different Green Chemistry principles into account such as waste prevention, atom economy, renewable feedstocks, catalysis, energetic efficiency and the use of benign solvents. A first part of this thesis is a contribution to the elucidation of the reaction mechanism. The work was undertaken with vicinal diols, which are the simplest model compounds of lignin. Based on a review of the literature, radical trapping experiments, kinetics, 13C KIE experiments, Hammett plots and multi-parametric correlations, the C-C cleavage of a non-oxo or oxo chelate has been identified as the rate determining step. Attempts were made to synthesise the chelate and identify it via MS. Moreover, three hypothetic pathways were posited to reach this intermediate. Isotopic labelling experiments, determination of reaction activation parameters via an Eyring plot and computations of the different pathways along EPR elucidation of reduced species, have been used to discriminate the operative mechanism. The second part of this thesis is devoted to the transfer of the reaction into water, which can be considered a beni, Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished

Efficient photocatalytic conversion of carbon dioxide into valuable reduction products is a priority goal for artificial photosynthesis. Iridium(III) photocatalysts with a combined 2-phenylpyridine (ppy) and 2,2':6',2 ''-terpyridine (tpy) ligand set have been shown to selectively reduce CO, to CO. Here, terpyridine modifications have been investigated that yield a turnover number (TON) of up to 265, a quantum yield of 0.10, and a photocatalyst lifespan of over 10 days. The key to success is the combined effect of adding aromatic substituents to the tpy ligand 4'-position and optimizing lighting conditions. Insights into the photocatalyst fate are provided by kinetics analysis and spectroelectrochemistry, which point out the critical role of the reductively quenched catalyst and its evolution to a spent "green" state via a dark deactivation pathway. The stereoelectronic effect of adding a 9-anthryl substituent together with the use of low-energy blue light proves instrumental in the management of excited and reduced species, dictating the overall performance of the molecular photocatalyst.

Plasma membrane function requires distinct leaflet lipid compositions. Two of the P-type ATPases (flippases) in yeast, Dnf1 and Dnf2, translocate aminoglycerophospholipids from the outer to the inner leaflet, stimulated via phosphorylation by cortically localized protein kinase Fpk1. By monitoring Fpk1 activity in vivo, we found that Fpk1 was hyperactive in cells lacking Gin4, a protein kinase previously implicated in septin collar assembly. Gin4 colocalized with Fpk1 at the cortical site of future bud emergence and phosphorylated Fpk1 at multiple sites, which we mapped. As judged by biochemical and phenotypic criteria, a mutant (Fpk1(11A)), in which 11 sites were mutated to Ala, was hyperactive, causing increased inward transport of phosphatidylethanolamine. Thus, Gin4 is a negative regulator of Fpk1 and therefore an indirect negative regulator of flippase function. Moreover, we found that decreasing flippase function rescued the growth deficiency of four different cytokinesis mutants, which suggests that the primary function of Gin4 is highly localized control of membrane lipid asymmetry and is necessary for optimal cytokinesis.

Plasma membrane function requires distinct leaflet lipid compositions. Two of the P-type ATPases (flippases) in yeast, Dnf1 and Dnf2, translocate aminoglycerophospholipids from the outer to the inner leaflet, stimulated via phosphorylation by cortically localized protein kinase Fpk1. By monitoring Fpk1 activity in vivo, we found that Fpk1 was hyperactive in cells lacking Gin4, a protein kinase previously implicated in septin collar assembly. Gin4 colocalized with Fpk1 at the cortical site of future bud emergence and phosphorylated Fpk1 at multiple sites, which we mapped. As judged by biochemical and phenotypic criteria, a mutant (Fpk1(11A)), in which 11 sites were mutated to Ala, was hyperactive, causing increased inward transport of phosphatidylethanolamine. Thus, Gin4 is a negative regulator of Fpk1 and therefore an indirect negative regulator of flippase function. Moreover, we found that decreasing flippase function rescued the growth deficiency of four different cytokinesis mutants, which suggests that the primary function of Gin4 is highly localized control of membrane lipid asymmetry and is necessary for optimal cytokinesis.

The morphogenesis-related NDR kinase (MOR) pathway regulates morphogenesis in fungi. In spite of the high conservation of its components, impairing their functions results in highly divergent cellular responses depending on the fungal species. The reasons for such differences are unclear. Here we propose that the species-specific connections between cell cycle regulation and the MOR pathway could be partly responsible for these divergences. We based our conclusion on the characterization of the MOR pathway in the fungus Ustilago maydis. Each gene that encodes proteins of this pathway in U. maydis was deleted. All mutants exhibited a constitutive hyperpolarized growth, contrasting with the loss of polarity observed in other fungi. Using a conditional allele of the central NDR kinase Ukc1, we found that impairing MOR function resulted in a prolonged G2 phase. This cell cycle delay appears to be the consequence of an increase in Cdk1 inhibitory phosphorylation. Strikingly, prevention of the inhibitory Cdk1 phosphorylation abolished the hyperpolarized growth associated with MOR pathway depletion. We found that the prolonged G2 phase resulted in higher levels of expression of crk1, a conserved kinase that promotes polar growth in U. maydis. Deletion of crk1 also abolished the dramatic activation of polar growth in cells lacking the MOR pathway. Taken together, our results suggest that Cdk1 inhibitory phosphorylation may act as an integrator of signaling cascades regulating fungal morphogenesis and that the distinct morphological response observed in U. maydis upon impairment of the MOR pathway could be due to a cell cycle deregulation. © 2012.

Better together: A novel hybrid N-heterocyclic carbene (NHC) palladium complex, integrating a totally inorganic and polyanionic decatungstate unit, has been synthesized following a convergent strategy. The interplay of the Pd binding domains with the inorganic scaffold is instrumental in accessing multi-turnover catalysis in C-C cross-coupling and aromatic dehalogenation reactions under MW-assisted protocols

Mitogen-activated protein kinase (MAPK) cascades and the calcium–calcineurin pathway control fundamental aspects of fungal growth, development and reproduction. Core elements of these signalling pathways are required for virulence in a wide array of fungal pathogens of plants and mammals. In this review, we have used the available genome databases to explore the structural conservation of three MAPK cascades and the calcium–calcineurin pathway in ten different fungal species, including model organisms, plant pathogens and human pathogens. While most known pathway components from the model yeast Saccharomyces cerevisiae appear to be widely conserved among taxonomically and biologically diverse fungi, some of them were found to be restricted to the Saccharomycotina. The presence of multiple paralogues in certain species such as the zygomycete Rhizopus oryzae and the incorporation of new functional domains that are lacking in S. cerevisiae signalling proteins, most likely reflect functional diversification or adaptation as filamentous fungi have evolved to occupy distinct ecological niches.

The project The Power of Play in a Grade 5 Classroom examines and offers answers to questions about the appropriate use of play in a Grade 5 class. The researcher has utilized playas a strategy for cognitive and social development with her Grade 5 students for several years and although she intuitively recognized the value of implementing such a learning strategy, she had not formally gathered evidence to support her position. In addition to reviewing literature pertaining to the topic, the research project brings forth supporting evidence from her classroom and curriculum practice which indicates that intermediate students who are provided with play opportunities in the class benefit emotionally, socially and academically. This document consists of personal reflections on action research done over several years.

The project The Power of Play in a Grade 5 Classroom examines and offers answers to questions about the appropriate use of play in a Grade 5 class. The researcher has utilized playas a strategy for cognitive and social development with her Grade 5 students for several years and although she intuitively recognized the value of implementing such a learning strategy, she had not formally gathered evidence to support her position. In addition to reviewing literature pertaining to the topic, the research project brings forth supporting evidence from her classroom and curriculum practice which indicates that intermediate students who are provided with play opportunities in the class benefit emotionally, socially and academically. This document consists of personal reflections on action research done over several years.

The project The Power of Play in a Grade 5 Classroom examines and offers answers to questions about the appropriate use of play in a Grade 5 class. The researcher has utilized playas a strategy for cognitive and social development with her Grade 5 students for several years and although she intuitively recognized the value of implementing such a learning strategy, she had not formally gathered evidence to support her position. In addition to reviewing literature pertaining to the topic, the research project brings forth supporting evidence from her classroom and curriculum practice which indicates that intermediate students who are provided with play opportunities in the class benefit emotionally, socially and academically. This document consists of personal reflections on action research done over several years.

The project The Power of Play in a Grade 5 Classroom examines and offers answers to questions about the appropriate use of play in a Grade 5 class. The researcher has utilized playas a strategy for cognitive and social development with her Grade 5 students for several years and although she intuitively recognized the value of implementing such a learning strategy, she had not formally gathered evidence to support her position. In addition to reviewing literature pertaining to the topic, the research project brings forth supporting evidence from her classroom and curriculum practice which indicates that intermediate students who are provided with play opportunities in the class benefit emotionally, socially and academically. This document consists of personal reflections on action research done over several years.

Better together: A novel hybrid N-heterocyclic carbene (NHC) palladium complex, integrating a totally inorganic and polyanionic decatungstate unit, has been synthesized following a convergent strategy. The interplay of the Pd binding domains with the inorganic scaffold is instrumental in accessing multi-turnover catalysis in C-C cross-coupling and aromatic dehalogenation reactions under MW-assisted protocols