Formazanate as redox-active, structurally versatile ligand platform:Zinc and boron chemistry

Redox-actieve liganden zijn liganden die in staat zijn actief deel te nemen aan het maken/breken van bindingen met behulp van redox-reacties, bijvoorbeeld door te fungeren als electron-donor of -acceptor. Wanneer dit type liganden gebonden is aan metaalcentra, biedt dit de mogelijkheid om ongebruikelijke redox-reacties te bewerkstelligen doordat instabiele oxidatietoestanden van het metaalcentrum worden vermeden. Dit geeft aanleiding tot nieuwe (katalytische) reactiviteit die met conventionele liganden niet toegankelijk is. De ontwikkeling van nieuwe liganden met redox-actieve eigenschappen kan zich verheugen op toenemende belangstelling, vanwege de kansen die dit biedt om edele metalen te vervangen door goedkopere en minder schaarse elementen voor toepassing in (homogene) katalyse. Het ligand systeem dat in dit proefschrift wordt beschreven is gebaseerd op de NNCNN-structuur van formazan verbindingen, wat grote overeenkomsten heeft met de veelvuldig toegepaste b-diketimine liganden. In dit proefschrift wordt de synthese van nieuwe coördinatiecomplexen van dit ligand met de elementen Zn en B beschreven, alsmede de chemische en fysische eigenschappen van deze verbindingen. De resultaten laten zien dat deze formazanaat anionen unieke redox-eigenschappen hebben en leggen een brede basis voor de verdere ontwikkeling van de (katalytische) reactiviteit van organometaalcomplexen met dit type ligand.Redox-active ligands are ligand platforms that can actively participate in the redox changes during chemical reactions by accepting or donating electrons from or to substrates. Utilizing this special feature, metal centers coordinated by redox-active ligands avoid reaching unstable oxidation states during chemical redox processes. Thus, such complexes can perform catalytic redox reactions that are not possible with conventional ligands. The research of redox-active ligands is getting more and more attention today; this is due to its potential of replacing precious metals in (homogeneous) catalysis with base metals. The ligand systems presented in this thesis are based on the formazan framework, which is a nitrogen-rich analogue of well-known b-diketimine ligands. The thesis focuses on Zn and B complexes and uses them to understand the chemical and physical properties of formazanate ligands. The results presented in this thesis establish a strong basis for future research into new (catalytic) chemistry mediated by complexes with redox-active formazanate ligands

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A crystallization-induced asymmetric transformation (CIAT) involving a radical-mediated racemization provides access to enantiopure secondary phosphine oxides. A consecutive CIAT is used to prepare enantio-and diastereo-pure tert-butyl(hydroxyalkyl)phenylphosphine oxides

Single nucleotide polymorphisms of one-carbon metabolism and cancers of the esophagus, stomach, and liver in a Chinese population.

One-carbon metabolism (folate metabolism) is considered important in carcinogenesis because of its involvement in DNA synthesis and biological methylation reactions. We investigated the associations of single nucleotide polymorphisms (SNPs) in folate metabolic pathway and the risk of three GI cancers in a population-based case-control study in Taixing City, China, with 218 esophageal cancer cases, 206 stomach cancer cases, 204 liver cancer cases, and 415 healthy population controls. Study participants were interviewed with a standardized questionnaire, and blood samples were collected after the interviews. We genotyped SNPs of the MTHFR, MTR, MTRR, DNMT1, and ALDH2 genes, using PCR-RFLP, SNPlex, or TaqMan assays. To account for multiple comparisons and reduce the chances of false reports, we employed semi-Bayes (SB) shrinkage analysis. After shrinkage and adjusting for potential confounding factors, we found positive associations between MTHFR rs1801133 and stomach cancer (any T versus C/C, SB odds-ratio [SBOR]: 1.79, 95% posterior limits: 1.18, 2.71) and liver cancer (SBOR: 1.51, 95% posterior limits: 0.98, 2.32). There was an inverse association between DNMT1 rs2228612 and esophageal cancer (any G versus A/A, SBOR: 0.60, 95% posterior limits: 0.39, 0.94). In addition, we detected potential heterogeneity across alcohol drinking status for ORs relating MTRR rs1801394 to esophageal (posterior homogeneity P = 0.005) and stomach cancer (posterior homogeneity P = 0.004), and ORs relating MTR rs1805087 to liver cancer (posterior homogeneity P = 0.021). Among non-alcohol drinkers, the variant allele (allele G) of these two SNPs was inversely associated with the risk of these cancers; while a positive association was observed among ever-alcohol drinkers. Our results suggest that genetic polymorphisms related to one-carbon metabolism may be associated with cancers of the esophagus, stomach, and liver. Heterogeneity across alcohol consumption status of the associations between MTR/MTRR polymorphisms and these cancers indicates potential interactions between alcohol drinking and one-carbon metabolic pathway

Asymmetric synthesis of N,O-heterocycles via enantioselective iridium-catalysed intramolecular allylic amidation

Chiral N,O-heterocycles were synthesized in high yields and excellent enantioselectivity up to 97% ee via iridium-catalysed intramolecular allylic substitution with nucleophilic attack by the amide oxygen atom. The resulting benzoxazine derivatives were further transformed into challenging chiral N,O-ketals bearing both a tertiary and a quaternary center with excellent diastereoselectivities

Spin-Crossover in a Pseudo-tetrahedral Bis(formazanate) Iron Complex

Spin-crossover in a pseudo-tetrahedral bis(formazanate) iron(II) complex (1) is described. Structural, magnetic, and spectroscopic analyses indicate that this compound undergoes thermal switching between an S=0 and an S=2 state, which is very rare in four-coordinate complexes. The transition to the high-spin state is accompanied by an increase in Fe-N bond lengths and a concomitant contraction of intraligand N-N bonds. The latter suggests that stabilization of the low-spin state is due to the π-acceptor properties of the ligand. One-electron reduction of 1 leads to the formation of the corresponding anion, which contains a low-spin (S=1/2) Fe(I) center. The findings are rationalized by electronic structure calculations using density functional theory

Pedagogía social : revista interuniversitaria

Monográfico con el título: "Redes territoriales de acción socioeducativa: una apuesta por la innovación social colaborativa"Título, resumen y palabras clave también en portuguésResumen basado en el de la publicaciónEstudio cualitativo, localizado en Estados Unidos, presenta un análisis en profundidad sobre el liderazgo en escuelas y organizaciones comunitarias que ayudan a conectar a los alumnos y a las familias con recursos educativos fundamentales. Los datos han sido recopilados a partir de 132 entrevistas con personas que han experimentado las complejidades sociales de la indigencia. Los resultados sugieren que el liderazgo participativo fomenta el aprendizaje, el simbolismo, el desarrollo de la identidad y la responsabilidad. El tipo de liderazgo promete brindar oportunidades para los desfavorecidos, que no tienen acceso a recursos o relaciones de importancia.ES

SinicView: A visualization environment for comparisons of multiple nucleotide sequence alignment tools

BACKGROUND: Deluged by the rate and complexity of completed genomic sequences, the need to align longer sequences becomes more urgent, and many more tools have thus been developed. In the initial stage of genomic sequence analysis, a biologist is usually faced with the questions of how to choose the best tool to align sequences of interest and how to analyze and visualize the alignment results, and then with the question of whether poorly aligned regions produced by the tool are indeed not homologous or are just results due to inappropriate alignment tools or scoring systems used. Although several systematic evaluations of multiple sequence alignment (MSA) programs have been proposed, they may not provide a standard-bearer for most biologists because those poorly aligned regions in these evaluations are never discussed. Thus, a tool that allows cross comparison of the alignment results obtained by different tools simultaneously could help a biologist evaluate their correctness and accuracy. RESULTS: In this paper, we present a versatile alignment visualization system, called SinicView, (for Sequence-aligning INnovative and Interactive Comparison VIEWer), which allows the user to efficiently compare and evaluate assorted nucleotide alignment results obtained by different tools. SinicView calculates similarity of the alignment outputs under a fixed window using the sum-of-pairs method and provides scoring profiles of each set of aligned sequences. The user can visually compare alignment results either in graphic scoring profiles or in plain text format of the aligned nucleotides along with the annotations information. We illustrate the capabilities of our visualization system by comparing alignment results obtained by MLAGAN, MAVID, and MULTIZ, respectively. CONCLUSION: With SinicView, users can use their own data sequences to compare various alignment tools or scoring systems and select the most suitable one to perform alignment in the initial stage of sequence analysis

Second-Hand Smoke–Induced Cardiac Fibrosis Is Related to the Fas Death Receptor Apoptotic Pathway without Mitochondria-Dependent Pathway Involvement in Rats

Exposure to environmental tobacco smoke has been epidemiologically linked to heart disease among nonsmokers. However, the molecular mechanism behind the pathogenesis of cardiac disease is unknown. In this study, we found that Wistar rats, exposed to tobacco cigarette smoke at doses of 5, 10, or 15 cigarettes for 30 min twice a day for 1 month, had a dose-dependently reduced heart weight to body weight ratio and enhanced interstitial fibrosis as identified by histopathologic analysis. The mRNA and activity of matrix metalloprotease-2 (MMP-2), representing the progress of cardiac remodeling, were also elevated in the heart. In addition, we used reverse-transcriptase polymerase chain reaction and Western blotting to demonstrate significantly increased levels of the apoptotic effecter caspase-3 in treated animal hearts. Dose-dependently elevated mRNA and protein levels of Fas, and promoted apoptotic initiator caspase-8 (active form), a molecule of a death-receptor–dependent pathway, coupled with unaltered or decreased levels of cytosolic cytochrome c and the apoptotic initiator caspase-9 (active form), molecules of mitochondria-dependent pathways, may be indicative of cardiac apoptosis, which is Fas death-receptor apoptotic-signaling dependent, but not mitochondria pathway dependent in rats exposed to second-hand smoke (SHS). With regard to the regulation of survival pathway, using dot blotting, we found cardiac insulin-like growth factor-1 (IGF-1) and IGF-1 receptor mRNA levels to be significantly increased, indicating that compensative effects of IGF-1 survival signaling could occur. In conclusion, we found that the effects of SHS on cardiomyocyte are mediated by the Fas death-receptor–dependent apoptotic pathway and might be related to the epidemiologic incidence of cardiac disease of SHS-exposed non-smokers