Theoretical study of the excited state lifetime by ligand modifications and the vibrational anharmonicity for Fe(II) and Ru(II) complexes

Els complexos dels metalls de transició s’han popularitzat degut a les seves diferents funcionalitats com a materials a escala nanoscòpica. Aquells que presenten entrecreuament d’espín són especialment interessants per aplicacions tecnològiques. Aquesta tesis descriu alguns dels factors que governen la temperatura de transició per entrecreuament d’espín (T1/2) i la relaxació dels estats excitats per l’entrecreuament d’espín induït per la llum. El primer capítol es centra en les característiques bàsiques de l’estructura electrònica i descriu alguns detalls de les propietats dels compostos que s’estudiaran posteriorment. Després de descriure els mètodes teòrics, en el capítol 3 s’investiga sobre com la vida dels estats excitats pot ser controlada a través de la modificació dels lligands en els complexos [Fe(bpy)3]2+ i [Ru(bpy)3]2+. Es va predir que amb l’ús de lligands menys sigma donadors, el temps de vida dels estats excitats podia créixer dos ordres de magnituds en comparació amb el complex de referència. En el capítol 4, s’ha posat a prova la capacitat de predir la diferència d’energia adiabàtica entre l’estat d’alt espín i el de baix espín en un nou mètode computacional. Aquesta és una propietat força difícil de calcular, tot i l’elevat esforç dipositat i la, en principi, major precisió presentada pel mètode, no hem estat capaços de presentar una alternativa viable als mètodes existents, els quals probablement donen una resposta correcta degut a una cancel•lació d’errors. L’últim capítol de recerca descriu l’efecte de la anharmonicitat vibracional en T1/2. Generalment, s’assumeix que aquest efecte és petit, però mai ha estat comprovat. Els nostres resultats demostren que l’anharmonicitat canvia la temperatura de transició, tot i que l’efecte és realment petit i altres efectes que no s’introdueixen en els càlculs teòrics haurien de ser resolts prèviament.Los complejos de metales de transición se han popularizado debido a sus diferentes funcionalidades como materiales a escala nanoscopica. Aquellos que presentan entrecruzamiento de espín son especialmente interesantes por sus aplicaciones tecnológicas. Esta tesis describe alguno de los factores que gobiernan la temperatura de transición por entrecruzamiento de espín (T1/2) y la relajación de los estados excitados por el entrecruzamiento de espín inducido por luz. El primer capítulo se centra en las características electrónicas básicas i describe algunos detalles de las propiedades de los compuestos que van a ser estudiados posteriormente. Después de describir los métodos teóricos, en el capítulo 3 se investiga como la vida de los estados excitados puede ser controlada a través de los ligandos en los complejos [Fe(bpy)3]2+ y [Ru(bpy)3]2+. Se predijo que con el uso de ligandos menos sigma dadores, el tiempo de vida de los estados excitados podía crecer dos órdenes de magnitud en comparación con los complejos de referencia. En el capítulo 4, se ha puesto a prueba la capacidad de predicción de la diferencia de energía adiabática entre el estado de alto espín y el de bajo espín para un nuevo método computacional. Esta es una propiedad bastante difícil de calcular, y a pesar del esfuerzo realizado y la mayor precisión que debía presentar el método, no hemos sido capaces de presentar una alternativa viable a los métodos existentes, los cuales probablemente dan una respuesta correcta debido a una cancelación de errores. El último capítulo de investigación describe el efecto de la anharmonicidad vibracional en T1/2. Habitualmente, este efecto se considera muy pequeño, pero no ha estado comprobado. Nuestros resultados demuestran que la anharmonicidad cambia la temperatura de transición, a pesar de que el efecto es pequeño y otros efectos no introducidos en los cálculos teóricos deberían ser resueltos anteriormente.Transition metal (TM) complexes have become popular as functional and tuneable nanoscale materials and those with spin-crossover (SCO) properties are especially interesting for technological applications. This thesis describes some of the factors that govern the transition temperature for spin-crossover (T1/2) and the excited state relaxation for light-induced SCO. The first chapter focusses on the basic features of the electronic structure and describes in some detail the properties of the compounds studied. After describing the theoretical methods, Chapter 3 explores how the excited state lifetime can be controlled by modifying the ligands in [Fe(bpy)3]2+ and [Ru(bpy)3]2+. Using weaker sigma donors in the Fe complex, the lifetime of the excited state was predicted to be two order of magnitude larger than in the parent compound. In chapter 4, a new and in principle more accurate computational method has been tested for its capacity to predict the HS-LS adiabatic energy difference. This is a notoriously difficult property to calculate and despite much effort, we have not been able to present an alternative to the yet existing methods, which are suspected to give the right answer because of a cancellation of errors. The last research chapter describes to what extent T1/2 is affected by neglecting vibrational anharmonicity. It is generally assumed to be small but this has never been tested. Our outcomes show that anharmonicity does change the transition temperature, but the effect is small and it is argued that other effects that are not taken into account in the theoretical treatments are much bigger and should be resolved first

4-CPA (4-chlorophenoxyacetic acid) induces the formation and development of defective “fenghou” (vitis vinifera × v. labrusca) grape seeds

For some horticultural plants, auxins can not only induce normal fruit setting but also form fake seeds in the induced fruits. This phenomenon is relatively rare, and, so far, the underlying mechanism remains unclear. In this study, “Fenghou” (Vitis vinifera × V. labrusca) grapes were artificially emasculated before flowering and then sprayed with 4-CPA (4-chlorophenoxyacetic acid) to analyze its effect on seed formation. The results show that 4-CPA can induce normal fruit setting in “Fenghou” grapes. Although more seeds were detected in the fruits of the 4-CPA-treated grapevine, most seeds were immature. There was no significant difference in the seed shape; namely, both fruit seeds of the grapevines with and without 4-CPA treatment contained a hard seed coat. However, the immature seeds lacked embryo and endosperm tissue and could not germinate successfully; these were considered defective seeds. Tissue structure observation of defective seeds revealed that a lot of tissue redifferentiation occurred at the top of the ovule, which increased the number of cell layers of the outer integument; some even differentiated into new ovule primordia. The qRT-PCR results demonstrated that 4-CPA application regulated the expression of the genes VvARF2 and VvAP2, which are associated with integument development in “Fenghou” grape ovules. Together, this study evokes the regulatory role of 4-CPA in the division and continuous redifferentiation of integument cells, which eventually develop into defective seeds with thick seed coats in grapes

Gene expression profiling of human bone marrow-derived mesenchymal stem cells during adipogenesis

Introduction. Adipogenesis comprises multiple processes by which mesenchymal stem cells differentiate into adipocytes. To increase our knowledge of the mechanism underlying adipogenic differentiation of human bone marrow mesenchymal stem cells (hMSCs), we performed full-genome gene expression microarray and gene ontology analyses of induced differentiation of hMSCs. Material and methods. Adipogenic differentiation of hMSCs was induced by an adipogenic medium, and total RNA was extracted from undifferentiated hMSCs (day 0) and differentiated adipocytes (day 14). Then microarray hybridization of RNA samples was performed. The GeneChip Operating Software was used to analyze the hybridization data to identify differentially expressed genes, which were performed Gene Ontology categorization and pathway analysis. Pathway-act-network and genes-act-network were built according to the Kyoto Encyclopedia of Genes and Genomes database. Some differentially expressed genes were subjected to qRT-PCR to verify the microarray data. Results. We detected a total of 3,821 differentially expressed genes, of which 753 were upregulated and 3,068 downregulated. These genes were well represented in a variety of functional categories, including collagen fibril organization, brown fat cell differentiation, cell division, and S phase of mitotic cell cycle. Subsequently, pathway analysis was conducted, and significant pathways (from top 50) were selected for pathway-act-network analysis, which indicated that the mitogen-activated protein kinase (MAPK) pathway and cell cycle were of high degrees (> 10). Gene-act-network analysis showed that insulin-like growth factor 1 receptor (IGF1R), histone deacetylase 1 (HDAC1), HDAC2, MAPK13, MAPK8, phosphoinositide-3-kinase regulatory subunit 1 (PI3KR1), and PI3KR2 also had high degrees (> 18). Conclusions. Collectively, these data provide novel information and could serve as a basis for future study to clarify the mechanisms underlying adipocyte differentiation of hMSCs

A reporter system for assaying influenza virus RNP functionality based on secreted Gaussia luciferase activity

<p>Abstract</p> <p>Background</p> <p>Influenza A virus can infect a wide variety of animal species including humans, pigs, birds and other species. Viral ribonucleoprotein (vRNP) was involved in genome replication, transcription and host adaptation. Currently, firefly luciferase (Fluc) reporter system was used in vRNP functional assay. However, its limitation for the testing by virus infection resulted in an increased need for rapid, sensitive, and biosafe techniques. Here, an influenza A virus UTR-driven gene reporter for vRNP assay based on secreted <it>Gaussia </it>luciferase (Gluc) activity was evaluated.</p> <p>Results</p> <p>By measuring Gluc levels in supernatants, reporter gene activity could be detected and quantitated after either reconstitution of influenza A virus polymerase complex or viral infection of 293T and A549 cells, respectively. As compared with Fluc reporter, Gluc-based reporter was heat-tolerant (65°C for 30 min) and produced 50-fold higher bioluminescent activity at 24 h posttransfection. Signals generated by Gluc reporter gene could be detected as early as 6 h post-infection and accumulated with time. Testing by viral infection, stronger signals were detected by Gluc reporter at a MOI of 0.001 than that of 1 and the effects of PB2-627K/E or amantadine on influenza vRNP activity were elucidated more effectively by the Gluc reporter system.</p> <p>Conclusions</p> <p>This approach provided a rapid, sensitive, and biosafe assay of influenza vRNP function, particularly for the highly pathogenic avian influenza viruses.</p

Neuraminidase and Hemagglutinin Matching Patterns of a Highly Pathogenic Avian and Two Pandemic H1N1 Influenza A Viruses

BACKGROUND: Influenza A virus displays strong reassortment characteristics, which enable it to achieve adaptation in human infection. Surveying the reassortment and virulence of novel viruses is important in the prevention and control of an influenza pandemic. Meanwhile, studying the mechanism of reassortment may accelerate the development of anti-influenza strategies. METHODOLOGY/PRINCIPAL FINDINGS: The hemagglutinin (HA) and neuraminidase (NA) matching patterns of two pandemic H1N1 viruses (the 1918 and current 2009 strains) and a highly pathogenic avian influenza A virus (H5N1) were studied using a pseudotyped particle (pp) system. Our data showed that four of the six chimeric HA/NA combinations could produce infectious pps, and that some of the chimeric pps had greater infectivity than did their ancestors, raising the possibility of reassortment among these viruses. The NA of H5N1 (A/Anhui/1/2005) could hardly reassort with the HAs of the two H1N1 viruses. Many biological characteristics of HA and NA, including infectivity, hemagglutinating ability, and NA activity, are dependent on their matching pattern. CONCLUSIONS/SIGNIFICANCE: Our data suggest the existence of an interaction between HA and NA, and the HA NA matching pattern is critical for valid viral reassortment

The Mycobacterium tuberculosis prolyl dipeptidyl peptidase cleaves the N-terminal peptide of the immunoprotein CXCL-10

Dipeptidyl peptidases constitute a class of non-classical serine proteases that regulate an array of biological functions, making them pharmacologically attractive enzymes. With this work, we identified and characterized a dipeptidyl peptidase from Mycobacterium tuberculosis (MtDPP) displaying a strong preference for proline residues at the P1 substrate position and an unexpectedly high thermal stability. MtDPP was also characterized with alanine replacements of residues of its active site that yielded, for the most part, loss of catalysis. We show that MtDPP catalytic activity is inhibited by well-known human DPP4 inhibitors. Using MALDI-TOF mass spectrometry we also describe that in vitro, MtDPP mediates the truncation of the C-X-C motif chemokine ligand 10, indicating a plausible role in immune modulation for this mycobacterial enzyme

Concentration, distribution and sources of perfluoroalkyl substances and organochlorine pesticides in surface sediments of the northern Bering Sea, Chukchi Sea and adjacent Arctic Ocean.

Perfluoroalkyl substances (PFAS) and organochlorine pesticides (OCPs) in surface sediments were investigated from the Bering Sea, the Chukchi Sea and adjacent Arctic Ocean in 2010. Total concentrations (dry weight) of Σ14PFAS in surface sediments (0.85 ± 0.22 ng g-1) of the Bering Sea were lower than that in the Chukchi Sea and adjacent Arctic Ocean (1.27 ± 0.53 ng g-1). Perfluoro-butanoic acid (PFBS) and perfluoro-octanoic acid (PFOA) were the dominant PFAS in these areas. The concentrations of Σ15OCPs in the sediment of the Bering Sea (13.00 ± 6.17 ng g-1) was slightly higher than that in the Chukchi and Arctic Ocean (12.05 ± 2.27 ng g-1). The most abundant OCPs were hexachlorocyclohexane isomers (HCHs) and dichlorodiphenyltrichloroethane (DDT) and its metabolites. The composition patterns of HCHs and DDTs indicated that they were mainly derived from the early residues via river runoff. Increasing trends of PFAS, HCHs and DDTs in surface sediments from the Bering Sea to the Arctic Ocean were found, indicating oceanic transport. In summary, the concentrations of OCPs were orders of magnitude greater than the observed PFAS concentrations, and the concentrations of PFAS and OCPs in surface sediments from the Bering Sea to the Chukchi Sea and adjacent Arctic Ocean are at the low to moderate levels by comparing with other coastal and marine sediments worldwide