6,207 research outputs found

    From Photosynthesis to Detoxification: Microbial Metabolisms Shape Earth’s Surface Chemistry

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    Earth’s chemistry, through geologic time and in the present, is inextricably linked with biologically mediated reactions. All major elemental cycles on Earth’s surface have arisen from two competing processes – life shaping its chemical environment through the evolution of key biochemical pathways, and the environment constraining metabolism by dictating which reactions will occur. Understanding this complicated interplay motivates the research presented in this thesis, which studies this phenomenon over two major elemental cycles – the modern Nitrogen (N) and ancient Carbon (C) cycle. Chapters One and Two focus on the evolution of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco), the enzyme that catalyzes the key carbon fixation step in modern oxygenic photosynthesis. This reaction also imparts a large kinetic isotope effect (KIE) that causes the fixed carbon to be relatively depleted in natural abundance ¹³C compared to its substrate; this isotopic fingerprint can be seen in both the modern C cycle and in rock records recording the ancient C cycle. Therefore, this KIE has been used both in vitro (outside the cell) by biochemical models to rationalize rubisco’s reaction mechanism, and in vivo (in the cell) as a proxy for environmental CO₂ concentrations in the past and present. However, both the in vitro and in vivo measurements are calibrated using modern organisms even though rubisco and oxygenic photosynthesis have undergone profound evolution over geologic time. Therefore, we measured the KIE in vitro and in vivo of a reconstructed ancestral Form IB rubisco dating to &gt;&gt; 1 Ga, and the KIE in vitro of a recently discovered Form I’ rubisco that presents a modern analogue to ancestral Form I rubiscos prior to the evolution of the small subunit. Overall, we find that the KIEs of both rubiscos are smaller than their modern counterparts, which is surprising given that the rock record indicates overall carbon isotope fractionations in vivo are larger in the past. In addition, we find that models strictly based on modern organisms may not apply to the past, questioning the basic assumption that uniformitarianism can be readily applied to biological processes. However, these models can be rescued by accounting for other aspects of cell physiology. Chapter Three focuses on disentangling the source of key metabolites, like nitrous oxide (N₂O) in the modern N cycle. Like Chapters 1 and 2, an isotopic fingerprint that measures the ‘preference’ of ¹⁵N for the central or outer nitrogen site in N₂O (“Site Preference” or “SP”) has primarily been calibrated using dissimilatory, or energy-generating, nitric oxide (NO) reductases (NORs). However, there exists a much larger and phylogenetically widespread class of NO-detoxifying enzymes; in particular, flavohemoglobin proteins (Fhp/Hmp) produce N₂O as a strategy to neutralize damaging NO-radicals in anoxic conditions. This enzyme, which generates N₂O in non-growing and anoxic conditions, may be more relevant to natural environments where N₂O production has been detected. Surprisingly, we found that Fhp imparts a distinct SP on N₂O that differs from both bacterial and eukaryotic NORs, and that this value better aligns with existing in situ measurements of N₂O from soils. In addition, we find that in strains with both Fhp and NOR, the Fhp signal dominates when cells are first exposed to high concentrations of NO in oxic conditions while growing before being shifted to an anoxic, non-growing state. Therefore, in addition to telling us ‘Who’s there,’ the SP fingerprint may also be able to tell us something about cell physiology in vivo. We propose a new framework for interpreting the source of N₂O based on SP values.</p

    Indirect daylight oxidative degradation of polyethylene microplastics by a bio-waste modified TiO2-based material

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    Microplastics are recognized as an emerging critical issue for the environment. Here an innovative chemical approach for the treatment of microplastics is proposed, based on an oxidative process that does not require any direct energy source (irradiation or heat). Linear low-density polyethylene (LLDPE) was selected as target commodity polymer, due to its widespread use, chemical inertness and inefficient recycling. This route is based on a hybrid material coupling titanium oxide with a bio-waste, rosin, mainly constituted by abietic acid, through a simple sol-gel synthesis procedure. The ligand-to-metal charge transfer complexes formed between rosin and Ti4+ allow the generation of reactive oxygen species without UV irradiation for its activation. In agreement with theorical calculations, superoxide radical ions are stabilized at ambient conditions on the surface of the hybrid TiO2. Consequently, an impressive degradation of LLDPE is observed after 1 month exposure in a batch configuration under indirect daylight, as evidenced by the products revealed by gas chromatography-mass spectrometry analysis and by chemical and structural modifications of the polymer surface. In a context of waste exploitation, this innovative and sustainable approach represents a promising cost-effective strategy for the oxidative degradation of microplastics, without producing any toxic by-products

    Materiales basados en especies de Pd soportadas sobre matrices sólidas como catalizadores eficientes para reacciones de interés en química fina

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    [ES] La presente tesis doctoral se basa en la síntesis, caracterización y uso de catalizadores basados en especies de Pd soportadas sobre matrices sólidas en reacciones de interés en química fina. En general, se ha pretendido obtener catalizadores multifuncionales, estables y reutilizables que se puedan separar fácilmente de la mezcla de reacción y que contribuyan a desarrollar protocolos más sostenibles que den lugar a compuestos orgánicos de interés. En primer lugar, el material [Pd/Al2O3], constituido por nanoagregados de Pd(0) de un tamaño medio de 2.8 nm y soportados sobre una matriz de tipo ¿-Al2O3 con elevada densidad de sitios ácidos, ha demostrado ser altamente activo y eficiente en la ciclación deshidrogenativa entre ureas y 1,2-dioles para la síntesis de imidazol-2-onas. Al utilizar ureas y 1,2-dioles desactivados, la cooperatividad Pd-Zn ha demostrado ser imprescindible para el éxito del proceso, obteniendo los mejores resultados al emplear el sistema de [Pd/Al2O3]-ZnO. Ambos materiales, [Pd/Al2O3] y [Pd/Al2O3]-ZnO, han demostrado ser reusables y estables bajo las condiciones de reacción al no presentar problemas de lixiviación. Además, este protocolo catalítico ha permitido obtener hasta 28 imidazol-2-onas con buenos resultados, demostrando su amplio potencial sintético. Por otra parte, el nanomaterial [Pd(0.75%)/Mg3Al-LDH]-300(D), constituido por nanopartículas de Pd(0) de un tamaño medio de 2.8 nm y soportado sobre una matriz básica de tipo dh-LDH, ha demostrado ser altamente activo para mediar la síntesis de propiolamidas mediante la aminocarbonilación oxidativa entre alquinos terminales y aminas secundarias, en presencia de CO/O2. Se ha determinado que un soporte con estructura dh-LDH con una relación de Mg/Al de 3 es el idóneo para estabilizar especies de [PdI2] generadas in situ en el medio de reacción así como para promover la activación de los reactivos de partida. El sistema catalítico ha demostrado ser reusable y estable bajo las condiciones de reacción, además de poseer una elevada aplicabilidad sintética al haber obtenido más de 60 propiolamidas diferentes, destacando el uso por primera vez en este tipo de procesos de aminas N-aromáticas y N-heterocíclicas. Finalmente, se ha llevado a cabo la síntesis de materiales híbridos derivados de soportar mediante interacciones no covalentes complejos de Pd con geometría plano-cuadrada sobre matrices grafénicas. Los resultados de caracterización apuntan a que estos materiales están constituidos, principalmente, por especies aisladas de Pd(II), demostrando el papel estabilizante de los ligandos utilizados al evitar la agregación del metal. Esos materiales han sido, en general, altamente activos y selectivos como catalizadores en la semi-hidrogenación de alquinos, y lo que es más relevante, se ha demostrado una sinergia complejo - grafeno en la actividad catalítica estudiada. El material de [Pd-Phen/OGr-C] ha sido reutilizado en varios ciclos y es estable bajo las condiciones de reacción. Además, este protocolo catalítico posee una elevada aplicabilidad, al haberse podido utilizar hasta con 37 alquinos diferentes obteniendo muy buenos resultados de rendimiento y quimioselectividad.[CA] La present tesi doctoral es basa en la síntesi, caracterització i ús de catalitzadors basats en espècies de Pd suportades sobre matrius sòlides en reaccions d'interés en química fina. En general, s'ha pretès obtenir catalitzadors multifuncionals, estables i reutilitzables que es puguen separar fàcilment de la mescla de reacció i que contribuïsquen a desenvolupar protocols més sostenibles que donen lloc a compostos orgànics d'interès. En primer lloc, el material [Pd/Al2O3], constituït per nanoagregats de Pd(0) d'una grandària mitjana de 2.8 nm i suportats sobre una matriu de tipus ¿-Al2O3 amb elevada densitat de llocs àcids, ha demostrat ser altament actiu i eficient en la ciclació deshidrogenativa entre urees i 1,2-diols per a la síntesi d'imidazol-2-ones. En utilitzar urees i 1,2-diols desactivats, la cooperativitat Pd-Zn ha demostrat ser imprescindible per a l'èxit del procés, aconseguint els millors resultats emprant el sistema de [Pd/Al2O3]-ZnO. Tots dos materials, [Pd/Al2O3] i [Pd/Al2O3]-ZnO, han demostrat ser reutilitzables i estables sota les condicions de reacció ja que no presenten problemes de lixiviació. A més, aquest protocol catalític ha permès obtenir fins a 28 imidazol-2-ones amb bons resultats, demostrant el seu ampli potencial sintètic. D'altra banda, el nanomaterial [Pd(0.75%)/Mg3Al-LDH]-300(D), constituït per nanopartícules de Pd(0) d'una grandària mitjana de 2.8 nm suportades sobre una matriu bàsica de tipus dh-LDH, ha demostrat ser altament actiu per a catalitzar la síntesi de propiolamides mitjançant l'aminocarbonilació oxidativa entre alquins terminals i amines secundàries, en presència de CO/O2. S'ha determinat que un suport amb estructura dh-LDH amb una relació de Mg/Al de 3 és l'idoni per a estabilitzar les espècies de [PdI2] generades in situ en el medi de reacció així com per a promoure l'activació dels reactius de partida. El sistema catalític ha demostrat ser reutilitzable i estable sota les condicions de reacció, a més de posseir una elevada aplicabilitat sintètica en haver obtingut més de 60 propiolamides diferents, destacant l'ús per primera vegada en aquesta mena de processos d'amines N-aromàtiques i N-heterocícliques. Finalment, s'ha dut a terme la síntesi de materials híbrids derivats de suportar mitjançant interaccions no covalents complexos de Pd amb geometria pla-quadrada sobre matrius grafèniques. Els resultats de caracterització apunten a que aquests materials estan constituïts, principalment, per espècies aïllades de Pd(II), demostrant el paper estabilitzant dels lligands utilitzats per a evitar l'agregació del metall. Aquests materials han sigut, en general, altament actius i selectius com a catalitzadors en la semi-hidrogenació d'alquins, i el que és més rellevant, s'ha demostrat una sinèrgia complex - grafè en l'activitat catalítica estudiada. El material [Pd-Phen/OGr-C] ha sigut reutilitzat en diversos cicles i es estable sota les condicions de reacció. A més, aquest protocol catalític posseeix una elevada aplicabilitat i s'ha pogut aplicar a 37 alquins diferents obtenint molt bons resultats de rendiment i quimioselectivitat.[EN] The present PhD thesis is focused on the synthesis, characterisation and use of catalysts based on Pd species supported on solid matrixes in reactions of interest in fine chemistry. In general, the aim is to obtain multifunctional, stable and reusable catalysts that can be easily separated from the reaction mixture and that contribute to the development of more sustainable protocols leading to relevant organic compounds. Firstly, the [Pd/Al2O3] material, consisting of Pd(0) nanoaggregates with an average size of 2.8 nm and supported on a ¿-Al2O3-type matrix with a high density of acid sites, has been designed as a highly active and efficient catalyst in the dehydrogenative cyclisation between ureas and 1,2-diols for the synthesis of imidazole-2-ones. When using ureas and deactivated 1,2-diols, Pd-Zn cooperativity has been shown to be essential for the success of the process, with the best results obtained using a [Pd/Al2O3]-ZnO system. Both materials, [Pd/Al2O3] and [Pd/Al2O3]-ZnO, have proved to be reusable and stable under the reaction conditions as they do not present leaching problems. Moreover, this catalytic protocol has allowed to obtain up to 28 imidazole-2-ones with good results, demonstrating it is wide synthetic potential. On the other hand, the nanomaterial [Pd(0.75%)/Mg3Al-LDH]-300(D), consisting of Pd(0) nanoparticles with an average size of 2.8 nm and supported on a basic dh-LDH-type matrix, has been shown to be highly active for catalysing the synthesis of propiolamides via oxidative aminocarbonylation between terminal alkynes and secondary amines in the presence of CO/O2. A dh-LDH-structured support with an Mg/Al ratio of 3 has been found to be suitable for stabilising [PdI2] species generated in situ in the reaction medium, as well as for promoting the activation of the starting reagents. The catalytic system has proved to be reusable and stable under the reaction conditions, besides having a high synthetic applicability as more than 60 different propiolamides have been obtained. It is especially relevant the use of N-aromatic and N-heterocyclic amines for the first time in this type of processes. Finally, the synthesis of hybrid materials derived from supporting Pd complexes with planar square geometry on graphene matrices through non-covalent interactions has been carried out. The characterisation results show that these materials are mainly constituted by isolated Pd(II) species, demonstrating the stabilising role of the ligands to avoid the aggregation of the metal. These materials have been, in general, highly active and selective as catalysts in the semi-hydrogenation of alkynes, and what is more relevant, a complex - graphene synergy has been demonstrated in the studied catalytic activity. In addition, [Pd-Phen/OGr-C] has shown to be reusable in several catalytic cycles and stable under the reaction conditions. Moreover, this catalytic protocol has demonstrated a high applicability, in fact it has been applied to 37 different alkynes with very good results, in terms of yield and chemoselectivity.Arango Daza, JC. (2023). Materiales basados en especies de Pd soportadas sobre matrices sólidas como catalizadores eficientes para reacciones de interés en química fina [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/20157

    Activating Methane and Other Small Molecules: Computational study of Zeolites and Actinides

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    Exploring the catalytic properties and reactivity of actinide complexes towards activation of small molecules is important as human activities have led to the increased distribution of these species in nature. Toward this end, it is important to have a computational protocol for studying these species, in this thesis we provide details on the performance of multiconfigurational pair-density functional theory (MC-PDFT) in actinide chemistry. MC-PDFT and Kohn-Sham Density Functional Theory (KS-DFT) perform well for these species with indications that the former can be used for species with even greater static electron correlation effect. In addition, we study the activity of organometallic trans-uranium complexes towards the electrocatalytic reduction of water. We conclude that, with a guided choice of ligand, neptunium complexes can provide similar reactivity when compared to organometallic uranium complexes.Conversion of methane to methanol has been a major focus of research interest over the years. This is largely due to the abundance of natural gas, of which methane is the major constituent. Copper-exchanged zeolites have been shown to be able to kinetically trap activated methane as strongly-bound methoxy groups, preventing over-oxidation to CO2, CO and HCOOH. In this stepwise process, there are three cycles; an initial activation step to form the copper oxo active site, methane C-H activation and lastly simultaneous desorption of methanol and re -activation of the active site.. We provide detailed description of the pathway for the formation of over oxidation products. It is observed that to ensure high selectivity to methanol and prevent further hydrogen atom abstraction by extra-framework species, the methyl group must be stabilized from the copper-oxo active sites. There is a temperature gradient between the steps in the methane-to-methanol conversion cycle which is an impediment to industrial adoption of this approach for methane-to-methanol conversion. To mitigate this, we have investigated the impact of heterometallic extra-framework motifs on the temperature gradients of each step. Using periodic DFT, we provide detailed descriptions of the mechanistic pathways for each of the three steps. We were subsequently able to design motif(s) with great methane C-H activities as well as the abilities to be formed and regenerated at nearly the same temperatures. We found [Cu-O-Ag] and [Cu-O-Pd] to be potential candidates for isothermal or near-isothermal operations of the methane-to-methanol conversion cycle. Finally, we provide insights to the changes in optical spectra of activated copper-exchanged zeolites, gaining an understanding of the evolution of these systems on a molecular level will provide opportunities to achieve improved reactivity

    Crystal Structures of Metal Complexes

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    This reprint contains 11 papers published in a Special Issue of Molecules entitled "Crystal Structures of Metal Complexes". I will be very happy if readers will be interested in the crystal structures of metal complexes

    Synthesis of multifunctional glyco-pseudodendrimers and glyco-dendrimers and their investigation as anti-Alzheimer agents

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    As the world population is aging, the cases of Alzheimer’s Disease (AD) are increasing. AD is a disorder of the brain which is characterized by the aggregation of amyloid beta (Aβ) plaques. This leads to the death of numerous brain cells thus affecting the cognitive and motor functions of the individual. Till date, no cure for the disease is available. Aβ are peptides with 40/42 amino acid residues but, their exact mechanism(s) of action in AD is under debate. Having different amino acid residues makes them susceptible to form hydrogen bonds. Dendrimers with sugar units are often referred to as glycopolymers and have been shown to have potential anti-amyloidogenic activity. However, they also have drawbacks, the synthesis involves multiple tedious steps, and dendrimers themselves offer only a limited number of functional units. Pseudodendrimers are another class of branched polymers based on hyperbranched polymers. Unlike the dendrimers, they are easy to synthesize with a dense shell of functional units on the surface. One of the main goals in this dissertation is the synthesis and characterization of pseudodendrimers and dendrimers based on 2,2-bis(hydroxymethyl)-propionic acid (bis-MPA), an aliphatic polyester scaffold, as it offers biocompatibility and easy degradability. Furthermore, they are decorated with mannose units on the surface using a ‘click’ reaction forming glyco-pseudodendrimers and glyco-dendrimers. A detailed characterization of their structures and physical properties was undertaken using techniques such as size exclusion chromatography, asymmetric flow field flow fractionation (AF4), and dynamic light scattering. The second main focus of this work has been to investigate the interaction of synthesized glyco-pseudodendrimers and glyco-dendrimers with Aβ 40 peptides. For this task, five different concentrations of the synthesized glycopolymers were tested with Aβ 40 using the Thioflavin T assay. The results of the synthesized polymers which produced the best results of showing maximum anti-aggregation behavior against Aβ 40 were confirmed with circular dichroism spectroscopy. AF4 was also used to investigate Aβ 40-glycopolymer aggregates, which has never been done before and constitutes the highlight of this dissertation. Atomic force microscopy was used to image Aβ 40-glycopseudodenrimer aggregates. A basic but important step in the development of drug delivery platforms is to evaluate the toxicity of the drugs synthesized. In this work, preliminary studies of the cytotoxicity of glyco-pseudodendrimers were performed in two different cell lines. Thus, this study comprises a preliminary investigation of the anti-amyloidogenic activity of glyco-pseudodendrimers synthesized on an aliphatic polyester backbone.:Abstract List of Tables List of Figures Abbreviations 1 Introduction 1.1 Objectives of the work 1.2 Thesis overview 2 Fundamentals and Literature 2.1 Alzheimer’s Disease and its impact 2.1.1 Neurological diagnosis of AD 2.1.2 Histopathology of AD 2.1.3 Amyloid precursor protein (APP) and its role in AD 2.2. Amyloid Beta (Aβ) peptide 2.2.1 Aβ peptide 2.2.2. Location and function 2.2.3 Amyloid hypothesis 2.2.4 The mechanism of Aβ aggregation 2.2.5 Amyloid fibrils 2.2.6 Toxicity of Aβ 2.3 Research methods to study Aβ aggregates 2.3.1 Models to study the mode of action of aggregates 2.3.2 Endogenous Aβ aggregates and synthetic aggregates 2.3.3 Strategies to alter aggregation of amyloids 2.4 Treatment and therapeutics 2.4.1 Current therapeutics 2.4.2 Current therapeutic research 2.4.2.1 Reduction of Aβ production 2.4.2.2 Reduction of Aβ plaque accumulation 2.4.2.2.1 Anti-amyloid aggregation agents 2.4.2.2.2 Metals 2.4.2.2.3 Immunotherapy 2.4.2.2.4 Dendrimers as potential anti-amyloidogenic agent 2.6 Dendrimers 2.6.1 Definition 2.6.2 Structure Table of Contents 2.6.3 Synthesis 2.6.4 Properties 2.7 Pseudodendrimers - a sub-class of hyperbranched polymer 2.7.1 Definition 2.7.2 Structure 2.7.3 Synthesis 3 Analytical Techniques 3.1 Size Exclusion Chromatography Coupled to Light Scattering (SEC-MALS) 3.2 Asymmetric Flow Field Flow Fractionation (AF4) 3.3 Dynamic Light Scattering 3.4 Molecular Dynamics Simulation 3.5 Nuclear Magnetic Resonance Spectroscopy 3.6 Thioflavin T fluorescence 3.6.1 Kinetic analysis 3.7 Circular Dichroism Spectroscopy 3.8 Atomic Force Microscopy 3.9 Cytotoxic assay 3.9.1 MTT assay 3.9.2 Determining the level of reactive oxygen species 3.9.3 Changes in mitochondrial transmembrane potential 3.9.4 Flow cytometric detection of phosphatidyl serine exposure 4 Experimental Details and Methodology 4.1 Details of chemicals/components used 4.1.1 Other materials 4.1.2 Peptide preparation 4.1.3 Buffer preparation 4.1.4 Fibril growth conditions 4.2 Synthesis and characterization of polymers 4.2.1 Synthesis and characterization of pseudodendrimers and dendrimers 4.2.1.1 Synthesis of hyperbranched polymer (1) 4.2.1.2 Synthesis of protected monomer 4.2.1.2.1 bis-MPA acetonide (2) 4.2.1.2.2 bis-MPA-acetonide anhydride (3) 4.2.1.3 Synthesis of protected pseudodendrimers (4, 6 and 8) and protected dendrimers (10, 12, and 14) 4.2.1.4 Deprotection of pseudodendrimers (5,7, and 9) and dendrimers (11,13 and 15) 4.2.2 Synthesis of glyco-pseudodendrimers and glyco-dendrimers 4.2.2.1 Pentynoic anhydride (16) 4.2.2.2 Synthesis of pentinate modified pseudodendrimers (17, 18 and 19) and dendrimers (20, 21 and 22) 4.2.2.3 3-Azido-1-propanol (23) 4.2.2.4 Mannose propyl azide tetraacetate (24) Table of Contents 4.2.2.5 Mannosepropylazide (25) 4.2.2.6 Glyco-pseudodendrimers (Gl-P) (26, 27 and 28) and glyco- dendrimers (Gl-D) (29, 30 and 31) 4.3 Analytical techniques and their general details 4.3.1 SEC-MALS - Instrumentation, software and analysis 4.3.2 AF4 - Instrumentation, software and analysis 4.3.2.1 Sample preparation 4.3.2.2 Method development for analysis of Gl-P and Gl-D 4.3.2.3 Method development for analysis of Aβ 40 and its interaction with Gl-P and Gl-D 4.3.3 Batch DLS - Instrumentation, software and analysis 4.3.3.1 Sample preparation 4.3.4 Theoretical calculations and molecular dynamics simulations 4.3.4.1 Ab-initio calculations 4.3.4.2 Modelling of the polymer structures 4.3.4.2.1 Pseudodendrimers 4.3.4.2.2 Dendrimers 4.3.4.2.3 Modification of the polymers with special end groups 4.3.4.2.4 Preparing of the THF solvent box 4.3.4.2.5 Solvation of the polymer structures 4.3.4.3 Molecular dynamics simulations 4.3.4.3.1 Evaluation of the simulation trajectories 4.4 Investigation of interaction of Gl-P and Gl-D with amyloid beta (Aβ 40) 4.4.1 ThT Assay - Instrumentation and software 4.4.1.1 Sample preparation 4.4.1.2 Kinetics based on ThT assay- software and data analysis 4.4.2 CD spectroscopy - Instrumentation and software 4.4.2.1 Sample preparation 4.4.3 AFM - Instrumentation and software 4.4.3.1 Substrate and sample preparation 4.4.3.2 Height determination and counting procedures 4.4.3.3 Topography and diameter 4.5 Cytotoxicity 4.5.1 Zeta potential 4.5.2 Cell culturing 4.5.3 Sample preparation 4.5.4 MTT assay 4.5.5 Changes in mitochondrial transmembrane potential (JC-1 method) 4.5.6 Flow cytometric detection of phosphatidyl serine exposure (Annexin V and PI method) 5 Results and Discussion 5.1 Synthesis and characterization of glyco-pseudodendrimers and glyco- dendrimers 5.1.1 Synthesis and characterization of hyperbranched polyester Table of Contents 5.1.2 Synthesis and characterization of pseudodendrimers P-G1-OH, P-G2-OH and P-G3-OH 5.1.3 Synthesis and characterization of dendrimers D-G4-OH, D-G5-OH and D-G6-OH 5.1.4 Synthesis and characterization of Gl-P and Gl-D 5.1.4.1 Molecular size determination of Gl-P and Gl-D using SEC 5.1.4.2 Particle size determination using batch DLS 5.1.4.3 Apparent densities 5.1.4.4 Molecular size determination of Gl-P and Gl-D using AF4 ..... 5.1.5 Molecular dynamics simulation 5.2 Investigation of interaction of Gl-P and Gl-D with amyloid beta (Aβ 40) ...... 5.2.1 ThT Assay 5.2.1.1 Kinetics based on ThT assay 5.2.2 CD spectroscopy 5.2.3 Time dependent AF4 5.3.2.1 Separation of Aβ 40 by AF4 5.3.2.2 Aβ 40 amyloid aggregation in the presence of Gl-P and Gl-D 5.2.4 AFM 5.2.4.1 Height 5.2.4.2 Topography and diameter 5.2.4.3 Length 5.2.4.4 Morphology 5.2.5 Cytotoxicity 5.2.5.1 MTT assay 5.2.5.2 Changes in mitochondrial transmembrane potential 5.2.5.3 Flow cytometric detection of phosphatidyl serine exposure 6 Conclusions and Outlook 7 Bibliography Appendix Acknowledgement

    Synthesis, Structural, Magnetic and Computational Studies of a One-Dimensional Ferromagnetic Cu(II) Chain Assembled from a New Schiff Base Ligand

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    A new asymmetrically substituted ONOO Schiff base ligand N-(2′-hydroxy-1′-naphthylidene)-3-amino-2-naphthoic acid (nancH2) was prepared from the condensation of 2–hydroxy–1–naphthaldehyde and 3–amino–2–naphthoic acid. nancH2 reacts with Cu2(O2CMe)4·2H2O in the presence of Gd(O2CMe)3·6H2O to afford a uniform one-dimensional homometallic chain, [CuII(nanc)]n (1). The structure of 1 was elucidated via single crystal X-ray diffraction studies, which revealed that the Cu(II) ions adopt distorted square planar geometries and are coordinated in a tridentate manner by an [ONO] donor set from one nanc2− ligand and an O− of a bridging carboxylate group from a second ligand. The bridging carboxylato group of the nanc2− ligand adopts a syn, anti-η1:η1:μ conformation linking neighboring Cu(II) ions, forming a 1D chain. The magnetic susceptibility of 1 follows Curie–Weiss law in the range 45–300 K (C = 0.474(1) emu K mol-1, θ = +7.9(3) K), consistent with ferromagnetic interactions between S = ½ Cu(II) ions with g = 2.248. Subsequently, the data fit well to the 1D quantum Heisenberg ferromagnetic (QHFM) chain model with g = 2.271, and J = +12.3 K. DFT calculations, implementing the broken symmetry approach, were also carried out on a model dimeric unit extracted from the polymeric chain structure. The calculated exchange coupling via the carboxylate bridge (J = +13.8 K) is consistent with the observed ferromagnetic exchange between neighbouring Cu(II) centres. © 2023 by the authors. This article belongs to the Special Issue Coordination Chemistry: Current Developments and Future Perspectives — a Themed Issue in Honor of Professor Spyros P. Perlepes on the Occasion of His 70th Birthday) This article contains supplementary material. It is available for download as a supplementary file

    Cu-based electrodes for ammonia and urea electrosynthesis

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