CdSe-based Semiconductor Nanocrystal: Synthesis, Characterization, and Applications

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de Materiales. Fecha de lectura: 19-09-2017Esta tesis tiene embargado el acceso al texto completo hasta el 19-03-201

Cosmographie avec des lentilles gravitationnelles fortes dans les amas de galaxies

Dans le modèle standard de cosmologie ΛCDM, environ 72% de la densité d'énergie totale de l'Univers se présente sous la forme d'énergie sombre qui causerait la présente accélération de l'Univers. Parmi les sondes cosmologiques couramment utilisées, l'effet de lentille gravitationnel forte dans les amas est une technique prometteuse fournissant des contraintes orthogonales sur les paramètres cosmologiques. Le programme HFF a permis une amélioration significative de l'estimation de la distribution de masse des amas. Cependant, la modélisation de l'effet de lentille forte dans les amas semble ne pas atteindre la résolution angulaire des observations HST. Cette thèse fournit une meilleure compréhension de l'impact des erreurs systématiques dans la modélisation paramétrique de l'effet de lentille forte dans les amas de galaxies et, donc, sur la détermination des paramètres cosmologiques. Premièrement, j'ai analysé deux amas de galaxies simulés, ayant les mêmes caractéristiques que les amas du programme HFF, Ares et Hera. J'ai utilisé plusieurs estimateurs afin d'évaluer la qualité de nos reconstructions obtenues, permettant de quantifier l'impact des erreurs systématiques dues, au choix des profils de densité et configurations et, ensuite, de la disponibilité d'images multiples dans la détermination de paramètres cosmologiques. Deuxièmement, en utilisant deux amas de galaxies, j'ai testé quatre modèles cosmologiques pour lesquels l'équation d'état de l'énergie sombre, w(z), est paramétrisée en fonction du redshift. J'ai réalisé plusieurs modélisations pour quantifier l'impact des erreurs systématiques liées à la position des images multiples sur les paramètres cosmologiques.In the standard cosmological model ΛCDM, about 70% of the energy density of the Universe is in the form of a dark energy that would cause the current acceleration of the Universe. Among the extensively used cosmological probes, using strong lensing features in galaxy clusters is a promising technique yielding orthogonal constraints on cosmological parameters. The program HFF has led to a significant improvement of cluster mass estimates. However, strong lensing modelling appears to be still unable to match the HST observations angular resolution.This thesis provides a better understanding of how systematic errors impact the retrieval of cosmological parameters in order to use strong lensing clusters as reliable cosmological probes. Firstly, I have analyzed two simulated HFF-like clusters, Ares and Hera, I use several estimators to assess the goodness of our reconstructions by comparing our multiple models, with the input models. This allows to quantify the impact of systematic errors arising from the choice of different density profiles and configurations and, secondly, from the availability of constraints in the parametric modelling of strong lensing clusters and therefore on the retrieval of cosmological parameters. Secondly, I probe four cosmological models in which the equation of state of dark energy, w(z), is parameterized as a function of redshift using strong lensing features in two galaxy clusters. To quantify how the cosmological constraints are biased due to systematic effects in the strong lensing modelling, I carry out several modelling attempts considering different uncertainties for the multiple images positions

Incorporation of Trinuclear Lanthanide(III) Hydroxo Bridged Clusters in Macrocyclic Frameworks

A cluster of lanthanide­(III) or yttrium­(III) ions, Ln₃(μ₃-OH)₂, (Ln­(III) = Nd­(III), Sm­(III), Eu­(III), Gd­(III), Tb­(III), Dy­(III), Yb­(III), or Y­(III)) can be bound in the center of a chiral macrocyclic amines H₃L1^<i>R</i>, H₃L1^<i>S</i>, and H₃L2^<i>S</i> obtained in a reduction of a 3 + 3 condensation product of (1<i>R</i>,2<i>R</i>)- or (1<i>S</i>,2<i>S</i>)-1,2-diaminocyclohexane and 2,6-diformyl-4-methylphenol or 2,6-diformyl-4-<i>tert</i>butylphenol. X-ray crystal structures of the Nd­(III), Sm­(III), Gd­(III), Dy­(III), and Y­(III) complexes reveal trinuclear complexes with Ln­(III) ions bridged by the phenolate oxygen atoms of the macrocycle as well as by μ₃-hydroxo bridges. In the case of the Nd­(III) ion, another complex form can be obtained, whose X-ray crystal structure reveals two trinuclear macrocyclic units additionally bridged by hydroxide anions, corresponding to a [Ln₃(μ₃-OH)]₂(μ₂-OH)₂ cluster encapsulated by two macrocycles. The formation of trinuclear complexes is confirmed additionally by ¹H NMR, electrospray ionization mass spectrometry (ESI MS), and elemental analyses. Titrations of free macrocycles with Sm­(III) or Y­(III) salts and KOH also indicate that a trinuclear complex is formed in solution. On the other hand, analogous titrations with La­(III) salt indicate that this kind of complex is not formed even with the excess of La­(III) salt. The magnetic data for the trinuclear Gd­(III) indicate weak antiferromagnetic coupling (<i>J</i> = −0.17 cm^–1) between the Gd­(III) ions. For the trinuclear Dy­(III) and Tb­(III) complexes the χ_<i>M</i><i>T</i> vs <i>T</i> plots indicate a more complicated dependence, resulting from the combination of thermal depopulation of <i>m</i>_<i>J</i> sublevels, magnetic anisotropy, and possibly weak antiferromagnetic and ferromagnetic interactions

Directed, Strong, and Reversible Immobilization of Proteins Tagged with a β-Trefoil Lectin Domain: A Simple Method to Immobilize Biomolecules on Plain Agarose Matrixes

A highly stable lipase from <i>Geobacillus thermocatenolatus</i> (BTL2) and the enhanced green fluorescent protein from <i>Aquorea victoria</i> (EGFP) were recombinantly produced N-terminally tagged to the lectin domain of the hemolytic pore-forming toxin LSLa from the mushroom Laetiporus sulphureus. Such a domain (LSL₁₅₀), recently described as a novel fusion tag, is based on a β-trefoil scaffold with two operative binding sites for galactose or galactose-containing derivatives. The fusion proteins herein analyzed have enabled us to characterize the binding mode of LSL₁₅₀ to polymeric and solid substrates such as agarose beads. The lectin-fusion proteins are able to be quantitatively bound to both cross-linked and non-cross-linked agarose matrixes in a very rapid manner, resulting in a surprisingly dynamic protein distribution inside the porous beads that evolves from heterogeneous to homogeneous along the postimmobilization time. Such dynamic distribution can be related to the reversible nature of the LSL₁₅₀–agarose interaction. Furthermore, this latter interaction is temperature dependent since it is 4-fold stronger when the immobilization takes place at 25 °C than when it does at 4 °C. The strongest lectin–agarose interaction is also quite stable under a survey of different conditions such as high temperatures (up to 60 °C) or high organic solvent concentrations (up to 60% of acetonitrile). Notably, the use of cross-linked agarose would endow the system with more robustness due to its better mechanical properties compared to the noncross-linked one. The stability of the LSL₁₅₀–agarose interaction would prevent protein leaching during the operation process unless high pH media are used. In summary, we believe that the LSL₁₅₀ lectin domain exhibits interesting structural features as an immobilization domain that makes it suitable to reversibly immobilize industrially relevant enzymes in very simple carriers as agarose

Oriented Attachment of Recombinant Proteins to Agarose-Coated Magnetic Nanoparticles by Means of a β‑Trefoil Lectin Domain

Design of generic methods aimed at the oriented attachment of proteins at the interfacial environment of magnetic nanoparticles currently represents an active field of research. With this in mind, we have prepared and characterized agarose-coated maghemite nanoparticles to set up a platform for the attachment of recombinant proteins fused to the β-trefoil lectin domain LSL₁₅₀, a small protein that combines fusion tag properties with agarose-binding capacity. Analysis of the agarose-coated nanoparticles by dynamic light scattering, Fourier transform infrared spectroscopy, and thermogravimetric studies shows that decoupling particle formation from agarose coating provides better results in terms of coating efficiency and particle size distribution. LSL₁₅₀ interacts with these agarose-coated nanoparticles exclusively through the recognition of the sugars of the polymer, forming highly stable complexes, which in turn can be dissociated ad hoc with the competing sugar lactose. Characterization of the complexes formed with the fusion proteins LSL-EGFP (LSL-tagged enhanced green fluorescent protein from Aquorea victoria) and LSL-BTL2 (LSL-tagged lipase from Geobacillus thermocatenolatus) provided evidence supporting a topologically oriented binding of these molecules to the interface of the agarose-coated nanoparticles. This is consistent with the marked polarity of the β-trefoil structure where the sugar-binding sites and the N- and C-terminus ends are at opposed sides. In summary, LSL₁₅₀ displays topological and functional features expected from a generic molecular adaptor for the oriented attachment of proteins at the interface of agarose-coated nanoparticles

Catalytic Cycle of the <i>N</i>‑Acetylglucosaminidase NagZ from <i>Pseudomonas aeruginosa</i>

The <i>N</i>-acetylglucosaminidase NagZ of Pseudomonas aeruginosa catalyzes the first cytoplasmic step in recycling of muropeptides, cell-wall-derived natural products. This reaction regulates gene expression for the β-lactam resistance enzyme, β-lactamase. The enzyme catalyzes hydrolysis of <i>N</i>-acetyl-β-d-glucosamine-(1→4)-1,6-anhydro-<i>N</i>-acetyl-β-d-muramyl-peptide (<b>1</b>) to <i>N</i>-acetyl-β-d-glucosamine (<b>2</b>) and 1,6-anhydro-<i>N</i>-acetyl-β-d-muramyl-peptide (<b>3</b>). The structural and functional aspects of catalysis by NagZ were investigated by a total of seven X-ray structures, three computational models based on the X-ray structures, molecular-dynamics simulations and mutagenesis. The structural insights came from the unbound state and complexes of NagZ with the substrate, products and a mimetic of the transient oxocarbenium species, which were prepared by synthesis. The mechanism involves a histidine as acid/base catalyst, which is unique for glycosidases. The turnover process utilizes covalent modification of D244, requiring two transition-state species and is regulated by coordination with a zinc ion. The analysis provides a seamless continuum for the catalytic cycle, incorporating large motions by four loops that surround the active site

Large-Area Heterostructures from Graphene and Encapsulated Colloidal Quantum Dots via the Langmuir–Blodgett Method

This work explores the assembly of large-area heterostructures comprised of a film of silica-encapsulated, semiconducting colloidal quantum dots, deposited via the Langmuir–Blodgett method, sandwiched between two graphene sheets. The luminescent, electrically insulating film served as a dielectric, with the top graphene sheet patterned into an electrode and successfully used as a top gate for an underlying graphene field-effect transistor. This heterostructure paves the way for developing novel hybrid optoelectronic devices through the integration of 2D and 0D materials