Publications by authors named "Belen Vaz"

The determination of binding constants is a key matter in evaluating the strength of host-guest interactions. However, the profound impact of self-ion pairing on this parameter is often underrated in aqueous solution, leading in some cases to a misinterpretation of the true potential of supramolecular assemblies. In the present study, we aim to shed further light on this critical factor by exploring the concentration-dependent behavior of a multicharged pillararene in water.

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Over the years, porphyrins have arisen as exceptional photosensitizers given their ability to act as chlorophyll-mimicking dyes, thus, transferring energy from the light-collecting areas to the reaction centers, as it happens in natural photosynthesis. For this reason, porphyrin-sensitized TiO-based nanocomposites have been widely exploited in the field of photovoltaics and photocatalysis in order to overcome the well-known limitations of these semiconductors. However, even though both areas of application share some common working principles, the development of solar cells has led the way in what is referred to the continuous improvement of these architectures, particularly regarding the molecular design of these photosynthetic pigments.

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The stereoselective synthesis of C-all--carotenoids with the formal hexahydrobenzofuran skeletons aurochrome, auroxanthin, and equinenone-5',8'-epoxide is reported. The synthesis is based on a one-pot or stepwise double Horner-Wadsworth-Emmons (HWE) reaction of a terminal enantiopure C-5,6-epoxycyclohexadienylphosphonate and a central C-trienedial. The ring expansion of the epoxycyclohexadienylphosphonate, generated by a Stille cross-coupling reaction, to the hexahydrobenzofuran skeleton was promoted by the reaction conditions of the HWE reaction prior to double-bond formation.

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Tear analysis has become an invaluable asset in clinical research in order to identify and quantify novel biomarkers for a wide array of conditions. The present work is intended to take this area of study one step further by implementing an innovative sensing platform through which exploration of low-molecular-weight compounds is conducted outperforming traditional analytical technologies. With this aim, carefully engineered plasmonic nanoassemblies have been synergistically combined with molecular-sieving materials giving rise to size-selective samplers with SERS detection capabilities.

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9--13,14-dihydroretinoic acid (9CDHRA), acts as an endogenous ligand of the retinoid X receptors (RXRs), and is an active form of a suggested new vitamin, vitamin A5/X. Nutritional-relevance of this pathway as well as its detailed role in vertebrate physiology, remain largely unknown. Since recent GWAS data and experimental studies associated RXR-mediated signaling with depression, we explored here the relevance of RXR and vitamin A5/X-mediated signaling in the control of stress adaptation and depressive-like behaviors in mice.

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Dehydrotryptophan derivatives have been prepared by palladium-catalyzed aminocyclization-Heck-type coupling cascades starting from -alkynylaniline derivatives and methyl α-aminoacrylate. Aryl, alkyl (primary, secondary, and tertiary), and alkenyl substituents have been introduced at the indole C-2 position. Further variations at the indole benzene ring, as well as the C-2-unsubstituted case, have all been demonstrated.

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In this manuscript, we report the first synthesis of an organic monomolecular emitter, which behaves as a circularly polarized luminescence (CPL)-based ratiometric probe. The enantiopure helical ortho-oligo(phenylene)ethynylene ( o-OPE) core has been prepared by a new and efficient macrocyclization reaction. The combination of such o-OPE helical skeleton and a pyrene couple leads to two different CPL emission features in a single structure whose ratio linearly responds to silver(I) concentration.

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The translocation of nanomaterials or complex delivery systems into the cytosol is a major challenge in nanobiotechnology. After receptor-mediated endocytosis, most nanomaterials are sequestered and undergo degradation, therapy inactivation, or exocytosis. Herein we explore a novel surface particle coating made of adsorbed carbon nanotubes that provides coated materials with new properties that reproduce the viral cell-invasive mechanisms, namely, receptor-mediated endocytosis, endolysosomal escape, and cytosolic particle release preserving cell viability.

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We report the isolation from the green dinoflagellate Lepidodinium chlorophorum and structural characterization of a new carotenoid termed lepidoxanthin (1), determined to be (3S,5R,6S,3'R,6'R)-5,6-epoxy-19-(2-decenoyloxy)-19'-acetoxy-4',5'-didehydro-5,6,5',6'-tetrahydro-β,ε-carotene-3,3'-diol. Its until now unidentified 19,19'-diacyloxy substitution constitutes a chemical signature that can aid in unraveling the evolutionary course of this unicellular algae based on the proposed biosynthethic pathway.

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We present a novel strategy based on the immobilization of palladium nanoparticles (Pd NPs) on filter paper for development of a catalytic system with high efficiency and recyclability. Oleylamine-capped Pd nanoparticles, dispersed in an organic solvent, strongly adsorb on cellulose filter paper, which shows a great ability to wick fluids due to its microfiber structure. Strong van der Waals forces and hydrophobic interactions between the particles and the substrate lead to nanoparticle immobilization, with no desorption upon further immersion in any solvent.

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The retinoid X receptors (RXRs) are ligand-activated transcription factors which heterodimerize with a number of nuclear hormone receptors, thereby controlling a variety of (patho)-physiological processes. Although synthetic RXR ligands are developed for the treatment of various diseases, endogenous ligand(s) for these receptors have not been conclusively identified. We show here that mice lacking cellular retinol binding protein (Rbp1-/-) display memory deficits reflecting compromised RXR signaling.

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Hollow inorganic nanostructures have attracted much interest in the last few years due to their many applications in different areas of science and technology. In this Feature Article, we overview part of our current work concerning the collective use of plasmonic and magnetic nanoparticles located in voided nanostructures and explore the more specific operational issues that should be taken into account in the design of inorganic nanocapsules. Along these lines, we focus our attention on the applications of silica-based submicrometer capsules aiming to stress the importance of creating nanocavities in order to further exploit the great potential of these functional nanomaterials.

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A new stereoselective synthesis of the C40-bis-acetylenic carotenoids all-trans-(3R,3'R)-alloxanthin and all-trans-3,4,7,8,3',4',7',8'-octadehydro-β,β-carotene, both compounds featuring a stereochemically labile C7-C10 enyne, based on a bi-directional Horner-Wadsworth-Emmons (HWE) reaction of a C15-phosphonate and a central C10-dialdehyde, is reported. The triene unit of the latter fragment was synthesized using the acyclic metathesis/dimerization reaction.

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We report herein the design of plasmonic hollow nanoreactors capable of concentrating light at the nanometer scale for the simultaneous performance and optical monitoring of thermally activated reactions. These reactors feature the encapsulation of plasmonic nanoparticles on the inner walls of a mesoporous silica capsule. A Diels-Alder cycloaddition reaction was carried out in the inner cavities of these nanoreactors to evidence their efficacy.

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The controversial molecular identification of the so-called chlorophyll cCS-170 has been settled. Despite its relevance as a potential biomarker in the study of eukaryotic picophytoplankton, the structure of this chlorophyll remained so far uncertain. A full characterization by NMR, UV-vis, and ESI-MS is reported, revealing this chlorophyll as [7-methoxycarbonyl-8-vinyl]-protochlorophyllide a.

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Hollow-shelled nanoreactors have emerged as efficient structures to maximize the potential of nanoparticles in the field of catalysis. In this Concept article, we underline the importance of both the morphology of the active nanoparticles as well as the composition and porosity of the shell for the catalytic performance of the overall nanocomposite. Different configurations are discussed, with a focus on preparative methods and applications in organic synthesis.

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A new stereocontrolled total synthesis of the configurationally labile C37 -norcarotenoid pyrrhoxanthin in enantiopure form has been completed. A highly stereoselective Horner-Wadsworth-Emmons (HWE) condensation of a C17-allylphosphonate and a C20-aldehyde was used as the last conjunctive step. Both a Sonogashira reaction to form the C17-phosphonate and the final HWE condensation proved to be compatible with the sensitive C7-C10 enyne E configuration.

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A multitechnique investigation on the self-assembly behavior of a biocompatible polymer in the high dilution regime is reported herein. The obtained results unambiguously reveal the existence of premicellar structures that may further extend the efficiency of traditional polymeric micelles as drug-delivery vehicles. Such an expansion in the excipient capacity arises from (i) the increased drug retention of submicellar assemblies due to their higher resistance to dilution and therefore to their improved circulation time and (ii) the superior carrier permeability of these premicellar aggregates as a result of their smaller size, which makes these drug vehicles more effectively targeted to the tumors through the so-called enhanced permeability and retention effect.

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The first total synthesis of (8R,6'R)-peridinin-5,8-furanoxide, a C37 xanthophyll norcarotenoid, has been achieved. The key steps of the synthetic sequence are a Julia-Kocienski condensation and a late stage stereoretentive Stille cross-coupling of an iodoallene.

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(2E,4E,6E,8E,10E,12E,14E)-2,15-Diiodo-6,11-dimethylhexadeca-2,4,6,8,10,12,14-heptaene, prepared by homometathesis, has been used in palladium-catalyzed Suzuki and Stille cross-coupling reactions with the appropriate partners to construct the C2-symmetric carotenoids β,β-carotene, lycopene, synechoxanthin and 4,4'-diapo-ψ,ψ-carotene-4,4'-dial.

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Wrch1/RhoU is an atypical member of the Rho family. A major structural difference is the extended N-terminus of Wrch1 (nWrch1) containing three putative SH3 domain-binding motifs whose specificities are unknown. To define the impact of this extended region on coupling Wrch1 to cellular signaling, we analyzed in this study nWrch1 interaction with Src homology 3 (SH3) domains of different adaptor proteins.

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A mechanism for the rearrangement of oxiranylpropargylic esters to cyclopentenones catalyzed by PtCl(2) is proposed based on DFT calculations (M06/6-31++G(d,p)). Although the basic steps are coincidental with those proposed by Sarpong et al., who characterized a 2H-pyran as intermediate, calculations have revealed other intricate details of this complex rearrangement.

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Introduction: Retinoid X receptors (subtypes RXRα or NR2B1, RXRβ or NR2B2 and RXRγ or NR2B3, which originate from three distinct genes) are promiscuous partners with heterodimeric associations to other members of the Nuclear Receptor (NR) superfamily. Some of the heterodimers are "permissive" and transcriptionally active in the presence of either an RXR ligand ("rexinoid") or a NR partner ligand, whereas others are "non-permissive" and unresponsive to rexinoids alone. In rodent models, rexinoids and partner agonists (mainly PPARγ, LXR, FXR) produce beneficial effects on insulin sensitization, diabetes and obesity, but secondary effects have also been noted, such as a raise in tryglyceride levels, supression of the thyroid hormone axis and induction of hepatomegaly.

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