Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 87
Filtrar
1.
J Inherit Metab Dis ; 2024 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-38973597

RESUMO

The protein encoded by COQ7 is required for CoQ10 synthesis in humans, hydroxylating 3-demethoxyubiquinol (DMQ10) in the second to last steps of the pathway. COQ7 mutations lead to a primary CoQ10 deficiency syndrome associated with a pleiotropic neurological disorder. This study shows the clinical, physiological, and molecular characterization of four new cases of CoQ10 primary deficiency caused by five mutations in COQ7, three of which have not yet been described, inducing mitochondrial dysfunction in all patients. However, the specific combination of the identified variants in each patient generated precise pathophysiological and molecular alterations in fibroblasts, which would explain the differential in vitro response to supplementation therapy. Our results suggest that COQ7 dysfunction could be caused by specific structural changes that affect the interaction with COQ9 required for the DMQ10 presentation to COQ7, the substrate access to the active site, and the maintenance of the active site structure. Remarkably, patients' fibroblasts share transcriptional remodeling, supporting a modification of energy metabolism towards glycolysis, which could be an adaptive mechanism against CoQ10 deficiency. However, transcriptional analysis of mitochondria-associated pathways showed distinct and dramatic differences between patient fibroblasts, which correlated with the extent of pathophysiological and neurological alterations observed in the probands. Overall, this study suggests that the combination of precise genetic diagnostics and the availability of new structural models of human proteins could help explain the origin of phenotypic pleiotropy observed in some genetic diseases and the different responses to available therapies.

2.
Int J Mol Sci ; 25(8)2024 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-38674005

RESUMO

We aimed to explore the relationship of adipose tissue concentrations of some persistent organic pollutants (POPs) with the risk of endometriosis and the endometriotic tissue expression profile of genes related to the endometriosis-related epithelial-mesenchymal transition (EMT) process. This case-control study enrolled 109 women (34 cases and 75 controls) between January 2018 and March 2020. Adipose tissue samples and endometriotic tissues were intraoperatively collected to determine concentrations of nine POPs and the gene expression profiles of 36 EMT-related genes, respectively. Associations of POPs with endometriosis risk were explored with multivariate logistic regression, while the relationship between exposure and gene expression profiles was assessed through Spearman correlation or Mann-Whitney U tests. After adjustment, increased endometriosis risk was associated with p,p'-DDT, PCB-180, and ΣPCBs. POP exposure was also associated with reduced gene expression levels of the CLDN7 epithelial marker and increased levels of the ITGB2 mesenchymal marker and a variety of EMT promoters (HMGA1, HOXA10, FOXM1, DKK1, CCR1, TNFRSF1B, RRM2, ANG, ANGPT1, and ESR1). Our findings indicate that exposure to POPs may increase the risk of endometriosis and might have a role in the endometriosis-related EMT development, contributing to the disease onset and progression. Further studies are warranted to corroborate these findings.


Assuntos
Endometriose , Exposição Ambiental , Transição Epitelial-Mesenquimal , Poluentes Orgânicos Persistentes , Endometriose/genética , Endometriose/patologia , Endometriose/induzido quimicamente , Endometriose/metabolismo , Humanos , Feminino , Transição Epitelial-Mesenquimal/genética , Adulto , Exposição Ambiental/efeitos adversos , Estudos de Casos e Controles , Poluentes Orgânicos Persistentes/efeitos adversos , Tecido Adiposo/metabolismo , Tecido Adiposo/patologia , Endométrio/metabolismo , Endométrio/patologia , Endométrio/efeitos dos fármacos , Fatores de Risco
3.
Inorg Chem ; 62(45): 18496-18509, 2023 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-37910080

RESUMO

The useful concepts of reticular chemistry, rigid and predictable metal nodes together with strong and manageable covalent interactions between metal centers and organic linkers, have made the so-called metal-organic frameworks (MOFs) a flourishing area of enormous applicability. In this work, the extension of similar strategies to supramolecularly assembled metal-organic materials has allowed us to obtain a family of isoreticular compounds of the general formula [Cu7(µ-adeninato-κN3:κN9)6(µ3-OH)6(µ-OH2)6](OOC-R-COO)·nH2O (R: ethylene-, acetylene-, naphthalene-, or biphenyl-group) in which the rigid copper-adeninato entities and the organic dicarboxylate anions are held together not by covalent interactions but by a robust and flexible network of synergic hydrogen bonds and π-π stacking interactions based on well-known supramolecular synthons (SMOFs). All compounds are isoreticular, highly insoluble, and water-stable and show a porous crystalline structure with a pcu topology containing a two-dimensional (2D) network of channels, whose dimensions and degree of porosity of the supramolecular network are tailored by the length of the dicarboxylate anion. The partial loss of the crystallization water molecules upon removal from the mother liquor produces a shrinkage of the unit cell and porosity, which leads to a color change of the compounds (from blue to olive green) if complete dehydration is achieved by means of gentle heating or vacuuming. However, the supramolecular network of noncovalent interactions is robust and flexible enough to reverse to the expanded unit cell and color after exposure to a humid atmosphere. This humidity-driven breathing behavior has been used to design a sensor in which the electrical resistance varies reversibly with the degree of humidity, very similar to the water vapor adsorption isotherm of the SMOF. The in-solution adsorption properties were explored for the uptake and release of the widely employed 5-fluorouracil, 4-aminosalycilic acid, 5-aminosalycilic acid, and allopurinol drugs. In addition, cytotoxicity activity assays were completed for the pristine and 5-fluorouracil-loaded samples.

4.
Inorg Chem ; 62(42): 17444-17453, 2023 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-37811902

RESUMO

A family of unprecedented supramolecularly assembled porous metal-organic compounds (SMOFs), based on [Cu6M(µ-adeninato)6(µ3-OH)6(µ-H2O)6]2+ cations (MII: Cu, Co, Ni, and Zn) and different dicarboxylate anions (fumarate, benzoate, and naphthalene-2,6-dicarboxylate), have been employed as precursors of catalysts for the thermocatalytic reduction of CO2. The selected metal-organic cation allows us to tune the composition of the SMOFs and, therefore, the features and performance of the final homometallic and bimetallic catalysts. These catalysts were obtained by thermolysis at 600 °C under a N2 atmosphere and consist of big metal particles (10-20 µm) placed on the surface of the carbonaceous matrix and very tiny metal aggregates (<10 nm) within this carbonaceous matrix. The latter are the most active catalytic sites for the CO2 thermocatalytic reduction. The amount of this carbonaceous matrix correlates with the organic content present in the metal-organic precursor. In this sense, CO2 thermocatalytic reduction experiments performed over the homometallic, copper only, catalysts with different carbon contents indicate that above a certain value, the increase of the carbonaceous matrix reduces the overall performance by encapsulating the nanoparticles within this matrix and isolating them from interacting with CO2. In fact, the best performing homometallic catalyst is that obtained from the precursor containing a small fumarate counterion. On the other hand, the structural features of these precursors also provide a facile route to work with a solid solution of nanoparticles as many of these metal-organic compounds can replace up to 1/7 of the copper atoms by zinc, cobalt, or nickel. Among these heterometallic catalysts, the best performing one is that of copper and zinc, which provides the higher conversion and selectivity toward CO. XPS spectroscopy and EDX mappings of the latter catalyst clearly indicate the presence of Cu1-xZnx nanoparticles covered by small ZnO aggregates that provide a better CO2 adsorption and easier CO release sites.

5.
Molecules ; 28(15)2023 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-37570613

RESUMO

The present study reports on a 2D lamellar coordination polymer (CP) of {[Zn(µ3-pmdc)(H2O)]·H2O}n formula (pmdc = pyrimidine-4,6-dicarboxylate). This CP is synthesized under an appropriate acid-base reaction between the gently mortared reagents in the solid state through a solvent-free procedure that avoids the presence of concomitant byproducts. The X-ray crystal structure reveals the occurrence of Zn2 entities connected through carboxylate groups of pmdc, which behave as triconnected nodes, giving rise to six-membered ring-based layers that are piled up through hydrogen bonding interactions. In addition to a routine physico-chemical characterization, the thermal evolution of the compound has been studied by combining thermogravimetric and thermodiffractometric data. The photoluminescence properties are characterized in the solid state and the processes governing the spectra are described using time-dependent density-functional theory (TD-DFT) with two different approaches employing different program packages. The emissive capacity of the material is further analyzed according to the dehydration and decreasing temperature of the polycrystalline sample.

6.
Inorg Chem ; 61(12): 4842-4851, 2022 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-35286083

RESUMO

Clustering chemistry is a key point in the design and synthesis of the secondary building units that comprise metal-organic frameworks (MOFs) based on group IV metals. In this work, the first stages of the zirconium-carboxylate clustering process in alcohol/water mixtures are studied in detail using the monocarboxylic benzoic and hydroxybenzoic acids to avoid the polymerization. Mass spectroscopy measurements performed on the reactions revealed the presence of hexa- and pentanuclear species even at low pH values and also evidenced the acid-base nature and pH dependence of the transformation between both species. The control on the chemistry governing the equilibria between these species has allowed us to isolate six new compounds in the solid state. The single-crystal X-ray diffraction analysis revealed that they are closely related to the well-known [Zr6(O)4(OH)4(OOC)12] secondary building unit found in many MOFs by removing carboxylic ligands in the case of the hexameric species ([Zr6(O)4(OH)4(OOC)8(H2O)8]4+) or by additionally removing one of the metal centers in the case of the pentameric entities ([Zr5(O)2(OH)6(OOC)4(H2O)11(alcohol)]6+). Going in detail, the unsaturated hexameric clusters exhibit different dispositions of their eight carboxylate ligands in such a way that the remaining four carboxylate-free positions are arranged according to a square planar or tetrahedral symmetry. It should be highlighted that the pentameric complexes imply an unprecedented core nuclearity in zirconium clusters and thus their isolation provides a novel building block for the design of metal-organic materials.

7.
Clin Transplant ; 32(12): e13433, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30365182

RESUMO

BACKGROUND AND AIMS: Biliary anastomosis is a frequent area of complications after liver transplantation (LT) and a potential area of "microangiopathy". The concept of a "marginal bile duct" is unexplored. The main aim was to make a preliminary evaluation of the utility of an innovative real-time oxygen microtension (pO2mt) testing device for the assessment of bile duct viability during LT and to correlate these pO2mt values with microvascular tissue quality by histopathology and outcomes. PATIENTS AND METHODS: Observational prospective cohort study with 23 patients. Oxygen microtension measurements were made placing a micropO2 probe in different areas of recipient and donor's bile duct intraoperative. RESULTS: Mean pO2mt in the graft bile duct at the level of the anastomosis 103.82 (31-157) mm Hg, being 121.52 (55-174) mm Hg 1.5 cm proximal to the hilar plate (P < 0.001). Mean pO2mt in the recipient's bile duct was 117.87 (62-185) mm Hg, while a value of 137.30 (81-198) mm Hg was observed 1.5 cm distal to the anastomosis (P < 0.001). Cystic duct resection (12 cases) was also related with higher pO2mt values at anastomosis [117.8 (93-157) vs 88.54 (31-124) mm Hg] and distal to anastomosis [135.6 (111-174) vs 106.2 (55-133) mm Hg; P < 0.001]. Patients with 1-, 3-, and 12-month biliary complications had significantly lower pO2mt in the intraoperative measurements. CONCLUSION: Our preliminary results show that distal borders of donor and recipient bile ducts may be low-vascularized areas. Tissue pO2mt is significantly higher in areas close to the hilar plate and to the duodenum in donor and recipient's sides, respectively. Bile duct injury and biliary complications are associated with worse tissue pO2mt.


Assuntos
Anastomose Cirúrgica/efeitos adversos , Doenças Biliares/diagnóstico , Sistema Biliar/metabolismo , Complicações Intraoperatórias/diagnóstico , Transplante de Fígado/efeitos adversos , Doadores Vivos/provisão & distribuição , Oxigênio/metabolismo , Sistema Biliar/patologia , Doenças Biliares/etiologia , Doenças Biliares/metabolismo , Feminino , Seguimentos , Humanos , Complicações Intraoperatórias/etiologia , Complicações Intraoperatórias/metabolismo , Masculino , Pessoa de Meia-Idade , Oxigênio/efeitos adversos , Oxigênio/análise , Prognóstico , Estudos Prospectivos , Fatores de Risco
8.
Inorg Chem ; 55(15): 7755-63, 2016 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-27409976

RESUMO

The present work provides two new examples of supramolecular metal-organic frameworks consisting of three-dimensional extended noncovalent assemblies of wheel-shaped heptanuclear [Cu7(µ-H2O)6(µ3-OH)6(µ-adeninato-κN3:κN9)6](2+) entities. The heptanuclear entity consists of a central [Cu(OH)6](4-) core connected to six additional copper(II) metal centers in a radial and planar arrangement through the hydroxides. It generates a wheel-shaped entity in which water molecules and µ-κN3:κN9 adeninato ligands bridge the peripheral copper atoms. The magnetic characterization indicates the central copper(II) center is anti-ferromagnetically coupled to external copper(II) centers, which are ferromagnetically coupled among them leading to an S = 5/2 ground state. The packing of these entities is sustained by π-π stacking interactions between the adenine nucleobases and by hydrogen bonds established among the hydroxide ligands, sulfate anions, and adenine nucleobases. The sum of both types of supramolecular interactions creates a rigid synthon that in combination with the rigidity of the heptameric entity generates an open supramolecular structure (40-50% of available space) in which additional sulfate and triethylammonium ions are located altogether with solvent molecules. These compounds represent an interesting example of materials combining both porosity and magnetic relevant features.


Assuntos
Adenina/química , Cobre/química , Imãs/química , Estruturas Metalorgânicas/química , Sulfato de Cobre/química , Cristalografia por Raios X , Ligação de Hidrogênio , Hidróxidos/química , Ligantes , Espectrofotometria Infravermelho , Temperatura
9.
Nano Lett ; 15(1): 224-8, 2015 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-25490236

RESUMO

We demonstrate a new class of semiconductor device: the optically triggered infrared photodetector (OTIP). This photodetector is based on a new physical principle that allows the detection of infrared light to be switched ON and OFF by means of an external light. Our experimental device, fabricated using InAs/AlGaAs quantum-dot technology, demonstrates normal incidence infrared detection in the 2-6 µm range. The detection is optically triggered by a 590 nm light-emitting diode. Furthermore, the detection gain is achieved in our device without an increase of the noise level. The novel characteristics of OTIPs open up new possibilities for third generation infrared imaging systems ( Rogalski, A.; Antoszewski, J.; Faraone, L. J. Appl. Phys. 2009, 105 (9), 091101).

10.
Chemistry ; 20(6): 1554-68, 2014 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-24403128

RESUMO

The understanding of the factors that affect the real pore-network structure for a given bulk material due to different synthetic procedures is essential to develop the material with the best adsorption properties. In this work, we have deeply studied the influence of the crystallinity degree over the adsorption capacity on three new isostructural MOFs with the formula {[CdM(µ4-pmdc)2(H2O)2]⋅solv}n (in which, pmdc = pyrimidine-4,6-dicarboxylate; solv = corresponding solvent; M(II) = Cd (1), Mn (2), Zn (3)). Compared with other methods, the solvent-free synthesis stands as the most effective route because, apart from enabling the preparation of the heterometallic compounds 2 and 3, it also renders the adsorbents with the highest performance, which is indeed close to the expected one derived from Grand Canonical Monte Carlo (GCMC) calculations. The structural analysis of the as-synthesised and evacuated frameworks reveals the existence of a metal atom exposed to the pore. The accessibility of this site is limited due to its atomic environment, which is why it is considered as a pseudo-open-metal site. The chemical and physical characterisation confirms that this site can be modified as the metal atom is replaced in compounds 2 and 3. To assess the effect of the metal replacement on the adsorption behaviour, an exhaustive study of CO2 experimental isotherms has been performed. The affinity of the pseudo-open metal sites towards CO2 and the distribution of the preferred adsorption sites are discussed on the basis of DFT and GCMC calculations.


Assuntos
Dióxido de Carbono/isolamento & purificação , Ácidos Carboxílicos/química , Compostos Organometálicos/química , Pirimidinas/química , Adsorção , Metais/química , Modelos Moleculares , Porosidade
11.
Eur J Nutr ; 53(2): 567-74, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-23892521

RESUMO

PURPOSE: Our objective was to compare the absorption of microencapsulated ferric saccharate (MFS) and ferrous sulfate (FS) in a fortified milk product, using a crossover design. METHODS: Seventeen non-iron-deficient healthy adults from both sexes participated in the study. On each intervention day (days 1 and 8), after an overnight fast, the volunteers consumed one type of product (test or control) and blood sampling was carried out at different times. The interventions days were separated by 7-day washout periods. This study was double blinded, crossover and randomized for nature of the test meals. The primary outcomes of the study were total serum iron and transferrin saturation. RESULTS: No significant differences could be observed in serum iron concentration during the 6-h postprandial study due to the type of milk product consumed, and there was neither an effect of time nor an interaction between the type of milk product and time. Transferrin saturation significantly increased after the intake of both products (P < 0.005), reaching a peak value between hours 2 and 4. No significant differences were detected between MFS and FS, indicating that iron absorption from MFS is equivalent to absorption from FS. CONCLUSIONS: MFS is a new ingredient that allows the fortification of a wide range of food products, including heat-processed and non-acidic products with similar absorption to FS, designed to produce neither organoleptic changes nor off-color development during storage of fortified food.


Assuntos
Compostos Férricos/farmacocinética , Compostos Ferrosos/farmacocinética , Ácido Glucárico/farmacocinética , Boca/metabolismo , Absorção , Adulto , Animais , Índice de Massa Corporal , Estudos Cross-Over , Método Duplo-Cego , Composição de Medicamentos , Feminino , Compostos Férricos/administração & dosagem , Óxido de Ferro Sacarado , Ferritinas/sangue , Compostos Ferrosos/administração & dosagem , Alimentos Fortificados , Ácido Glucárico/administração & dosagem , Humanos , Ferro/sangue , Masculino , Leite , Período Pós-Prandial
12.
Dalton Trans ; 53(22): 9482-9494, 2024 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-38767604

RESUMO

The synthesis, characterization and photocatalytic hydrogen evolution reaction (HER) performance of a series of metal-organic gels (MOGs) constructed from titanium(IV)-oxo clusters and dicarboxylato linkers (benzene-1,4-dicarboxylato and 2-aminobenzene-1,4-dicarboxylato) are described. All the MOGs exhibit a microstructure comprised of metal-organic nanoparticles intertwined into a highly meso-/macroporous structure, as demonstrated by cryogenic transmission electron microscopy and gas adsorption isotherms. Comprehensive chemical characterization enabled the estimation of the complex formula for these defective materials, which exhibit low crystallinity and linker vacancies. To gain deeper insights into the local structure, X-ray absorption fine structure (XAFS) spectroscopy experiments were performed and compared to that of the analogous crystalline metal-organic framework. Additionally, the ultraviolet-visible absorption properties and optical band gaps were determined from diffuse reflectance spectroscopy data. The MOGs were studied as light absorbers for the sacrificial photocatalytic HER under simulated solar light irradiation using a platinum co-catalyst by either (1) in situ photodeposition or (2) ex situ doping process, through a post-synthetic metalation of the MOG structure. The chemical analysis of the metalation, along with high-angle annular dark-field scanning transmission electron microscopy, revealed that although the in situ addition of the co-catalyst led to greater HER rates (227 vs. 110 µmolH2 gMOG-1 h-1 for in situ and ex situ, respectively), the ex situ modification provided a finer distribution of platinum nanoparticles along the porous microstructure and, as a result, it led to a more efficient utilization of the co-catalyst (45 vs. 110 mmolH2 gPt-1 h-1).

13.
Sci Total Environ ; 926: 171858, 2024 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-38522529

RESUMO

Forest ecosystems worldwide currently face worrying episodes of forest decline, which have boosted weakening and mortality of the trees. In the Mediterranean region, especially in the southeast Iberian Peninsula, Pinus sylvestris forests are severely affected by this phenomenon, and it has been commonly attributed to drought events. Remarkably, the role of root microbiota on pine decline has been overlooked and remains unclear. We therefore used metabarcoding to identify the belowground microbial communities of decline-affected and unaffected pine trees. Taxonomic composition of bacterial and fungal rhizosphere communities, and fungal populations dwelling in root endosphere showed different profiles depending on the health status of the trees. The root endosphere of asymptomatic trees was as strongly dominated by 'Candidatus Phytoplasma pini' as the root of decline-affected pines, accounting for >99 % of the total bacterial sequences in some samples. Notwithstanding, the titer of this phytopathogen was four-fold higher in symptomatic trees than in symptomless ones. Furthermore, the microbiota inhabiting the root endosphere of decline-affected trees assembled into a less complex and more modularized network. Thus, the observed changes in the microbial communities could be a cause or a consequence of forest decline phenomenon. Moreover, 'Ca. Phytoplasma pini' is positively correlated to Pinus sylvestris decline events, either as the primary cause of pine decline or as an opportunistic pathogen exacerbating the process once the tree has been weaken by other factors.


Assuntos
Microbiota , Pinus sylvestris , Pinus , Mudança Climática , Florestas , Árvores
14.
Biodivers Data J ; 12: e113943, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38444837

RESUMO

Background: Dataset of annual monitoring of herbivory effects on the conservation status of the endangered species Androcymbiumeuropaeum (Lange) K. Richt and its associated plant communities is presented in this manuscript. This dataset encompasses the annual monitoring of herbivory effects on the conservation status of the endangered species Androcymbiumeuropaeum. Since 2010, the SERPAM Department (Service of Evaluation, Restoration and Protection of Mediterranean Agrosystems) at the Zaidin Experimental Station, belonging to the Spanish National Research Council (CSIC-EEZ), has conducted annual sampling to assess the impact of both domestic and wild livestock, specifically rabbits, on the pastures where A.europaeum lives. The study consisted of a randomised block design, implementing three distinct treatments to evaluate different management strategies: (1) rabbit and domestic herbivory, (2) exclusion of domestic livestock and (3) exclusion of rabbits and domestic livestock. Within each treatment, two types of monitoring were conducted. Firstly, the abundance of A.europaeum was estimated by counting individuals within 50 cm x 50 cm quadrats. Secondly, plant species diversity was assessed along 2-m long transects using the modified Point-Quadrat method. The research was conducted within the Cabo de Gata-Níjar Natural Park in southern Spain, specifically in the Amoladeras Nature Reserve in Almería. New information: The dataset contains information spanning from 2010 to 2023, providing valuable insights into the annual monitoring of herbivory effects on the conservation status of A.europaeum, contributing to our understanding of the species' interaction with domestic and wild animal in the studied area.

15.
Anal Chem ; 85(9): 4475-82, 2013 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-23534339

RESUMO

Theory for interfacial proton transfer voltammetry of a molecular film containing any acid/base loading has been developed under equilibrium conditions. Diagnostic criteria to disentangle the interplay between diffuse layer and ionization effects are outlined. Easy-to-use analytical expressions for the voltammetric features are derived for the particular case of an invariant diffuse layer effect, which turn out to be entirely analogous to those for a surface redox conversion with Frumkin interactions. It is demonstrated that, regardless of the electrolyte concentration, significant ionization of the external acid groups located nearby the diffuse layer is sufficient for the fulfillment of this relevant particular case. A strategy is outlined to determine the amount, the intrinsic pKa, and the burial depth of the voltammetrically active groups from the surface concentration dependence of the main voltammetric features. Self-assembled monolayers of 11-mercaptoundecanoic acid deposited on Au(111), containing higher amounts of buried carboxylic groups than previously reported, have been studied to assess more critically the influence of electrostatic effects on the ionization process. Preliminary evidence suggests that the protonation/deprotonation voltammetric wave involves physisorbed rather than chemisorbed thiol molecules. Application of the present theoretical approach to this system reveals that the voltammetrically active carboxylic groups are located close to the electrode surface and become more acidic upon increasing their surface concentration.


Assuntos
Técnicas Eletroquímicas , Ácidos Graxos/análise , Prótons , Compostos de Sulfidrila/análise , Eletrólitos/análise , Ouro/química , Concentração de Íons de Hidrogênio , Oxirredução , Propriedades de Superfície
16.
Opt Express ; 21 Suppl 2: A295-304, 2013 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-23482292

RESUMO

Light trapping is becoming of increasing importance in crystalline silicon solar cells as thinner wafers are used to reduce costs. In this work, we report on light trapping by rear-side diffraction gratings produced by nano-imprint lithography using interference lithography as the mastering technology. Gratings fabricated on crystalline silicon wafers are shown to provide significant absorption enhancements. Through a combination of optical measurement and simulation, it is shown that the crossed grating provides better absorption enhancement than the linear grating, and that the parasitic reflector absorption is reduced by planarizing the rear reflector, leading to an increase in the useful absorption in the silicon. Finally, electro-optical simulations are performed of solar cells employing the fabricated grating structures to estimate efficiency enhancement potential.

17.
J Surg Res ; 181(2): e83-91, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-22906559

RESUMO

BACKGROUND: Orthotopic liver transplantation (OLT) is currently the elective treatment for advanced liver cirrhosis and acute liver failure. Ischemia/reperfusion damage may jeopardize graft function during the postoperative period. Cardiotrophin-1 (CT-1) has demonstrated cytoprotective properties in different experimental models of liver injury. There is no evidence to demonstrate its potential use in the prevention of the ischemia/reperfusion injury that occurs during OLT. The present study is the first report to show that the administration of CT-1 to donors would benefit the outcome of OLT. MATERIALS AND METHODS: We tested the cytoprotective effect of CT-1 administered to the donor prior to OLT in an experimental pig model. Hemodynamic changes, hepatic histology, cell death parameters, activation of cell signaling pathways, oxidative and nitrosative stress, and animal survival were analyzed. RESULTS: Our data showed that CT-1 administration to donors increased animal survival, improved cardiac and respiratory functions, and reduced hepatocellular injury as well as oxidative and nitrosative stress. These beneficial effects, related to the activation of AKT, ERK, and STAT3, reduced caspase-3 activity and diminished IL-1ß and TNF-α expression together with IL-6 upregulation in liver tissue. CONCLUSIONS: The administration of CT-1 to donors reduced ischemia/reperfusion injury and improved survival in an experimental pig model of OLT.


Assuntos
Citocinas/uso terapêutico , Transplante de Fígado , Cuidados Pré-Operatórios/métodos , Substâncias Protetoras/uso terapêutico , Traumatismo por Reperfusão/prevenção & controle , Coleta de Tecidos e Órgãos , Animais , Biomarcadores/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/fisiologia , Citocinas/farmacologia , Esquema de Medicação , Hemodinâmica/efeitos dos fármacos , Hepatectomia , Mediadores da Inflamação/metabolismo , Estimativa de Kaplan-Meier , Fígado/efeitos dos fármacos , Fígado/metabolismo , Transplante de Fígado/mortalidade , Estresse Oxidativo/efeitos dos fármacos , Substâncias Protetoras/farmacologia , Distribuição Aleatória , Traumatismo por Reperfusão/etiologia , Traumatismo por Reperfusão/mortalidade , Fenômenos Fisiológicos Respiratórios/efeitos dos fármacos , Suínos
18.
Ecol Appl ; 23(6): 1267-76, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24147400

RESUMO

Most of the world's plantations were established on previously disturbed sites with an intensive land-use history. Our general hypothesis was that native forest regeneration within forest plantations depends largely on in situ biological legacies as a source of propagules. To test this hypothesis, we analyzed native oak regeneration in 168 pine plantation plots in southern Spain in relation to land use in 1956, oak patch proximity, and pine tree density. Historical land-use patterns were determined from aerial photography from 1956, and these were compared with inventory data from 2004-2005 and additional orthophoto images. Our results indicate that oak forest regeneration in pine plantations depends largely on land-use legacies, although nearby, well-conserved areas can provide propagules for colonization from outside the plantation, and pine tree density also affected oak recruit density. More intense land uses in the past meant fewer biological legacies and, therefore, lower likelihood of regenerating native forest. That is, oak recruit density was lower when land use in 1956 was croplands (0.004 +/- 0.002 recruits/m2 [mean +/- SE]) or pasture (0.081 +/- 0.054 recruits/m2) instead of shrubland (0.098 +/- 0.031 recruits/m2) or oak formations (0.314 +/- 0.080 recruits/m2). Our study shows that land use in the past was more important than propagule source distance or pine tree density in explaining levels of native forest regeneration in plantations. Thus, strategies for restoring native oak forests in pine plantations may benefit from considering land-use legacies as well as distance to propagule sources and pine density.


Assuntos
Agricultura , Ecossistema , Pinus/fisiologia , Quercus/fisiologia , Espanha , Árvores
19.
Nanotechnology ; 24(34): 345402, 2013 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-23912379

RESUMO

A colloidal deposition technique is presented to construct long-range ordered hybrid arrays of self-assembled quantum dots and metal nanoparticles. Quantum dots are promising for novel opto-electronic devices but, in most cases, their optical transitions of interest lack sufficient light absorption to provide a significant impact in their implementation. A potential solution is to couple the dots with localized plasmons in metal nanoparticles. The extreme confinement of light in the near-field produced by the nanoparticles can potentially boost the absorption in the quantum dots by up to two orders of magnitude.In this work, light extinction measurements are employed to probe the plasmon resonance of spherical gold nanoparticles in lead sulfide colloidal quantum dots and amorphous silicon thin-films. Mie theory computations are used to analyze the experimental results and determine the absorption enhancement that can be generated by the highly intense near-field produced in the vicinity of the gold nanoparticles at their surface plasmon resonance.The results presented here are of interest for the development of plasmon-enhanced colloidal nanostructured photovoltaic materials, such as colloidal quantum dot intermediate-band solar cells.

20.
Commun Chem ; 6(1): 4, 2023 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-36697803

RESUMO

Nowadays, there are many reliable characterization techniques for the study of adsorption properties in gas phase. However, the techniques available for the study of adsorption processes in solution, rely on indirect characterization techniques that measure the adsorbate concentration remaining in solution. In this work, we present a sensing method based on the magnetic properties of metal-organic frameworks (MOFs) containing paramagnetic metal centres, which stands out for the rapidity, low cost and in situ direct measurement of the incorporated adsorbate within the porous material. To illustrate this sensing technique, the adsorption in solution of four MOFs have been characterized: MIL-88A(Fe), MOF-74(Cu, Co) and ZIF-67(Co). Our simple and efficient method allows the direct determination of the adsorbed mass, as well as the measurement of adsorption isotherm curves, which we hope will greatly advance the study of adsorption processes in solution, since this method is independent of the chemical nature of the adsorbate that often makes its quantification difficult.

SELEÇÃO DE REFERÊNCIAS
Detalhe da pesquisa