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What Controls Photocatalytic Water Oxidation on Rutile TiO2(110) under Ultra-High-Vacuum Conditions?

Annapaola Migani and Lluís Blancafort

J. Am. Chem. Soc., 2017, 139 (34), pp 11845–11856

The photocatalytic O–H dissociation of water absorbed on a rutile TiO2(110) surface in ultrahigh vacuum (UHV) is studied with spin-polarized density functional theory and a hybrid exchange-correlation functional (HSE06), treating the excited-state species as excitons with triplet multiplicity. This system is a model for the photocatalytic oxidation of water by TiO2 in an aqueous medium, which is relevant for the oxygen evolution reaction and photodegradation of organic pollutants. We provide a comprehensive mechanistic picture where the most representative paths correspond to excitonic configurations with the hole located on three- and two-coordinate surface oxygen atoms (O3s and O2s). Our picture explains the formation of the species observed experimentally. At near band gap excitation, the O3s path leads to the generation of hydroxyl anions which diffuse on the surface, without net oxidation. In contrast, free hydroxyl radicals are formed at supra band gap excitation (e.g., 266 nm) from an interfacial exciton that undergoes O–H dissociation. The oxidation efficiency is low because the path associated with the O2s exciton, which is the most favored one thermodynamically, is unreactive because of a high propensity for charge recombination. Our results are also relevant to understand the reactivity in the liquid phase. We assign the photoluminescence measured for atomically flat TiO2(110) surfaces in an aqueous medium to the O3s exciton, in line with the proposal based on experiments, and we have identified a species derived from the O2s exciton with an activated O2s–Ti bond that may be relevant in photocatalytic applications in an aqueous medium.
 

Microvesicle release and micellar attack as the alternative mechanisms involved in the red-blood-cell-membrane solubilization induced by arginine-based surfactants

M. Elisa Fait, Melisa Hermet, Francesc Comelles, Pere Clapés, H. Ariel Alvarez, Eduardo Prieto, Vanesa Herlax, Susana R. Morcelle  and  Laura Bakás

RSC Advances,7, 60, 37549-37558, 2017

Two novel arginine-based surfactants, Bz-Arg-NHC10 and Bz-Arg-NHC12, were characterized with respect to surface properties and their interaction with human red-blood-cell (HRBC) membranes. The values for critical micellar concentration (CMC), the maximum surfactant adsorption at the air–liquid interface, and the area per molecule indicated better surface properties for Bz-Arg-NHC12. The observation of cylindrical worm-like aggregates of Bz-Arg-NHCn via atomic-force microscopy supported the predictions based on the value of the surfactant-packing parameter (SPP). Erythrocyte-membrane solubilization was effected by surfactant aggregates since cell lysis became evident at only surfactant concentrations above the CMC. Changes in HRBC shape observed at different surfactant concentrations led to the conclusion that a slow mechanism based on the insertion of surfactant monomers into the HRBC membrane, followed by a shedding of microvesicles was responsible for the hemolysis produced by both surfactants at the lower concentrations tested. In contrast, the extraction of membrane lipids upon collisions between HRBCs and surfactant aggregates competes with and prevents microvesicle release at the higher concentrations assayed.
 

Green synthesis of silver nanoparticles in oil-in-water microemulsion and nano-emulsion using geranium leaf aqueous extract as a reducing agent

Ruben Dario Rivera-Rangel. M. Pilar González-Muñoz. Mario Avila-Rodriguez. .Teresa Alejandra Razo-Lazcano. Conxita Solans

Colloids and Surfaces A: Physicochemical and Engineering Aspects 2017

A green synthesis of silver nanoparticles was developed, using a low-toxic system of microemulsion and nano-emulsion with castor oil as the oily phase, Brij 96 V and 1,2-hexanediol as the surfactant and co-surfactant respectively. Geranium (P. hortorum) leaf aqueous extract was employed as a reducing agent. The content and concentration of a metallic precursor and geranium leaf extract (GLE) in the systems used makes it possible to obtain different sizes of silver nanoparticles from 25 to 150 nm. The characterization by FTIR and Z potential shows that the biomolecules of the plant extract act as a reducing and capping agent, giving negative charges to the nanoparticle surface. The present study represents a contribution to the green synthesis of silver nanoparticles that can be extended to other metals.
 

Comparative study of the diagnostic and prognostic value of antibodies against chimeric citrullinated synthetic peptides and CCP3/CCP3.1 assays

María J. Gómara, Javier Rodríguez, María J. Bleda, Juan P. Salvador, Raimon Sanmartí and Isabel Haro

Clin Chem Lab Med 2017

Background:
The objective of the study was to compare the diagnostic yield of home-made ELISA tests based on synthetic chimeric fibrin/filaggrin citrullinated peptides (CFFCPs) with CCP3 and CCP3.1 commercial tests to detect anti-citrullinated protein/peptide antibodies (ACPAs) in rheumatoid arthritis (RA) patients. The prognostic value is also studied in a cohort of patients with early RA. Moreover, we transfer immunological assays from microtiter plates to microarray formats to allow the simultaneous analysis of several peptide sequences and reduce the volume of serum from patients.
Methods:
The diagnostic study includes: 100 RA patients who fulfilled the 1987 ACR criteria; 100 healthy blood donors; 35 patients with SLE according ACR criteria; 35 patients with PsA fulfilling the Wright and Moll criteria and 30 patients with HCV infection. The prognostic value study includes 50 patients with early RA with follow-up data available. All samples are from outpatients attending the Rheumatology Department of the Hospital Clinic of Barcelona.
Results:
Similar sensitivity, specificity and predictive values for the diagnosis of RA of CCFCPs compared to CCP3/CCP3.1 were obtained. Although a high concordance is observed between anti-CFFCPs and anti-CCP3/CCP3.1 in the early patients that rendered Larsen radiographic progression, CFFCPs could be a better marker of radiographic outcome. Strong correlations between the microarray and ELISA results were found for individual CFFCPs peptides.
Conclusions:
The development of multiplexing techniques combining a different spectrum of markers in a single analysis, including CFFCP peptides, could allow a more detailed analysis of the autoantibodies reactivity found in the sera of patients suffering of this heterogeneous disease.
 

Preparation of a Nanoemulsion with Carapa guianensis Aublet (Meliaceae) Oil by a Low-Energy/Solvent-Free Method and Evaluation of Its Preliminary Residual Larvicidal Activity

Flávia L. M. Jesus, Fernanda B. de Almeida, Jonatas L. Duarte, Anna E. M. F. M. Oliveira, Rodrigo A. S. Cruz, Raimundo N. P. Souto, Ricardo M. A. Ferreira, Regina Gendzelevski Kelmann, José C. T. Carvalho, Ana C. Lira-Guedes, Marcelino Guedes, Conxita Solans and Caio P. Fernandes

Evidence-based Complementary and Alternative Medicine 2017, 6756793, 2017

Andiroba (Carapa guianensis) seeds are the source of an oil with a wide range of biological activities and ethnopharmacological uses. However, few studies have devoted attention to innovative formulations, including nanoemulsions. The present study aimed to obtain a colloidal system with the andiroba oil using a low-energy and organic-solvent-free method. Moreover, the preliminary residual larvicidal activity of the nanoemulsion against Aedes aegypti was evaluated. Oleic and palmitic acids were the major fatty acids, in addition to the phytosterol ß-sitosterol and limonoids (tetranortriterpenoids). The required hydrophile-lipophile was around 11.0 and the optimal nanoemulsion was obtained using polysorbate 85. The particle size distribution suggested the presence of small droplets (mean diameter around 150?nm) and low polydispersity index (around 0.150). The effect of temperature on particle size distribution revealed that no major droplet size increase occurred. The preliminary residual larvicidal assay suggested that the mortality increased as a function of time. The present study allowed achievement of a potential bioactive oil in water nanoemulsion that may be a promising controlled release system. Moreover, the ecofriendly approach involved in the preparation associated with the great bioactive potential of C. guianensis makes this nanoemulsion very promising for valorization of this Amazon raw material.

 

A copper-templated, bifunctional organocatalyst: a strongly cooperative dynamic system for the aldol reaction

Anna Serra-Pont, Ignacio Alfonso, Jordi Solà and  Ciril Jimeno

Org. Biomol. Chem., 15, 6584-6591,2017

The study of novel metal-templated dynamic organocatalytic systems has led to the identification of CuSO4 as the most efficient template to assemble monofunctional prolinamide- and thiourea-modified pyridine ligands. The structural and electronic requirements to assemble an efficient catalyst have been disclosed: both pyridine ligands must bear a 1,3-substitution pattern, and the thiourea ligand serves as a reducing agent to copper(I) as well. Eventually, the cooperative effects achieved with such a simple system deliver high reaction rates and stereoselectivities at room temperature in the asymmetric aldol reaction, requiring only 1 mol% of copper salt.
 

Surface chemistry and germination improvement of Quinoa seeds subjected to plasma activation

A. Gómez-Ramírez, López-Santos, M. Cantos, J. L. García, R. Molina, J. Cotrino, J. P. Espinós & A. R. González-Elipe

Scientific Reports 7, Article number: 5924 (2017)

Plasma treatment is recognized as a suitable technology to improve germination efficiency of numerous seeds. In this work Quinoa seeds have been subjected to air plasma treatments both at atmospheric and low pressure and improvements found in germination rate and percentage of success. Seed water uptake by exposure to water vapor, although slightly greater for plasma treated seeds, did not justify the observed germination improvement. To identify other possible factors contributing to germination, the chemical changes experienced by outer parts of the seed upon plasma exposure have been investigated by X-ray photoemission spectroscopy (XPS) and scanning electron microscopy (SEM-EDX). XPS revealed that the outer layers of the Quinoa plasma treated seeds were highly oxidized and appeared enriched in potassium ions and adsorbed nitrate species. Simultaneously, SEM-EDX showed that the enrichment in potassium and other mineral elements extended to the seed pericarp and closer zones. The disappearance from the surface of both potassium ions and nitrate species upon exposure of the plasma treated seeds to water vapor is proposed as a factor favoring germination. The use of XPS to study chemical changes at seed surfaces induced by plasma treatments is deemed very important to unravel the mechanisms contributing to germination improvement.
 

Comparison between several reactors with Trametes versicolor immobilized on lignocellulosic support for the continuous treatments of hospital wastewater

J.Torána. P.Blánqueza and G.Caminal

Bioresource Technology 243, 966-974, 2017

Hospital wastewater is a major source of pharmaceutically active compounds (PhACs), which are not all removed in conventional wastewater treatment plants. White rot fungi can degrade PhACs, but their application has been limited to non-sterile conditions due to the competition with other microorganisms for growth. In this study, immobilization of Trametes versicolor on different lignocellulosic supports was studied as strategy to ensure fungal survival under continuous treatment conditions. A fluidized bed reactor and a trickling packed-bed reactor with T. versicolor immobilized on pallet wood were employed for the removal of ibuprofen, ketoprofen and naproxen. Best results were obtained with the trickling packed-bed reactor, which operated for 49 days with high removal values in real hospital wastewater.
 

Structural study of a new HIV-1 entry inhibitor and interaction with the HIV-1 fusion peptide in dodecylphosphocholine micelles

Yolanda Pérez, María José Gómara, Eloísa Yuste, Patricia Gómez-Gutierrez, Juan Jesús Pérez, and Isabel Haro

Chem. Eur. J. 10.1002/chem.201702531

Previous studies support the hypothesis that the envelope GB virus C E1 protein interferes HIV-1 entry and a peptide, derived from the region (139-156) of this protein, has defined as a novel HIV-1 entry inhibitor. In this work, we firstly focus on the characterization of the peptide structural features which are determinant for its anti-HIV-1 activity and secondly, on the study of its interaction of with the proposed viral target (the HIV-1 fusion peptide). We report the peptide structure determined by NMR spectroscopy in DPC micelles solved using restrained molecular dynamics calculations. The acquisition of different NMR experiments in DPC micelles (peptide-peptide titration, diffusion NMR and addition of paramagnetic relaxation agents) allows the proposal of an inhibition mechanism. We conclude that an 18-mer peptide from nonpathogenic E1 GBV-C protein, with a helix-turn-helix structure, inhibits HIV-1 by binding to the HIV-1 fusion peptide at membrane level interfering with those domains in HIV-1 that are critical for stabilizing the six-helix bundle formation in a membranous environment.

 

Twisted intramolecular charge transfer in a carbazole-based chromophore. The stable [(4-N-carbazolyl)-2,3,5,6-tetrachlorophenyl]bis(2,3,5,6-tetrachlorophenyl)methyl radical

Luis Juliá,  Alejandra Gilabert,  Lluís Fajarí,  Ignasi Sirés,  Marta Reig,  Enric Brillas,  Dolores Velasco Castrillo  and  Josep M. Anglada

New J. Chem., 2017

A neutral stable organic radical adduct 1 composed of a donor-acceptor dyad is reported. The electron-donor part is the carbazolyl ring directly linked to the electron-acceptor polychlorotriphenylmethyl radical through the para-position of a phenyl ring. In the synthetic procedure a C(sp2)-H bond is transformed into a C(sp2)-N bond through the radical-radical cross-coupling process. Theoretical calculations predict that the tetrachlorophenyl bridge moiety lies perpendicular to the carbazolyl group to minimize the repulsion with the chlorine atoms in ortho. The electron paramagnetic resonance (epr) spectrum of 1 exhibits a small coupling of the electronic spin with the carbazolyl nitrogen (0.32 G), the spin density being mainly located in the central sp2 carbon atom (30.22 G). The radical adduct presents a charge transfer band (? = 598-640 nm) showing hypsochromic shift with solvent polarity. In DMF solution, 1 exhibits a new weak band (? = 493 nm) which is tentatively attributed to a zwitterionic structure of the molecule resulting from a net electron transfer from the nitrogen to the central sp2 carbon atom. Cyclic voltammetry of 1 confirms the amphoteric character of the molecule. Computed values of ionization potential (IP) and electron affinity (EA) are in good agreement with the experimental values.
 


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