Morphological,electrochemical and photoelectrochemical characterization of nanotubular TiO2 synthetized electrochemically from different electrolytes

The electrochemical synthesis of auto-organized TiO₂ arrays generated by Ti anodization in different non-aqueous electrolytes was analyzed. Propylene carbonate-based electrolytes seem to be good electrolytic media for the controlled growth of titania nanotube structures. Scanning electron microscopy (SEM) analysis indicated that, depending on the media employed in the synthesis of the TiO₂ nanotubes, different aspect ratios (length/diameter) could be obtained. Impedance analysis using the passive pit model gave the electrical properties of the layers during the different stages of nanotubes formation. Mott–Schottky analysis and the impedance results showed that the TiO₂ nanotubes layers were n-type semiconductors with highly defective walls on top of a resistive barrier layer. Photoelectrochemical measurements showed that tetra(4-carboxyphenyl)porphyrin (TCPP) adsorbed onto the TiO₂ nanotube arrays, which could be employed as an efficient photosensitizer for solar-energy conversion by TCPP-sensitized nanotubular TiO₂ electrodes.     

A hybrid all-atom/coarse grain model for multiscale simulations of DNA

Hybrid simulations of molecular systems, which combine all-atom (AA) with simplified (or coarse grain, CG) representations, propose an advantageous alternative to gain atomistic details on relevant regions while getting profit from the speedup of treating a bigger part of the system at the CG level. Here we present a reduced set of parameters derived to treat a hybrid interface in DNA simulations. Our method allows us to forthrightly link a state-of-the-art force field for AA simulations of DNA with a CG representation developed by our group. We show that no modification is needed for any of the existing residues (neither AA nor CG). Only the bonding parameters at the hybrid interface are enough to produce a smooth transition of electrostatic, mechanic and dynamic features in different AA/CG systems, which are studied by molecular dynamics simulations using an implicit solvent. The simplicity of the approach potentially permits us to study the effect of mutations/modifications as well as DNA binding molecules at the atomistic level within a significantly larger DNA scaffold considered at the CG level. Since all the interactions are computed within the same classical Hamiltonian, the extension to a quantum/classical/coarse-grain multilayer approach using QM/MM modules implemented in widely used simulation packages is straightforward.     

Molecular interactions and structure of a supramolecular arrangement of glucose oxidase and palladium nanoparticles

This paper presents studies about the molecular interactions and redox processes involved in the formation of palladium nanoparticles associated to glucose oxidase (GOx-PdNPs) in a supramolecular arrangement. The synthesis occurs in two steps, the Pd reduction and the formation of the 80 nm sized supramolecular aggregates containing multiples units of GOx associated to 3.5 nm sized PdNPs. During synthesis, GOx molecules interact with Pd salt leading to metal ion and FAD reduction probably via the thiol group of the cysteine 521 residue. For the growing of PdNPs, formic acid was necessary as a co-adjuvant reducing agent. Besides the contribution for the redox processes, GOx is also necessary for the NP stability preventing the formation of precipitates resulted from uncontrolled growing of NPs Cyclic voltammetry of the GOx-PdNPs demonstrated electroactivity of the bionanocomposite immobilized on ITO (indium-tin oxide) electrode surface and also the NP is partially blocked due to strong interaction GOx and the surface of PdNPs. Vibrational spectroscopy (FTIR) showed that significant structural changes occurred in GOx after the association to PdNP. These mechanistics and structural studies can contribute for modulation of bionanocomposites properties.     

Nanostructures on surfaces of the metalorganic compound {Fe2(CO)6[µ-S2C6H2(OH)2]} and its potential as catalyst precursor for the synthesis of carbon nanotubes

The compound {Fe(2)(CO)(6)[μ-S(2)C(6)H(2)(OH)(2)]} is organized by H-bond interactions on graphite and SiO(2) surfaces as micron-length nanofibres. Thermal degradation of these fibres adsorbed on SiO(2) leads to a very homogeneous surface filled with Fe(2)O(3) nanoparticles (ca. 2.5 nm diameter) suitable to produce few-walled carbon nanotubes laying on a clean surface.     

Distinct hepatic lipid profile of hypertriglyceridemic mice determined by easy ambient sonic-spray ionization mass spectrometry

Easy ambient sonic-spray ionization mass spectrometry (EASI-MS) was used to interrogate the hepatic lipid profiles of hypertriglyceridemic and control normotriglyceridemic mice. The analyses of ex vivo complex lipid mixtures were made directly with EASI-MS without accompanying separation steps. Intense ions for phosphatidylcholines and triacylglycerols were observed in the positive ion mode whereas the spectra in the negative ion mode provided profiles of phosphatidylethanolamines and phosphatidylinositol. EASI-MS was coupled to high-performance thin-layer chromatography for analysis of free fatty acids. Fourier transform–ion cyclotron resonance–mass spectrometry was also employed to confirm the identity of the detected lipids. We demonstrated higher incorporation of oleic acid in phosphatidylcholine and triacylglycerol composition, higher relative abundance of arachidonic acid containing phosphatidylinositol, and overall distinct free fatty acid profile in the livers of genetic hypertriglyceridemic mice. We propose that these alterations in liver lipid composition are related to the higher tissue and body metabolic rates described in these hypertriglyceridemic mice.     

Hexylacrylate-based mixed-mode monolith,a stationary phase for the nano-HPLC separation of structurally related enkephalins

The potential of an in situ photopolymerized hexylacrylate-based monolithic stationary phase-bearing sulfonic acid groups was investigated by studying the chromatographic retention of small structurally related peptides (enkephalins) by nano-LC. Several retention mechanisms were highlighted. First, a reverse-phase chromatographic behavior toward neutral solutes due to hexylacrylate-moieties was demonstrated. Second, an evaluation of the influences of buffer pH suggested the involvement of a cation-exchange mechanism due to the presence of 2-acrylamido-2-methyl-1-propanesulfonic acid. This cation-exchange phenomenon was confirmed by the clear influence of Na⁺ concentration in the mobile phase on peptide retention.     

Development and validation of an HPLC-PDA method for the determination of myrsinoic acid B in the extracts of Rapanea ferruginea Mez

New, simple, rapid and precise HPLC-PDA method has been developed and validated for quantification of biomarker myrsinoic acid B in stem bark extracts of Rapanea ferruginea Mez. The method employs a Phenomenex C18 column (250 mm × 4.6 mm I.D., 5 μm) with acetonitrile:methanol:water (pH 2.6 with phosphoric acid) at 48:30:22 as mobile phase, at a flow rate of 0.7 mL min⁻¹ and photo diode array (PDA) detection at 270 nm. The validation data show that the method is specific, accurate, precise and robust. The method was linear, over a range of 5-100.0 μg mL⁻¹, with a limit of detection of 0.369 μg mL⁻¹ and limit of quantification of 1.233 μg mL⁻¹. The method has also shown consistent recoveries (average of 101.3% and 0.12% RSD) of the biomarker, with low intra and inter-day relative standard deviation (1.26% and 1.62%, respectively). The evaluated hydroethanolic extract and dry extract presented MAB values of 63.53 and 36.07 mg g⁻¹, respectively.     

Theoretical and infrared studies on the conformational isomerism of trans-2-bromo-alkoxycyclohexanes

The infrared spectra of trans-2-bromo-alkoxycyclohexanes (alcoxy = OMe, OEt, O(i)Pr and O(t)Bu) were obtained for the neat liquid, and the C-Br stretching mode was quantitatively analyzed to give insight about the conformational isomerism of these compounds. Frequency calculations supported the band assignments, and the relative band intensities suggest that the diaxial conformer is prevalent for the methoxy and tert-butoxy derivatives (51 and 56%, respectively), while the diequatorial form is preponderant for the ethoxy and isopropoxy derivatives (76 and 77%, respectively). Therefore, the size of the alkoxy group plays a determinant role in determining the conformational preferences of the title compounds.     

Transparent and conductive thin films of graphene/polyaniline nanocomposites prepared through interfacial polymerization

This communication reports a simple, one-pot procedure for the synthesis and processing of transparent and conductive thin films of graphene/polyaniline nanocomposites based on an interfacial polymerization. Thin films presenting transmittance of 89% and sheet resistance of 60.6 ? sq(-1) are spontaneously obtained and can be easily transferred to suitable substrates.     

Selective and Scalable Electrosynthesis of 2H-2-(Aryl)-benzo[d]-1,2,3-triazoles and Their N-Oxides by Using Leaded Bronze Cathodes

Electrosynthesis of 2H-2-(aryl)benzo[d]-1,2,3-triazoles and their N-oxides from 2-nitroazobenzene derivatives is reported. The electrolysis is conducted in a very simple undivided cell under constant current conditions with a leaded bronze cathode and a glassy carbon anode. The product distribution between 2H-2-(aryl)benzo[d]-1,2,3-triazoles and their N-oxides can be guided by simply controlling the current density and the amount of the charge applied. The reaction tolerates several sensitive functional groups in reductive electrochemistry. The usefulness and the applicability of the synthetic method is demonstrated by a formal synthesis of an antiviral compound.