Hydrogen activation by high-valent oxo-molybdenum(VI) and -rhenium(VII) and -(V) compounds

The high-valent oxo-molybdenum(VI) and -rhenium(VII) and -(V) derivatives MoO2Cl2, ReCH3O3 (MTO) and ReIO2(PPh3)2 catalyze the selective hydrogenation of alkynes to alkenes at 80 degrees C under 40 atm of pressure. The reduction of sulfoxides to sulfides has also been performed by oxo-rhenium and -molybdenum complexes using hydrogen as a reducing agent. Activation of hydrogen by MoO2Cl2 and MoO2(S2CNEt2)2 was shown by means of DFT calculations to proceed by H-H addition to the Mo=O bond, followed by hydride migration to yield a water complex.     

Dissolvable Carboxymethylcellulose Microneedles for Noninvasive and Rapid Administration of Diclofenac Sodium

The aim of this study is to prepare dissolvable biopolymeric microneedle (MN) patches composed solely of sodium carboxymethylcellulose (CMC), a water-soluble cellulose derivative with good film-forming ability, by micromolding technology for the transdermal delivery of diclofenac sodium salt (DCF). The MNs with ≈456 µm in height displayed adequate morphology, thermal stability up to 200 °C, and the required mechanical strength for skin insertion (>0.15 N needle⁻¹). Experiments in ex vivo abdominal human skin demonstrate the insertion capability of the CMC_DCF MNs up to 401 µm in depth. The dissolution of the patches in saline buffer results in a maximum cumulative release of 98% of diclofenac after 40 min, and insertion in a skin simulant reveals that all MNs completely dissolve within 10 min. Moreover, the MN patches are noncytotoxic toward human keratinocytes. These results suggest that the MN patches produced with CMC are promising biopolymeric systems for the rapid administration of DCF in a minimally invasive manner.     

Development of a new sequential injection in-line cloud point extraction system for flame atomic absorption spectrometric determination of manganese in food samples

A preconcentration method for manganese determination by sequential injection cloud point extraction with subsequent detection by flame atomic absorption spectrometry (FAAS) has been developed. The enrichment of Mn was performed after a preliminary on-line cloud point extraction and entrapment of manganese-containing surfactant aggregated within a minicolumn packed with cotton. The laboratory-made reagent 4-(5′-bromo-2′-thiazolylazo)orcinol (Br-TAO) and the surfactant Triton X-114 were used for cloud point extraction. The manganese ions were eluted with sulphuric acid solution and directly introduced into the FAAS. Chemical and flow variables affecting the preconcentration were studied. Using a sample volume of 2.80 mL the limit of detection and enrichment factor were calculated to be 0.5 μg L⁻¹ and 14, respectively. The sample frequency is 48 h⁻¹, considering a total run cycle of 75 s. The accuracy of the proposed method has been demonstrated by the analysis of the certified reference biological materials rice flour and tomato leaves. The method has been applied to determination of manganese in food samples.     

Immuno-column for on-line quantification of human serum IgG antibodies to Helicobacter pylori in human serum samples

This study report an human serum IgG antibodies to Helicobacter pylori quantitation procedure based on the multiple use of an immobilized H. pylori antigen on an immuno-column incorporated into an a flow-injection (FI) analytical system. The immuno-adsorbent column was prepared by packing 3-aminopropyl-modified controlled-pore glass (APCPG) covalently linking H. pylori antigens in a 3-cm of Teflon tubing (0.5 i.d.). Antibodies in the serum sample are allowed to react immunologically with the immobilized H. pylori antigen, and the bound antibodies are quantified by alkaline phosphatase (AP) enzyme-labeled second antibodies specific to human IgG. p-Aminophenyl phosphate (pAPP) was converted to p-aminophenol (pAP) by AP and an electroactive product was quantified on glassy carbon electrode (GCE) modified with multiwall carbon nanotubes (MWCNT) (GCE-CNTs) at 0.30 V. The total assay time was 25 min. The calculated detection limits for amperometric detection and the ELISA procedure are 0.62 and 1.8 UmL(-1), respectively. Reproducibility assays were made using repetitive standards of H. pylori-specific antibody and the intra- and inter-assay coefficients of variation were below 5%. The immuno-affinity method showed higher sensitivity and lower time-consumed, demonstrate its potential usefulness for early assessment of human serum immunoglobulin G (IgG) antibodies to H. pylori.     

Multivariate near infrared spectroscopy models for predicting the methyl esters content in biodiesel

Biodiesel is the main alternative to fossil diesel. The key advantages of its use are the fact that it is a non-toxic renewable resource, which leads to lower emissions of polluting gases. European governments are targeting the incorporation of 20% of biofuels in the general fuels until 2020.Chemically, biodiesel is a mixture of fatty acid methyl esters, derived from vegetable oils or animal fats, which is usually produced by a transesterification reaction, where the oils/fats react with an alcohol, in the presence of a catalyst. The European Standard (EN 14214) establishes 25 parameters that have to be analysed to certify biodiesel quality and the analytical methods that should be used to determine those properties.This work reports the use of near infrared (NIR) spectroscopy to determine the esters content in biodiesel as well as the content in linolenic acid methyl esters (C18:3) in industrial and laboratory-scale biodiesel samples. Furthermore, calibration models for myristic (C14:0), palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2) acid methyl esters were also obtained. Principal component analysis was used for the qualitative analysis of the spectra, while partial least squares regression was used to develop the calibration models between analytical and spectral data. The results confirm that NIR spectroscopy, in combination with multivariate calibration, is a promising technique to assess the biodiesel quality control in both laboratory-scale and industrial scale samples.     

Comparative Analysis of the Distribution of Copper in Green and Brown Brazilian Propolis Extracts

We proposed here a novel analytical procedure for copper speciation in green and brown propolis extracts using SEC—HPLC—GFAAS with 0.5% m v^?1 SDS in 2.5 m mol L^?1 Tris–HCl (pH 7.4) as the mobile phase buffer solution. Both basic (0.05 mol L^?1 NaOH) and acid (0.05 mol L^?1 HCl) conditions were evaluated for sample extraction. Depending on the extraction procedure, differences in copper distribution were identified. Copper was mainly associated with high-molecular-weight (HMW) fractions in green propolis extract when extracted with basic solution, whereas with acid extraction solution, only low-molecular-weight (LMW) fractions were obtained in both samples. Furthermore, combined analysis of results obtained using SEC-UV and GF AAS confirmed the association of copper with LMW and HMW species.     

Phenolic profile of hazelnut (Corylus avellana L.) leaves cultivars grown in Portugal

In this study, phenolic compounds of hazelnut leaves of 10 different cultivars with the same cultural, geographical, geological and climatic conditions were analyzed by HPLC/DAD and HPLC/DAD/MS/MS - ESI. Eight phenolic compounds (3-caffeoylquinic acid, 5-caffeoylquinic acid, caffeoyltartaric acid, p-coumaroyltartaric acid, myricetin 3-rhamnoside, quercetin 3-glycoside, quercetin 3-rhamnoside and kaempferol 3-rhamnoside) were identified and quantified. All of the analyzed samples showed a similar phenolic profile, in which myricetin 3-rhamnoside and quercetin 3-rhamnoside were the major compounds and caffeoyltartaric and p-coumaroyltartaric acids were present in vestigial amounts.     

Quantification, 2DE analysis and identification of enriched glycosylated proteins from mouse muscles: Difficulties and alternatives

One of the problems with 2DE is that proteins present in low amounts in a sample are usually not detected, since their signals are masked by the predominant proteins. The elimination of these abundant proteins is not a guaranteed solution to achieve the desired results. The main objective of this study was the comparison of common and simple methodologies employed for 2DE analysis followed by MS identification, focusing on a pre‐purified sample using a wheat germ agglutinin (WGA) column. Adult male C57Black/Crj6 (C57BL/6) mice were chosen as the model animal in this study; the gastrocnemius muscles were collected and processed for the experiments. The initial fractionation with succinylated WGA was successful for the elimination of the most abundant proteins. Two quantification methods were employed for the purified samples, and bicinchoninic acid (BCA) was proven to be most reliable for the quantification of glycoproteins. The gel staining method, however, was found to be decisive for the detection of specific proteins, since their structures affect the interaction of the dye with the peptide backbone. The Coomassie Blue R‐250 dye very weakly stained the gel with the WGA purified sample. When the same gel was stained with silver nitrate, however, MS could positively assign 12 new spots. The structure of the referred proteins was not found to be prone to interaction with Coomassie blue.     

Photoresponsive Binding Dynamics in High-Affinity Cucurbit[8]uril-Dithienylethene Host-Guest Complexes

The use of external stimuli to control the binding kinetics in supramolecular systems is of critical importance for the development of advanced molecular machines and devices. In this work, a study focused on the kinetics of a water-soluble host-guest system based on cucurbit[8]uril and two dithienylethene (DTE) photoswitches is reported. It is shown that for the DTE guest comprising two anionic sulfonate side arms appended to pyridinium moieties, the formation/dissociation of the pseudorotaxane structures is slowed down by more than 100000-fold with respect to its bipyridinium analogue. The decrease in ingression rate leads to the emergence of a competitive metastable product with the open DTE isomer that has an important influence in the overall binding kinetics. Moreover, the host-guest dissociation kinetics is demonstrated to be approximately 100-fold slower for the closed DTE isomer (t_1/2=107 h vs. t_1/2=1.2 h for the open isomer) allowing control over the dissociation rate with light.     

Characterization and cytotoxicity of a benzocaine inclusion complex

Benzocaine (BZC), is a local anesthetic widely used in topical formulations as well as in throat pastilles. A disadvantage is that the compound presents low aqueous solubility. The present work describes the preparation and characterization of an inclusion complex between BZC and β-cyclodextrin (β-CD), followed by cytotoxicity assays. The association constant (Ka) was calculated using solubility isotherms, at different temperatures, and an HPLC procedure, at room temperature, employing a reverse phase C18 column, with a mobile phase consisting of water/acetonitrile. Ka obtained with solubility isotherms at temperatures of 25, 35, and 45 °C were 229.8, 317.1, and 520.3 M^?1, respectively. Employing HPLC, Ka was 38.0 M^?1. The difference in the Ka value could be explained because HPLC analyses were conducted using organic solvent, which affected the host–guest interaction. Moreover, the continuous flow could have altered the degree of association of the drug with β-CD. The BZC/CD inclusion complex was characterized using infrared spectroscopy, thermogravimetry, and X-ray diffraction. Analysis showed a good agreement with literature, suggesting that the complex was established. Cytotoxicity assays using fibroblast V79 cells showed that BZC/CD formulation was not cytotoxic, demonstrating its potential to reduce the toxicity of the anesthetic. The assays demonstrated an effective interaction between BZC and CD, and that the inclusion complex was less toxic to V79 cells than the plain BZC, turning it a good alternative to decrease its toxicity when administered to patients.