Microwave-assisted digestion procedures for biological samples with diluted nitric acid: Identification of reaction products

Microwave-assisted sample preparation using diluted nitric acid solutions is an alternative procedure for digesting organic samples. The efficiency of this procedure depends on the chemical properties of the samples and in this work it was evaluated by the determination of crude protein amount, fat and original carbon. Soybeans grains, bovine blood, bovine muscle and bovine viscera were digested in a cavity-microwave oven using oxidant mixtures in different acid concentrations. The digestion efficiency was evaluated based on the determination of residual carbon content and element recoveries using inductively coupled plasma optical emission spectrometry (ICP OES). In order to determine the main residual organic compounds, the digests were characterized by nuclear magnetic resonance (¹H NMR). Subsequently, studies concerning separation of nitrobenzoic acid isomers were performed by ion pair reversed phase liquid chromatography using a C18 stationary phase, water:acetonitrile:methanol (75:20:5, v/v/v) + 0.05% (v/v) TFA as mobile phase and ultraviolet detection at 254 nm. Sample preparation based on diluted acids proved to be feasible and a recommendable alternative for organic sample digestion, reducing both the reagent volumes and the variability of the residues as a result of the process of decomposition. It was shown that biological matrices containing amino acids, proteins and lipids in their composition produced nitrobenzoic acid isomers and other organic compounds after cleavage of chemical bonds.     

Proanthocyanidin glycosides from the leaves of Quercus ilex L. (Fagaceae)

From the polar extracts of the leaves of Quercus ilex L., two new proanthocyanidin glycosides, namely afzelechin-(4α→8)-catechin-3-O-β-glucopyranoside (1) and afzelechin-(4α→8)-catechin-3-O-α-rhamnopyranoside (2), were isolated in addition to catechin (3), proanthocyanidin B₃ (4), prodelphinidin C (5), dehydrodicatechin A (6), quercetin (7) and six known flavonol glucosides with their acylated derivatives (8-13) and ellagic acid (14). The structures of all isolated compounds were established by spectroscopic means, mainly 1D and 2D NMR, as well as LC/MS and HR-MS spectrometric analyses. The absolute configuration of compound 1 was determined by CD measurements. The proanthocyanidin glycosides are especially interesting, as they possess the sugar in the upper unit of the dimer, which is rare for this type of compounds.     

Syntheses of aza and fluorine-substituted 3-(piperidin-4-yl)-4,5-dihydro-1H-benzo[d][1,3]diazepin-2(3H)-ones

A practical and expedient synthesis of the title compounds is described. They were prepared by Stille reaction of nitro halopyridines 4 or nitro fluro-halobenzenes 10, followed by Michael addition of tert-butyl 4-aminopiperidine-1-carboxylate to the resulting activated vinyl compounds 5 and 11, hydrogenation (-NO₂→-NH₂), cyclic urea formation, Boc removal, and HCl salt formation. However, N3 and F1 analogs could not be made by this general strategy. Activated vinyl compounds 5a and 5d when reacted with tert-butyl 4-aminopiperidine-1-carboxylate did not stop at the desired Michael addition stage; but proceeded to produce azaindolines 8 and 9. Michael addition did not occur to compound 11d; instead, the fluorine atom was displaced.     

Novel Antiretroviral Therapeutic Strategies for HIV

When the first cases of HIV infection appeared in the 1980s, AIDS was a deadly disease without any therapeutic alternatives. Currently, there is still no cure for most cases mainly due to the multiple tissues that act as a reservoir for this virus besides the high viral mutagenesis that leads to an antiretroviral drug resistance. Throughout the years, multiple drugs with specific mechanisms of action on distinct targets have been approved. In this review, the most recent phase III clinical studies and other research therapies as advanced antiretroviral nanodelivery systems will be here discussed. Although the combined antiretroviral therapy is effective in reducing viral loading to undetectable levels, it also presents some disadvantages, such as usual side effects, high frequency of administration, and the possibility of drug resistance. Therefore, several new drugs, delivery systems, and vaccines have been tested in pre-clinical and clinical trials. Regarding drug delivery, an attempt to change the route of administration of some conventional antiretrovirals has proven to be successful and surpassed some issues related to patient compliance. Nanotechnology has brought a new approach to overcoming certain obstacles of formulation design including drug solubility and biodistribution. Overall, the encapsulation of antiretroviral drugs into nanosystems has shown improved drug release and pharmacokinetic profile.     

First measurement of the rho spectral function in high-energy nuclear collisions

We report on a precision measurement of low-mass muon pairs in 158 AGeV indium-indium collisions at the CERN SPS. A significant excess of pairs is observed above the yield expected from neutral meson decays. The unprecedented sample size of 360,000 dimuons and the good mass resolution of about 2% allow us to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum is consistent with a dominant contribution from pi+pi- -->rho -->mu+mu- annihilation. The associated space-time averaged spectral function shows a strong broadening, but essentially no shift in mass. This may rule out theoretical models linking hadron masses directly to the chiral condensate.     

Diffusion coefficient distribution from NMR-DOSY experiments using Hopfield neural network

Diffusion ordered spectroscopy (DOSY) is a powerful two-dimensional NMR method to study molecular translation in various systems. The diffusion coefficients are usually retrieved, at each frequency, from a fit procedure on the experimental data, considering a unique coefficient for each molecule or mixture. However, the fit can be improved if one regards the decaying curve as a multiexponential function and the diffusion coefficient as a distribution. This work presents a computer code based on the Hopfield neural network to invert the data. One small-molecule binary mixture with close diffusion coefficients is treated with this approach, demonstrating the effectiveness of the method.     

Quantifying chaos for ecological stoichiometry

The theory of ecological stoichiometry considers ecological interactions among species with different chemical compositions. Both experimental and theoretical investigations have shown the importance of species composition in the outcome of the population dynamics. A recent study of a theoretical three-species food chain model considering stoichiometry [B. Deng and I. Loladze, Chaos 17, 033108 (2007)] shows that coexistence between two consumers predating on the same prey is possible via chaos. In this work we study the topological and dynamical measures of the chaotic attractors found in such a model under ecological relevant parameters. By using the theory of symbolic dynamics, we first compute the topological entropy associated with unimodal Poincare? return maps obtained by Deng and Loladze from a dimension reduction. With this measure we numerically prove chaotic competitive coexistence, which is characterized by positive topological entropy and positive Lyapunov exponents, achieved when the first predator reduces its maximum growth rate, as happens at increasing δ1. However, for higher values of δ1 the dynamics become again stable due to an asymmetric bubble-like bifurcation scenario. We also show that a decrease in the efficiency of the predator sensitive to prey's quality (increasing parameter ζ) stabilizes the dynamics. Finally, we estimate the fractal dimension of the chaotic attractors for the stoichiometric ecological model.     

Quantitative assessment of voice quality following laser surgery for reinke''s edema

Although laser surgery has been widely advocated for use in the treatment of vocal fold papilloma because it does not incur bleeding, it has been questioned for use in treating Reinke's edema due to the possibility of heat dispersion to normal surrounding tissue and of scarring. We present a series of 8 cases in which laser surgery was the method of treatment for bilateral Reinke's edema. In each case, voice therapy was selected as the initial treatment; laser surgery was performed following voice therapy. Prior to and following surgery, videostroboscopic examinations were performed on the subjects. Only 4 subjects were available for assessment at the 1-month postoperative period. From the audio track of the videotape, the speaking fundamental frequency, perturbation measures for the vowel /i/, and noise-to-harmonic ratio of a completely voiced sentence were obtained. From the videostroboscopic recordings, the symmetry of the vocal folds, the presence or absence of the mucosal wave and the glottic closure pattern, prior to and after surgery, were judged independently by 3 examiners. The fundamental frequencies approximated the normal male and female ranges for those subjects seen 1 month after surgery. In addition, the noise-to-harmonic ratio and the relative average perturbation improved. Stroboscopy revealed irregularities in the symmetry of vocal folds, mucosal wave, and glottic closure 1 month after surgery.     

Tuning Selectivity and Sensitivity of Mixed‐polymeric Tetraruthenated Metalloporphyrins Modified Electrodes as Voltammetric Sensors of Chloramphenicol

Mixed Ni?Co tetraruthenated porphyrin films were successfully electropolymerized on glassy carbon electrodes in alkaline solutions (pH=13) of NiTRP and CoTRP, giving excellent electrocatalytic responses for determination of the antibiotic drug chloramphenicol. Electrodes with four different compositions were obtained by varying the ratio of NiTRP and CoTRP in the deposition solution. For the characterization of these materials, SEM, ICP‐MS, EIS and CV were explored. The porphyrin modified glassy carbon electrodes presented two oxidation peaks for chloramphenicol (except for Ni‐25). The potential shifted to lower values as the percentage of CoTRP increased decreasing its oxidation potential in more than 200 mV for Ni‐50 as compared to Ni‐100. Interestingly, the materials with cobalt content larger than 50 % did not show the typical catalytic response of the Ni^IIIOOH species, but rather showed an increase in current at potentials larger than 0.4 V, demonstrating the key role played by nickel in this type of materials. The composition of polymeric mixed porphyrin materials influenced the oxidation current response of both redox waves, resulting in different sensitivities on the calibration curves.