Structure and antimycobacterial activity of the novel organometallic [Pd(C-bzan)(SCN)(dppp)] compound

The organometallic compound [Pd(C-bzan)(SCN)(dppp)] {bzan = N-benzylideneaniline, dppp = 1,3-bis(diphenylphosphino)propane} was synthesized and characterized by elemental analyses, infrared and H-1 and P-31(H-1) NMR spectroscopies. The crystal and molecular structures of the title complex were determined by single-crystal X-ray diffraction techniques. In vitro antimycobacterial evaluation demonstrated that the compound [Pd(C-bzan)(SCN)(dppp)] displayed a MIC of 5.15 mu M, which is superior than those values found for some commonly used anti-TB drugs and other Pd(II) complexes. (C) 2012 Elsevier B.V. All rights reserved.

PD controller synthesis from open-loop response measurements of rotating system

In this work, a method of computing PD stabilising gains for rotating systems is presented based on the D-decomposition technique, which requires the sole knowledge of frequency response functions. By applying this method to a rotating system with electromagnetic actuators, it is demonstrated that the stability boundary locus in the plane of feedback gains can be easily plotted, and the most suitable gains can be found to minimise the resonant peak of the system. Experimental results for a Laval rotor show the feasibility of not only controlling lateral shaft vibration and assuring stability, but also helps in predicting the final vibration level achieved by the closed-loop system. These results are obtained based solely on the input-output response information of the system as a whole.

Differential expression of the costimulatory molecules CD86, CD28, CD152 and PD-1 correlates with the host-parasite outcome in leprosy

Leprosy is a spectral disease exhibiting two polar sides, namely, lepromatous leprosy (LL) characterised by impaired T-cell responses and tuberculoid leprosy in which T-cell responses are strong. Proper T-cell activation requires signalling through costimulatory molecules expressed by antigen presenting cells and their ligands on T-cells. We studied the influence of costimulatory molecules on the immune responses of subjects along the leprosy spectrum. The expression of the costimulatory molecules was evaluated in in vitro-stimulated peripheral blood mononuclear cells of lepromatous and tuberculoid patients and healthy exposed individuals (contacts). We show that LL patients have defective monocyte CD86 expression, which likely contributes to the impairment of the antigen presentation process and to patients anergy. Accordingly, CD86 but not CD80 blockade inhibited the lymphoproliferative response to Mycobacterium leprae. Consistent with the LL anergy, there was reduced expression of the positive signalling costimulatory molecules CD28 and CD86 on the T-cells in these patients. In contrast, tuberculoid leprosy patients displayed increased expression of the negative signalling molecules CD152 and programmed death-1 (PD-1), which represents a probable means of modulating an exacerbated immune response and avoiding immunopathology. Notably, the contacts exhibited proper CD86 and CD28 expression but not exacerbated CD152 or PD-1 expression, suggesting that they tend to develop a balanced immunity without requiring immunosuppressive costimulatory signalling.

Antioxidant Effects of Quercetin and Catechin Encapsulated into PLGA Nanoparticles

Polymeric nanoparticles (PLGA) have been developed for the encapsulation and controlled release of quercetin and catechin. Nanoparticles were fabricated using a solvent displacementmethod. Physicochemical properties were measured by light scattering, scanning electron microscopy and zeta-potential, X-ray diffraction, infrared spectroscopy and differential scanning calorimetry. Encapsulation efficiency and in vitro release profiles were obtained from differential pulse voltammetry experiments. Antioxidant properties of free and encapsulated flavonoids were determined by TBARS, fluorescence spectroscopy and standard chelating activity methods. Relatively small (d approximate to 400 nm) polymeric nanoparticles were obtained containing quercetin or catechin in a non-crystalline form (EE approximate to 79%) and the main interactions between the polymer and each flavonoid were found to consist of hydrogen bonds. In vitro release profiles were pH-dependant, the more acidic pH, the faster release of each flavonoid from the polymeric nanoparticles. The inhibition of the action of free radicals and chelating properties, were also enhanced when quercetin and catechin were encapsulated within PLGA nanoparticles. The information obtained from this study will facilitate the design and fabrication of polymeric nanoparticles as possible oral delivery systems for encapsulation, protection and controlled release of flavonoids aimed to prevent oxidative stress in human body or food products.

Electrocatalytic Activity of Pd, Pt, and Rh for the Electro-oxidation of Ethanol in Alkaline Electrolyte: An Online DEMS Study

The electro-oxidation of ethanol was investigated on electrodeposited layers of Pd, Pt, and Rh in alkaline electrolyte. The reaction products were monitored by experiments of online differential electrochemical mass spectrometry (DEMS). Potentiodynamic curves for the ethanol electro-oxidation catalyzed by these three different metal electrocatalysts showed similar onset potentials, but the highest Faradaic current peak was observed for the Pt electrocatalyst. Online DEMS experiments evidenced similar amounts of CO2 for the three different materials, but Pd presented the higher production of ethylacetate (acetic acid). This indicated that the electrochemical oxidation of ethanol on the Pd surface occurred to a higher extent. The formation of methane, which was observed for Pt and Rh, after potential excursions to lower potentials, was absent for Pd. On the basis of the obtained results, it was stated that, on Pt and Rh, the formation of CO2 occurs mainly via oxidation of CO and CH (x,ad) species formed after dissociative adsorption of ethanol or ethoxy species that takes place only at low potentials. This indicates that the dissociative adsorption of ethanol or ethoxy species is inhibited at higher potentials on Pt and Rh. On the other hand, on the Pd electrocatalyst, the reaction may occur via nondissociative adsorption of ethanol or ethoxy species at lower potentials, followed by oxidation to acetaldehyde and, after that, by a further oxidation step to acetic acid on the electrocatalyst surface. Additionally, in a parallel route, the acetaldehyde molecules adsorbed on the Pd surface can be deprotonated, yielding a reaction intermediate in which the carbon-carbon bond is less protected, and therefore, it can be dissociated on the Pd surface, producing CO2, after potential excursions to higher potentials.

Ni/Pd@MIL-101: Synergistic Catalysis with Cavity-Conform Ni/Pd Nanoparticles

Deutsche Forschungsgemeinschaft [SFB 840]

Adsorption of NO on the Rh-13, Pd-13, Ir-13, and Pt-13 Clusters: A Density Functional Theory Investigation

The adsorption of NO on transition-metal (TM) surfaces has been widely studied by experimental and theoretical techniques; however, our atomistic understanding of the interaction of nitrogen monoxide (NO) with small TM clusters is far from satisfactory, which compromises a deep understanding of real catalyst devices. In this study, we report a density functional theory study of the adsorption properties of NO on the TM13 (TM = Rh, Pd, Ir, Pt) clusters employing the projected augmented wave method. We found that the interaction of NO with TM13 is much more complex than that for NO/TM(111). In particular, for low symmetry TM13 clusters, there is a strong rearrangement of the electronic charge density upon NO adsorption and, as a consequence, the adsorption energy shows a very complex dependence even for adsorption sites with the same local effective coordination. We found a strong enhancement of the binding energy of NO to the TM13 clusters compared with the TM(111) surfaces, as the antibonding NO states are not occupied for NO/TM13, and the general relationship based on the d-band model between adsorption energy and the center of gravity of the occupied d-states does not hold for the studied TM13 clusters, in particular, for clusters with low symmetry. In contrast with the adsorption energy trends, the geometric NO/TM13 parameters and the vibrational N-O frequencies for different coordination sites follow the same trend as for the respective TM(111) surfaces, while the changes in the frequencies between different surfaces and TM13 clusters reflect the strong NO-TM13 interaction.

Effect of liposome-encapsulated nisin and bacteriocin-like substance P34 on Listeria monocytogenes growth in Minas frescal cheese

The efficacy of liposome-encapsulated nisin and bacteriocin-like substance (BLS) P34 to control growth of Listeria monocytogenes in Minas frescal cheese was investigated. Nisin and BLS P34 were encapsulated in partially purified soybean phosphatidylcholine (PC-1) and PC-1-cholesterol (7:3) liposomes. PC-1 nanovesicles were previously characterized. PC-1-cholesterol encapsulated nisin and BLS P34 presented, respectively, 218 nm and 158 nm diameters, zeta potential of -64 mV and -53 mV, and entrapment efficiency of 88.9% and 100%. All treatments reduced the population of L monocytogenes compared to the control during 21 days of storage of Minas frescal cheese at 7 degrees C. However, nisin and BLS P34 encapsulated in PC-1-cholesterol liposomes were less efficient in controlling L monocytogenes growth in comparison with free and PC-1 liposome-encapsulated bacteriocins. The highest inhibitory effect was observed for nisin and BLS P34 encapsulated in PC-1 liposomes after 10 days of storage of the product The encapsulation of bacteriocins in liposomes of partially purified soybean phosphatidylcholine may be a promising technology for the control of food-borne pathogens in cheeses. (C) 2012 Elsevier B.V. All rights reserved.