Hydrogenation of biphenyl and isomeric terphenyls over a Pt-containing catalyst

Catalytic hydrogenation of benzene, biphenyl, and ortho-, metha-, and para-isomers of terphenyl over a 3 wt.% Pt/C at 180 °C and 70 atm was studied. The directions of hydrogenation of each substrate were revealed. Relationships between structures of the substrate and hydrogen consumption rates were found. It was shown that hydrogenation rate decreases on going from benzene to terphenyl and with increasing degree of the substrate hydrogenation. Hydrogenation rate of terphenyl isomers decreases in the following order: p-terphenyl > > m-terphenyl > o-terphenyl.     

Deteriorated Geometrical Stiffness for Higher Order Finite Elements with Application to Panel Flutter

Higher order elements were first design for linear problems where, in certain situations, they present advantages over the lower order elements. A method to efficiently extend their use to geometrical nonlinear problems as panel flutter and postbuckling behavior is presented. The chaotic and limit-cycle oscillations of an isotropic plate are obtained based on direct integration of the discretized equation of motion. The plate is modeled using the von Karman theory and the geometrical nonlinearities are separated in a nonlinear term of the first kind which manifests especially in the prebuckling and buckling regimes, and a nonlinear term of the second kind which is responsible for the postbuckling behavior. A fifth order, fully compatible element has been used to model thin plates while the inplane loads where introduced through a membrane element. The aerodynamics was modeled using the first order 'piston theory. The method introduces the concept of a deteriorated form of the second geometric matrix which is equivalent to neglecting higher order terms in the strain energy of the plate. This allows for a drastic reduction in the computational effort with no observable loss of accuracy. Well established results in the literature are used to validate the method.     

Gold nanowire networks: synthesis, characterization, and catalytic activity

Gold nanowire networks (AuNWNs) with average widths of 17.74 nm (AuNWN(1)) or 23.54 nm (AuNWN(2)) were synthesized by direct reduction of HAuCl(4) with sodium borohydride powder in deep eutectic solvents, such as ethaline or reline, at 40 °C. Their width and length were dependent on the type of solvent and the NaBH(4)/HAuCl(4) molar ratio (32 in ethaline and 5.2 in reline). High resolution transmission electron microscopy (HR-TEM) analysis of the gold nanowire networks showed clear lattice fringes of polycrystalline nanopowder of d = 2.36, 2.04, 1.44, and 1.23 ? corresponding to the (111), (200), (220), or (311) crystallographic planes of face centered cubic gold. The purified AuNWNs were used as catalysts for the chemical reduction of p-nitroaniline to diaminophenylene with sodium borohydride in aqueous solution. The reaction was monitored in real time by UV-vis spectroscopy. The results show that the reduction process is six times faster in the presence of gold nanowire networks stabilized by urea from the reline (AuNWN(2)) than in the presence of gold nanowire networks stabilized by ethylene glycol from ethaline (AuNWN(1)). This is due to a higher number of corners and edges on the gold nanowires synthesized in reline than on those synthesized in ethaline as proven by X-ray diffraction (XRD) patterns recorded for both types of gold nanowire networks. Nevertheless, both types of nanomaterials determined short times of reaction and high conversion of p-nitroaniline to diaminophenylene. These gold nanomaterials represent a new addition to a new generation of catalysts: gold based catalysts.     

Poly(D,L-lactide-co-glycolide)/hydroxyapatite core-shell nanosphere. Part 2: Simultaneous release of a drug and a prodrug (clindamycin and clindamycin phosphate)

The novel concept of a simultaneous, controlled release of a drug and a prodrug with different physico-chemical properties was applied in order to prolong the release period of antibiotics and estimate their high local concentrations, which are the necessary preconditions for the treatment of some chronic infection diseases. For this purpose poly(D,L-lactide-co-glycolide)/hydroxyapatite (PLGA/HAp) core-shell nanostructures were used as the carrier of clindamycin-base, as a drug, and clindamycin-2-phosphate, as a prodrug model. As a result, a two-step release was observed: the controlled release of the more soluble phosphate form and the sustained release of the less-soluble base form of clindamycin, resulting in a high overall concentration of the released drug during the period of 30 days in vitro. The HAp phase within the PLGA core-shells, applied as a drug carrier, delayed the process of the degradation of the polymer; however, the presence of the drug affected the process of degradation and this influence was the dominant factor in the control over the degradation of the polymer phase of PLGA/HAp and the consequent kinetics of the drug release.     

Thiazole orange-induced c-di-GMP quadruplex formation facilitates a simple fluorescent detection of this ubiquitous biofilm regulating molecule

Recently, there has been an explosion of research activities in the cyclic dinucleotides field. Cyclic dinucleotides, such as c-di-GMP and c-di-AMP, have been shown to regulate bacterial virulence and biofilm formation. c-di-GMP can exist in different aggregate forms, and it has been demonstrated that the polymorphism of c-di-GMP is influenced by the nature of cation that is present in solution. In previous work, polymorphism of c-di-GMP could only be demonstrated at hundreds of micromolar concentrations of the dinucleotide, and it has been a matter of debate if polymorphism of c-di-GMP exists under in vivo conditions. In this Article, we demonstrate that c-di-GMP can form G-quadruplexes at low micromolar concentrations when aromatic molecules such as thiazole orange template the quadruplex formation. We then use this property of aromatic molecule-induced G-quadruplex formation of c-di-GMP to design a thiazole orange-based fluorescent detection of this important signaling molecule. We determine, using this thiazole orange assay on a crude bacterial cell lysate, that WspR D70E (a constitutively activated diguanylate cyclase) is functional in vivo when overexpressed in E. Coli . The intracellular concentration of c-di-GMP in an E. Coli cell that is overexpressed with WspR D70E is very high and can reach 2.92 mM.     

A method of calculating the second dimension retention index in comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry

A method was developed to calculate the second dimension retention index of comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC/TOF-MS) data using n-alkanes as reference compounds. The retention times of the C(7)-C(31) alkanes acquired during 24 isothermal experiments cover the 0-6s retention time area in the second dimension retention time space, which makes it possible to calculate the retention indices of target compounds from the corresponding retention time values without the extension of the retention space of the reference compounds. An empirical function was proposed to show the relationship among the second dimension retention time, the temperature of the second dimension column, and the carbon number of the n-alkanes. The proposed function is able to extend the second dimension retention time beyond the reference n-alkanes by increasing the carbon number. The extension of carbon numbers in reference n-alkanes up to two more carbon atoms introduces <10 retention index units (iu) of deviation. The effectiveness of using the proposed method was demonstrated by analyzing a mixture of compound standards in temperature programmed experiments using 6 different initial column temperatures. The standard deviation of the calculated retention index values of the compound standards fluctuated from 1 to 12 iu with a mean standard deviation of 5 iu.     

Application of complementary mass spectrometric techniques to the identification of ketoprofen phototransformation products

Ketoprofen (KP) is a nonsteroidal anti-inflammatory drug, which during UV irradiation rapidly transforms into benzophenone derivatives. Such transformation products may occur after topical application of KP, which is then exposed to sunlight resulting in a photo-allergic reaction. These reactions are mediated by the benzophenone moiety independently of the amount of allergen. The same reactions will also occur during wastewater or drinking water treatment albeit their effect in the aqueous environment is yet to be ascertained. In addition, only a few such transformation products have been recognised. To enable the detection and structural elucidation of the widest range of KP transformation products, this study applies complementary chromatographic and mass spectrometric techniques including gas chromatography coupled to single quadrupole or ion trap mass spectrometry and liquid chromatography hyphenated with quadrupole-time-of-flight mass spectrometry. Based on structural information gained in tandem and multiple MS experiments, and on highly accurate molecular mass measurements, chemical structures of 22 transformation products are proposed and used to construct an overall breakdown pathway. Among the identified transformation products all but two compounds retained the benzophenone moiety--a result, which raises important issues concerning the possible toxic synergistic effects of KP and its transformation products. These findings trigger further research into water treatment technologies that would limit their entrance into environmental or drinking waters.     

iMatch: a retention index tool for analysis of gas chromatography-mass spectrometry data

A method was developed to employ National Institute of Standards and Technology (NIST) 2008 retention index database information for molecular retention matching via constructing a set of empirical distribution functions (DFs) of the absolute retention index deviation to its mean value. The effects of different experimental parameters on the molecules' retention indices were first assessed. The column class, the column type, and the data type have significant effects on the retention index values acquired on capillary columns. However, the normal alkane retention index (I(norm)) with the ramp condition is similar to the linear retention index (I(T)), while the I(norm) with the isothermal condition is similar to the Kováts retention index (I). As for the I(norm) with the complex condition, these data should be treated as an additional group, because the mean I(norm) value of the polar column is significantly different from the I(T). Based on this analysis, nine DFs were generated from the grouped retention index data. The DF information was further implemented into a software program called iMatch. The performance of iMatch was evaluated using experimental data of a mixture of standards and metabolite extract of rat plasma with spiked-in standards. About 19% of the molecules identified by ChromaTOF were filtered out by iMatch from the identification list of electron ionization (EI) mass spectral matching, while all of the spiked-in standards were preserved. The analysis results demonstrate that using the retention index values, via constructing a set of DFs, can improve the spectral matching-based identifications by reducing a significant portion of false-positives.     

One-pot synthesis of (E)-styryl ketones from styrenes

A new, efficient protocol for the highly stereoselective one-pot synthesis of (E)-styryl ketones from styrenes based on sequential ruthenium-catalyzed silylative coupling-rhodium-catalyzed desilylative acylation reactions is reported.     

Pd-induced ordering of 2D Pt nanoarrays on phosphonated calix[4]arenes stabilised graphenes

p-Phosphonic acid calix[4]arenes render high stability to exfoliated graphenes in water. These calix[4]arenes modified graphenes can be used as highly effective substrates to nucleate ultra-small Pd nanoparticles, which in turn serve as galvanic reaction templates for the generation of high density 2D arrays of Pt nanoparticles.