Identification of metabolites of rupestonic acid in rat urine by liquid chromatography combined with electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry

Rupestonic acid, a potential anti‐influenza agent, is an important and characteristic compound in Artemisia rupestris L., a well‐known traditional Uighur medicine for the treatment of colds. In the present study, high‐performance liquid chromatography combined with electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry was used to detect and identify the metabolites in rat urine after oral administration of rupestonic acid. A total of 10 metabolites were identified or partially characterized. The structure elucidations of the metabolites were performed by comparing the changes in accurate molecular masses and fragment ions with those of the parent compound. The results showed that the main metabolites of rupestonic acid in rat urine were formed by oxidation, hydrogenation and glucuronidation. A metabolism pathway was proposed for the first time based on the characterized structures. This metabolism study can provide essential information for drug discovery, design and clinical application of rupestonic acid. Copyright © 2014 John Wiley & Sons, Ltd.     

Improvement in dye sensitized solar cells from past to present

Several emerging renewable technologies are available to satisfy the current energy demand and to minimize the effect of environmental degradation caused by high consumption of fossil fuels. These technologies are not mature enough to solve this problem but require more time for improving the efficiency, and cost reduction to become the economical alternative of fossil fuels. In this paper Dye-sensitized solar cell (DSSC) has been discussed in detail owing to advancement in the technology. Since each component of DSSC is responsible for a specific function, therefore, comprehensive literature studies has been done on individual section to understand the technology in depth. All the advancement in sensitizer, semiconductors, electrolyte, electrodes, additives, sealing and anchoring groups are included in this review with performance parameter of DSSC. Focus of this article is to provide summary of all available literature since beginning to date.     

Surface characteristics of V-Ga alloys after irradiation by Ar<Superscript>+</Superscript> and N<Superscript>+</Superscript> ions

V-5Ga-6Cr and V-5Ga-0.05Ce vanadium alloys irradiated by Ar⁺ and N⁺ ions with energies of 20 keV have been investigated. Irradiation by Ar⁺ and N⁺ ions leads to strengthening of the surface layers of samples. Their thicknesses exceed the projectile ranges of these ions (16.4 and 32.8 nm, respectively) in vanadium by more than two orders of magnitude. The experimentally determined penetration depth of argon ions is less that 70 nm. The sample side irradiated by Ar⁺ ions has a predominant orientation of crystallites in the (100) and (211) planes, while the unirradiated sample has a (110) surface. The lattice parameter of the irradiated sample does not differ from that of the initial sample. Possible mechanisms by which modified deep layers are formed during ion bombardment are discussed.     

Modulation of the photocycle of a LOV domain photoreceptor by the hydrogen-bonding network

An extended hydrogen-bonding (HB) network stabilizes the isoalloxazine ring of the flavin mononucleotide (FMN) chromophore within the photosensing LOV domain of blue-light protein receptors, via interactions between the C(2)═O, N(3)H, C(4)═O, and N(5) groups and conserved glutamine and asparagine residues. In this work we studied the influence of the HB network on the efficiency, kinetics, and energetics of a LOV protein photocycle, involving the reversible formation of a FMN-cysteine covalent adduct. The following results were found for mutations of the conserved amino acids N94, N104, and Q123 in the Bacillus subtilis LOV protein YtvA: (i) Increased (N104D, N94D) or strongly reduced (N94A) rate of adduct formation; this latter mutation extends the lifetime of the flavin triplet state, i.e., adduct formation, more than 60-fold, from 2 μs for the wild-type (WT) protein to 129 μs. (ii) Acceleration of the overall photocycle for N94S, N94A, and Q123N, with recovery lifetimes 20, 45, and 85 times faster than for YtvA-WT, respectively. (iii) Slight modifications of FMN spectral features, correlated with the polarization of low-energy transitions. (iv) Strongly reduced (N94S) or suppressed (Q123N) structural volume changes accompanying adduct formation, as determined by optoacoustic spectroscopy. (v) Minor effects on the quantum yield, with the exception of a considerable reduction for Q123N, i.e., 0.22 vs 0.49 for YtvA-WT. The data stress the importance of the HB network in modulating the photocycle of LOV domains, while at the same time establishing a link with functional responses.     

Corrosion resistance investigation of vanadium alloys in liquid lithium

A major concern in using vanadium alloys for first wall/blanket systems in fusion reactors is their activity with regard to nonmetallic impurities in the coolants. This paper presents the results of studying the corrosion resistance in high-purity liquid lithium (with the nitrogen and carbon content of less than 10^–3 wt %) of vanadium and vanadium alloys (V–1.86Ga, V–3.4Ga–0.62Si, V–4.81Ti–4.82Cr) both in the initial state and preliminarily irradiated with Ar+ ions with energy of 20 keV to a dose of 10²² m^–2 at an irradiation temperature of ~400°C. The degree of corrosion was estimated by measuring the changes in the weight and microhardness. Corrosion tests were carried out under static isothermal conditions at a temperature of 600°C for 400 h. The identity of corrosion mechanisms of materials both irradiated with Ar ions and not irradiated, which consisted in an insignificant penetration of nitrogen into the materials and a substantial escape of oxygen from the materials, causing the formation of a zone with a reduced microhardness near the surface, was established. The influence of the corrosive action of lithium on the surface morphology of the materials under study was found, resulting in the manifestation of grain boundaries and slip lines on the sample surface, the latter being most clearly observed in the case of preliminary irradiation with Ar ions.     

High-Temperature Heat Capacity and Thermal Extension of FeTa2O6

Physics of the Solid State - The heat capacity of synthesized iron tantalate FeTa2O6 was measured in the temperature range of 323–1103 K by the ratio method using a thermal analyzer combining...     

Effect of co-sensitization in new hybrid photo-refractive materials based on PVK polymer matrix and inorganic LiNbO<Subscript>3</Subscript> nano-crystals

A new class of photo-refractive (PR) composite materials based on poly(N-vinylcarbazole) (PVK) (co-)sensitized with nano-crystalline lithium niobate (LiNbO₃) is presented. The steady-state performance, as well as the kinetics of the photo-refractive grating formation, was investigated by degenerate four-wave mixing (DFWM) and two-beam-coupling (TBC) experiments. We found an optimum content of LiNbO₃ nano-particles of only 10⁻³ wt.%. Even at concentrations as low as 10⁻⁷ wt.% a notable effect of the nano-crystals was detected. This yields materials with improved PR performance compared to that of the standard PR polymer material sensitized by TNF only. The role of LiNbO₃ nano-particles is discussed in detail: The particles support generation and transport of the free-charge carriers. Furthermore, they increase the electron trap density.     

Design and synthesis of bombykol analogues for probing pheromone-binding protein-ligand interactions

Mono-, difluorinated, and thioanalogues of Bombyx mori female sex pheromones (bombykol, 1) were designed according to the ab initio calculations. These rationally designated analogues were synthesized using hydroboration and Sonogashira coupling strategy via (5E,7Z)-undecadien-1-ol (10) as a common intermediate. A new simplified binding assay based on nanoLC-linear ion trap ESI-MS for quantifying complexation of the B. mori pheromone-binding protein (BmPBP) with native (1) and prepared analogues was developed. The binding properties of native 1 and thioanalogue 4 with PBP were studied in detail. The dissociation constant (K_D) of 1 and 4 was determined to be 2.1×10⁻⁶ M and 2.4×10⁻⁶ M, respectively. The similar values for both ligands correlated with ab initio calculations. The new binding assay could be used to determine the K_D of other PBPs.