Between photocatalysis and photosynthesis: Synchrotron spectroscopy methods on molecules and materials for solar hydrogen generation

Energy research is to a large extent materials research, encompassing the physics and chemistry of materials, including their synthesis, processing toward components and design toward architectures, allowing for their functionality as energy devices, extending toward their operation parameters and environment, including also their degradation, limited life, ultimate failure and potential recycling. In all these stages, X-ray and electron spectroscopy are helpful methods for analysis, characterization and diagnostics for the engineer and for the researcher working in basic science.This paper gives a short overview of experiments with X-ray and electron spectroscopy for solar energy and water splitting materials and addresses also the issue of solar fuel, a relatively new topic in energy research. The featured systems are iron oxide and tungsten oxide as photoanodes, and hydrogenases as molecular systems. We present surface and subsurface studies with ambient pressure XPS and hard X-ray XPS, resonant photoemission, light induced effects in resonant photoemission experiments and a photo-electrochemical in situ/operando NEXAFS experiment in a liquid cell, and nuclear resonant vibrational spectroscopy (NRVS). (C) 2012 Elsevier B.V. All rights reserved.

Anthracene-Containing Conjugated Polymer Showing Four Optical Transitions Upon Doping: A Spectroscopic Study

An anthracene-containing poly(arylene-ethynylene)-alt-poly(arylene-vinylene) (PAE-PAV) of general constitutional unit (PhCCAnthrCCPhCHCHAnthrCHCH)(n) bearing two 2-ethylhexyloxy solubilizing side chains on each phenylene (Ph) unit has been synthesized and characterized. The basic electrochemical characterization was done, showing the existence of two non-reversible oxidation and one reversible reduction peaks. The optical properties, the real and imaginary part of the dielectric function, were probed using spectroscopic ellipsometry (SE). The vibrational structure of the undoped/doped polymer was investigated using Fourier transformed infrared spectroscopy. A strong change in the polaronic absorption was observed during the doping, which after modeling revealed the existence of two separated transitions. The optical changes upon doping were additionally recorded using the SE technique. Similar to the results from FT-IR spectroscopy, two new in-the-gap absorptions were found. Moreover, the electrical conductivity as well as the mobility of positive carriers were measured. In the undoped state, the conductivity of the polymer was found to be below the detection limit (

Modulation of redox regulatory molecules and electron transport chain activity in muscle of air breathing fish Heteropneustes fossilis under air exposure stress

Responses of redox regulatory system to long-term survival (> 18 h) of the catfish Heteropneustes fossilis in air are not yet understood. Lipid and protein oxidation level, oxidant (H2O2) generation, antioxidative status (levels of superoxide dismutase, catalase, glutathione peroxidase and reductase, ascorbic acid and non-protein sulfhydryl) and activities of respiratory complexes (I, II, III and IV) in mitochondria were investigated in muscle of H. fossilis under air exposure condition (0, 3, 6, 12 and 18 h at 25 A degrees C). The increased levels of both H2O2 and tissue oxidation were observed due to the decreased activities of antioxidant enzymes in muscle under water deprivation condition. However, ascorbic acid and non-protein thiol groups were the highest at 18 h air exposure time. A linear increase in complex II activity with air exposure time and an increase up to 12 h followed by a decrease in activity of complex I at 18 h were observed. Negative correlation was observed for complex III and V activity with exposure time. Critical time to modulate the above parameters was found to be 3 h air exposure. Dehydration induced oxidative stress due to modulation of electron transport chain and redox metabolizing enzymes in muscle of H. fossilis was clearly observed. Possible contribution of redox regulatory system in muscle tissue of the fish for long-term survival in air is elucidated. Results of the present study may be useful to understand the redox metabolism in muscle of fishes those are exposed to air in general and air breathing fishes in particular.

A promising ketone containing alternating copolymer for organic photovoltaics

An alternating copolymer containing dithienylcyclopentadienone, thiophene and benzothiadiazole was synthesized by palladium (0) catalyzed Stille coupling reaction. Structural characterization of the synthesized alternating copolymer was carried out by NMR and FTIR spectroscopy. This solution processable copolymer shows an excellent thermal stability and has a broad absorption range from 300-800 nm. High LUMO energy level and low band gap of the synthesized copolymers suggest that, this copolymer will be a better donor material for application in organic photovoltaics. Particle size analysis and molecular weight determination of the synthesized copolymer through dynamic light scattering experiment indicates that, high molecular weight copolymer was obtained by this polymerization route. Photovoltaic devices were fabricated from the blend of copolymer and phenyl-C61- butyric acid methyl ester as the active material. Fabricated photovoltaic device results show that this alternating copolymer is a promising candidate for use in organic photovoltaics.

Identification and characterization of novel indole based small molecules as anticancer agents through SIRT1 inhibition

In our pursuit to develop new potential anticancer leads, we designed a combination of structural units of indole and substituted triazole; and a library of 1-{1-methyl-2-4-phenyl-5-(propan-2-ylsulfanyl)-4H-1,2,4-triazol-3-yl ]-1H-indol-3-yl}methanamine derivatives was synthesized and characterized. Cytotoxic evaluations of these molecules over a panel of three human cancer cell lines were carried out. Few molecules exhibited potent growth inhibitory action against the treated cancer cell lines at lower micro molar concentration. An in vitro assay investigation of these active compounds using recombinant human SIRT1 enzyme showed that one of the compounds (IT-14) inhibited the deacetylation activity of the enzyme. The in vivo study of IT-14 exemplified its promising action by reducing the prostate weight to the body weight ratio in prostate hyperplasia animal models. A remarkable decrease in the disruption of histoarchitecture of the prostate tissues isolated from IT-14 treated animal compared to that of the positive control was observed. The molecular interactions with SIRT1 enzyme were also supported by molecular docking simulations. Hence this compound can act as a lead molecule to treat prostatic hyperplasia. (C) 2013 Elsevier Masson SAS. All rights reserved.

Microstructural evolution and mechanical properties of Mg composites containing nano-B4C hybridized micro-Ti particulates

In this work, the microstructural evolution and mechanical properties of extruded Mg composites containing micro-Ti particulates hybridized with varying contents of nano-B4C are investigated, and compared with Mg-5.6Ti. Microstructural characterization showed the presence of uniformly distributed micro-Ti particles embedded with nano-B4C particulates that resulted in significant grain refinement. Electron back scattered diffraction (EBSD) analyses of Mg-(5.6Ti + x-B4C)(BM) hybrid composites showed that the addition of hybridized particle resulted in relatively more recrystallized grains, realignment of basal planes and extension of weak basal fibre texture when compared to Mg-5.6Ti. The evaluation of mechanical properties indicated improved strength with ductility retention in Mg-(5.6Ti + x-B4C)(BM) hybrid composites. When compared to Mg-5.6Ti, the superior strength properties of the Mg-(5.6Ti + xB(4)C)(BM) hybrid composites are attributed to the presence of nano-reinforcements, the uniform distribution of the hybridized particles, better interfacial bonding between the matrix and the reinforcement particles and the matrix grain refinement achieved by nano-B4C addition. The ductility enhancement obtained in hybrid composites can be attributed to the fibre texture spread and favourable basal plane orientation achieved due to nano B4C addition. (C) 2013 Elsevier B.V. All rights reserved.

The N-terminal region containing the zinc finger domain of tobacco streak virus coat protein is essential for the formation of virus-like particles

Tobacco streak virus (TSV), a member of the genus Ilarvirus (family Bromoviridae), has a tripartite genome and forms quasi-isometric virions. All three viral capsids, encapsidating RNA 1, RNA 2 or RNA 3 and subgenomic RNA 4, are constituted of a single species of coat protein (CP). Formation of virus-like particles (VLPs) could be observed when the TSV CP gene was cloned and the recombinant CP (rCP) was expressed in E. coli. TSV VLPs were found to be stabilized by Zn2+ ions and could be disassembled in the presence of 500 mM CaCl2. Mutational analysis corroborated previous studies that showed that an N-terminal arginine-rich motif was crucial for RNA binding; however, the results presented here demonstrate that the presence of RNA is not a prerequisite for assembly of TSV VLPs. Instead, the N-terminal region containing the zinc finger domain preceding the arginine-rich motif is essential for assembly of these VLPs.

Successful data recovery from oscillation photographs containing strong polycrystalline diffraction rings from an unknown small-molecule contaminant: preliminary structure solution of Salmonella typhimurium pyridoxal kinase (PdxK)

Pyridoxal kinase (PdxK; EC 2.7.1.35) belongs to the phosphotransferase family of enzymes and catalyzes the conversion of the three active forms of vitamin B-6, pyridoxine, pyridoxal and pyridoxamine, to their phosphorylated forms and thereby plays a key role in pyridoxal 5 `-phosphate salvage. In the present study, pyridoxal kinase from Salmonella typhimurium was cloned and overexpressed in Escherichia coli, purified using Ni-NTA affinity chromatography and crystallized. X-ray diffraction data were collected to 2.6 angstrom resolution at 100 K. The crystal belonged to the primitive orthorhombic space group P2(1)2(1)2(1), with unitcell parameters a = 65.11, b = 72.89, c = 107.52 angstrom. The data quality obtained by routine processing was poor owing to the presence of strong diffraction rings caused by a polycrystalline material of an unknown small molecule in all oscillation images. Excluding the reflections close to powder/polycrystalline rings provided data of sufficient quality for structure determination. A preliminary structure solution has been obtained by molecular replacement with the Phaser program in the CCP4 suite using E. coli pyridoxal kinase (PDB entry 2ddm) as the phasing model. Further refinement and analysis of the structure are likely to provide valuable insights into catalysis by pyridoxal kinases.

Pure shift NMR approach for fast and accurate extraction of heteronuclear couplings

The direct and accurate determination of heteronuclear ((n)J(HX), X = F-19, P-31) couplings from the one dimensional H-1-NMR spectrum is severely hampered due to the simultaneous presence of large numbers of (n)J(HH). The present study demonstrates the utility of the pure shift NMR approach for spectral simplification, and precise and direct measurement of heteronuclear couplings. As a consequence of refocusing of homonuclear couplings ((n)J(HH)) by the pure shift NMR, only heteronuclear couplings ((n)J(HX)) appear as simple multiplets at the resonance position of each chemically non-equivalent proton, enabling their direct measurement from the 1D-H-1 spectrum. The experiment is demonstrated on a number of molecules containing either F-19 or P-31, where (n)J(HF) and (n)J(HP) could be precisely measured in a straightforward manner. The distinct advantage of the experiment is demonstrated on molecules containing more than one fluorine atom, where most of the available NMR experiments fail or have restricted utility.

Enhancing the high temperature plasticity of a Cu-containing austenitic stainless steel through grain boundary strengthening

The addition of 3 wt% Cu to heat-resistant SUS 304H austenitic steel enhances its high temperature mechanical properties. To further improve the properties, particularly the creep resistance and ductility at high temperatures, a post-solutionizing heat-treatment method that involves an intermediated annealing either at 700 or 800 degrees C after solutionizing for durations up to 180 min was employed. The purpose this heat-treatment is to precipitate planar Cr23C6 at the grain boundaries, which results in the boundaries getting serrated. Detailed microstructural analyses of these `grain boundary engineered' alloys was conducted and their mechanical performance, both at room temperature and at 750 degrees C, was evaluated. While the grain size and texture are unaffected due to the high temperature hold, the volume fraction of Sigma 3 twin boundaries was found to increase significantly. While the strength enhancement was only marginal, the ductility was found to increase significantly, especially at high temperature. A marked increase in the creep resistance was also noted, which is attributed to the reduction of the grain boundary sliding by the grain boundary serrations and the suppression of grain boundary cavitation through the optimization of the volume fraction and spacing of the Cr23C6 precipitates. The special heat-treatment performed with holding time of 3 h at 700 degrees C resulted in the optimum combination of strength, ductility and creep resistance at high temperature. (C) 2014 Elsevier B.V. All rights reserved.

Self-assembled dipeptide nanotubes constituted by flexible beta-phenylalanine and conformationally constrained alpha,beta-dehydrophenylalanine residues as drug delivery system

Peptide based self assembled nanostructures have attracted growing interest in recent years due to their numerous potential applications particularly in biomedical sciences. Di-peptide Phe-Phe was shown previously to self-assemble into nanotube like structures. In this work, we studied the affect of peptide backbone length and conformational flexibility on the self assembly process by using two dipeptides based on the Phe-Phe backbone (beta Phe-Phe and beta Phe-Delta Phe): one containing a flexible beta Phe amino acid, and the other containing both a flexible bPhe as well as a backbone constraining Alpha Phe (alpha,beta-dehydrophenylalanine) amino acid. Electron microscopy and X-ray diffraction experiments revealed that these new di-peptides can self-assemble into nanotubes having different properties than the native Phe-Phe nanotubes. These nanotubes were stable over a broad range of temperatures and the introduction of non-natural amino acids provided them with stability against the action of nonspecific proteases. Moreover, these dipeptides showed no cytotoxicity towards HeLa and L929 cells, and were able to encapsulate small drug molecules. We further showed that anticancerous drug mitoxantrone was more efficient in killing HeLa and B6F10 cells when entrapped in nanotubes as compared to free mitoxantrone. Therefore, these beta-phenylalanine and alpha, beta-dehydrophenylalanine containing dipeptide nanotubes may be useful in the development of biocompatible and proteolytically stable drug delivery vehicles.

RES-TOCSY: A facile approach for accurate determination of magnitudes, and relative signs of (n)J(HF)

The RES-TOCSY experiment for accurate determination of heteronuclear (n)J(HF) is reported. The main feature of the proposed technique is the accurate measurement of magnitudes of heteronuclear couplings from the displacement of cross sections of the 2D spectrum and their relative signs from the slopes of their displacement vectors. The experiment is highly advantageous as the couplings of smaller magnitudes hidden within line widths could also be accurately determined, and also in situations when the spectrum does not display any coupling fine structures. The efficient utility of the developed pulse sequence is unambiguously established on fluorine containing aromatic and aliphatic molecules. (C) 2014 Elsevier B.V. All rights reserved.

The Presence of Multiple Cellular Defects Associated with a Novel G50E Iron-Sulfur Cluster Scaffold Protein ( ISCU) Mutation Leads to Development of Mitochondrial Myopathy

Background: Muscle-specific deficiency of iron-sulfur (Fe-S) cluster scaffold protein (ISCU) leads to myopathy. Results: Cells carrying the myopathy-associated G50E ISCU mutation demonstrate impaired Fe-S cluster biogenesis and mitochondrial dysfunction. Conclusion: Reduced mitochondrial respiration as a result of diminished Fe-S cluster synthesis results in muscle weakness in myopathy patients. Significance: The molecular mechanism behind disease progression should provide invaluable information to combat ISCU myopathy. Iron-sulfur (Fe-S) clusters are versatile cofactors involved in regulating multiple physiological activities, including energy generation through cellular respiration. Initially, the Fe-S clusters are assembled on a conserved scaffold protein, iron-sulfur cluster scaffold protein (ISCU), in coordination with iron and sulfur donor proteins in human mitochondria. Loss of ISCU function leads to myopathy, characterized by muscle wasting and cardiac hypertrophy. In addition to the homozygous ISCU mutation (g.7044GC), compound heterozygous patients with severe myopathy have been identified to carry the c.149GA missense mutation converting the glycine 50 residue to glutamate. However, the physiological defects and molecular mechanism associated with G50E mutation have not been elucidated. In this report, we uncover mechanistic insights concerning how the G50E ISCU mutation in humans leads to the development of severe ISCU myopathy, using a human cell line and yeast as the model systems. The biochemical results highlight that the G50E mutation results in compromised interaction with the sulfur donor NFS1 and the J-protein HSCB, thus impairing the rate of Fe-S cluster synthesis. As a result, electron transport chain complexes show significant reduction in their redox properties, leading to loss of cellular respiration. Furthermore, the G50E mutant mitochondria display enhancement in iron level and reactive oxygen species, thereby causing oxidative stress leading to impairment in the mitochondrial functions. Thus, our findings provide compelling evidence that the respiration defect due to impaired biogenesis of Fe-S clusters in myopathy patients leads to manifestation of complex clinical symptoms.

Cationic gemini lipids containing polyoxyethylene spacers as improved transfecting agents of plasmid DNA in cancer cells

Lipoplex nano-aggregates have been analyzed through biophysical characterization (electrostatics, structure, size and morphology), and biological studies (transfection efficiency and cell viability) in five cancer cell lines. Lipoplexes were prepared from pEGFP-C3 plasmid DNA (pDNA) and mixed liposomes, constituted by a zwitterionic lipid (DOPE) and a gemini cationic lipid (GCL) synthesized in this work, bis(hexadecyl dimethyl ammonium) oxyethylene], referred to as (C16Am)(2)(C2O)(n), (where n is the oxyethylene spacer length, n = 1, 2 or 3, between the ammonium heads). Cryo-TEM micrographs show nano-aggregates with two multilamellar structures, a cluster-type (at low-to-medium GCL composition) and a fingerprint-type that coexists with the cluster-type at medium GCL composition and appears alone at high GCL composition. SAXS diffractograms show that these lipoplexes present three lamellar structures, two of them coexisting at low and high GCL composition. The optimized transfection efficiency (TE) of pDNA was higher for lipoplexes containing GCLs with a longer (n = 3) or shorter (n = 1) polyoxyethylene spacer, at high GCL composition (alpha - 0.7) with low charge ratio (rho(eff) 2). In the all cancer cell lines studied, the TE of the optimized formulations was much better than those of both lipofectamine 2000 and lipoplexes with GCLs of the bis(hexadecyl dimethyl ammonium) alkane series recently reported. Probably, (a) the coexistence of two lamellar structures at high GCL composition synergizes the TE of these lipid vectors, (b) the orientation of the polyoxyethylene region in (C16Am)(2)(C2O)(3)/DOPE may occur in such a way that the spacing between two cationic heads becomes smaller than that in (C16Am)(2)(C2O)(2)/DOPE which is poor in terms of TE, and (c) the synergistic interactions between serum proteins and (C16Am)(2)(C2O)(n)/DOPE-pDNA lipoplexes containing a polyoxyethylene spacer improve TE, especially at high GCL content. Lipoplexes studied here show very low levels of toxicity, which confirm them as improved vectors of pDNA in gene therapy.

Synthesis of 5,6-dihydro-4H-1,3-thiazine containing peptide mimics from N-(3-hydroxypropyl)thioamides and epimerization studies

The first synthesis of 1,3-thiazine fused peptide mimics is described from N-(3-hydroxypropyl)thioamides under MsCl/NEt3 conditions. The method is amenable to oligopeptidomimics with polar and apolar side chains. Substantial epimerization occurs at chiral C(2) exo methines in non-Pro fused mimics even under neutral conditions. H-1 NMR and crystal structure analyses indicate that the Thi analogues primarily associate with each other through intermolecular hydrogen bonds, involving the nitrogen of 1,3-thiazine and the N-H of the fused residue, which may be the basis for enamination-racemization process in these peptide mimics. (C) 2014 Elsevier Ltd. All rights reserved.