Catalytic behavior of nanoparticle α-PtO2 for ethanol oxidation

Fusion method is used to prepare α-PtO₂ and has a special needle-like microcrystalline morphology, with a diameter of ca. 6 nm and a length of ca. 50 nm. The two Pt–O bonds of α-PtO₂ are different in strength and α-PtO₂ decomposes thermally to Pt⁰ in two steps. α-PtO₂ is a p-type oxide semiconductor with a band-gap of 1.84 eV. α-PtO₂ is easily reduced by ethanol, its reduction product, Pt⁰, can directionally catalyze the oxidation of ethanol to acetic acid in the presence of air, while acetaldehyde, acetal and ethyl acetate are intermediates.     

Comparison between 2-hydroxypropyl-��-cyclodextrin and 2-hydroxypropyl-��-cyclodextrin for inclusion complex formation with danazol

Complexation in solution between danazol and two different cyclodextrins [2-hydroxypropyl-??-cyclodextrin (HP-??-CD) and 2-hydroxypropyl-??-cyclodextrin (HP-??-CD)] was studied using phase solubility analysis, and one- and two-dimensional ¹H-NMR. The increase of danazol solubility in the aqueous cyclodextrin solutions showed a linear relationship (A_L profile). The apparent stability constant, K _1:1, of each complex was calculated and found to be 51.7 × 10³ and 7.3 × 10³ M^?1 for danazol?CHP-??-CD and danazol?CHP-??-CD, respectively. ¹H-NMR spectroscopic analysis of varying ratios of danazol and the different cyclodextrins in a mixture of EtOD?CD₂O confirmed the 1:1 stoichiometry. Cross-peaks, from 2D ROESY ¹H-NMR spectra, between protons of danazol and H3?? and H5??of cyclodextrins, which stay inside the cyclodextrin cavity, proved the formation of an inclusion complex between danazol and the cyclodextrins. For HP-??-CD, the inclusion complex is formed by entrance of the isooxazole and the A rings of danazol in the cyclodextrin cavity. For HP-??-CD, two different inclusion structures may exist simultaneously in solution: one with the isooxazole and A ring in the cavity and the other with the C and D ring inside the cavity. DLS showed that self-aggregation of the CD??s was absent in the danazol HP-??-CD system up to a CD concentration of 10% and in the danazol HP-??-CD system up to a CD concentration of 5%.     

Effects of CuCl2��6H2O and ZnCl2��6H2O on the viscosity of aqueous ethanol mixtures

The effects of CuCl₂ and ZnCl₂ on the viscosity in aqueous ethanol mixtures (10%–50% v/v) were studied in the concentration range 1.0×10⁻²–8.0×10⁻² mol·dm⁻³ at different temperatures. It was found that the viscosities increased with an increase in the concentration of the salts and percent composition of ethanol content, whereas it decreased with an increase in temperature. Ion-ion and ion-solvent interactions are determined with the help of A- and B-coefficients of Jones-Dole equation. The values of A- and B-coefficients are irregular and increase with a rise in temperature and also with an increase in ethanol contents for both salts. Negative values of B-coefficients show that ion solvent interactions is comparatively small and suggest that CuCl₂ and ZnCl₂ behave as structure breakers in aqueous ethanol mixtures. Thermodynamic parameters like the energy of activation (E _η ) and change in entropy of activation (ΔS*) were also evaluated which confirm the structure breaker behavior of salts in aqueous ethanol mixtures.     

Effects of sugar ring puckering, anti-syn interconversion and intramolecular interactions on N-glycosidic bond cleavage in 3-methyl-2��-deoxyadenosine and 2��-deoxyadenosine

The effects of structural parameters and intramolecular interactions on N-glycosidic bond length in 3-methyl-2??- deoxyadenosine (3MDA) and 2??-deoxyadenosine (DA) were investigated employing quantum mechanical methods. All calculations were performed at B3LYP/6-311++G** level in the gas phase. The N-glycosidic bond length strongly depends on sugar configuration; it is shorter in syn conformation relative to anti in many cases where they have the same sugar ring configuration. The sugar conformation can influence the N-glycosidic bond through interaction with the O4?? atom. The impact of intramolecular improper hydrogen bonds and H-H bonding interactions on N-glycosidic bond length was investigated in DA and 3MDA and their modeled structures. Improper hydrogen bonds decrease N-glycosidic bond length while H-H bonding interactions increase it.     

Completely green synthesis of colloid Adams' catalyst α-PtO2 nanocrystals and derivative Pt nanocrystals with high activity and stability for oxygen reduction

We report a first solution strategy for controlled synthesis of Adams' catalyst (i.e., α-PtO(2)) by a facile and totally green approach using H(2)PtCl(6) and water as reactants. The prepared α-PtO(2) nanocrystals (NCs) are ultrasmall in size and have very "clean" surfaces, which can be reduced to Pt NCs easily in ethanol under ambient conditions. Such Adams' catalysts have been applied as electrocatalysts beyond the field of heterogeneous catalysis. Noticeably, the water-only synthesized α-PtO(2) NCs and their derivative Pt NCs all exhibit much higher oxygen reduction reaction (ORR) activities and stabilities than that of the state-of-art Pt/C electrocatalysts. This study provides an example on the organics-free synthesis of α-PtO(2) and Pt NCs as promising cathode catalysts for fuel cell applications and, particularly, this simple, straightforward method may open a new way for the synthesis of other "clean" functional nanomaterials.     

Msx2 mediates the inhibitory action of TNF-�� on osteoblast differentiation

TNF-α, a proinflammatory cytokine, inhibits osteoblast differentiation under diverse inflammatory conditions; however, the underlying mechanisms in terms of the TNF-α signaling pathway remain unclear. In this study, we examined the role of Msx2 in TNF-α-mediated inhibition of alkaline phosphatase (ALP) expression and the signaling pathways involved. TNF-α down-regulated ALP expression induced by bone morphogenetic protein 2 (BMP2) in C2C12 and Runx2^-/- calvarial cells. Over-expression of Msx2 suppressed BMP2-induced ALP expression. Furthermore, TNF-α induced Msx2 expression, and the knockdown of Msx2 by small interfering RNAs rescued ALP expression, which was inhibited by TNF-α. TNF-α activated the NF-κB and the JNK pathways. Inhibition of NF-κB or JNK activation reduced the inhibitory effect of TNF-α on ALP expression, whereas TNF-α-induced Msx2 expression was only suppressed by the inhibition of the NF-κB pathway. Taken together, these results indicate that Msx2 mediates the inhibitory action of TNF-α on BMP2-regulated osteoblast differentiation and that the TNF-α-activated NF-κB pathway is responsible for Msx2 induction.     

Liquid�Cliquid extraction studies with 4,4��-biphenylene-spaced bis-��-diketones

4,4??-biphenylene spaced lipophilic bis-??-diketone ligands of the type 4,4??-bis(RC(O)CH₂C(O))C₁₂H₈ (R = Pr, Ph, hexyl, octyl, nonyl) have been prepared and used for the liquid?Cliquid extraction of d-block metal ions. These ligands are expected to interact with divalent metal ions to form charge-neutral trinuclear metallocycles of type [M₃(L ³ )₃(solvent)] as has been demonstrated with the previously reported derivative of H₂ L ³ (R =  ^t Bu), the X-ray structure of which is reported. Liquid?Cliquid extraction studies were performed in a two-phase water/chloroform system employing a radiotracer technique for cobalt(II) and zinc(II). These experiments involved the systematic variation of ligand, metal and 4-ethylpyridine concentrations to probe the stoichiometries of the species extracted. Synergistic extraction was observed when 4-ethylpyridine was present with the ligand in the organic phase. Competitive extraction studies demonstrated the ligands are highly selective for copper(II) over cobalt(II), nickel(II), zinc(II) and cadmium(II).     

A density functional theory study of the ��mythic�� Lindlar hydrogenation catalyst

A Lindlar catalyst is a popular heterogeneous catalyst that consists of 5?wt.% palladium supported on porous calcium carbonate and treated with various forms of lead and quinoline. The additives strategically deactivate palladium sites. The catalyst is widely used for the partial hydrogenation of acetylenic compounds in organic syntheses. Alkyne reduction is stereoselective, occurring via syn addition to give the cis-alkene. Even if it has been employed for about 60?years, there is a lack of molecular level understanding of the Lindlar catalyst. We have applied density functional theory simulations to understand the structure and the nature of the interplay between the multiple chemical modifiers in the Lindlar catalyst. Indeed, the poisons influence different parameters controlling selectivity to the alkene: Pb modifies the thermodynamic factor and hinders the formation of hydrides, while quinoline isolates Pd sites thus minimizing oligomerization.     

Colorimetric ��naked-eye�� sensor for anions based on conformational flexible tripodal receptor

A new tripodal receptor for anion sensing based on amide-pyridinium as recognition site and nitro-benzene as signaling unit was designed and successfully synthesized. This receptor showed high selectivity and strong binding affinity toward AcO^? over the investigated anions, especially over H₂PO₄ ^?. Addition of AcO^? induced clear color change of solution from colorless to yellow, realizing the ??naked-eye?? detection. UV?CVis and ¹H NMR experiments indicated the selectivity might origin from the synergistic effects arising from hydrogen bonding, electrostatic interactions and conformational change.     

Preparation of monodispersed ��-Fe2O3 nanoparticles by a hydrothermal synthetic route

Monodispersed ??-Fe₂O₃ nanoparticles modified by sodium dodecylbenzene sulfonate (SDBS) surfactant and assisted by glycerol have been successfully synthesized via a hydrothermal process using FeCl₃·6H₂O as the starting precursor. These nanoparticles possess good crystallinity and have an average particle size of 100 nm. The as-prepared products are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and a superconducting quantum interference device magnetometer. SDBS and glycerol played an important role in controlling the final morphology of the products. Magnetic hysteresis measurements reveal that monodispersed ??-Fe₂O₃ nanoparticles exhibit normal ferromagnetic behaviors with the remanent magnetization and coercivity of 0.2389 emu/g and 2339.0 Oe at room temperature.     

The protein folding transition-state ensemble from a Gō-like model

Characterizing the structure of transition states (TS) is a first step towards understanding two-state protein folding mechanisms. However, a direct experimental characterization of these states is challenging and indirect information derived from protein engineering methodologies (?-value analysis) is often difficult to interpret. We present here a theoretical study on the nature of the transition state ensemble for three representative proteins covering the major structural classes using a mean-field C(α)-based Gō-model. We identify that transition state ensembles are dominated by local contacts, indicating that most non-local contacts form only upon crossing the macroscopic folding free energy barrier. We demonstrate that the mean ?-value corresponds to the fraction of stabilization energy gained at the barrier-top in two-state-like systems, and that it depends monotonically on the stability conditions. Furthermore, we show that there is a fundamental connection between small destabilization and large ?-values that in turn depends on the location of the mutated residue in the structure. These results that are in agreement with the recent empirical findings highlight the importance of local energetics in determining folding mechanisms.     

Purity assessment for 17��-estradiol

Purity assessment for high-purity organic substances is regarded as one of the core competences of national metrology institutes. For this reason, Consultative Committee for Amount of Substance??Metrology in Chemistry (CCQM) regularly organized intercomparison studies to compare and demonstrate the degree of equivalence of national measurement capabilities for purity determination. This paper reports the method development work for the participation in a recent CCQM key comparison on purity assessment for estradiol. An indirect consecutive estimation approach was adopted to determine the purity of the estradiol sample, i.e., through the identification and quantification of all possible impurities present in the sample. In the course of assessment, a variety of analytical techniques were applied. The most challenging part was to identify and estimate the amount of unknown organic-related substance present in the testing material. For the moisture determination, a gas chromatography with thermal conductivity detection (GC?CTCD) method was employed to supplement the results obtained using coulometric Karl Fischer titration technique. Inorganic impurities and volatile organic compounds residual were analyzed using inductively coupled plasma mass spectrometry (ICP?CMS) and gas chromatography?Cmass spectrometry (GC?CMS) techniques, respectively, and their contributions were found to be comparatively insignificant.     

��Gold standard�� coupled-cluster study of acetylene pentamers and hexamers via molecular tailoring approach

Due to high scaling order of MP2 and CCSD(T) methods, it is either difficult or at times even impossible to treat even moderately sized molecular systems with elaborate basis sets such as aug-cc-pVXZ (X?=?D, T, Q). In the present work, several structures of acetylene pentamers and hexamers are explored at MP2 and CCSD(T) levels of theory as?prototypical examples of clusters bound by CH···?? interactions. To enable this investigation, fragment-based method Molecular Tailoring Approach (MTA) is employed. It is shown that these acetylene assemblies can be treated with substantial reduction in computational resources and time, yet retaining a sub-millihartree accuracy in the energy. Further, using standard extrapolation methodologies, stabilization energies at the complete basis set limit of the acetylene clusters under consideration are determined at MP2 and CCSD(T) levels of theory. To test out the feasibility of treating a large cluster at MP2 level, a demonstrative calculation on a dodecamer of acetylene is reported.     

Preparation of nanoparticles and hollow spheres of ��-Fe2O3 and their properties

Uniform nanoparticles and hollow microspheres of hematite (??-Fe₂O₃) were obtained via a hydrothermal method by using iron (III) chloride as a precursor. The effects of reactant concentration, reaction time and temperature on the morphology of the samples were studied. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and superconducting quantum interference device magnetometer (SQUID) measurement. ??-Fe₂O₃ nanoparticles show a superparamagnetic behavior and the average size of the spherical particles was around 60 nm. However, hollow microspheres show a normal ferromagnetic behavior at room temperature with remanent magnetization and coercivity of 0.2482 emu/g and 2,516 Oe, respectively, and their average diameter was around 2 ??m. The effects of reactant concentration and reaction temperature on the formation of the products were investigated. The experimental results reveal that the magnetic properties of hematite can be tuned by controlling the morphology.     

Preparation and characterization of the inclusion complex of Ofloxacin with ��-CD and HP-��-CD

The formation of the inclusion complexes of Ofloxacin with cyclodextrins (CDs) including ??-cyclodextrin (??-CD), and hydroxypropyl-??-cyclodextrin (HP-??-CD) were studied by Fluorescence, UV?CVis absorption spectroscopy and nuclear magnetic resonance spectroscopy (NMR) in solution. Experimental conditions including the concentration of various CDs and media acidity were investigated in detail at room temperature. The results suggested that in different pH solutions, CDs have different inclusive capacity to different forms Ofloxacin. ??-CD was most suitable for inclusion of neutral form and HP-??-CD was suitable for acidic form. The binding constant (K) of the inclusion complex was determined by fluorescence measurement, and the complexation ratio was determined as 1:1 in the concentration range used in this study. A mechanism was proposed to explain the inclusion process based on the experimental NMR data.     

Enantioselective extraction of hydrophilic 2-chloromandelic acid enantiomers by hydroxypropyl-��-cyclodextrin: experiments and modeling

Enantioselective extraction of hydrophilic 2-chloromandelic acid (CMA) enantiomers from organic to aqueous phase with hydroxypropyl-??-cyclodextrin (HP-??-CD) as the selector was investigated. Equilibrium of the extraction system was modeled using a reactive extraction model with a homogeneous aqueous phase reaction. The influence of important process variables on the extraction efficiency, such as the type of the organic solvent and ??-cyclodextrin derivatives (??-CDs), concentration of the selector, pH and temperature, was investigated by experiment and modeling. Important parameters of this model were determined experimentally. Results showed that the experimental data agree with the model prediction perfectly and the model was further applied to accurately predict the extraction efficiency influenced simultaneously by pH and the concentration of HP-??-CD. Combining the experiment and the model data, the best extraction conditions were: pH of 2.5, HP-??-CD concentration of 0.05 mol L^?1, and temperature of 5°C, providing the enantioselectivity of 1.285 and the performance factor (pf) of 0.011.     

TGF-��-treated antigen presenting cells suppress collagen-induced arthritis through the promotion of Th2 responses

Collagen-induced arthritis (CIA) is mediated by self-reactive CD4⁺ T cells that produce inflammatory cytokines. TGF-β₂-treated tolerogenic antigen-presenting cells (Tol-APCs) are known to induce tolerance in various autoimmune diseases. In this study, we investigated whether collagen-specific Tol-APCs could induce suppression of CIA. We observed that Tol-APCs could suppress the development and severity of CIA and delay the onset of CIA. Treatment of Tol-APCs reduced the number of IFN-γ- and IL-17-producing CD4⁺ T cells and increased IL-4- and IL-5-producing CD4⁺ T cells upon collagen antigen stimulation in vitro. The suppression of CIA conferred by Tol-APCs correlated with their ability to selectively induce IL-10 production. We also observed that treatment of Tol-APCs inhibited not only cellular immune responses but also humoral immune responses in the process of CIA. Our results suggest that in vitro-generated Tol-APCs have potential therapeutic value for the treatment of rheumatoid arthritis as well as other autoimmune diseases.     

��Jumping�� crystals: structures and properties of CuII complexes with N-methylimidazolyl- and N-methyltriazolyl-substituted nitronyl nitroxides

To find the factors favorable for the appearance of chemomechanical activity of heterospin crystals, a series of new heterospin complexes were synthesized and characterized. It includes [Cu(tfac)₂L^Im ₂]·2CH₂Cl₂, [Cu(tfac)₂L^Im ₂]·2EtOH, [[Cu(pfu)₂]₂L^Im ₃]·1/2CH₂Cl₂, [Cu(pfh)₂L^Im ₂]·1/2CH₂Cl₂, [Cu(piv)₂L^Im ₂]·2MeOH, [Co(piv)₂L^Im ₂], [ $ Cu(hfac)_2 L^{CD_3 } _2 $ ], [Cu(hfac)₂L^Tr]₂·CH₂Cl₂, and [Cu(hfac)₂L^Tr ₂] (L^Im, $ L^{CD_3 } $ , and L^Tr are N-methylimidazolyl-, N-trideuteriomethylimidazolyl-, and N-methyltriazolyl-substituted nitronyl nitroxides, respectively; tfac, hfac, pfu, pfh, and piv are the charged coordinated diamagnetic ligands 1,1,5,5-tetrafluoropentane-2,4-dionate, 1,1,1,5,5,5-hexafluoropentane-2,4-dionate, 1,1,1,2,2,3,3,4,4,8,8,9,9,10,10,11,11,11-octadecafluoroundecane-5,7-dionate, 1,1,1,5,5,6,6,6-octafluorohexane-2,4-dionate, and 2,2-dimethylpropionate, respectively). The crystal and molecular structures of all compounds were determined. The results of the X-ray diffraction study of the complex [Ni(hfac)₂L^Im ₂] synthesized earlier are reported. In the solid state of the complexes [Cu(pfh)₂L^Im ₂] and [Co(piv)₂L^Im ₂], the paramagnetic ligands are cis-coordinated to the central atom in a monodentate fashion via the donor N atom of the imidazole ring. In the dinuclear complexes [[Cu(pfu)₂]₂L^Im ₃] and [Cu(hfac)₂L^Tr]₂, the paramagnetic ligands are also in cis positions but act as bridges through coordination of the donor N atoms of the azole ring and the O atom of the nitronyl nitroxide moiety to different Cu²⁺ ions. In the solid complexes $ Cu(hfac)_2 L^{CD_3 } _2 $ , [Cu(hfac)₂L^Tr ₂], [Cu(tfac)₂L^Im ₂]·2CH₂Cl₂, [Cu(tfac)₂L^Im ₂]·2EtOH, and [Cu(piv)₂L^Im ₂]·2MeOH, the nitronyl nitroxide radicals in the mononuclear heterospin molecules are in trans positions. The packing motif in the crystal structures of the complexes $ Cu(hfac)_2 L^{CD_3 } _2 $ , [Cu(tfac)₂L^Im ₂]·2CH₂Cl₂, and [Cu(tfac)₂L^Im ₂]·2EtOH is the same as that in the previously studied complexes [M(hfac)₂L^Im ₂] exhibiting chemomechanical activity. Among the complexes under consideration, only crystals of $ Cu(hfac)_2 L^{CD_3 } _2 $ can exhibit chemomechanical activity, that is to make jumps upon heating or irradiation. The results of the present study suggest that the packing of the solid-state structure plays a key role in the generation of mechanical activity of the crystals.