Xanthones isolated from Gentianella acuta and their protective effects against H2O2-induced myocardial cell injury

In the present study, two new xanthones, (5′S,8′S)-1,3,5,8-tetrahydroxyxanthone(7→2′)-1,3,5,8-tetrahydroxy-5′,6′,7′,8′-tetrahydroxanthone (1), 5-hydroxy-3,4,6-trimethoxyxanthone-1-O-β-D-glucopyranoside (2), and eight known xanthones (3–10) were isolated from the whole plants of Gentianella acuta. Their structures were identified by the spectroscopic analyses (HR-ESI-MS, and 1D and 2D NMR). Meanwhile, cell-protective effects against H₂O₂-induced H9c2 cardiomyocyte injury and cytotoxic activities of compounds 1–10 were also determined.     

A quantitative colorimetric assay of H2O2 and glucose using silver nanoparticles induced by H2O2 and UV

A simple spectrophotometric assay of H2O2 and glucose using Ag nanoparticles has been carried out. Relying on the synergistic effect of H2O2 reduction and ultraviolet （UV） irradiation, Ag nanoparticles with enhanced absorption signals were synthesized. H2O2 served as a reducing agent in the Ag nanoparticles formation in which Ag＋ was reduced to Ago by O2- generated via the decomposition of H2O2 in alkaline media. On the other hand, photoreduction of Ag＋ to Ago under UV irradiations also contributed to the nanoparticles formation. The synthesized nanoparticles were characterized by TEM, XPS, and XRD. The proposed method could determine H2O2 with concentrations ranging from 5.0× 10^-7 to 6.0× 10^-5 tool/ L The detection limit was estimated to be 2.0 × 10^-7 mol/L. Since the conversion of glucose to gluconic acid catalyzed by glucose oxidase was companied with the formation of H2O2, the sensing protocol has been successfully utilized for the determination of glucose in human blood samples. The results were in good agreement with those determined by a local hospital. This colorimetric sensor thus holds great promises in clinical applications.     

Skin Bond Electron Relaxation Dynamics of Germanium Manipulated by Interactions with H2, O2, H2O,H2O2, HF,and Au

Although germanium performs amazingly well at sites surrounding hetero‐coordinated impurities and under‐coordinated defects or skins with unusual properties, having important impact on electronic and optical devices, understanding the behavior of the local bonds and electrons at such sites remains a great challenge. Here we show that a combination of density functional theory calculations, zone‐resolved X‐ray photoelectron spectroscopy, and bond order length strength correlation mechanism has enabled us to clarify the physical origin of the Ge 3d core‐level shift for the under‐coordinated (111) and (100) skin with and without hetero‐coordinated H₂, O₂, H₂O, H₂O₂, HF impurities. The Ge 3d level shifts from 27.579 (for an isolated atom) by 1.381 to 28.960 eV upon bulk formation. Atomic under‐coordination shifts the binding energy further to 29.823 eV for the (001) and to 29.713 eV for the (111) monolayer skin. Addition of O₂, HF, H₂O, H₂O₂ and Au impurities results in quantum entrapment by different amounts, but H adsorption leads to polarization.     

Congmujingnosides B-G,triterpene saponins from the stem of Aralia chinensis and their protective effects against H2O2-induced myocardial cell injury

Phytochemical investigation of the stem of Aralia chinensis yielded six new oleanane-type triterpene saponins named as congmujingnosides B-G (1–6). The new ones were elucidated on the basis of the chemical and spectroscopic analysis. Protective effects of compounds 1?6 were tested against H₂O₂-induced H9c2 cardiomyocyte injury, and the data showed that compounds 1 and 5 had significant cell-protective effects. No significant DPPH radical scavenging activity was observed for compounds 1?6.     

Enthalpies of crystallization of NaCl,KCl, LiCl·H2O,MgCl2 6H2O,CaCl2 6H2O and BaCl2·2H2O from aqueous solution at 298.15 K

The enthalpies of crystallization of NaCl, KCl, LiCl·H₂O, MgCl₂·6H₂O, CaCl₂·6H₂O and BaCl₂·2H₂O from aqueous solution were determined by means of different calculation methods on the basis of the earlier-measured differential and integral enthalpies of solution of the above salts. The obtained crystallization enthalpies are discussed and compared with the appropriate literature data.

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Zusammenfassung Es wurden die Kristallisationenthalpien des NaCl, KCl, LiCl·H₂O, MgCl₂·6H₂O, CaCl₂·6H₂O und BaCl₂·2H₂O aus wässerigen Lösungen bestirnt. Es wurden vorher gemessene differenzierte und integrale Enthalpien von oben genannten gelösten Salze ausgenutzt, bei denen verschiedene Berechnungsmethoden angewandt wurden. Die gewonenen Kristallisationenthalpien wurden mit entsprechenden Literaturangaben erörtert und vergliechen.

     

Synthetic architectures of TiO2/H2Ti5O11.H2O, ZnO/H2Ti5O11.H2O, ZnO/TiO2/H2Ti5O11.H2O, and ZnO/TiO2 nanocomposites

Although synthetic investigations of inorganic nanomaterials had been carried out extensively over the past decade, few of them have been devoted to fabrication of complex nanostructures that comprise multicomponents/phases (i.e., composite nanobuilding blocks), especially in the area of structural/morphological architecture. In this work, nanobelts of a protonated pentatitanate (H(2)Ti(5)O(11).H(2)O) were synthesized hydrothermally for the first time. Two technologically important transition-metal-oxides TiO(2) and ZnO were then grown respectively or sequentially onto the surface of the as-prepared nanobelts in aqueous mediums. With a main emphasis on organizational manipulation, the present investigation examines general issues of morphological complexity, synthetic interconvertibility, and material combinability related to fabrication of inorganic nanocomposites. Using this model material system, we demonstrate that complex binary and tertiary composite building blocks of TiO(2)/H(2)Ti(5)O(11).H(2)O, ZnO/H(2)Ti(5)O(11).H(2)O, ZnO/TiO(2)/H(2)Ti(5)O(11).H(2)O, and ZnO/TiO(2) can be architected stepwise in solution. Structural features of these nanocomposites have also been addressed.     

The self-cooling effect in the process of dehydration of Li2SO4·H2O,CaSO4·2H2O and CuSO4·5H2O in vacuum

The third-law method has been applied to the results of kinetic studies reported in the literature and obtained in this work to determine the E parameters of the Arrhenius equation and investigate the impact of self-cooling on the dehydration kinetics of Li₂SO₄·H₂O, CaSO₄·2H₂O and CuSO₄·5H₂O. The values obtained (104, 98 and 88 kJ mol^-1, respectively) are about 20% higher compared to the literature data calculated by the Arrhenius-plots method. This discrepancy is connected with the severe effect of self-cooling, which can reach several ten degrees at maximum temperatures of experiments. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relaxation of H2O from its /04>- vibrational state in collisions with H2O, Ar, H2, N2, and O2

We report rate coefficients at 293 K for the collisional relaxation of H2O molecules from the highly excited /04>(+/-) vibrational states in collisions with H2O, Ar, H2, N2, and O2. In our experiments, the mid R:04(-) state is populated by direct absorption of radiation from a pulsed dye laser tuned to approximately 719 nm. Evolution of the population in the (/04>(+/-)) levels is observed using the combination of a frequency-quadrupled Nd:YAG laser, which selectively photolyses H2O(/04>(+/-)), and a frequency-doubled dye laser, which observes the OH(v=0) produced by photodissociation via laser-induced fluorescence. The delay between the pulse from the pump laser and those from the photolysis and probe lasers was systematically varied to generate kinetic decays. The rate coefficients for relaxation of H2O(/04>(+/-)) obtained from these experiments, in units of cm3 molecule(-1) s(-1), are: k(H2O)=(4.1+/-1.2) x 10(-10), k(Ar)=(4.9+/-1.1) x 10(-12), k(H2)=(6.8+/-1.1) x 10(-12), k(N2)=(7.7+/-1.5) x 10(-12), k(O2)=(6.7+/-1.4) x 10(-12). The implications of these results for our previous reports of rate constants for the removal of H2O molecules in selected vibrational states by collisions with H atoms (P. W. Barnes et al., Faraday Discuss. Chem. Soc. 113, 167 (1999) and P. W. Barnes et al., J. Chem. Phys. 115, 4586 (2001).) are fully discussed.     

Determination of long-range intermolecular interaction energies using RPA/moment function methods. Application to H2O,H2O2 and H2O/H2O2 mixtures

The fully expanded expression for the Boltzmann-averaged pairwise intermolecular interaction energy of two molecules of arbitrary symmetry in the long-range (interaction < kT) limit has recently been determined explicitly as a series in r⁻ⁿ (r is the intermolecular separation) for n < 11. The resultant expression contains only multipolar products (point moment functions: PMFs) and energy terms which are characteristic of the ground state and excitation properties of the isolated molecules. These quantities are determined for H₂O and H₂O₂ using the single particle-hole RPA method, and the interaction energy contributions determined by direct state summation. Static electric dipole polarizabilities are determined as a by-product of the procedure, and are shown to agree closely with finite field results using a comparable basis. For the chiral H₂O₂/H₂O₂ system, the r⁻⁶ and r⁻⁹ discrimination energies are also calculated, suggesting that the r⁻⁹ contributions could well exceed the r⁻⁶ discriminatory terms for separations less than 20 au.     

Additive-Free,Robust H2 Production from H2O and DMF by Dehydrogenation Catalyzed by Cu/Cu2O Formed In Situ

Hydrogen production from organic/inorganic hydrides is a promising strategy for the development of novel clean energy resources to replace fossil fuels and satisfy ever-increasing energy demands. Most current processes involve small flammable chemicals and are catalyzed by noble metals in basic media with the release of the greenhouse gas CO₂. Herein, we describe an alternative pathway for highly efficient and robust H₂ production through a dehydrogenation reaction between water and N,N-dimethylformamide catalyzed by Cu/Cu₂O catalysts formed in situ. The catalysts exhibit high and robust activity for H₂ production. Importantly, the formation of H₂ as the sole gas and the valuable by-product N,N-dimethylaminoformic acid make this process clean and valuable with 100 % atom economy.     

Primary, secondary metabolites, H2O2, malondialdehyde and photosynthetic responses of Orthosiphon stimaneus Benth. to different irradiance levels

The resource availability hypothesis predicts an increase in the allocation to secondary metabolites when carbon gain is improved relative to nutrient availability, which normally occurs during periods of low irradiance. The present work was carried out to confirm this hypothesis by investigating the effects of decreasing irradiance on the production of plant secondary metabolites (flavonoids and phenolics) in the herbal plant Orthosiphon stamineus, and to characterize this production by carbohydrate, H(2)O(2), and malondialdehyde (MDA) levels, net photosynthesis, leaf chlorophyll content and carbon to nitrogen ratio (C/N). Four levels of irradiance (225, 500, 625 and 900 μmol/m(2)/s) were imposed onto two-week old seedlings for 12 weeks in a randomized complete block design experiment. Peak production of total flavonoids, phenolics, soluble sugar, starch and total non-structural carbohydrate ocurred under low irradiance of 225 μmol/m(2)/s, and decreased with increasing irradiance. The up-regulation of secondary metabolites could be explained by the concomitant increases in H(2)O(2) and MDA activities under low irradiance. This condition also resulted in enhanced C/N ratio signifying a reduction in nitrogen levels, which had established significant negative correlations with net photosynthesis, total biomass and total chlorophyll content, indicating the possible existence of a trade-off between growth and secondary metabolism under low irradiance with reduced nitrogen content. The competition between total chlorophyll and secondary metabolites production, as exhibited by the negative correlation coefficient under low irradiance, also suggests a sign of gradual switch of investment from chlorophyll to polyphenols production.     

Infrared spectra of Li2SeO4.H2O,Li2SO4.H2O and Li2(S,Se)O4.H2O

On of the hydrogen bonds formed by water molecules in lithium selenate monohydrate is evidently stronger than in the corresponding sulfate, whereas the other one is weaker. The temperature dependence of the stretching and bending modes of water is similar in both compounds, their frequencies decreasing on lowering the temperature. The study of mixed sulfate—selenate compounds made it possible to clearly show that the effective symmetry of the tetrahedral ions is higher than their local crystallographic one.     

Differential enthalpies of solution of LiCl·H2O,NaCl, KCl,MgCl2·6H2O,CaCl2·6H2O,and BaCl2·2H2O in water at 298.15 K,near the saturation concentration

The direct measurements of differential enthalpies of solution Δ_sol H ₂, of LiCl·H₂O, NaCl, KCl, MgCl₂·6H₂O, CaCl₂·6H₂O and BaCl₂·2H₂O, as the function of molality,m, in the region of concentrated solutions were performed. On this basis the enthalpies of crystallization, Δ_cryst H _m, were calculated and compared to the appropriate literature data.     

Isomeric [C,H3,N,O]+˙ ions and their neutral counterparts

The isomeric ions [H₂NC(H)O]⁺˙, [H₂NCOH]⁺˙, [H₃CNO]⁺˙ and [H₂CNOH]⁺˙ were examined in the gas phase by mass spectrometry. Ab initio molecular orbital theory was used to calculate the relative stabilities of [H₂NC(H)O]⁺˙, [H₂NCOH]⁺˙, [H₃NCO]⁺˙ and their neutral counterparts. Theory predicted [H₂NC(H)O]⁺˙ to be the most stable ion. [H₂NCOH]⁺˙ ions were generated via a 1,4-hydrogen transfer in [H₂NC(O)OCH₃]⁺˙, [H₂NC(O)C(O)OH]⁺˙ and [H₂NC(O)CH₂CH₃]⁺˙. Its metastable dissociation takes place via [H₃NCO]⁺˙ with the isomerization as the rate-determining step. [H₂CNOH]⁺˙ undergoes a rate-determining isomerization into [H₃CNO]⁺˙ prior to metastable fragmentation. Neutralization-reionization mass spectrometry was used to identify the neutral counterparts of these [H₃,C,N,O]⁺˙ ions as stable species in the gas phase. The ion [H₃NCO]⁺˙ was not independently generated in these experiments; its neutral counterpart was predicted by theory to be only weakly bound.     

Adsorption of O, H, OH, and H2O on Ag(100)

The adsorption of H(2)O and its dissociation products, O, H, and OH, on Ag(100) has been studied using an ab initio embedding method. Results at different sites (atop, bridge, and hollow) are presented. The four-fold hollow site is found to be the most stable adsorption site for O, H, and OH, and the calculated adsorption energies are 87.1, 42.7, and 76.2 kcal mol(-1), respectively. The adsorption energy of water at the atop and bridge sites is almost identical with values of 11.1 and 12.0 kcal mol(-1), respectively. The formation of adsorbed OH species by adsorption of water on oxygen-precovered Ag(100) is predicted to be exothermic by 36 kcal mol(-1).     

SCF MO LCGO studies on the hydration of ions: The systems H+H2O,Li+H2O,and Na+H2O

The energy surfaces of the systems LiOH ₂ ⁺ and NaOH ₂ ⁺ are studied for a number of different geometries within the SCF MO LCAO framework, using a gaussian basis set to approximate the wavefunction. In the minimum energy geometry of both systems the positive ion is bound to the oxygen atom of the water molecule. The computed binding energies and bond distances are: B ^SCF(LiOH ₂ ⁺ ) = 36.0 kcal/mole, d(LiO) = 3.57 a.u., and B ^SCF(NaOH ₂ ⁺ ) = 25.2 kcal/mole, d(NaO) = 4.23 a.u., resp. The results are compared with those of H₃O⁺ and discussed in view of ion-solvent interaction in aquous solutions.It is a pleasure to thank our technical staff for the careful preparation of the input for the programs and for its enthusiastic and skilful assistance in running the computer.