Effect of manganese stress on the mineral content of the leaves of wheat seedlings by use of X-ray fluorescence excited by synchrotron radiation

The present study describes the potential of the synchrotron radiation based X-ray fluorescence spectroscopy technique for the rapid, sensitive, user friendly and simultaneous monitoring of the changes in the elemental profile of the wheat seedlings stressed by excess manganese (Mn). For this, X-ray fluorescence spectra of the leaves of the control and Mn treated wheat seedlings have been recorded by synchrotron radiation X-ray of energy 15?keV. The analyses of the recorded spectra show the presence of elements chlorine, potassium, calcium, manganese, iron, copper, nickel, and zinc. A calibration-free approach, PyMca has been used for the quantitative estimation of the detected elements in the leaves of the control and Mn treated wheat seedlings. The excess supply of Mn to wheat seedlings results in the accumulation of manganese in the leaves of the seedlings. The accumulation of manganese in wheat seedlings negatively affects the uptake and translocation of calcium, potassium, and iron while it has stimulating effect on the uptake of copper and zinc.     

Dynamics of PEGylated–Dextran–Spermine Nanoparticles for Gene Delivery to Leukemic Cells

Leukemic cells are hard-to-transfect cell lines. Many transfection reagents which can provide high gene transfer efficiency in common adherent cell lines are not effective to transfect established blood cell lines or primary leukemic cells. This study aims to examine a new class of cationic polymer non-viral vector, PEGylated–dextran–spermine (PEG-D-SPM), to determine its ability to transfect the leukemic cells. Here, the optimal conditions of the complex preparation (PEG-D-SPM/plasmid DNA (pDNA)) were examined. Different weight-mixing (w/w) ratios of PEG-D-SPM/pDNA complex were prepared to obtain an ideal mixing ratio to protect encapsulated pDNA from DNase degradation and to determine the optimal transfection efficiency of the complex. Strong complexation between polymer and pDNA in agarose gel electrophoresis and protection of pDNA from DNase were detected at ratios from 25 to 15. Highest gene expression was detected at w/w ratio of 18 in HL60 and K562 cells. However, gene expression from both leukemic cell lines was lower than the control MCF-7 cells. The cytotoxicity of PEG-D-SPM/pDNA complex at the most optimal mixing ratios was tested in HL60 and K562 cells using MTS assay and the results showed that the PEG-D-SPM/pDNA complex had no cytotoxic effect on these cell lines. Spherical shape and nano-nature of PEG-D-SPM/pDNA complex at ratio 18 was observed using transmission electron microscopy. As PEG-D-SPM showed modest transfection efficiency in the leukemic cell lines, we conclude that further work is needed to improve the delivery efficiency of the PEG-D-SPM.     

Mixed-ligand metal complexes containing an ONS Schiff base and imidazole/benzimidazole ligands: synthesis,characterization, crystallography and biological activity

Salicylaldehyde-4-methylthiosemicarbazone (H₂MTSali) has been prepared via the condensation reaction of 4-methyl-3-thiosemicarbazide and salicylaldehyde. Four new mixed-ligand copper(II) and nickel(II) complexes with a general formula [M(MTSali)L] (M = Cu²⁺ or Ni²⁺; L = co-ligand) were synthesized, where L is either imidazole (im) or benzimidazole (bzim). The Schiff base and its mixed-ligand complexes were characterized by IR and UV/Vis spectroscopy, and the complexes by molar conductivity and magnetic susceptibility measurements. The spectroscopic data indicated that the Schiff base behaves as a tridentate ONS donor ligand coordinating via the phenoxide-oxygen, azomethine-nitrogen, and thiolate-sulphur atoms. Magnetic data indicate a square planar environment for the nickel(II) complexes while molar conductance values indicate that the metal complexes are essentially non-electrolytes in DMSO solution. X-ray crystallography shows Cu(MTSali)bzim (1) and Ni(MTSali)bzim (3) to be isostructural, with the metal(II) ions being coordinated by a N₂OS donor set that defines an approximate square planar geometry; in both cases, the benzimidazole is splayed with respect to the coordination plane. The copper(II) complexes were active against MDA-MB-231 and MCF-7 breast cancer cell lines, more so than H₂MTSali, whereas the nickel(II) complexes were inactive.     

Recovery of iron/iron oxide nanoparticles from solution: comparison of methods and their effects

Most methods currently being used to recover Fe⁰-core/oxide-shell nanoparticles from solutions (including the solvents they are synthesized or stored in) are potentially problematic because they may alter the particle composition (e.g., depositing salts formed from solutes) or leave the particles prone to transformations during subsequent storage and handling (e.g., due to residual moisture). In this study, several methods for recovery of nanoparticles from aqueous solution were studied to determine how they affect the structure and reactivity of the recovered materials. Simple washing of the nanoparticles during vacuum filtration (i.e., “flash drying”) can leave up to ~17 wt% residual moisture. Modeling calculations suggest this moisture is mostly capillary or matric water held between particles and particle aggregates, which can be removed by drying for short periods at relative vapor pressures below 0.9. Flash drying followed by vacuum drying, all under N₂, leaves no detectable residue from precipitation of solutes (detectable by X-ray photoelectron spectroscopy, XPS), no significant changes in overall particle composition or structure (determined by transmission electron microscopy, TEM), and negligible residual moisture (by thermogravimetric analysis, TGA). While this improved flash-drying protocol may be the preferred method for recovering nanoparticles for many purposes, we found that Fe⁰-core/oxide-shell nanoparticles still exhibit gradual aging during storage when characterized electrochemically with voltammetry.     

Reversible dehydrogenation of magnesium borohydride to magnesium triborane in the solid state under moderate conditions

Thermal decomposition of magnesium borohydride, Mg(BH(4))(2), in the solid state was studied by a combination of PCT, TGA/MS and NMR spectroscopy. Dehydrogenation of Mg(BH(4))(2) at 200 °C en vacuo results in the highly selective formation of magnesium triborane, Mg(B(3)H(8))(2). This process is reversible at 250 °C under 120 atm H(2). Dehydrogenation at higher temperature, >300 °C under a constant argon flow of 1 atm, produces a complex mixture of polyborane species. A borohydride condensation mechanism involving metal hydride formation is proposed.     

Immobilizing Highly Catalytically Active Pt Nanoparticles inside the Pores of Metal-Organic Framework: A Double Solvents Approach

Ultrafine Pt nanoparticles were successfully immobilized inside the pores of a metal-organic framework, MIL-101, without aggregation of Pt nanoparticles on the external surfaces of framework by using a "double solvents" method. TEM and electron tomographic measurements clearly demonstrated the uniform three-dimensional distribution of the ultrafine Pt NPs throughout the interior cavities of MIL-101. The resulting Pt@MIL-101 composites represent the first highly active MOF-immobilized metal nanocatalysts for catalytic reactions in all three phases: liquid-phase ammonia borane hydrolysis, solid-phase ammonia borane thermal dehydrogenation, and gas-phase CO oxidation.     

Interaction of lithium hydride and ammonia borane in THF

The two-step reaction between LiH and NH(3)BH(3) in THF leads to the production of more than 14 wt% of hydrogen at 40 degrees C.     

Steady state and time resolved laser-induced fluorescence of garlic plants treated with titanium dioxide nanoparticles

The study involves investigation of the effect of the interaction of titanium dioxide nanoparticles with garlic plant by spectroscopy techniques. For this, garlic plants have been grown in the laboratory under controlled conditions of light flux, temperature, humidity, and nutrient media. The growth and biomass parameters in terms of shoot length, fresh, and dry mass are found to increase upon the treatment of titanium dioxide nanoparticles while a reduction is observed in the root length of the garlic plants. The steady state laser-induced fluorescence, time resolved laser-induced fluorescence, and ultraviolet visible spectra of the control and titanium dioxide nanoparticles-treated plants have been acquired. The curve fitting data reveal that titanium dioxide nanoparticles decrease the intensity and fluorescence intensity ratio of red and far red chlorophyll fluorescence bands indicating increase in the photosynthetic activity and chlorophyll content. The evaluation of life time of the excited chlorophyll molecule shows that life time is effected by the treatment of the titanium dioxide nanoparticles. The results pertaining to ultraviolet visible measurement indicate increase in the concentration of chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, and quercetin in the leaves of garlic plants treated with titanium dioxide nanoparticles.     

Interaction of Zinc Oxide and Copper Oxide Nanoparticles with Chlorophyll: A Fluorescence Quenching Study

The present study aims to investigate the interactions of zinc oxide nanoparticles and copper oxide nanoparticles with the major photosynthetic pigment chlorophyll using ultraviolet-visible, steady state, and time resolved laser induced fluorescence spectroscopy. The steady state fluorescence measurements show that zinc oxide and copper oxide nanoparticles quench the fluorescence of chlorophyll in concentration-dependent manner. The Stern-Volmer plot for the chlorophyll-zinc oxide nanoparticles is linear, and the value of quenching constant has been observed to increase with temperature indicating the possibility of dynamic quenching. A decrease in the lifetime of chlorophyll with increase in the concentration of zinc oxide nanoparticles confirms the involvement of dynamic quenching in the chlorophyll–zinc oxide nanoparticle interaction. In the case of copper oxide nanoparticles, the Stern-Volmer plot deviates from linearity observed in the form of upward curvature depicting the presence of both static and dynamic quenching. In addition, the lifetime of chlorophyll decreases with increase in the concentration of copper oxide nanoparticles displaying the dominance of dynamic quenching in the chlorophyll-copper oxide nanoparticle interaction. The decrease observed in the value of binding constant with increasing temperature and negative values of change in enthalpy, entropy, and Gibb’s free energy indicates that van der Waal and hydrogen bonding are the prominent forces during the interaction of chlorophyll with both zinc oxide and copper oxide nanoparticles and that the process is spontaneous and exothermic. The interaction of zinc oxide and copper oxide nanoparticles with chlorophyll occurs through electron transfer mechanism. The obtained results are useful in understanding the sensitization processes involving chlorophyll and zinc oxide and copper oxide nanoparticles.     

The diammoniate of diborane: crystal structure and hydrogen release

[(NH(3))(2)BH(2)](+)[BH(4)](-) is formed from the room temperature decomposition of NH(4)(+)BH(4)(-), via a NH(3)BH(3) intermediate. Its crystal structure has been determined and contains disordered BH(4)(-) ions in 2 distinct sites. Hydrogen release is similar to that from NH(3)BH(3) but with faster kinetics.