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In this study, we investigated the effect of Ni/SiO2 hollow spheres (HS) particle size on the activity for 4-nitrophenol (4-NP) reduction. The SiO2 HS, which serves as Ni support was synthesised by sol-gel method using polystyrene (PS) particles with various diameters. TEM images show that the diameters of the SiO2 HS were 330, 445, and 490 nm. To prepare the Ni/SiO2 HS, Ni particles were immobilised by the impregnation method. SEM images of the Ni/SiO2 HS with a diameter of 330 nm show uniform spherical particles. The Ni were confirmed the surface of SiO2 HS using the EDX. Meanwhile, small particles with irregular shapes were observed in the Ni/SiO2 HS with diameters of 445 and 490 nm. The reaction for 4-nitrophenol reduction was evaluated using the obtained samples. We found that the sample with a diameter of 330 nm shows high activity. Additionally, we reveal that the SiO2 HS enhances the activity by adsorbing the 4-NP. [ABSTRACT FROM AUTHOR]

In this study, we investigated the preparation conditions of polystyrene (PS)@TiO2 core–shell particles and their photocatalytic activity during the decomposition of methylene blue (MB). TiO2 shells were formed on the surfaces of PS particles using the sol–gel method. Homogeneous PS@TiO2 core–shell particles were obtained using an aqueous NH3 solution as the promoter of the sol–gel reaction and stirred at room temperature. This investigation revealed that the temperature and amount of the sol–gel reaction promoter influenced the morphology of the PS@TiO2 core–shell particles. The TiO2 shell thickness of the PS@TiO2 core–shell particles was approximately 5 nm, as observed using transmission electron microscopy. Additionally, Ti elements were detected on the surfaces of the PS@TiO2 core–shell particles using energy-dispersive X-ray spectroscopy analysis. The PS@TiO2 core–shell particles were used in MB decomposition to evaluate their photocatalytic activities. For comparison, we utilized commercial P25 and TiO2 particles prepared using the sol–gel method. The results showed that the PS@TiO2 core–shell particles exhibited higher activity than that of the compared samples. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa cytochrome c(sub 551) and a series of its mutants exhibiting various thermostabilities are studied by paramagnetic (super 1)H NMR and cyclic voltammetry to elucidate the molecular mechanics responsible for control of the redox potentials [E(super o')] of the proteins. The study revealed that the [E(super o')] value of the protein is regulated by two molecular mechanisms operating independently of each other.

A new pressure-proof cell compartment installed in a circular dichroic spectrometer is developed. The analysis for both redox states of the two proteins shows that the stability of oxidized cyt c influences its redox function more than the reduced form does.

Electrochemical measurements taken at 25 degree Celsius using temperature dependent cyclic voltammetry were utilized for studying the relationship between redox function and protein stability of cytochromes c. The findings suggest that the overall protein stability, Fe-S bond stability, and redox property of cytochrome c were mutually related.

The results of paramagnetic (Super1) H NMR and optical studies on a homologous cytochrome c(cyt c) series, which demonstrate that interactions among amino acid side chains in distal regions influence heme axial coordinations in cyt c is presented. The conclusion states that alteration in interaction among acid side chains in the protein interior influence the stability of Fe-methionine coordination at the heme active site, which in turn affects thermostability of the protein.

The surface of a glassy carbon electrode was modified with a DNA-alginate complex film in which water-soluble DNA was encapsulated into a calcium-alginate gel. The resulting modified electrode (DAFE) was used to detect ethidium bromide (EtBr), after its accumulation on the electrode. The intercalative behavior of EtBr for dsDNA in the film was investigated by measuring the electrode response based on the intercalation of EtBr separated from nonspecific interactions (electrostatic interaction). The accumulation of EtBr in the dsDAF was enhanced by applying a negative potential below -200 mV at the dsDAFE. When a positive potential above +700 mV was applied to the dsDAFE for a constant time with stirring in a Tris buffer solution, the amount accumulated decreased. These results indicate that it is possible to electrochemically control the accumulation and release of EtBr when a dsDAFE is used. In addition, the accumulation and detection of EtBr in spiked river water samples and daunomycin, an antitumor agent, is described. [ABSTRACT FROM AUTHOR]

The functional properties of the Arg residue at the E10 helical position in myoglobin and hemoglobin lacking the highly conserved His residue at the E7 position have received considerable interest as to the structure–function relationship of the oxygen-binding hemoproteins, because Arg E10 in such proteins has been shown to play similar roles to those His E7 plays in ordinary proteins. One of the components of hemoglobin from the larval hemolyph of Tokunagayusurika akamusi is also a naturally occurring E7 genetic variant with Ile E7 and Arg E10. This study demonstrated, for the first time, that the positively charged, elongated, and flexible side-chain of Arg E10 in T.akamusi hemoglobin contributes to stabilization of the coordination of biologically relevant Cl− to heme iron. Determination of the dynamics of the Cl− binding to T. akamusi ferric hemoglobin involving paramagnetic 1H-NMR indicated that the Cl− affinity increases with decreasing pH as a result of the fact that the binding rate increases with decreasing pH, whereas the dissociation rate is almost completely independent of pH. The pH-dependent character of the Cl− binding rate correlated well with the ionization state of heme peripheral side-chain propionate groups, which was clearly manifested in the pH-dependent shift changes of heme methyl proton signals, suggesting that negative charges of heme propionate groups constitute a kinetic barrier for Cl− entry into the heme pocket. These findings provide an insight into the pH-dependent ligand binding properties of T. akamusi hemoglobin. [Copyright &y& Elsevier]

Pseudomonas aeruginosa cytochrome c(551) and a series of its mutants exhibiting various thermostabilities have been studied by paramagnetic (1)H NMR and cyclic voltammetry in an effort to elucidate the molecular mechanisms responsible for control of the redox potentials (E degrees ') of the proteins. The study revealed that the E degrees ' value of the protein is regulated by two molecular mechanisms operating independently of each other. One is based on the Fe-Met coordination bond strength in the protein, which is determined by the amino acid side chain packing in the protein, and the other on the pK(a) of the heme 17-propionic acid side chain, which is affected by the electrostatic environment. The former mechanism alters the magnitude of the E degrees ' value throughout the entire pH range, and the latter regulates the pK values reflected by the pH profile of the E degrees ' value. These findings provide novel insights into functional regulation of the protein, which could be utilized for tuning the E degrees ' value of the protein by means of protein engineering.

5,10,15,20-Tetra(N-methyl-pyridinium-4-yl)-21H,23H-porphyrin has shown to bind to the major groove of AT-rich DNA predominantly through electrostatic interaction between positively charged N-methyl pyridinium moieties of the porphyrin and negatively charged phosphodiester backbone. Solution structure of the complex between the porphyrin and a double-stranded DNA fragment has been inferred from the measurements of the mixing time-dependent intermolecular nuclear Overhauser effects (NOEs).

Heme, iron(III)-protoporphyrin IX complex, and a parallel-quadruplexed d(TTAGGG) have been shown for the first time to form a coordination complex with a guanine bound to heme iron as an axial ligand.