Supramolecular nanostructured assemblies of different types of porphyrins with fullerene using TiO2 nanoparticles for light energy conversion

TiO₂ nanoparticles were modified with porphyrin derivatives, 5-[4-benzoic acid]-10,15,20-tris[3,5-di-tert-butylphenyl]-21H,23H-porphyrin (Ar-H₂P-COOH), 5-[4-benzoic acid]-10,20-tris[3,5-di-tert-butylphenyl]-21H,23H-porphyrin (H-H₂P-COOH), and 5,10,15,20-tetra[4-benzoic acid]-21H,23H-porphyrin (H₂P-4COOH). The porphyrin-modified TiO₂ nanoparticles were deposited on nanostructured OTE/SnO₂ electrode together with nanoclusters of fullerene (C₆₀) in acetonitrile-toluene (3/1, v/v) using an electrophoretic deposition technique to afford the porphyrin-modified TiO₂ composite electrode denoted as OTE/SnO₂/(porphyrin-modified TiO₂ nanoparticle+C₆₀)_n. The porphyrin-modified TiO₂ composite electrodes have efficient light absorbing properties in the visible region, exhibiting the photoactive response under visible light excitation using redox couple. The incident photon-to-photocurrent efficiency (IPCE) values of supramolecular nanostructured electrodes of porphyrin-modified TiO₂ nanoparticles with fullerene [OTE/SnO₂/(Ar-H₂P-COO-TiO₂+C₆₀)_n, OTE/SnO₂/(H-H₂P-COO-TiO₂+C₆₀)_n, and OTE/SnO₂/(H₂P-4COO-TiO₂+C₆₀)_n] are much larger than those of the reference systems of porphyrin-modified TiO₂ nanoparticles without C₆₀ [OTE/SnO₂/(Ar-H₂P-COO-TiO₂)_n, OTE/SnO₂/(H-H₂P-COO-TiO₂)_n, and OTE/SnO₂/(H₂P-4COO-TiO₂)_n]. In particular, the maximum IPCE value (41%) is obtained for OTE/SnO₂/(H-H₂P-COO-TiO₂+C₆₀)_n under the bias potential of 0.2 V versus SCE. This indicates that the formation of supramolecular complexes between porphyrins and fullerene on TiO₂ nanoparticles plays an important role in improvement of the light energy conversion properties.     

High-throughput and high-resolution two dimensional mapping of pI and m/z using a microchip in a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer

We have developed a high-throughput, two-dimensional-mapping (isoelectric point [pI], mass-to-charge ratio [m/z]) method by combining a capillary isoelectric focusing chip sealed with removable resin tape and a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer. Sample proteins are separated in a meandering channel on the chip and immediately frozen. The tape is then removed and the proteins are freeze-dried. The freeze-drying maintains the separation state of the proteins and prevents movement of the sample solution, which can reduce pI resolution. A matrix solution is then applied and mass spectrometry is carried out by laser irradiation. The whole process takes less than 70 min, more than 10 times faster than with two-dimensional, polyacrylamide gel electrophoresis.     

Miniaturized thermal lens and fluorescence detection system for microchemical chips

We have developed a miniaturized two-way detection system using thermal lens and fluorescence spectroscopies for microchip chemistry. The system was composed of laser diode (LD) modules, fiber-based optics combined with a gradient index lens, and miniaturized detection units for thermal lens and fluorescence signals. The detection limits in the thermal lens and fluorescence spectroscopies were 6.3 x 10(-9)M for Ni(II) phthalocyanine tetrasulfonic acid and 3.0 x 10(-9)M for cy5, respectively. The performance of the system with the miniaturized thermal lens was equivalent to that of a conventional thermal lens microscope. The fluorescence sensitivity was comparable to sensitivities offered by conventional miniaturized systems.     

Does bulk metallic glass of elemental Zr and Ti exist?

To verify the high-pressure formation of the bulk metallic glass in elemental Zr and Ti, which Zhang and Zhao [Nature (London) 430, 332 (2004)] and Y. Wang et al. [Phys. Rev. Lett. 95, 155501 (2005)] recently reported, the high-pressure states were investigated by our newly developed in situ angle-dispersive x-ray diffraction using a two-dimensional detector and x-ray transparent anvils. Despite the disappearance of all the Bragg peaks in the one-dimensional energy-dispersive data, two-dimensional angle-dispersive data showed several intense Bragg spots even at the conditions where the amorphization was reported. This finding suggests that Zr and Ti do not transform into an amorphous state, but that their grain size becomes large, which causes the missing Bragg peaks in energy-dispersive data.     

12-O-acetylphorbol-13-decanoate potently inhibits cytopathic effects of human immunodeficiency virus type 1 (HIV-1), without activation of protein kinase C.

Through bioactivity-guided fractionation, eight phorbol diesters, including five new ones (1-5), were isolated from the seeds of Croton tiglium collected in Egypt. 12-O-Acetylphorbol-13-decanoate (6) and 12-O-decanoylphorbol-13-(2-methylbutyrate) (4) potently inhibited the HIV-1-induced cytopathic effect on MT-4 cells (IC100 values of 7.6 ng/ml and 7.81 micrograms/ml, and CC0 values of 62.5 micrograms/ml and 31.3 micrograms/ml, respectively) without activating protein kinase C.     

Promotion effect of metal oxides on C-O bond dissociation in CO hydrogenation over Rh/SiO2 Catalyst — possible role of partially reduced state cations

In CO hydrogenation over Rh/SiO₂ catalysts, the effect of additive metal oxides on C-O bond dissociation was studied by using pulse surface reaction rate analysis (PSRA). The addition of oxides of Al, Ti, Cr, V, and Mn resulted in an increase in the rate constant for the dissociation according to this sequence, while the oxides of Cu, Zn, and Ag added decreased the rate constant to almost the same extent. In contrast to these metal oxides, MoO₃ and WO₃ did not change the dissociation activity. CO adsorption measurement indicated that all of the added metal oxides covered a considerable portion of the Rh metal surface, although the efficiency of covering was different from one metal oxide to another. Covering the Rh metal surface with an added metal oxide should decrease the rate constant of C-O bond dissociation, because ensemble sites, consisting of a group of surface Rh atoms and considered necessary for the dissociation, were destroyed. The suppression effect resulted from the destruction of the ensemble sites by adding the oxides of Cu, Zn, and Ag. For other metal oxides, temperature-programmed reduction (TPR) or O₂ uptake measurement revealed that the added oxides, especially those existing on the Rh metal surface, were in a partially reduced state under reaction conditions. Owing to its high affinity for an oxygen atom, the cation in a partially reduced state participated in the reaction in such a way that the oxygen end of adsorbed CO species was bound to the cation so as to dissociate the C-O bond, which resulted in promotion of the dissociation. The observed promotion was explained in terms of the enhancement owing to the high affinity sufficient to overcome the suppression caused by destroying ensemble sites. Lack of the promotion effect of MoO₃ and WO₃ might result from a balance between promotion due to the high affinity of the partially reduced Mo or W and suppression caused by destroying ensemble sites. Excellent correlation was observed between the intrinsic activity increase, from which the suppression effect was excluded, and the heat of formation of metal oxide including MoO₃ and WO₃. Since the heat of formation of metal oxide is considered to be a measure of the affinity, this correlation supports the idea that the high affinity of additive cations for an oxygen atom is of primary importance in the promotion of C-O bond dissociation in CO hydrogenation.     

Synthesis of two regiospecific isomers of monotosyl-γ-cyclodextrin

Tosylation of -cyclodextrin in an aqueous alkaline solution gave two regiospecific isomers (2-monotosyl--cyclodextrin(1) and 6-monotosyl--cyclodextrin(2)), that could recognize and catalyze small sized guest molecules; 2-monotosyl--CD recognized small sized guest molecules more effectively than did 6-monotosyl--CD.     

Ag Clusters as Active Species for HC-SCR Over Ag-Zeolites

The addition of hydrogen in the reaction atmosphere is effective in promoting the activity of Ag/alumina and Ag-zeolites on the selective reduction of NO by hydrocarbons (HC-SCR) at low temperatures. The increment of NO conversion over Ag-MFI corresponds to the periodic addition of hydrogen into C₃H₈-SCR conditions. The UV–VIS spectra of Ag-MFI have revealed that the addition of hydrogen results in the formation of Ag_n^δ+ clusters due to partial reduction and agglomeration of Ag species. The coincidence of the formation of the Ag_n^δ+ clusters and the increment of NO conversion suggests that Ag_n^δ+ clusters are the highly active species for HC-SCR. From analysis by H₂-TPR, UV–VIS, and EXAFS, the structure of Ag_n^δ+ clusters on Ag-MFI is identified as being Ag₄²⁺ on average. The formation of Ag clusters was strongly affected by the type of zeolites: The major Ag species are Ag⁺ ions for MOR, Ag_n^δ+ clusters for MFI and BEA, and relatively large metallic Ag_mparticles for Y. The sequence of Ag agglomeration (MOR < MFI < BEA < Y) is in accordance with the strength of the acid sites of zeolites. It can be expected that the interaction between the positive charge of Ag_n^δ+ clusters and acid sites, i.e., the ion-exchange site of zeolites, stabilizes Ag_n^δ+ clusters. The type of Ag species under HC-SCR conditions depends on the concentration of gas-phase oxidants (NO, O₂) and reductants (H₂, HC), and also on the number and strength of the zeolite acid sites.     

Anti-lipid peroxidative effect of an extract of the stems of Kadsura heteroclita and its major constituent, kadsurin, in mice.

Three-days successive p.o. administration of an EtOH extract of the stems of Kadsura heteroclita (Schizandraceae) or its major constituent, kadsurin, resulted in significant decreases of CCl4-induced lipid-peroxidation products, such as thiobarbituric acid reactive substances (TBA-RS), conjugated dienes and fluorescent products in the liver of mice. In contrast, a significant restoration of superoxide dismutase (SOD) activity reduced by CCl4-intoxication was observed in the administered groups, suggesting that the subchronic treatment of mice with the EtOH extract or kadsurin induce enzymes capable of scavenging oxygen radical species in the liver, though the extract and kadsurin themselves may have an anti-oxidant property.     

Biotransformation of a C-glycosylflavone, abrusin 2''-O-beta-D-apioside, by human intestinal bacteria

After anaerobic incubation of abrusin 2'-O-beta-D-apioside (1) with a human fecal suspension, five metabolites were isolated and identified as abrusin (2), 1-(2',6'-dihydroxy-3',4'-dimethoxyphenyl)-3-(4'-hydroxyphenyl)propan-1- one (5), 5,6-dimethoxybenzene-1,3-diol (6), 3-(4'-hydroxyphenyl)propionic acid (7) and 3-phenylpropionic acid (8). However, methyl ether derivatives of abrusin (4'-O-methylabrusin and 4'-O-, 5-O-dimethylabrusin) resisted degradation under the same conditions.