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______________________________________________________________________The molar amounts of defective sites (M d ) in several titanium(IV) oxide (TiO 2 ) powders were determined using photoinduced reaction of electron accumulation in deaerated aqueous solutions containing sacrificial hole scavengers and subsequent reduction of methylviologen to its cation radical. The measurements of pH dependence of typical anatase and rutile TiO 2 powders showed that these defective sites were of electronic energy just below the conduction band edge of TiO 2 in ranges of 0-0.35 V for anatase and 0-0.25 V for rutile. A linear relation of M d with the rate constant of electron-hole recombination determined by femtosecond pump-probe diffuse reflection spectroscopy revealed that M d could be a quantitative parameter of recombination between a 2 photoexcited electron and a positive hole. The tendency for M d to increase, but not proportionally, with increase in the specific surface area suggested that these defective sites are mainly located near the external surfaces of TiO 2 particles. A reciprocal correlation between photocatalytic activity for water oxidation in aqueous silver sulfate solution and M d revealed that the rate of recombination is one of the predominant physical properties governing the activities of TiO 2 powders in this reaction system. ______________________________________________________________________ IntroductionPolycrystalline titanium(IV) oxide (TiO 2 ) has been widely used as semiconductor photocatalysts in liquid-solid as well as in gas-liquid regimes 1-9 because of its sufficient photostability in various circumstances, nontoxicity for environments, and potent ability to induce various types of redox reactions. 10,11 It is well known that photocatalytic activity strongly depends on bulk and surface physicochemical properties of the TiO 2 powder, such as the kind of crystal structure, 12-15 surface area and particle size, [16][17][18][19][20] Experimental SectionMaterials. Several kinds of titanium oxide (TiO 2 ) powders, those from commercial sources (Degussa P-25, Merck, Ishihara CR-EL, and Hombikat UV-100), reference catalysts supplied from the Catalysis Society of Japan (JRC-TIO-1, -2, -3, and -5), and powders synthesized by the HyCOM method 6,28,29 followed by a calcination at 1073 K under O 2 (designated as HyCOM (1073)), were used. In a separate experiment to quantify the amount of accumulated electrons by another chemical reaction, a deaerated aqueous solution containing colloidal platinum particles was added to the photoirradiated suspension under Ar instead of the addition of MV 2+ . After shaking the mixture for a few minutes, the gas phase was analyzed using a gas chromatograph (GC, Shimadzu, GC-8A, equipped with an MS-5A column (GL Sciences) and a TCD detector). Measurement of the amount of accumulated electrons in photoirradiated TiOPP-DR spectroscopy. Details of PP-DR spectroscopy were reported previously 40,41 and are briefly summarized as follows. The light source consisted of a mode-lo...

Several growth factors (or cytokines) have been recently investigated for their use as potential therapeutics for periodontal tissue regeneration. The objective of this study was to evaluate periodontal tissue regeneration, including new bone and cementum formation, following topical application of recombinant basic fibroblast growth factor (bFGF, FGF-2) to furcation class II defects. Twelve furcation class II bone defects were surgically created in six beagle dogs, then recombinant bFGF (30 micro g/site) + gelatinous carrier was topically applied to the bony defects. Six weeks after application, periodontal regeneration was analyzed. In all sites where bFGF was applied, periodontal ligament formation with new cementum deposits and new bone formation was observed histomorphometrically, in amounts greater than in the control sites. Basic FGF-applied sites exhibited significant regeneration as represented by the new bone formation rate (NBR) (83.6 +/- 14.3%), new trabecular bone formation rate (NTBR) (44.1 +/- 9.5%), and new cementum formation rate (NCR) (97.0 +/- 7.5%). In contrast, in the carrier-only sites, the NBR, NTBR, and NCR were 35.4 +/- 8.9%, 16.6 +/- 6.2%, and 37.2 +/- 15.1%, respectively. Moreover, no instances of epithelial down growth, ankylosis, or root resorption were observed in the bFGF-applied sites examined. The present results indicate that topical application of bFGF can enhance considerable periodontal regeneration in artificially created furcation class II bone defects of beagle dogs.

Nanocrystalline anatase titanium(IV) oxide (TiO 2 ) particles were synthesized by hydrothermal crystallization in organic media (HyCOM) followed by calcination at various temperatures up to 1273 K, and they were characterized by analysis of surface adsorption of the substrates, as well as by X-ray diffraction (XRD) and Brunauer-Emmet-Teller (BET) surface area measurements. These HyCOM TiO 2 samples were used for three kinds of photocatalytic reactions: mineralization of acetic acid (AcOH) in aerated aqueous suspensions, dehydrogenation of 2-propanol (2-PrOH) by in situ platinized powders, and silver-metal deposition from silver ions (Ag + ) in deaerated aqueous suspensions of bare TiO 2 samples. Dependence of the photocatalytic activities on calcination temperature (T c ) and on the amount of adsorbed substrates in each reaction and correlations with the physical properties of HyCOM TiO 2 were examined. In the case of mineralization of AcOH, the activitiy of each sample was almost proportional to the amount of surface-adsorbed AcOH in the dark, and the uncalcined (as-prepared) HyCOM TiO 2 showed the highest activity, which was monotonically reduced with T c , that is, with decrease in the amount of surface-adsorbed AcOH. On the other hand, in the case of silver-metal deposition, the photocatalytic activity was enhanced by calcination at higher temperature, despite the simultaneous decrease in the amount of surface-adsorbed Ag + in the dark. Overall, the effects of calcination on the photocatalytic activities for several reaction systems strongly suggested that photocatalytic activity depends on two significant factors, adsorbability and recombination probability, corresponding to the specific surface area and crystallinity, respectively, and that the balance of these two factors determines the T c dependence.

Nitrate was photocatalytically reduced to nitrogen molecules with a high selectivity in a basic aqueous suspension of palladium and copper-loaded titanium(IV) oxide powders in the presence of oxalate anion as a hole scavenger.

β-Hexosaminidase, which is generally present in the lysosome, is essential for glycoprotein metabolism in the maintenance of cell homeostasis. In mast cells (MCs), large amounts of β-hexosaminidase are present in the granules as opposed to the lysosome, and the biological role of MC β-hexosaminidase has yet to be fully elucidated. Therefore, we investigated the biological role of β-hexosaminidase in MC granules. Bone marrow-derived MCs from C57BL/6 (BL/6-BMMC) or β-hexosaminidase gene–deficient (hexb−/−-BMMC) mice were transplanted into MC-deficient (WBB6F1/J-KitW/KitW-v [W/Wv]) mice to generate MC-reconstituted models. In asthma model experiments, no differences were observed in the symptoms of BL/6, W/Wv, BL/6-BMMC–reconstituted W/Wv, or hexb−/−-BMMC–reconstituted W/Wv mice. In Staphylococcus epidermidis experimental infection model experiments, the severity of symptoms and frequency of death were markedly higher in W/Wv and hexb−/−-BMMC–reconstituted W/Wv mice than in BL/6 and BL/6-BMMC–reconstituted W/Wv mice. The growth of S. epidermidis in an in vitro study was clearly inhibited by addition of BL/6-BMMC lysate, but not by addition of hexb−/−-BMMC lysate. Moreover, suppression of bacterial proliferation was completely recovered when bacteria were incubated with hexb−/−-BMMC lysate plus β-hexosaminidase. Transmission electron microscopy indicated that the cell wall of S. epidermidis was heavily degraded following coincubation of bacteria with BL/6-BMMC lysate, but not following coincubation with hexb−/−-BMMC lysate. These findings strongly suggest that MC granule β-hexosaminidase is crucial for defense against bacterial invasion, but is not involved in the allergic response. Our results also suggest that the bactericidal mechanism of β-hexosaminidase involves degradation of bacterial cell wall peptidoglycan.

Size-selective photoetching was applied to silica-coated cadmium selenide (SiO 2 /CdSe) nanoparticles to precisely control their photoluminescence properties. The absorption spectra of CdSe was blue-shifted by irradiation of monochromatic light, and finally, the absorption onset agreed with the wavelength of irradiation light, indicating that CdSe particles were photoetched to smaller ones until the irradiated photons were not absorbed by the photoetched particles and that the SiO 2 shell layer surrounding the CdSe core prevented coalescence between the photoetched particles. Although as-prepared SiO 2 /CdSe did not exhibit photoluminescence, the application of size-selective photoetching to SiO 2 /CdSe resulted in the development of the band gap emission, with the degree being enhanced with progress of the photoetching. The peak wavelength of photoluminescence decreased with a decrease in the wavelength used for the photoetching, so that the luminescence color could be tuned between red and blue. Partial photoetching of SiO 2 /CdSe nanoparticle films produced intense band gap emission of CdSe at the photoetched area, while the remainder of the SiO 2 / CdSe films did not exhibit detectable photoluminescence, resulting in the formation of a clear photoluminescence image under UV irradiation. This technique makes it possible to produce a multicolored photoluminescence image by irradiation with monochromatic lights having various wavelengths using a single source material.

Photocatalytic reduction of nitrate ion (NO 3 -) in an aqueous suspension of metal-loaded titanium(IV) oxide (TiO 2 ) was examined in the presence of oxalic acid (OA) as a hole scavenger. Conversion of NO 3 -into ammonia (NH 3 ) competed with hydrogen liberation, and the NH 3 production selectivity increased with the order of loaded metal, (Pt, Pd, Co) < (Ni, Au) < (Ag, Cu), which was attributable to the efficiency of reduction of protons by photogenerated electrons at the loaded metal, i.e., hydrogen overvoltage of the loaded metal.TiO 2 powder loaded with Cu showed higher NH 3 yield and selectivity as well as higher efficiency of OA consumption.TiO 2 with in situ-deposited Cu gave results comparable to those of a Cu pre-loaded photocatalyst.