Role of Visible Light-Activated Photocatalyst on the Reduction of Anthrax Spore-Induced Mortality in Mice

BACKGROUND: Photocatalysis of titanium dioxide (TiO(2)) substrates is primarily induced by ultraviolet light irradiation. Anion-doped TiO(2) substrates were shown to exhibit photocatalytic activities under visible-light illumination, relative environmentally-friendly materials. Their anti-spore activity against Bacillus anthracis, however, remains to be investigated. We evaluated these visible-light activated photocatalysts on the reduction of anthrax spore-induced pathogenesis. METHODOLOGY/PRINCIPAL FINDINGS: Standard plating method was used to determine the inactivation of anthrax spore by visible light-induced photocatalysis. Mouse models were further employed to investigate the suppressive effects of the photocatalysis on anthrax toxin- and spore-mediated mortality. We found that anti-spore activities of visible light illuminated nitrogen- or carbon-doped titania thin films significantly reduced viability of anthrax spores. Even though the spore-killing efficiency is only approximately 25%, our data indicate that spores from photocatalyzed groups but not untreated groups have a less survival rate after macrophage clearance. In addition, the photocatalysis could directly inactivate lethal toxin, the major virulence factor of B. anthracis. In agreement with these results, we found that the photocatalyzed spores have tenfold less potency to induce mortality in mice. These data suggest that the photocatalysis might injury the spores through inactivating spore components. CONCLUSION/SIGNIFICANCE: Photocatalysis induced injuries of the spores might be more important than direct killing of spores to reduce pathogenicity in the host

Direct versus hydrogen-assisted CO dissociation on the Fe (100) surface: a DFT study

Keywords: CO dissociation; density functional calculations; Fischer–Tropsch mechanism; iron; surface chemistry CO dissociation: Three most probable pathways to CO dissociation on the Fe¿(100) surface exist (see picture): a) direct, CO¿C+O (—) and H-assisted b) H+CO¿HCO¿CH + O (—) or c) CO+H¿COH¿C+OH (—). Under high hydrogen pressure conditions and highly occupied surfaces the formation of HCO and subsequent dissociation to CH+O may at best compete with direct dissociation

Ab-initio calculations of the direct and hydrogen-assisted dissociation of CO on Fe(3 1 0)

Via the formation process of the adsorbed intermediates formyl (HCO) and hydroxy-carbene (COH), the thermodynamics of the hydrogen-assisted CO dissociation on Fe(3 1 0) is investigated by means of first-principles total-energy calculations. A comparison with direct CO dissociation in the presence of coadsorbed atomic hydrogen leads to the conclusion that the direct process is the only thermodynamically viable route for CO dissociation on Fe(3 1 0), with strongly endothermic formation energies for both intermediates, HCO and COH