A metal sulfide photocatalyst composed of ubiquitous elements for solar hydrogen production.

A visible-light-sensitive tin sulfide photocatalyst was designed based on a ubiquitous element strategy and density functional theory (DFT) calculations. Computational analysis suggested that tin monosulfide (SnS) would be more efficient than SnS2 as a photocathode for hydrogen production because of the low ionization potential and weak ionic character of SnS. To test this experimentally, nanoparticles of SnS were loaded onto a mesoporous electrode using a wet chemical method, and the bandgap of the synthesized SnS quantum dots was found to be tunable by adjusting the number of successive ionic layer adsorption and reaction (SILAR) cycles, which controls the magnitude of the quantum confinement effect. Efficient hydrogen production was achieved when the bandgap of SnS was wider than that of the bulk form.

Rational design of fluorescein-based fluorescence probes. Mechanism-based design of a maximum fluorescence probe for singlet oxygen.

Fluorescein is one of the best available fluorophores for biological applications, but the factors that control its fluorescence properties are not fully established. Thus, we initiated a study aimed at providing a strategy for rational design of functional fluorescence probes bearing fluorescein structure. We have synthesized various kinds of fluorescein derivatives and examined the relationship between their fluorescence properties and the highest occupied molecular orbital (HOMO) levels of their benzoic acid moieties obtained by semiempirical PM3 calculations. It was concluded that the fluorescence properties of fluorescein derivatives are controlled by a photoinduced electron transfer (PET) process from the benzoic acid moiety to the xanthene ring and that the threshold of fluorescence OFF/ON switching lies around -8.9 eV for the HOMO level of the benzoic acid moiety. This information provides the basis for a practical strategy for rational design of functional fluorescence probes to detect certain biomolecules. We used this approach to design and synthesize 9-[2-(3-carboxy-9,10-dimethyl)anthryl]-6-hydroxy-3H-xanthen-3-one (DMAX) as a singlet oxygen probe and confirmed that it is the most sensitive probe currently known for (1)O(2). This novel fluorescence probe has a 9,10-dimethylanthracene moiety as an extremely fast chemical trap of (1)O(2). As was expected from PM3 calculations, DMAX scarcely fluoresces, while DMAX endoperoxide (DMAX-EP) is strongly fluorescent. Further, DMAX reacts with (1)O(2) more rapidly, and its sensitivity is 53-fold higher than that of 9-[2-(3-carboxy-9,10-diphenyl)anthryl]-6-hydroxy-3H-xanthen-3-ones (DPAXs), which are a series of fluorescence probes for singlet oxygen that we recently developed. DMAX should be useful as a fluorescence probe for detecting (1)O(2) in a variety of biological systems.

Novel Fluorescent Probes for Singlet Oxygen.

The first fluorescent chemical traps for (1)O(2) have been developed. DPAXs react specifically with (1)O(2) to yield the corresponding endoperoxides, DPAX-EPs (see scheme; X = H, Cl, F). DPAXs scarcely fluoresce, while DPAX-EPs are strongly fluorescent. Since the fluorescence of these probes is unaffected by H(2)O(2), superoxide, and nitric oxide, they are useful for the selective detection of (1)O(2) in biological systems.

Participation of reactive oxygen species in phototoxicity induced by quinolone antibacterial agents.

To elucidate the mechanism of phototoxicity induced as a side effect by some of the new quinolone antibiotics, we studied sparfloxacin (SPFX), lomefloxacin, enoxacin, ofloxacin, and ciprofloxacin. We first examined the photosensitized formation of reactive oxygen species such as singlet oxygen (1O2) and superoxide anion (O2-) mediated by the new quinolones. Although a large number of studies have been reported, there is no direct evidence that these drugs generate reactive oxygen species. We employed a near-infrared emission spectrometer to detect 1O2-specific emission (1268 nm), and the nitroblue tetrazolium reduction method to detect O2-. All the quinolones investigated in this study were found to produce 1O2. Four drugs, but not SPFX, produced O2-. We also examined photodynamic DNA strand-breaking activity as a possible mechanism to explain the participation of reactive oxygen species in the phototoxicity of the drugs. All the drugs exhibited photodynamic DNA strand-breaking activity. The inhibitory effect of scavengers of reactive oxygen species indicated that the main active species was 1O2. The DNA strand-breaking activity was correlated not with the 1O2-forming ability, but with the affinity of the drugs for DNA. This result may be due to the short lifetime of 1O2. These data suggested that the phototoxicity of the new quinolones was related to DNA damage caused by reactive oxygen species, especially 1O2.

[Objective evaluation of apparent accommodation of pseudophakic eyes].

In 23 (9 males and 14 females) pseudophakic eyes which had a biconvex type intraocular lens (IOL) implanted after cataract extraction, we objectively measured changes in the anterior chamber (AC) depth caused by axial movement of the IOL accompanying accommodation of the contralateral phakic fellow eye, using a Schimpflug slit image with an anterior eye segment image analysis system (Nidek, EAS-1000, Japan). In 114 phakic eyes of 57 persons as controls, AC depths accompanying accommodation from distances of 5 m to 30 cm and 10 cm decreased with increasing age. The decreased mean value of AC depth with accommodation from distances of 5 m to 30 cm was 0.17 mm in patients in their teens, 0.15 mm in patients in their 20 s, 0.10 mm in the 30 s, 0.06 mm in the 40 s, 0.05 mm in the 50 s, and 0.03 mm in the 60 s. The decrease of AC depth with accommodation at a distance of 10 cm was 0 in patients in their 60 s. In the pseudophakic eye changes in anterior chamber depth caused by focusing at short distances were less than 0.04 mm, and decreasing rate of anterior chamber depth (DRAC) was less than 1% in all the pseudophakic eyes. Movement of IOL on the optical axis was too subtle to account for apparent accommodation of the pseudophakic eye.