Atsuko Nishigaki

π-π and σ-π Interactions in α, ω-di-(9-anthryl) and di-(1-naphthyl) oligosilanes studied by time-resolved fluorescence in solution

The photophysical properties of two series of oligosilanes, (1-naphthyl)-(SiMe2)n-(1-naphthyl) (1−5) and (9-anthryl)-(SiMe2)n-(9-anthryl) (6−10) with n = 1−4 and 6, were investigated. In these compounds, two types of interactions, a π−π interaction between two aromatic groups and a σ−π interaction between aromatics and a silicon chain unit, were observed. Intramolecular excimer emission was observed in cyclohexane when n ≥ 2. The strongest excimer emission of 2 and 7 is different from the Hirayama rule (n = 3) proposed for carbon analogues and also shows that intramolecular cycloaddition is minor. The time-resolved fluorescence spectra of an anthryl series revealed that the time constant of excimer formation varied depending on the chain length (82−152 ps). In the cases of 4, 5, and 10, charge-transfer (CT) emission was observed in acetonitrile or THF. The time constant of the CT-state formation for 10 was relatively slow (45 ps), which may indicate a conformational change. Monomer emission from the local...

Application of Molecular Orbital Calculations to Interpret the Chlorophyll Spectral Forms in Pea Photosystem II

Abstract The energy and oscillator strength of electronic transitions of chlorophyll (Chl)–amino acid complexes were calculated by using molecular orbital methods. The energies varied widely with coordinated amino acids and the difference between the maximum and minimum energy was about 830 cm−1. This energy difference was comparable with the spreading of absorption bands for light-harvesting Chl–protein complexes of photosystem II (LHC II) of green plants. The feature of the Qy band for pea LHC II was interpreted with the aid of the calculated energies and oscillator strengths. Four spectral components of the band were assigned to individual Chl–amino acid complexes.

Valproic acid and ASK1 deficiency ameliorate optic neuritis and neurodegeneration in an animal model of multiple sclerosis.

Optic neuritis, which is an acute inflammatory demyelinating syndrome of the central nervous system, is one of the major complications in multiple sclerosis (MS). Herein, we investigated the therapeutic potential of valproic acid (VPA) on optic neuritis in experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. EAE was induced in C57BL/6 mice by immunization with MOG35-55 and VPA (300mg/kg) was administered via intraperitoneal injection once daily from day 3 postimmunization until the end of the experimental period (day 28). VPA treatment suppressed neuroinflammation and decreased the clinical score of EAE at an early phase (from day 12-14 after immunization). We also examined the effects of apoptosis signal-regulating kinase 1 (ASK1), an evolutionarily conserved signaling intermediate for innate immunity, in EAE mice. ASK1 deficiency strongly suppressed microglial activation and decreased the clinical score of EAE at a late phase (day 25, 27 and 28 after immunization). When VPA was administered to ASK1-deficient EAE mice, the clinical score was suppressed in both early and late phases (from day 12-28 after immunization) and showed synergistic effects on protection of retinal neurons. Our findings raise intriguing possibilities that the widely prescribed drug VPA and ASK1 inhibition may be useful for neuroinflammatory disorders including optic neuritis and MS.

Polycyclic Aromatic Hydrocarbons in Sediments and Bivalves on the Pacific Coast of Japan: Influence of Tsunami and Fire

Surface sediments and at least one edible bivalve species (Ruditapes philippinarum, Mytilus galloprovincialis, and Crassostrea gigas) were collected from each of seven intertidal sites in Japan in 2013. The sites had experienced varying levels of tsunami and fire disturbance following the major earthquake of 2011. Eight polycyclic aromatic hydrocarbons (PAHs) were identified and analyzed by gas chromatography–mass spectrometry. Total sediment PAH concentration (CT), the sum of the average concentrations of the eight PAHs, was 21–1447 μg kg-1-dry. Relative to the average level of one type of PAH in sediments collected around Japan in 2002 (benzo[a]pyrene = 21 μg kg-1-dry), five of the seven sites showed concentrations significantly lower than this average in 2013. The CTs for the three bivalves (134–450 μg kg-1-dry) were within the range of the previous reports (2.2–5335 μg kg-1-dry). The data suggest that the natural disaster did not increase PAH concentrations or affect the distribution within sediment or bivalves in Tohoku district. Although PAH concentrations at the sites pose no risk to human health, the findings highlight that the observed PAH levels derive from pre- rather than post-quake processes.

DETERMINATION OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) IN SEDIMENTS AND BENTHOS COLLECTED ON THE COAST OF CHIBA

Eight polycyclic aromatic hydrocarbons (PAHs) including benzo[a]pyrene were analyzed in sediment and benthos collected on the coast of Chiba Prefecture in Japan by gas chromatography-mass spectrometry (GC/MS). The total concentration of the PAHs ranged from 8 to 18 μ g/kg-dry in the sediments and from 36 to 59 μ g/kg-wet in the benthos, Mactra quadrangularis, Scoletoma nipponica, and Arenicola basiliensis. The PAH composition in the sediments and the benthos was similar at four sampling points and dominated by phenanthrene (Phe), fluoranthene (Flu), and pyrene (Pyr). The ratios of abundance of Flu to that of Pyr, Flu/Pyr, and of Phe/anthracene suggest that the PAHs in the benthos are derived from the combustion of fossil fuels. The ratio, R, of the PAH concentration in the benthos to that in the sediment is 2.0 for Scoletoma nipponica and 1.8 for Arenicola basiliensis in average, indicating that the bioaccumulation is not significant in the benthos. However, the R value for perylene in Scoletoma nipponica was 3.7 times as large as the average.

THE FATE AND BEHAVIOR OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) THROUGH FEEDING AND EXCRETION OF ANNELIDS

The concentration of polycyclic aromatic hydrocarbons (PAHs) in sediment and excrements of annelids was measured by gas chromatography-mass spectrometry (GC/MS) and the movement of PAHs in the tidal flat was investigated. The PAH concentrations ranged 4.4–80.4 and 61.2–286.9 μg/kg-dry for the excrement of Arenicola basiliensis and of Marphysa sanguinea, respectively; the former contained about 10 times as much PAHs as the sediment and the latter about 100 times. The difference in the PAH concentration between the two organisms was attributed to their feeding behavior; M. sanguinea intakes much more detritus containing PAHs than A. basiliensis. Moreover, after the excrement of M. sanguinea had stood on the sediment for 2 hours, the PAH concentrations decreased to half. The reduction of the PAHs may arise from chemical changes owing to microorganisms and/or enzymes in the excrement of M. sanguinea.

Characteristics of Phosphorescence of Ionic Organic Compounds Adsorbed on Filter Paper

Abstract The phosphorescence spectra and lifetimes of ionic organic compounds, such as 4-hydroxy-3-methoxybenzaldehyde, 2-amino-1-naphthalene sulfonic acid, and 9-anthracenemethanol, adsorbed on filter paper were measured as a function of the substrate temperature (T) in the range of 93 – 373 K and the preparation concentration (c) of the solutions. The molecule-substrate interaction leading to room temperature phosphorescence is discussed on the basis of the experimental data.

Study on the Degradation of Polycyclic Aromatic Hydrocarbons (PAHs) in the Excrement of Marphysa sanguinea

To clarify the degradation of polycyclic aromatic hydrocarbons (PAHs) in the environment, we measured the PAH concentration in fecal pellets excreted by the annelid, Marphysa sanguinea, in a tidal flat and investigated the time dependence of the concentration. The degradation of PAHs in the annelids excrement approximately obeyed a pseudo first-order rate equation for initial 2 h. The half-lives of the PAHs were estimated to be 1.7–2.2 h. The cause of such rapid reduction in PAHs was discussed by taking into consideration the decomposition by enzymes and/or by microorganism in the excrement. Finally, the PAH reduction was ascribed to the transformation of PAHs into their derivatives by extracellular enzymes, produced by microorganisms in the excrement of M. sanguinea.

Determination of Polycyclic Aromatic Hydrocarbons in the fecal Materials of Mactra veneriformis and Excrement of Marphysa sanguinea

The concentration of polycyclic aromatic hydrocarbons (PAHs) was measured in the sediment, a bivalve (Mactra veneriformis), fecal materials (feces and pseudofeces) of M. veneriformis, and excrement (feces) of an annelid (Marphysa sanguinea), which were collected in the Yoro tidal flat in Chiba, Japan. The total PAH concentration was 350 μg/kg-dry in the fecal materials of M. veneriformis and 977 μg/kg-dry in the excrement of M. sanguinea; these values were about 8–23 times as large as that of the sediment. The concentration of the fecal materials stayed constant even after 24 h, whereas that of the excrement decreased to half in 2 h. The sediment and fecal materials of M. veneriformis showed a high level of PAHs with lower molecular weight such as phenanthrene, fluoranthene, and pyrene; on the other hand, the excrement of M. sanguinea showed a high level of PAHs with higher molecular weight such as chrysene, benzo[b]fluoranthene, benzo[a]pyrene, and perylene. The logarithm of the concentration factor, defined as the ratio of the concentration of individual PAHs in the fecal materials or excrement to that in the sediment, correlated with the logarithm of the n-octanol/water partition coefficient for the PAHs (R 2 = 0.803). These findings indicate that the sources and characteristics of the fecal materials of M. veneriformis and the excrement of M. sanguinea are different.