Three kinds of photochemical reactions are known in flavins as chromophores of photosensor proteins, reflecting the various catalytic reactions of the flavin in flavoenzymes. Sensor of blue light using the flavin FAD (BLUF) domains exhibit a unique photoreaction compared with other flavin-binding photoreceptors in that the chromophore does not change its chemical structure between unphotolyzed and intermediate states. Rather, the hydrogen bonding environment is altered, whereby the conserved Gln and Tyr residues near FAD play a crucial role. One proposal for this behavior is that the conserved Gln changes its chemical structure from a keto to an enol. We applied light-induced difference Fourier transform infrared (FTIR) spectroscopy to AppA-BLUF. The spectra of AppA-BLUF exhibited a different feature upon N-Gln labeling compared with the previously reported spectra from BlrB, a different BLUF domain. The FTIR signals were interpreted from quantum mechanics/molecular mechanics (QM/MM) calculation as the keto-enol tautomerization and rotation of the Gln63 side chain in the AppA-BLUF domain. The former was consistent with the result from BlrB, but the latter was not uniquely determined by the previous study. QM/MM calculation also indicated that the infrared signal shape is influenced depending on whether a Trp side chain forms a hydrogen bond with the Gln side chain. FTIR spectra and QM/MM simulations concluded that Trp104 does not flip out but is maintained in the intermediate state. In contrast, our data revealed that the Trp residue at the corresponding position in BlrB faces outward in both states.

Thirty-nine paddy pesticides and 11 of their metabolites were monitored in the Sakura River during the rice cultivation season in 2007 and 2008. Pesticide concentrations in the river water depended on the timing of pesticide application. Herbicides that were shipped to Ibaraki Prefecture in large amounts or had high water solubility, a low soil adsorption constant value, or large usage rates were detected at high peak concentrations. The concentrations of nursery-box-applied fungicides and insecticides peaked immediately after transplanting. The concentrations of pesticide metabolites, such as bromobutide-desbromo, cafenstrol-descarbamoyl, clomeprop-propionic acid, carbofuran, and fenthion-sulfoxide depended on the degradation rates and metabolic pathways of the parent compounds and on the stability of the metabolites in water and soil. Clomeprop-propionic acid, carbofuran, and fenthion-sulfoxide, which were formed from rapidly degradable pesticides, were detected at much higher peak concentrations than the parent compounds. © Pesticide Science Society of Japan Keywords: paddy pesticide, application timing, river water, physicochemical property, metabolic pathway, environmental fate. Original Articlefield area is under rice cultivation. After soil puddling and land leveling in late April, rice seedlings are transplanted in early May. Intermittent irrigation starts in mid-June and continues throughout the growing period, except during the midsummer drainage period from late June to mid-July. Generally, heading occurs from late July to early August, and harvest starts in early September, after drainage of the paddy water in late August. 15)Early-mid-season herbicides are applied within 2 weeks after transplanting (early to mid-May), and mid-season herbicides are applied 2-3 weeks after transplanting (late May to early June). Depending on the emergence of weeds, a lateseason herbicide might be used in June.16) Fungicides and insecticides are used on rice seedlings in nursery boxes before transplanting and for direct application to paddy fields before heading or harvest. Recently, nursery-box application has become increasing popular in the Sakura River basin. Aerial spraying of paddy pesticides was not conducted in the basin in 2007 and 2008 (Japan Agricultural Aviation Association: private communication; unpublished data). Analyzed compoundsTwenty-nine herbicides, 2 fungicides, and 8 insecticides were selected for analysis (Table 1), in consideration of the amounts of paddy pesticides shipped to Ibaraki Prefecture recently. We selected 11 metabolites of the herbicides and insecticides in accord with previous studies 11,14,17,18) as a reference. All analytical standards were purchased from Wako Pure Chemicals Industries (Japan), Hayashi Pure Chemicals Industries (Japan), or Kanto Chemicals (Japan). Sample collection and analysisThe sampling site (Kimijima Bridge) is located midway along the course of the Sakura River (Fig. 1). Water samples (approximately 3000 ml per sample) were collected once a week on Monday fr...

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Laboratory experiments were performed to determine the sampling rates of pesticides for the polar organic chemical integrative samplers (POCIS) used in Japan. The concentrations of pesticides in aquatic environments were estimated from the accumulated amounts of pesticide on POCIS, and the effect of water temperature on the pesticide sampling rates was evaluated. The sampling rates of 48 pesticides at 18, 24, and 30 °C were obtained, and this study confirmed that increasing trend of sampling rates was resulted with increasing water temperature for many pesticides.

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In this study, the species sensitivity distributions (SSDs) of 68 pesticides commonly used in Japanese paddy fields were analyzed based on collected acute toxicity data as a higher-tier ecological effect assessment. Then, based on each SSD, the 5% hazardous concentration (HC 5 ) values were calculated as the predicted no-effect concentrations for aquatic ecosystems. The differences between HC 5 and registration criteria were small (within 10-fold) for 50 of the 68 pesticides. However, there were more than 10-fold differences for 9 insecticides and 9 herbicides of specific modes of action. These results suggest that the current effect assessment scheme could underestimate the effect of such pesticides. This is caused by the mode of action specific properties of species sensitivity difference.