Oishi, Yutaro; Otaki, Rie; Iijima, Yukari; Kumagai, Eri; Aoki, Motohide; Tsuzuki, Mikio; Fujiwara, Shoko; Sato, Norihiro
In: Communications Biology, 5 (1), pp. 19, 2022, ISSN: 2399-3642.
Membrane lipid remodeling contributes to the environmental acclimation of plants. In the green lineage, a betaine lipid, diacylglyceryl-N,N,N-trimethylhomoserine (DGTS), is included exclusively among green algae and nonflowering plants. Here, we show that the green alga Chlorella kessleri synthesizes DGTS under phosphorus-deficient conditions through the eukaryotic pathway via the ER. Simultaneously, phosphatidylcholine and phosphatidylethanolamine, which are similar to DGTS in their zwitterionic properties, are almost completely degraded to release 18.1% cellular phosphorus, and to provide diacylglycerol moieties for a part of DGTS synthesis. This lipid remodeling system that substitutes DGTS for extrachloroplast phospholipids to lower the P-quota operates through the expression induction of the BTA1 gene. Investigation of this lipid remodeling system is necessary in a wide range of lower green plants for a comprehensive understanding of their phosphorus deficiency acclimation strategies.
Miyauchi, Hiroki; Harada, Kohei; Suzuki, Yoshino; Okada, Katsuhiko; Aoki, Motohide; Umemura, Tomonari; Fujiwara, Shoko; Tsuzuki, Mikio
In: Algal Research, 58 , pp. 102394, 2021, ISSN: 2211-9264.
Wastewater treatment using microalgae is receiving growing attention. Here, we have developed a portable tubular system containing an algal cell-coated solid surface for phosphorous recovery. P-depleted Chlorella cells attached to a solid surface removed phosphate from the medium about 70 times faster than P-replete cells. When the cell density was 20 g dry cell weight m−2 or less, P-depleted cells on the solid surface absorbed phosphate from the medium at almost the same rate as in liquid, the maximum capacity per solid surface area being about 6 mg P m−2 min−1. P in inorganic wastewater from chemical factories (ethanol factories; about 4 mg L−1) and in pond water (0.06 mg L−1) was mostly removed within 3 h with a simple device composed of a single solid-surfaced sheet (0.002 m−2) and a portable compact tubular device including 12 such sheets (totally 0.5 m−2), respectively. Simultaneously, cellular growth was confirmed with both wastewater and pond water. These findings suggested that the attached cell culture system, in which medium exchange to prepare P-depleted cells is much easier than in liquid cultures, is promising for dual use for biomass production and wastewater treatment.
今崎, 龍之介; 近藤, 啓太; 谷, 夏海; 青木, 元秀; 熊田, 英峰; 内田, 達也; 長縄, 豪; 嶋田, 泰佑; 田口, 嘉彦; 佐藤, 浩明; 安井, 隆雄; 梅村, 知也
超薄層クロマトグラフィー用の水平式ミニチュアTLC展開槽の試作と評価 Journal Article
In: 分析化学, 69 (10.11), pp. 553-558, 2020.
Tani, Hidenori; Numajiri, Ayaka; Aoki, Motohide; Umemura, Tomonari; Nakazato, Tetsuya
In: Scientific Reports, 9 , pp. 20299, 2019, ISSN: 2045-2322.
Long noncoding RNAs (lncRNAs) are non-protein-coding transcripts >200 nucleotides in length that have been shown to play important roles in various biological processes. The mechanisms underlying the induction of lncRNA expression by chemical exposure remain to be determined. We identified a novel class of short-lived lncRNAs with half-lives (t1/2) ≤4 hours in human HeLa Tet-off cells, which have been suggested to express many lncRNAs with regulatory functions. As they may affect various human biological processes, short-lived lncRNAs may be useful indicators of the degree of stress on chemical exposure. In the present study, we identified four short-lived lncRNAs, designated as OIP5-AS1, FLJ46906, LINC01137, and GABPB1-AS1, which showed significantly upregulated expression following exposure to hydrogen peroxide (oxidative stress), mercury II chloride (heavy metal stress), and etoposide (DNA damage stress) in human HepG2 cells. These lncRNAs may be useful indicators of chemical stress responses. The levels of these lncRNAs in the cells were increased because of chemical stress-induced prolongation of their decay. These lncRNAs were degraded by nuclear RNases, which are components of the exosome and XRN2, and chemical exposure inhibited the RNase activities within the cells.
シングルプローブ質量分析法を用いた単一生細胞中の薬物の定量 Journal Article
In: ぶんせき, 2019 (12), pp. 558-559, 2019, ISSN: 0386-2178.
Nagashima, Shun; Takeda, Keisuke; Ohno, Nobuhiko; Ishido, Satoshi; Aoki, Motohide; Saitoh, Yurika; Takada, Takumi; Tokuyama, Takeshi; Sugiura, Ayumu; Fukuda, Toshifumi; Matsushita, Nobuko; Inatome, Ryoko; Yanagi, Shigeru
In: Life Science Alliance, 2 (4), 2019.
Mitochondrial abnormalities are associated with developmental disorders, although a causal relationship remains largely unknown. Here, we report that increased oxidative stress in neurons by deletion of mitochondrial ubiquitin ligase MITOL causes a potential neuroinflammation including aberrant astrogliosis and microglial activation, indicating that mitochondrial abnormalities might confer a risk for inflammatory diseases in brain such as psychiatric disorders. A role of MITOL in both mitochondrial dynamics and ER-mitochondria tethering prompted us to characterize three-dimensional structures of mitochondria in vivo. In MITOL-deficient neurons, we observed a significant reduction in the ER-mitochondria contact sites, which might lead to perturbation of phospholipids transfer, consequently reduce cardiolipin biogenesis. We also found that branched large mitochondria disappeared by deletion of MITOL. These morphological abnormalities of mitochondria resulted in enhanced oxidative stress in brain, which led to astrogliosis and microglial activation partly causing abnormal behavior. In conclusion, the reduced ER-mitochondria tethering and excessive mitochondrial fission may trigger neuroinflammation through oxidative stress.
竹内, 理子; 力石, 嘉人; 小川, 奈々子; 風呂田, 郷史; 大河内, 直彦; 青木, 元秀; 内田, 達也; 梅村, 知也; 熊田, 英峰
化合物レベル炭素安定同位体比分析のための高等植物中のステロール及び脂肪酸の分離精製法の確立 Journal Article
In: 分析化学, 68 (5), pp. 297-306, 2019.
Murota, Chisato; Fujiwara, Shoko; Tsujishita, Maki; Urabe, Kanae; Takayanagi, Shuta; Aoki, Motohide; Umemura, Tomonari; Eaton-Rye, Julian J.; Pitt, Frances D.; Tsuzuki, Mikio
Hyper-resistance to arsenate in the cyanobacterium Synechocystis sp. PCC 6803 is influenced by the differential kinetics of its pst-ABC transporters and external phosphate concentration exposure Journal Article
In: Algal Research, 38 , pp. 101410, 2019, ISSN: 2211-9264.
Phosphate transporters, which take up not only phosphate but also arsenate, have attracted attention for phosphorus (P) resource recovery from eutrophic environments and arsenic (As) removal from polluted areas by bioremediation. The cyanobacterium Synechocystis sp. PCC 6803 can grow in a higher ratio of arsenate (150 mM) to phosphate (0.2 mM) in comparison with plants and microalgae. Analysis of the As resistance of the Pst1 and Pst2 phosphate transporter deletion mutants (Δpst1 and Δpst2) showed that the Δpst1 strain is more sensitive to arsenate under P-replete conditions but more resistant under P-deplete conditions compared with Δpst2 cells and wild type. This pattern in sensitivity is attributed to the levels of initial As accumulation and pst gene expression. Moreover, the ratio of phosphate uptake to arsenate uptake rates at 10 μM was 7–10:1 in the wild type and the Δpst2 mutant, while that in Δpst1 and Δ pstS1 (phosphate-binding protein from the pst1 gene cluster), were about 1.5:1, suggesting a high selectivity of Pst1 for phosphate.
Hirose, Atsumi; Kasai, Takuya; Aoki, Motohide; Umemura, Tomonari; Watanabe, Kazuya; Kouzuma, Atsushi
In: Nature communications, 9 (1), pp. 1083, 2018, ISSN: 2041-1723.
Electrochemically active bacteria (EAB) receive considerable attention for their utility in bioelectrochemical processes. Although electrode potentials are known to affect the metabolic activity of EAB, it is unclear whether EAB are able to sense and respond to electrode potentials. Here, we show that, in the presence of a high-potential electrode, a model EAB Shewanella oneidensis MR-1 can utilize NADH-dependent catabolic pathways and a background formate-dependent pathway to achieve high growth yield. We also show that an Arc regulatory system is involved in sensing electrode potentials and regulating the expression of catabolic genes, including those for NADH dehydrogenase. We suggest that these findings may facilitate the use of EAB in biotechnological processes and offer the molecular bases for their ecological strategies in natural habitats.[on SciFinder (R)]
Aoki, Motohide; Sato, Norihiro
In: Bio-Protocol, 7 (1), pp. 1–9, 2018, ISSN: 2331-8325.
Umemura, Tomonari; Matsui, Yuichiro; Sakagawa, Shinnosuke; Fukai, Taku; Fujimori, Eiji; Kumata, Hidetoshi; Aoki, Motohide
2017, ISBN: 9784431564638.
textcopyright Springer Japan KK 2017. Elemental abundances of prokaryotic and eukaryotic cells as well as organelles were provided as the number of atoms per cell (or organelle). In order to examine the specific uptake of vital elements by cells, E. coli cells were grown in different media and harvested at several time points during the cell growth and proliferation. The major-to-ultratrace elements in the cells were determined by micro-flow injection (µFI)-ICP-MS after microwave-assisted acid digestion of less than 10 mg of dry weight sample. Cyanobacteria and chlorella were also cultivated to compare elemental abundance differences among species. In addition, to further examine the localization and utilization of vital elements in the cells, chloroplasts and mitochondria were isolated from the tissues of spinach leaves, potato tuber, and bovine liver by density-gradient centrifugation using Percoll. The concentration data obtained by ICP-MS measurements were normalized to a per cell (or organelle) basis, taking into account the cell size and water content. Among about 60 elements detectable by ICP-MS, more than 30 elements were quantitatively determined, and it was clearly found that essential elements participating in specific vital functions such as redox reactions were highly accumulated in the microorganisms and organelles.
Tani, Hidenori; Okuda, Sayaka; Nakamura, Kaoru; Aoki, Motohide; Umemura, Tomonari
In: PloS one, 12 (7), 2017, ISSN: 19326203.
textcopyright 2017 Tani et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Whole transcriptome analyses have revealed a large number of novel long non-coding RNAs (lncRNAs). Although accumulating evidence demonstrates that lncRNAs play important roles in regulating gene expression, the detailed mechanisms of action of most lncRNAs remain unclear. We previously reported that a novel class of lncRNAs with a short half-life (t 1/2 textless 4 h) in HeLa cells, termed short-lived non-coding transcripts (SLiTs), are closely associated with physiological and pathological functions. In this study, we focused on 26 SLiTs and nuclear-enriched abundant lncRNA, MALAT1(t 1/2 of 7.6 h in HeLa cells) in neural stem cells (NSCs) derived from human induced pluripotent stem cells, and identified four SLiTs (TUG1, GAS5, FAM222-AS1, and SNHG15) that were affected by the following typical chemical stresses (oxidative stress, heavy metal stress and protein synthesis stress). We also found the expression levels of LINC00152 (t 1/2 of 2.1 h in NSCs), MALAT1 (t 1/2 of 1.8 h in NSCs), and their neighboring genes were elevated proportionally to the chemical doses. Moreover, we confirmed that the overexpression of LINC00152 or MALAT1 upregulated the expressions of their neighboring genes even in the absence of chemical stress. These results reveal that LINC00152 and MALAT1 modulate their neighboring genes, and thus provide a deeper understanding of the functions of lncRNAs.
Sato, Norihiro; Kobayashi, Satomi; Aoki, Motohide; Umemura, Tomonari; Kobayashi, Isao; Tsuzuki, Mikio
In: Biochemical and Biophysical Research Communications, 470 (1), pp. 123–129, 2016, ISSN: 0006291X.
Sulfoquinovosyl diacylglycerol is one of the lipids that construct thylakoid membranes, and is distributed from cyanobacteria to plastids in plants including a red lineage. One of the most primitive red algae, Cyanidioschyzon melorae, similar to cyanobacteria and green plants, possesses homologs of the SQD1 and SQD2 genes that code for UDP-sulfoquinovose and sulfoquinovosyl diacylglycerol synthases, respectively, for the synthesis of sulfoquinovosyl diacylglycerol. We here revealed the structural properties of SQD1 and SQD2 homologs in C. melorae intrinsic to those of the authentic proteins, and verified their enzymatic functions through heterologous expression in cyanobacterial disruptants as to the corresponding genes. The results demonstrated that the system of sulfoqunovosyl diacylglycerol synthesis could have been conserved through evolution of cyanobacteria to plastids in a red lineage, which is compatible with the monophyletic origin of plastids.
Sakurai, Toshihiro; Aoki, Motohide; Ju, Xiaohui; Ueda, Tatsuya; Nakamura, Yasunori; Fujiwara, Shoko; Umemura, Tomonari; Tsuzuki, Mikio; Minoda, Ayumi
In: Bioresource Technology, 200 , pp. 861–866, 2016, ISSN: 18732976.
The unicellular red alga Galdieria sulphuraria grows efficiently and produces a large amount of biomass in acidic conditions at high temperatures. It has great potential to produce biofuels and other beneficial compounds without becoming contaminated with other organisms. In G. sulphuraria, biomass measurements and glycogen and lipid analyses demonstrated that the amounts and compositions of glycogen and lipids differed when cells were grown under autotrophic, mixotrophic, and heterotrophic conditions. Maximum biomass production was obtained in the mixotrophic culture. High amounts of glycogen were obtained in the mixotrophic cultures, while the amounts of neutral lipids were similar between mixotrophic and heterotrophic cultures. The amounts of neutral lipids were highest in red algae, including thermophiles. Glycogen structure and fatty acids compositions largely depended on the growth conditions.
Chikamatsu, Kazuhiro; Aoki, Motohide; Uchida, Tatsuya; Umemura, Tomonari; Kumata, Hidetoshi
Optimization of the Extraction Solvent for Polycyclic Aromatic Hydrocarbons (PAHs) from Road Dusts by Using Pressurized Solvent Extraction and Evaluation of Its Impact on Source Diagnostic Isomer Pair Ratios of PAHs Journal Article
In: Bunseki Kagaku, 65 (4), pp. 193–202, 2016.
Aoki, Motohide; Tsuzuki, Mikio; Sato, Norihiro
In: Bio-Protocol, 6 (21), pp. 1–6, 2016.
Cytochrome (Cyt) b559, an important and essential core component of photosystem II in the photosynthetic electron transport system, is a heme-bridged heterodimer protein composed of an alpha subunit (PsbE) and a beta subunit (PsbF), and its reduced form has an absorption maximum in the $alpha$- band at 559 nm. The amounts of Cyt b559 can be determined by spectrophotometrical measurement of reduced minus oxidized difference spectra that are normalized with absorbance of isosbestic point at 580 nm. The authors use differential extinction coefficients of Cyt b559 [$Delta$$epsilon$(559-580 nm) = 15.5 mM-1textperiodcenteredcm-1], which have been reported by Garewal and Wasserman (1974). In addition to the Cyt b559, this procedure can be used for quantitation of Cyt b6 and Cyt f, the subunits of the Cyt b6/f complex, and P700, one of the core components of photosystem I. This protocol, which is adapted from Fujita and Murakami (1987), is used in a cyanobacterium, Synechococcus elongatus PCC 7942, and also in other cyanobacterial strains including Synechocystis sp. PCC 6803.
Yanai, Hikaru; Egawa, Saki; Yamada, Kenta; Ono, Junpei; Aoki, Motohide; Matsumoto, Takashi; Taguchi, Takeo
In: Asian Journal of Organic Chemistry, 3 (4), pp. 556–563, 2014, ISSN: 21935807.
Aoki, Motohide; Nakamura, Yoshisuke; Akamine, Runa; Kumata, Hidetoshi; Umemura, Tomonari
Discovery of the cyanobacterial biomarker respond to toxic metal based on the lipidomics Journal Article
In: Biomedical Research on Trace Elements, 25 (2), pp. 83, 2014, ISBN: 0916-717X.
Inoue, Kana; Aoki, Motohide; Fujiwara, Kitao
In: Journal of Environmental Science and Health, Part A, 48 (11), pp. 1311–1317, 2013, ISSN: 1093-4529.
青木, 元秀; 松井, 雄一郎; 藤原, 祺多夫; 都筑, 幹夫
微細藻類を利用したストロンチウムおよびセシウムの回収 Journal Article
In: 東京薬科大学研究紀要, 16 , pp. 1–8, 2013.
Aoki, Motohide; Matsumoto, Hiroe; Takahashi, Tatsuya; Sato, Kazuya; Kumata, Hidetoshi; Fujiwara, Kitao
In: Kuang, Tingyun; Lu, Congming; Zhang, Lixin (Ed.): Photosynthesis Research for Food, Fuel and Future—15th International Conference on Photosynthesis, pp. 586–589, Zhejiang University Press, Springer-Verlag GmbH, 2013, ISBN: 978-3-642-32033-0.
The aim of this study was to elucidate the mechanism of thallium (Tl) ion toxicity in photosynthetic organisms. The physiological and biochemical responses to Tl exposure were analyzed in the cyanobacterium Synechocystis sp. PCC6803, which is a widly used model to study photosynthesis. We examined the photosynthetic activities of Tl+-exposed cells, the extent of Tl accumulation, and the properties of membrane lipids. Exposure to Tl+ at 2.0 and 5.0 for 24 h decreased the net photosynthetic activities of cells to 92% and 34%, respectively. After exposure to 2.5 µM Tl+, cells concentrated the Tl to 20.8 µM on a packed cell volume basis. Exposure of Synechocystis to 0–2.5 µM Tl+ resulted in an approximately 9-fold concentration factor. Treatment with 2.0 µM Tl+ for 48 h decreased the total lipid content of the cells by 38%. Further, we observed the ultrastructure of cells treated with Tl+. The cells exposed to 5 µM Tl+ for 24 h showed thylakoid membrane fragmentation and generated less-dense particles following osmium staining. During this time, the net photosynthetic oxygen evolution of the cells was reduced to 34%. These results suggest that the accumulation of Tl in cells affects the integrity of the photosynthetic apparatus.
Fujiwara, Kitao; Horiuchi, Keishiro; Goryoda, Sayuri; Hashidume, Yasuhiro; Horiguchi, Naoko; Miyakawa, Takeshi; Takasu, Masako; Aoki, Motohide
In: Journal of environmental science and engineering A, 1 (3), pp. 364-370, 2012, ISSN: 1934-8932.
Fluorescence correlation spectroscopy (FCS) without objective image magnification (without using con-focal microscope) was applied to observe the variation in cell size of Escherichia coli (E. coli) induced by the anti-cancer agent MitomycinC (MMC). In the system without image magnification followed in this study, the suspension of E. coli cells was stirred, and the difference in movement due to the different cell sizes induced by the compulsive solution flow was detected. The addition of 0.1-0.4 $mu$g/L of MMC elongated the E. coli cell length from about 3.6 to 7.8 $mu$m. The flow cell (i.d. = about 1 mm) also produced a size-dependent correlation curve. The present system is not based on single molecular FCS but is inexpensive and effective at observing the variation in cell size induced by environmental changes.
Aoki, Motohide; Tsuzuki, Mikio; Sato, Norihiro.
In: BMC Research Notes, 5 , pp. 98, 2012, ISSN: 1756-0500.
Background: Sulfoquinovosyl diacylglycerol (SQDG) is present in the membranes of cyanobacteria and their postulated progeny, plastids, in plants. A cyanobacterium, Synechocystis sp. PCC 6803, requires SQDG for growth: its mutant (SD1) with the sqdB gene for SQDG synthesis disrupted can grow with external supplementation of SQDG. However, upon removal of SQDG from the medium, its growth is retarded, with a decrease in the cellular content of SQDG throughout cell division, and finally ceases. Concomitantly with the decrease in SQDG, the maximal activity of photosynthesis at high-light intensity is repressed by 40%. Findings: We investigated effects of SQDG-defect on physiol. aspects in Synechocystis with the use of SD1. SD1 cells defective in SQDG exhibited normal photosynthesis at low-light intensity as on culturing. Meanwhile, SD1 cells defective in SQDG were impaired in light-activated heterotrophic growth as well as in photoautotrophic growth. Flow cytometric anal. of the photoautotrophically growing cells gave similar cell size histograms for the wild type and SD1 supplemented with SQDG. However, the profile of SD1 defective in SQDG changed such that large part of the cell population was increased in size. Of particular interest was the microscopic observation that the mitotic index, i.e., population of dumbbell-like cells with a septum, increased from 14 to 29 % in the SD1 culture without SQDG. Flow cytometric anal. also showed that the enlarged cells of SD1 defective in SQDG contained high levels of Chl, however, the DNA content was low. Conclusions: Our expts. strongly support the idea that photosynthesis is not the limiting factor for the growth of SD1 defective in SQDG, and that SQDG is responsible for some physiol. fundamental process common to both photoautotrophic and light-activated heterotrophic growth. Our findings suggest that the SQDG-defect allows construction of the photosynthetic machinery at an elevated level for an increase in cell mass, but represses DNA synthesis. SQDG may be essential for normal replication of chromosomal DNA for completion of the cell cycle. [on SciFinder(R)]
Fujiwara, Kitao; Osako, Yuta; Sasaki, Takana; Kumata, Hidetoshi; Aoki, Motohide; Kawashima, Norio.
In: Bunseki Kagaku, 59 (11), pp. 1021–1028, 2010, ISSN: 0525-1931.
COD is one of the most popular methods for evaluating org. pollutants. In the present paper, a chemiluminescence detection method for measuring the concn. of permanganate ion after reacting with org. compds. is described; the chemiluminescence occurs based on the direct reaction between permanganate and luminol. In order to use this system, a buffer soln., the concns. of permanganate and luminol were inspected. Fifty $mu$M of MnO4 was reacted with the sample, and then the chemiluminescence was detected with a mixt. soln. (250 mL of 1.5 mM luminol, 250 mL of 0.01 M 1,10-phenanthroline, and 500 mL of 1 M ammonium sulfate at pH 9.6, adjusted with 25% ammonium soln.). Also, a method for reducing the COD was proposed: where the sample soln. flows a 100 m length PFA (perfluoroalkoxy-fluororesin) microtube (i.d. = 0.2 mm and o.d. = 0.4 mm). The PFA tube was wound around the outside of a quartz tube (o.d. = 30 mm
Fujiwara, Kitao; Suematsu, Hitoshi; Kiyomiya, Emiko; Aoki, Motohide; Sato, Mamiko; Moritoki, Nobuko
In: Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering, 43 (10), pp. 1167–73, 2008, ISSN: 1093-4529.
SiO(2) nano-particles were found to exhibit size-dependent toxicity toward the alga, Chlorella kessleri. Small SiO(2) nano-particles exhibit stronger toxicity: 50% inhibitory concentrations (IC(50)) value for 5 nm = 0.8 +/- 0.6%, 26 nm = 7.1 +/- 2.8%, and 78 nm = 9.1 +/- 4.7%. Enlargement of the cell body was observed by flow cytometry, which is due to the presence of structures that obstructed cell division. Optical and transmission microscopes were used to observe coagulated cells with incomplete division. Although the physiological effect of SiO(2) nano-particles was not clear, SiO(2) nano-particles are toxic, at least for algae in aquatic media. Under the transmission electron microscope, several amorphous structures appeared in the cells that were exposed to 5-nm silica nano-particles.
Aoki, Motohide; Suematsu, Hitoshi; Kumata, Hidetoshi; Kitao, Fujiwara
In: Allen, J; Gantt, E; Gol-beck, J; Osmond, B (Ed.): Photosynthesis. Energy from the Sun, pp. 1399–1402, Springer-Verlag, Heidelberg, Germany, 2008, ISBN: 978-1-4020-6707-5.
Fujiwara, Kitao; Hirokawa, Shun; Aoki, Motohide.
In: Analytical Sciences, 24 (12), pp. 1623–1627, 2008, ISSN: 0910-6340.
As a tool for micrometer-level size detn., fluorescence correlation spectroscopy (FCS), performed based on our previous report, was compared to flow cytometry (FCM). For this purpose, std. fluorescent beads were subjected to both methods. And hence, it was found that our FCS is a useful method with satisfactory precision for size detns. of individual particles at micrometer size levels, while providing the av. size for a mixt. of two kinds of particles with different sizes. [on SciFinder(R)]
Fujiwara, Kitao; Matsumoto, Yoshiko; Kawakami, Hayato; Aoki, Motohide; Tuzuki, Mikio
In: Bulletin of the Chemical Society of Japan, 81 (4), pp. 478–488, 2008.
Fujiwara, Kitao; Hirokawa, Shun; Aoki, Motohide.
In: Analytical Sciences, 23 (10), pp. 1237–1239, 2007, ISSN: 0910-6340.
The performance of fluorescence correlation spectrometry (FCS) was examd. for studying the solns. suspended with the fluorescent particles of various sizes from 50 nm to 10 $mu$m in diam. and for different sizes of pinholes: the particles were made to move by simply stirring the soln. in the quartz fluorescence cuvette. Without using any magnification tool for the optical image, this FCS system successfully distinguishes images with a size of smaller than 1 $mu$m. This system was applied for detn. of the sizes of microalgae. [on SciFinder(R)]
Fujiwara, Kitao; Ishige, Yuko; Inoue, Yu-Ichi; Taigo, Sunao; Sasaki, Takana; Aoki, Motohide; Shirasaki, Hidekazu; Furuno, Masahiro.
In: Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering, 42 (3), pp. 225–2230, 2007, ISSN: 1093-4529.
The solar-induced decompn. of 10 polycyclic arom. hydrocarbons (PAHs) was obsd. in aq. media. All 10 PAHs obsd. were half-decompd. within 120 min. Among anthracene derivs., the decompn. rates were: anthracene = 1-methylanthracene < 2-methylanthracene < 9-methylanthracene < 9,10-dimethylanthracene ∼ 2-aminoanthracene. The addn. of com. humic acid had no effect on the decompn. rates of these PAHs. Deuterium water also hastened the decompn. of PAH. The products obtained by the solar radiation of PAH after extn. to DCM were mainly ketone and hydroxyl derivs. To explain these results, reactivities and electron charges at the constituent carbon atoms in each anthracene deriv. were examd. by an ab initio MO calcn. method. [on SciFinder(R)]
Aoki, Motohide; Sato, Norihiro; Meguro, Ayano; Tsuzuki, Mikio
The roles of sulfolipid, sulfoquinovosyl diacylglycerol, within the evolution of photosyntheitic organisms Inproceedings
In: vab der Est, A; Bruce, Lawrence D. (Ed.): Photosynthesis: Fundamental aspects to global perspectives, pp. 751–753, the International Society of Photosynthesis Research Alliance Communications Group, 810 East Tenth Street, Lawrence, Kansas 66044, 2005, ISBN: 1891276395, 9781891276392.
Aoki, Motohide; Sato, Norihiro; Meguro, Ayano; Tsuzuki, Mikio
In: European Journal of Biochemistry, 271 (4), pp. 685–693, 2004, ISSN: 00142956.
Sulfoquinovosyl diacylglycerol (SQDG) is involved in the maintenance of photosystem II (PSII) activity in Chlamydomonas reinhardtiiMinoda, A., Sato, N., Nozaki, H., Okada, K., Takahashi, H., Sonoike, K. & Tsuzuki, M. et al. (2002) Eur. J. Biochem.269, 2353-2358. To understand the spread of the taxa in which PSII interacts with SQDG, especially in cyanobacteria, we produced a mutant defective in the putative sqdB gene responsible for SQDG synthesis from two cyanobacteria, Synechocystis sp. PCC6803 and Synechococcus sp. PCC7942. The mutant of PCC6803, designated SD1, lacked SQDG synthetic ability and required SQDG supplementation for its growth. After transfer from SQDG-supplemented to SQDG-free conditions, SD1 showed decreased net photosynthetic and PSII activities on a chlorophyll (Chl) basis with a decrease in the SQDG content. Moreover, the sensitivity of PSII activity to 3-(3,4-dichlorophenyl)-1,1-dimethylurea and atrazine was increased in SD1. However, SD1 maintained normal amounts of cytochrome b559 and D1 protein (the subunits comprising the PSII complex) on a Chl basis, indicating that the PSII complex content changed little, irrespective of a decrease in the SQDG content. These results suggest that the role of SQDG is the conservation of the PSII properties in PCC6803, consistent with the results obtained with C. reinhardtii. In contrast, the SQDG-null mutant of PCC7942 showed the normal level of PSII activity with little effect on its sensitivity to PSII herbicides. Therefore, the difference in the SQDG requirement for PSII is species-specific in cyanobacteria; this could be of use when investigating the molecular evolution of the PSII complex.
Sato, Norihiro; Aoki, Motohide; Maru, Yukihiro; Sonoike, Kintake; Minoda, Ayumi; Tsuzuki, Mikio.
In: Planta, 217 (2), pp. 245–251, 2003, ISSN: 0032-0935.
To examine the role of sulfoquinovosyl diacylglycerol (SQDG) in thylakoid membranes, the authors compared the structural and functional properties of photosystem II (PSII) between a mutant of Chlamydomonas reinhardtii defective in SQDG (hf-2) and the wild type. The PSII core complex of hf-2, as compared with that of the wild type, showed structural fragility when solubilized with a detergent, dodecyl $beta$-D-maltoside, suggesting that the phys. properties of the PSII complex were altered by the loss of SQDG. On the other hand, exposure of the cells to 41° for 120 min in the dark decreased the PSII activity to 70% and 50% of the initial levels in the wild type and hf-2, resp., which implies that the PSII activity, in the absence of SQDG, becomes less stable under heat-stress conditions. PSII inactivated to 60% of the initial level by dark incubation at 41° was reactivated by following illumination even at 41° to more than 90% in the wild type, but only to 70% in hf-2. These results suggest that PSII inactivated by heat recovers through some mechanism dependent on light, and that SQDG participates in functioning of the mechanism. The conformational disorder of PSII caused by the defect in SQDG might be correlated with the increased susceptibility of its activity to heat-stress. [on SciFinder(R)]