Electrochemical activities of NaNi0.5Mn0.5O2 and NaCrO2, having the analogous layered structure to LiCoO2, were investigated in 1 mol dm-3 NaClO4 propylene carbonate at room temperature. Almost all sodium ions were extracted from the NaNi0.5Mn0.5O2 and NaCrO2 electrodes by galvanostatic oxidation to 4.5 V accompanied with several phase transitions. Layered NaNi0.5Mn0.5O2 electrode showed a highly reversible capacity of 185 mAh g-1 as positive electrode in Na cell in the potential region between 2.5 and 4.5 V versus Na. A NaCrO2 electrode was hardly electroactive after oxidation up to 4.5 V. When galvanostatic cycling was carried in the limited potential domain between 2 and 3.5 V, both electrodes showed discharge capacities of 100 - 120 mAh g-1 with satisfactory capacity retention. Layered LiCrO2 (R-3m) and NaCrO2 (R-3m) possess the quite similar crystal structures and the same transition metal, nevertheless they were inactive and active in Li and Na cells, respectively.

To investigate the flow of the metal nutrients iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu) during rice seed germination, we performed microarray analysis to examine the expression of genes involved in metal transport. Many kinds of metal transporter genes were strongly expressed and their expression levels changed during rice seed germination. We found that metal transporter genes such as ZIP family has tendency to decrease in their expressions during seed germination. Furthermore, imaging of the distribution of elements (Fe, Mn, Zn, and Cu) was carried out using Synchrotronbased X-ray microfluorescence at the Super Photon ring-8 GeV (SPring-8) facility. The change in the distribution of each element in the seeds following germination was observed by in vivo monitoring. Iron, Mn, Zn, and Cu accumulated in the endosperm and embryos of rice seeds, and their distribution changed during rice seed germination. The change in the patterns of mineral localization during germination was different among the elements observed.

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Marine mammals and seabirds tend to exhibit high accumulations of mercury, cadmium, and selenium in their livers and kidneys. In this study, chemical forms of mercury, cadmium, and selenium accumulated in the livers and kidneys of northern fur seal (Callorhinus ursinus), Risso's dolphin (Grampus griseus), and black-footed albatross (Diomedea nigripes) were studied by extended X-ray absorption fine structure (EXAFS) spectroscopy to reveal the detoxification mechanisms of these metals. It was found that mercury and selenium exist in the form of HgSe in the liver of northern fur seal. Mercury levels were found to be higher than those of Se, based on their molar ratio, in black-footed albatross. XAFS analysis disclosed an existence of chalcogenide containing both Hg-Se and the Hg-S bonds, suggesting the existence of a solid solution Hg(Se, S) as granules in black-footed albatross. In contrast, Cd concentrations in the kidney were higher than those in the liver for northern fur seal, black-footed albatross, and Risso's dolphin. It was found that Cd was bound to sulfur, which was probably derived from the metallothionein. The Cd-O bond was observed in the tissues of northern fur seal.

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boron ͉ plant reproduction ͉ NpGUT1 S patially and temporally controlled intercellular attachment is indispensable for the organized development of higher organisms. In higher plants, intercellular attachment is mediated by cell wall pectin, which consists of homogalacturonan and the rhamnogalacturonan (RG)-I and RG-II domains (1-3). Pectin is a highly complex polysaccharide. Because pectin-defective mutants show lethal embryonic phenotypes, few genes for pectin biosynthesis have been identified (4). Recently, we established a system for mutant production by T-DNA transformation called nolac (for nonorganogenic callus with loosely attached cells), which involves the in vitro culture of leaf disks of haploid Nicotiana plumbaginifolia (4, 5). The mutant callus line nolac-H18 is defective in intercellular attachment, which results in the formation of crumbled callus that does not form buds. The T-DNA-tagged gene in this line, NpGUT1, contains a putative glycosyltransferase catalytic domain of the group pfam03016 in glycosyltransferase family 47 (GT47), which has similarities to sequences in animal exostosins (6). The insertion in NpGUT1 causes defects in the glucuronic acid of pectin RG-II, which drastically reduces the formation of borate cross-linked RG-II (dRG-II-B) (4). The substitution of 2-O-Me galactose for 2-O-Me fucose in the RG-II of the Arabidopsis mur1 mutant also reduces the rate of formation and the stability of the RG-II dimer (7). The mutant phenotypes of nolac-H18 and mur1-1 indicate that the entire structure of the side chain of RG-II is essential for the borate cross-linking of the RG-II dimer. The functions of MUR1 and NpGUT1 likely differ because the addition of excess borate could not rescue the nolac phenotype (4), although it did rescue the mur1-1 phenotype (7).RG-II is present in the primary cell walls of angiosperms, gymnosperms, and pteridophytes, and its glycosyl sequence is highly conserved in all vascular plants examined to date (8). This conservation is remarkable because the other pectin domains, homogalacturonan and RG-I, are rare in monocots and pteridophytes. In addition, RG-II has a complex composition of at least 12 different glycosyl residues linked together by Ͼ20 different glycosidic linkages. Pectin RG-II is known to be the main binding site in higher plants for boron, an essential microelement for various plant species (8). These facts suggest that the structure and organization of RG-II-B are essential for the development of land plants.Previously, we showed that NpGUT1 is predominantly expressed in meristematic tissues and is indispensable for the formation of shoot meristems (4). We recently found that NpGUT1 expression in plants is higher during the reproductive stage than in the vegetative stage, and that the suppression of NpGUT1 expression in flower buds results in flowers that are completely sterile, despite containing flower organs with nearly normal morphogenesis.Boron deficiency causes problems in the growth and development of higher plants (9-11), especially in ...

Marine mammals accumulate mercury in their tissues at high concentration and detoxify by forming mercury selenide (HgSe, tiemannite) mainly in the liver. We investigated the possibility of formation of HgSe in various tissues (liver, kidney, lung, spleen, pancreas, muscle and brain) other than the liver of the striped dolphin (Stenella coeruleoalba). We applied a combination method of micro-X-ray fluorescence (μ-XRF) imaging and micro-X-ray diffraction (μ-XRD) using a synchrotron radiation X-ray microbeam to analyze the tissue samples directly with minimal sample preparation. By this method, many accumulation points for Hg and Se on a micron scale were found in thin sections of the spleen and liver tissue and consequently, the XRF spectra and the XRD pattern of the hot spots confirmed the presence of tiemannite, HgSe. On the other hand, the insoluble fractions after enzyme digestion of the nuclear and mitochondrial fractions of all tissues were subjected to X-ray absorption fine structure (XAFS) analysis. XAFS analysis confirmed the presence of HgSe in all the tissues examined (liver, kidney, lung, spleen, pancreas, muscle and brain) of the striped dolphin. The presence of HgSe in all the tissues examined suggests that Se would be involved in the detoxification process of Hg in various tissues other than the liver. This contribution seems to be large especially in the liver and spleen but relatively small in the kidney, pancreas and brain, because the proportion of insoluble fraction containing HgSe was lower in these tissues (25 to 46%). This is the first report on the presence of tiemannite HgSe in various tissues of marine mammals.

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