Publications (42) View all
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Article: Solution equilibrium behind the room-temperature synthesis of nanocrystalline titanium dioxide.
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ABSTRACT: Formation of nanocrystalline and monodisperse TiO2 from a water soluble and stable precursor, ammonium oxo-lactato-titanate, (NH4)8Ti4O4(Lactate)8·4H2O, often referred to as TiBALDH or TALH, is demonstrated to be due to a coordination equilibrium. This compound, individual in the solid state, exists in solution in equilibrium with ammonium tris-lactato-titanate, (NH4)2Ti(Lactate)3 and uniform crystalline TiO2 nanoparticles (anatase) stabilized by surface-capping with lactate ligands. This equilibrium can be shifted towards nano-TiO2via application of a less polar solvent like methanol or ethanol, dilution of the solution, introduction of salts or raising the temperature, and reverted on addition of polar and strongly solvating media such as dimethyl sulfoxide, according to NMR. Aggregation and precipitation of the particles were followed by DLS and could be achieved by a decrease in their surface charge by adsorption of strongly hydrogen-bonding cations, e.g. in solutions of ammonia, ethanolamine or amino acid arginine or by addition of ethanol. The observed equilibrium may be involved in formation of nano-titania on the surface of plant roots exerting chelating organic carboxylate ligands and thus potentially influencing plant interactions.Nanoscale 03/2013; · 5.91 Impact Factor -
Article: Immunolocalization of hemicelluloses in Arabidopsis thaliana stem. Part II: Mannan deposition is regulated by phase of development and its patterns of temporal and spatial distribution differ between cell types.
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ABSTRACT: Microdistribution of mannans in Arabidopsis stem was examined using immunolocalization with mannan-specific monoclonal antibodies (LM21 and LM22). Mannan labeling in secondary xylem cells (except for protoxylem vessels) was initially detected in the cell wall during S(2) formation and increased gradually during development. Labeling in metaxylem vessels (vessels) was detected earlier than that in xylary fibers (fibers), but was much weaker than fibers. The S(1) layer of vessels and fibers showed much less labeling than the S(2) layer. Some strong labeling was also detected in pit membranes of vessel pits. Interfascicular fibers (If-fibers) showed more heterogeneous labeling patterns than fibers by LM21. Unlike fibers, If-fibers also revealed some strong labeling in the cell corner of the S(1) layer, indicating different mannan labeling patterns between If-fibers and fibers. Interestingly, protoxylem vessels (proto-vessels) showed strong labeling at the early stage of secondary xylem formation with more intense labeling in the outer- than inner cell wall even though fibers and vessels showed no or very low labeling at this stage. Labeling intensity of proto-vessels was also much stronger than vessels and stronger or slightly weaker than fibers by LM21 and LM22, respectively. Using pectinase and mild alkali treatment, the presence of mannans in parenchymatous cells was also confirmed. Together our observations indicate that there are temporal and spatial variations in mannan labeling between cell types in the secondary xylem of Arabidopsis stems. Some similar features of mannan labeling between Arabidopsis and poplar are also discussed.Planta 06/2012; 236(5):1367-79. · 3.00 Impact Factor -
Article: Immunolocalization of hemicelluloses in Arabidopsis thaliana stem. Part I: temporal and spatial distribution of xylans.
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ABSTRACT: We investigated the microdistribution of xylans in different cell types of Arabidopsis stem using immunolocalization methods with LM10 and LM11 antibodies. Xylan labeling in xylary fibers (fibers) was initially detected at the cell corner of the S(1) layer and increased gradually during fiber maturation, showing correlation between xylan labeling and general secondary cell wall formation processes in fibers. Metaxylem vessels (vessels) showed earlier development of secondary cell walls than fibers, but revealed almost identical labeling patterns to fibers during maturation. No difference in labeling patterns and intensity was detected in the cell wall of fibers, vessels and protoxylem vessels (proto-vessels) between LM10 and LM11, indicating that vascular bundle cells may be chemically composed of a highly homogeneous xylan type. Interestingly, interfascicular fibers (If-fibers) showed different labeling patterns between the two antibodies and also between different developmental stages. LM10 showed no labeling in primary cell walls and intercellular layers of If-fibers at the S(1) formation stage, but some labeling was detected in middle lamella cell corner regions at the S(2) formation stage. In contrast, LM11 revealed uniform labeling across the If-fiber cell wall during all developmental stages. These results suggest that If-fibers have different xylan deposition processes and patterns from vascular bundle cells. The presence of xylan was also confirmed in parenchyma cells following pectinase treatment. Together our results indicate that there are temporal and spatial differences in xylan labeling between cell types in Arabidopsis stem. Differences in xylan labeling between Arabidopsis stem and poplar are also discussed.Planta 06/2012; 236(4):1275-88. · 3.00 Impact Factor -
Article: Ultrastructure of the S2 layer in relation to lignin distribution inPinus radiata tracheids
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ABSTRACT: The ultrastructure of the S2 layer in relation to its lignin distribution was examined using transmission electron microscopy in the tracheids ofPinus radiata. The S2 layer had a striated appearance at low magnification. Observations at higher magnifications showed lignin to be distributed inhomogeneously in this layer, appearing as a mosaic of electron-dense and electron-lucent regions. These regions are scattered, showing a pattern of often interconnecting sinuous features in a predominantly radial profile. The significance of these features of the S2 layer is discussed, particularly in relation to the available information from recent ultrastructural observations on the appearance of cellulose microfibrils and the pattern of their distribution in the S2 layer using rapid freeze-deep etching in conjunction with transmission electron microscopy. Predictions are made as to the likely distribution and arrangement of cellulose microfibrils in the S2 layer based on the pattern of lignin distribution observed in this layer.Journal of Wood Science 05/2012; 48(2):95-98. · 0.96 Impact Factor -
Article: TEM/FE-SEM studies on tension wood fibres of Acer spp., Fagus sylvatica L. and Quercus robur L.
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ABSTRACT: Tension wood (TW) fibres from maple, beech and oak were analysed with special emphasis on the cell wall fine structure and deposition of aromatic compounds within the gelatinous layer (GL). For this purpose, transmission electron microscopy (TEM) was applied after section staining with potassium permanganate. There was evidence for the occurrence of aromatic compounds in the GLs of fibres of all three species. Some GLs showed a concentric sub-layering. Hence, conclusions about the biosynthetic activities during cell wall formation in TW could be derived. Additional information about structural characteristics of TW fibres were obtained by means of field emission electron microscopy. High-resolution micrographs of cell walls were used for measurements of diameter and microfibril angle (MFA) of cellulose aggregates (CAG). CAG of 7nm were observed although their diameter varied greatly in the GLs. MFA in the secondary wall of TW was slightly smaller than in opposite wood. The microscopic methods provided complementary ultrastructural and topochemical information on tension wood fibres. The subcellular localisation of aromatic compounds and the observations of the ultrastructural morphology will contribute to the understanding of origin and functionality of TW and its characteristic GL.Wood Science and Technology 04/2012; 43(7):691-702. · 1.73 Impact Factor
