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541.
Priadi C Le Pape P Morin G Ayrault S Maillot F Juillot F Hochreutener R Llorens I Testemale D Proux O Brown GE 《Environmental science & technology》2012,46(7):3712-3720
Zinc is one of the most widespread trace metals (TMs) in Earth surface environments and is the most concentrated TM in the downstream section of the Seine River (France) due to significant anthropogenic input from the Paris conurbation. In order to better identify the sources and cycling processes of Zn in this River basin, we investigated seasonal and spatial variations of Zn speciation in suspended particulate matter (SPM) in the oxic water column of the Seine River from upstream to downstream of Paris using synchrotron-based extend X-ray absorption fine structure (EXAFS) spectroscopy at the Zn K-edge. First-neighbor contributions to the EXAFS were analyzed in SPM samples, dried and stored under a dry nitrogen atmosphere or under an ambient oxygenated atmosphere. We found a sulfur first coordination environment around Zn (in the form of amorphous zinc sulfide) in the raw SPM samples stored under dry nitrogen vs an oxygen first coordination environment around Zn in the samples stored in an oxygenated atmosphere. These findings are supported by scanning electron microscopy and energy dispersive X-ray spectrometry observations. Linear combination fitting of the EXAFS data for SPM samples, using a large set of EXAFS spectra of Zn model compounds, indicates dramatic changes in the Zn speciation from upstream to downstream of Paris, with amorphous ZnS particles becoming dominant dowstream. In contrast, Zn species associated with calcite (either adsorbed or incorporated in the structure) are dominant upstream. Other Zn species representing about half of the Zn pool in the SPM consist of Zn-sorbed on iron oxyhydroxides (ferrihydrite and goethite) and, to a lesser extent, Zn-Al layered double hydroxides, Zn incorporated in dioctahedral layers of clay minerals and Zn sorbed to amorphous silica. Our results highlight the importance of preserving the oxidation state in TM speciation studies when sampling suspended matter, even in an oxic water column. 相似文献
542.
Yassine El Mendili Nirina Randrianantoandro Jean-Marc Greneche Fabien Grasset 《Science and Technology of Advanced Materials》2016,17(1):597-609
The effects of laser irradiation on γ-Fe2O3 4 ± 1 nm diameter maghemite nanocrystals synthesized by co-precipitation and dispersed into an amorphous silica matrix by sol-gel methods have been investigated as function of iron oxide mass fraction. The structural properties of γ-Fe2O3 phase were carefully examined by X-ray diffraction and transmission electron microscopy. It has been shown that γ-Fe2O3 nanocrystals are isolated from each other and uniformly dispersed in silica matrix. The phase stability of maghemite nanocrystals was examined in situ under laser irradiation by Raman spectroscopy and compared with that resulting from heat treatment by X-ray diffraction. It was concluded that ε-Fe2O3 is an intermediate phase between γ-Fe2O3 and α-Fe2O3 and a series of distinct Raman vibrational bands were identified with the ε-Fe2O3 phase. The structural transformation of γ-Fe2O3 into α-Fe2O3 occurs either directly or via ε-Fe2O3, depending on the rate of nanocrystal agglomeration, the concentration of iron oxide in the nanocomposite and the properties of silica matrix. A phase diagram is established as a function of laser power density and concentration. 相似文献
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Cristina Martinez-Hernandez Mariana del Carmen Aguilera-Puga Dr. Fabien Plisson 《Chembiochem : a European journal of chemical biology》2023,24(14):e202300058
Current cancer treatments damage healthy cells and tissues, causing short-term and long-term side effects. New treatments are desired that show greater selectivity toward cancer cells and evade the common mechanisms of multidrug resistance. Membranolytic anticancer peptides (mACPs) hold promise against cancer and multidrug resistance. Amphipathicity, hydrophobicity, and net charge of mACPs participate in their respective interactions with cell membranes and their overall inhibition of cancer cells. To support the design of cell-line selective mACPs, we investigated the relationships that amino acid composition, physicochemical properties, sequence motifs, and sequence homology could have with their potency and selectivity towards several healthy and cancer cell lines. Sequence length and net charge are known to affect the selectivity of mACPs between cancer and healthy cell lines. Our study reveals that increasing the net charge or flexibility (i. e., small and aliphatic residues) influences their selectivity between cancer cell lines with comparable lipid compositions. 相似文献