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1.
It is thought that the extensive industrial use of arsenic, gallium and indium, which have applications as the materials for III–V semiconductors, will increase human exposure to these compounds in the near future. We have undertaken the development of new biological indicators for assessing exposure to these elements. Element-specific alterations in protein synthesis patterns were expected to occur following exposure to arsenic compounds. We examined alterations in protein synthesis in primary cultures of rat kidney proximal tubule epithelial cells by sodium arsenite, gallium chloride and indium chloride, utilizing two-dimensional gel electrophoresis. After incubation with the chemicals for 20 h, newly synthesized proteins were labeled with [35S]methionine. A protein with a molecular weight (Mr) of 30 000 was markedly induced on exposure to 10 μM arsenite or 300 μM gallium chloride, and synthesis of proteins with Mr values of 85 000, 71 000, 65 000, 51 000, 38 000 and 28 000 were also increased by exposure to arsenite and gallium chloride. No significant changes were observed upon exposure to indium. Some of these increased proteins could be heat-shock proteins. 相似文献
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Christabel E. Fowler Catherine Buchber Joël Patarin Alain Walcarius 《Applied Surface Science》2007,253(12):5485-5493
Diatomaceous earth was functionalized by grafting organotrialkoxysilane precursors onto the surface of the porous silica cell walls of this biomineral. Vinyl- and mercapto-containing structures were prepared in aqueous media without disruption of the diatomic architecture. Successful grafting of the organic moieties was confirmed using solid state 29Si MAS NMR spectroscopy, and the presence of the intact diatom framework by scanning electron microscopy. The sorption properties of mercaptopropyl-functionalized diatoms towards heavy metals was studied by measuring the accessibility and diffusion rates of mercury(II) species to the binding sites (-SH) by the means of electrochemical methods. 相似文献
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Minimizing molecular mobility for desiccation preservation of biologics close to ambient temperature using trehalose glasses require quantitative characterization of their enthalpic relaxation at various end water contents. Differential scanning calorimetry (DSC) was used to characterize three different water contents: 0%, 1.5% and 10% over a wide range of aging temperatures. Results showed the characteristic time (τ) varies both with the water content and the aging temperature. τ increased with lowered aging temperature but showed a non-monotonous relationship as a function of water content. Fragility of trehalose glasses was analyzed using thermophysical parameters obtained from relaxation studies. The study showed trehalose to be a fragile glass former at all water contents, with 0% water samples showing a relatively stronger glass. A compromise between molecular mobility and glass fragility led to an optimal water content close to 1.5% and an aging temperature close to room temperature. This would ensure a τ value of 9000 h, which corresponds to a storage period of a year. 相似文献
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De Proft F Fowler PW Havenith RW Schleyer Pv Van Lier G Geerlings P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(4):940-950
Current-density maps were calculated by the ipsocentric CTOCD-DZ/6-311G** (CTOCD-DZ=continuous transformation of origin of current density-diamagnetic zero) approach for three sets of inorganic monocycles: S(4) (2+), Se(4) (2+), S(2)N(2), P(5) (-) and As(5) (-) with 6 pi electrons; S(3)N(3) (-), S(4)N(3) (+) and S(4)N(4) (2+) with 10 pi electrons; and S(5)N(5) (+) with 14 pi electrons. Ipsocentric orbital analysis was used to partition the currents into contributions from small groups of active electrons and to interpret the contributions in terms of symmetry- and energy-based selection rules. All nine systems were found to support diatropic pi currents, reinforced by sigma circulations in P(5) (-), As(5) (-), S(3)N(3) (-), S(4)N(3) (+), S(4)N(4) (2+) and S(5)N(5) (+), but opposed by them in S(4) (2+), Se(4) (2+) and S(2)N(2). The opposition of pi and sigma effects in the four-membered rings is compatible with height profiles of calculated NICS (nucleus-independent chemical shifts). 相似文献
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Deza M Dutour M Fowler PW 《Journal of chemical information and computer sciences》2004,44(4):1282-1293
Two connections between fullerene structures and alternating knots are established. Knots may appear in two ways: from zigzags, i.e., circuits (possibly self-intersecting) of edges running alternately left and right at successive vertices, and from railroads, i.e., circuits (possibly self-intersecting) of edge-sharing hexagonal faces, such that the shared edges occur in opposite pairs. A z-knot fullerene has only a single zigzag, doubly covering all edges: in the range investigated (n = 74) examples are found for C(34) and all C(n)() with n >/= 38, all chiral, belonging to groups C(1), C(2), C(3), D(3), or D(5). An r-knot fullerene has a railroad corresponding to the projection of a nontrivial knot: examples are found for C(52) (trefoil), C(54) (figure-of-eight or Flemish knot), and, with isolated pentagons, at C(96), C(104), C(108), C(112), C(114). Statistics on the occurrence of z-knots and of z-vectors of various kinds, z-uniform, z-transitive, and z-balanced, are presented for trivalent polyhedra, general fullerenes, and isolated-pentagon fullerenes, along with examples with self-intersecting railroads and r-knots. In a subset of z-knot fullerenes, so-called minimal knots, the unique zigzag defines a specific Kekulé structure in which double bonds lie on lines of longitude and single bonds on lines of latitude of the approximate sphere defined by the polyhedron vertices. 相似文献
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Some surface aspects of the thermal and X-ray induced degradation of a cellulose nitrate have been studied by FAB/SIMS.The pristine material gives peaks at 30 and 46 amu, indicative of NO+ and NO2+ originating from the nitrate ester groups. The thermally degraded material indicates these peaks at slightly lower intensities, whereas the X-ray degraded material shows little evidence for their appearance. These data complement recent ESCA data on the same systems.1The conclusion is that electromagnetic degradation is predominantly a surface effect, whereas thermal degradation is a bulk oriented phenomenon. 13C nmr has been used to add further evidence for this last point. 相似文献