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High enantioselectivity (ee up to 84%) has been achieved in heterogeneous asymmetric epoxidation using a silica-bound unsymmetrical (salen)-manganese(III) complex; amorphous silica can be used in the same way as MCM-41, showing a positive effect in the catalyst recycling.
The title molecule forms a honeycomb network of molecular and nitro-trimer synthons with guest species included in the hexagonal voids.
Copper(II) nitrate reacts with the rigid polydentate triple-connecting dpyatriz ligand in acetonitrile to an unprecedented infinite molecular ladder in which five-coordinated copper pseudo-dimer are bridged by nitrate anions and the coordination polymer chains are linked by hexacoordinated copper ions leading to the formation of large guest cavities.
Glucokinase from Bacillus stearothermophilus was irreversibly inactivated by the reactive dichlorotriazinyl dye Procion Blue MX-3G at pH 8.0. The enzyme was protected from inactivation by the substrate MgATP. Kinetic data implied that the dye occupied the MgATP-binding site. The apparent Km values for MgATP and D-glucose were found to be 70 microM and 210 microM respectively, and the Kd of the pure reactive dye was 16 microM; 1 mol of the pure reactive dye bound to 1 mol of glucokinase subunit. The dye was shown to have potential as an affinity probe for glucokinase. Glycerokinase from the same bacterium was inactivated by Procion Blue MX-3G at high concentrations (5 mM), but only after a period of increased enzyme activity. Kinetic data indicated that the dye preferentially attacked the glycerol-binding site. The apparent Km values for MgATP and glycerol were found to be 38 microM and 13 microM respectively, and 4 mol of reactive dye could be bound to 1 mol of glycerokinase subunit. This was surprising in view of the MgATP-dependent elution of glycerokinase from immobilized Procion Blue MX-3G.
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Atrazine technical was evaluated for its embryotoxic, fetotoxic, and teratogenic potential in both rats and rabbits. The compound was orally administered at doses of 0, 10, 70, or 700 mg/kg.d to groups of rats on gestational d 6-15, while rabbits were administered doses of 0, 1, 5, or 75 mg/kg.d on gestational d 7-19. Maternal toxicity was observed at doses greater than or equal to 70 mg/kg.d in rats and at doses greater than or equal to 5 mg/kg.d in rabbits. Minor fetal effects, concurrent with maternal toxicity, were observed in rats at doses greater than or equal to 70 mg/kg.d. Among rabbits, fetal effects concurrent with severe maternal toxicity were only observed at the 75 mg/kg.d dose level. There were no adverse maternal or fetal effects in either rats or rabbits at the low dose levels. These findings indicated that pregnant rabbits were more sensitive than pregnant rats to the effects produced by atrazine technical and the compound was not teratogenic at maternally toxic dose levels in either species.
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Wild-type and an atrazine-resistant biotype of Brassica napus, in which a glycine is substituted for the serine-264 of the D1protein, were grown over a wide range of constant irradiances in a growth cabinet. In the absence of serine-264, the function of photosystem II (PSII) was changed as reflected by changes in chlorophyll fluorescence parameters and in photosynthetic oxygen-evolving activity. The photochemical quenching coefficient was lower, showing that a larger proportion of the primary quinone acceptor is reduced at all irradiances. At low actinic irradiances, the nonphotochemical quenching coefficient was higher, showing a greater tendency for heat emission. Decreased rates of light-limited photosynthesis (quantum yield) and lower oxygen yields per single-turnover flash were also observed. These changes were observed even when the plants had been grown under low irradiances, indicating that the changes in PSII function are direct and not consequences of photoinhibition. In spite of the lowered PSII efficiency under light-limiting conditions, the light-saturated photosynthesis rate of the atrazine-resistant mutant was similar to that of the wild type. An enhanced susceptibility to photoinhibition was observed for the atrazine-resistant biotype compared to the wild type when plants were grown under high and intermediate, but not low, irradiance. We conclude that the replacement of serine by glycine in the D1 protein has a direct effect on PSII function, which in turn causes increased photoinhibitory damage and increased rates of turnover of the D1 protein. Both the intrinsic lowering of light-limited photosynthetic efficiency and the increased sensitivity to photoinhibition probably contribute to reduced crop yields in the field, to different extents, depending on growth conditions.
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Anatomical and physiological characteristics of leaves of triazinesusceptible and -resistant biotypes of common groundsel (Senecio vulgaris L.) were studied in order to explain the differences in light-saturated photosynthetic rates previously reported. Leaves were of uniform leaf plastochron index from greenhouse-grown plants. Susceptible plants had greater leaf fresh and dry weights and leaf areas, while resistant plants had greater specific leaf mass (mg fresh weight/cm(2)). Susceptible plants had greater amounts of total chlorophyll per unit leaf weight and a higher chlorophyll a/b ratio. Soluble protein in leaves was higher in susceptible chloroplasts on a weight and area basis, but similar to resistant chloroplasts on a unit chlorophyll basis. Activity of ribulose 1,5-bisphosphate carboxylase was higher in resistant plants on a fresh weight, leaf area, and milligram chlorophyll basis. Stomatal frequency, length, and arrangement were similar between biotypes, as were transpiration and conductance. Resistant leaves had less air space (v/v), more cells in palisade and spongy mesophyll, and a greater volume of palisade tissue than spongy, when compared to susceptible leaves. Differences in leaf structure and function between biotypes are probably due to a complex of developmental adaptations which may be only indirectly related to modified photosystem II in resistant plants. These results indicate that the consistently lower rates of net photosynthesis and yield in resistant plants cannot be explained solely on the basis of these leaf characteristics. Several possible mechanisms to account for reduced productivity are suggested.
Two atrazine resistant nutants of Chenopodium album L. and their susceptible progenitor were analyzed for lipid composition. In the phosphatidyldiacylglycerol the Delta3-trans-hexadecenoic acid (C16:1 trans) percentage was higher in the two resistant phenotypes. However, this difference appears later in the development of the leaves and is not clearly observed in young leaves and seedlings. Thus, the increase of the C16:1 trans during the leaf development of the resistant phenotypes is probably a secondary effect of the psbA mutation that arises in compensation for some photosynthesis deficiency. The significance of the lipid differences shown between the two resistant mutants is discussed in terms of whether they are responsible of the two different levels of herbicide resistance observed in the field.
The title compound, [Na(C(12)H(8)N(2))(3)](C(3)H(2)N(3)S(3)), contains an Na(+) centre which is ionicly bonded to three 1,10-phenanthroline (phen) ligands and one trithiocyanurate(1-) (ttcH(2)) anion. In the crystal structure, the anions are linked via hydrogen bonds to form linear chains. The S and H atoms of the ttcH(2) anion participate in intermolecular N-H.S hydrogen bonding, with N.S distances of 3.298 (2) and 3.336 (2) A. The phen ligands are almost parallel, with dihedral angles of 3.92 (5), 11.75 (5) and 15.45 (5) degrees; moreover, they are nearly perpendicular to the ttcH(2) chains, with angles of 81.94 (7), 85.86 (7) and 85.96 (7) degrees.
The title compound, C21H15N3O3, crystallizes in two polymorphic forms. In the orthorhombic polymorph, (I), in space group Fdd2 with Z' = 1, the molecules lie in general positions, while in the monoclinic polymorph, (II), in space group C2/c with Z' = 1/2, the molecules lie across twofold rotation axes. In each polymorph, the molecules are linked by a single C-H.pi(arene) hydrogen bond, forming chains in polymorph (I) and sheets in (II).
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The structure of the title compound C9 H11 AsN6O3-2H2O, contains a planar organic moiety bonded to pentavalent arsenic. The lattice is stabilized by a combination of aromatic stacking interactions and by a hydrogen-bonding network involving water molecules of crystallization.
Brown MX-5BR specifically and irreversibly inactivates tryptophanyl-tRNA synthetase from Bacillus stearothermophilus at pH 8.5. The enzyme is protected from inactivation by the substrates tryptophan and ATP and to lesser extents by ADP, AMP, the product inorganic pyrophosphate and other nucleotides such as GTP. The Kd of the pure reactive dye for the enzyme was measured to be 6.7 X 10(-6) M. The Km values of the two substrates tryptophan and MgATP were found to be 1 x 10(-5) M and 5 x 10(-5) M respectively. The aminated dye is a competitive inhibitor of tryptophanyl-tRNA synthetase with respect to both tryptophan and MgATP with Ki values of 2 x 10(-4) M against both substrates. The use of this dye as an active-site-directed affinity label is discussed.
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This paper describes the results of 5 years of research on interactive effects of mixtures of aldicarb, atrazine, and nitrate on endocrine, immune, and nervous system function. The concentrations of chemicals used were the same order of magnitude as current maximum contaminant levels (MCLs) for all three compounds. Such levels occur in groundwater across the United States. Dosing was through voluntary consumption of drinking water. We used fractional and full factorial designs with center replicates to determine multifactor effects. We used chronic doses in experiments that varied in duration from 22 to 103 days. We tested for changes in thyroid hormone levels, ability to make antibodies to foreign proteins, and aggression in wild deer mice, Peromyscus maniculatus, and white outbred Swiss Webster mice, Mus musculus, ND4 strain. Endocrine, immune, and behavior changes occurred due to doses of mixtures, but rarely due to single compounds at the same concentrations. Immune assay data suggest the possibility of seasonal effects at low doses. We present a multiple-level model to help interpret the data in the context of human health and biological conservation concerns. We discuss six testing deficiencies of currently registered pesticides, and suggest areas of human health concerns if present trends in pesticide use continue.