OXIDATION OF MICROCYSTINS BY PERMANGANATE, OZONE AND FERRYL-TETRAPOLYPHOSPHATE COMPLEX: KINETICS AND MECHANISM

Department of Urban and Environmental Engineering (Environmental Science and Engineering)Microcystins (MCs) are the most common cyanotoxins (known as potent hepatotoxins and tumor promoters), and express their toxicity by inhibiting protein phosphatases activity. Because of their highly acute toxicity, the World Health Organization has set a provisional drinking water guideline value of 1 ??g L-1 for MC-LR. Previous studies have shown that physical water treatment methods are not sufficient to control the dissolved MCs. Chemical oxidation has been suggested as a promising alternative to treat the dissolved MCs and has been extensively studied. In this dissertation, three different oxidation systems including potassium permanganate (KMnO4; Mn(VII)), ozone (O3) and Fenton reaction using ferrous ion coupled with tetrapolyphosphate in the presence of oxygen and hydrogen peroxide (i.e., Fe(II)-TPP/O2 and Fe(II)-TPP/H2O2 systems) were investigated for the effective control of MCs in terms of kinetics and mechanism. Firstly, oxidation of six common MCs (MC-RR, -LR, -YR, -LF, -LW and -LA) by Mn(VII) was studied, focusing on the pH- and temperature-dependent reaction kinetics, the effect of dissolved organic matter (DOM), and the oxidation mechanisms. Second-order rate constants for the reactions of the six MCs with Mn(VII) (kMn(VII),MC) were determined at pH 7.2 and 21??C. Their pH- and temperature-dependency was also investigated. The degradation of MCs in natural waters was modeled using a kinetic model composed of Mn(VII) exposure (???[Mn(VII)]dt) values. The correlation analysis between various characteristics of DOM in natural waters and ???[Mn(VII)]dt was investigated to improve the practical applicability of the kinetic prediction model for the removal efficiency of MCs by Mn(VII). In addition, a thorough product study of MC-LR oxidation by Mn(VII) was performed using liquid chromatography-mass spectrometry (LC/MS). Based on the identified 17 products, oxidation pathways are proposed. New oxidation products (primary products from the oxidation of alkene groups, and secondary products, possibly from the hydrolysis of amide groups) were identified. Secondly, the oxidative degradation by O3 and ???OH of the above-mentioned MCs was investigated, focusing on the pH- and temperature-dependent reaction kinetics. Second-order rate constants for the reactions of the six MCs with O3 and ???OH (kO3,MC and k???OH,MC) were determined at pH 6???9 and 5???33??C via the competition kinetic method using cinnamic acid (CA, for O3) and para-chlorobenzoic acid (for ???OH), respectively. Since the second-order rate constants of CA with O3 (kO3,CA) reported in the literature are different from each other, the kO3,CA values at various pH and temperature conditions were directly determined using stopped-flow spectrometry. In order to verify the determined kinetic values, the oxidation of MCs in two natural waters was predicted by the kinetic model using O3 and ???OH exposure values. Lastly, Fe(II)-TPP/O2 and Fe(II)-TPP/H2O2 systems were assessed for the oxidative degradation of MC-LR. The degradation of MC-LR by Fe(II)-TPP/O2 and H2O2 systems was optimized by varying the molar ratio of TPP:Fe(II) and H2O2 concentration. The degradation of MC-LR was also examined by varying the pH from 3 to 11 in the Fe(II)-TPP/O2 and Fe(II)-TPP/H2O2 systems. The results exhibited two pH optima for MC-LR degradation ie, ~ 7 and 9, which can be attributed to pH-dependent reactivity changes of the resultant oxidants (most likely the ferryl-tetrapolyphostate complex, Fe(IV)-TPP complex). LC/MS identified 22 products of MC-LR by the oxidation of Fe(IV)-TPP complex, including four primary oxidation products. One of the primary products, in particular, was formed via oxidative cleavage of the alkene group in the Mdha moiety of MC-LR. This compound and its secondary oxidation products are rarely found when MC-LR is transformed by other oxidants, which is believed to reflect a unique reaction pathway involving Fe(IV)-TPP complex. The reduction of the hepatotoxicity of the reaction solution during the Fe(IV)-TPP oxidation was confirmed by a decrease in MC-LR concentration.ope

Higgs phenomenology in the Peccei-Quinn invariant NMSSM

We study the Higgs phenomenology in the Peccei-Quinn invariant NMSSM (PQ-NMSSM) where the low energy mass parameters of the singlet superfield are induced by a spontaneous breakdown of the Peccei-Quinn symmetry. In the generic NMSSM, scalar mixing among CP-even Higgs bosons is constrained by the observed properties of the SM-like Higgs boson, as well as by the LEP bound on the chargino mass and the perturbativity bound on the singlet Yukawa coupling. In the minimal PQ-NMSSM, scalar mixing is further constrained due to the presence of a light singlino-like neutralino. It is noticed that the $2\sigma$ excess of the LEP $Zb\bar b$ events at $m_{b\bar b}\simeq$ 98 GeV can be explained by a singlet-like 98 GeV Higgs boson in the minimal PQ-NMSSM with low $\tan\beta$, stops around or below 1 TeV, and light doublet-higgsinos around the weak scale.Comment: 31 pages, 4 figures; v2: references added, light stop effects discussed, bound on the Higgs invisible decay rate correcte

Sterol carrier protein-x gene and effects of sterol carrier protein-2 inhibitors on lipid uptake in Manduca sexta

<p>Abstract</p> <p>Background</p> <p>Cholesterol uptake and transportation during the feeding larval stages are critical processes in insects because they are auxotrophic for exogenous (dietary) cholesterol. The midgut is the main site for cholesterol uptake in many insects. However, the molecular mechanism by which dietary cholesterol is digested and absorbed within the midgut and then released into the hemolymph for transportation to utilization or storage sites is poorly understood. Sterol carrier proteins (SCP), non-specific lipid transfer proteins, have been speculated to be involved in intracellular cholesterol transfer and metabolism in vertebrates. Based on the high degree of homology in the conserved sterol transfer domain to rat and human SCP-2, it is supposed that insect SCP-2 has a parallel function to vertebrate SCP-2.</p> <p>Results</p> <p>We identified the <it>Manduca sexta </it>sterol carrier protein-x and the sterol carrier protein-2 (MsSCP-x/SCP-2) gene from the larval fat body and the midgut cDNAs. The MsSCP-x/SCP-2 protein has a high degree of homology in the SCP-2 domain to other insects' SCP-2. Transcripts of MsSCP-2 were detected at high levels in the midgut and the fat body of <it>M. sexta </it>during the larval stages. Recombinant MsSCP-2 bound to NBD-cholesterol with high affinity, which was suppressed by sterol carrier protein-2 inhibitors.</p> <p>Conclusions</p> <p>The results suggest that MsSCP-2 may function as a lipid carrier protein <it>in vivo</it>, and targeting insect SCP-2 may be a viable approach for the development of new insecticides.</p

Eigenvalue Sensitivity Analysis for a Combined Beam Structure with Varying Constraints

An eigenvalue sensitivity formula for a combined beam structure due to the variation of its shape or joint coordinates is proposed based on the Lagrange multiplier technique for a free vibration equation of the structure. The shape variation is decomposed into the length and the orientation variation of each beam to obtain individual effects on the total sensitivity. The sensitivity equations due to the length and the orientation variations are expressed as an energy density form and the cross product of joint forces and displacements respectively. Several numerical examples are also presented to validate the proposed formulation and to show how to implement the idea

Synthesis of layered (2-D) V-based bimetallic oxalates from non-aqueous media that cannot be synthesized from aqueous media

Journal ArticleThe reaction of (NBu4)3[VIII(ox)3] (1, ox = oxalate) and M(II) (M= Fe, Co, Ni, Cu) ions in MeCN, leads to the isolation of V-based coordination polymers of [N(n-Bu)4][FeIIVIII(ox)3]? 0.30{[N(n-Bu)4](BF4)} (2), [N(n-Bu)4][CoIIVIII(ox)3]?0.75{[N(n-Bu)4](BF4)} (3), [N(n-Bu)4][NiIIVIII(ox)3]?0.20{[N(n-Bu)4](BF4)}?0.20MeCN (4), and [N(n-Bu)4][CuIIVIII(ox)2](BF4)2 (5) composition

N,N,N′,N′-Tetra­kis(pyridin-4-yl)methane­diamine monohydrate

In the title compound, C21H18N6·H2O, two 4,4′-dipyridyl­amine groups are linked by a methyl­ene C atom, which sits on a twofold axis. The lattice water mol­ecule is located slightly off a twofold axis, and is therefore disordered over two positions. In the crystal, the organic mol­ecules and the water mol­ecule are linked by O—H⋯N hydrogen bonds. The organic mol­ecules exhibit extensive offset face-to-face π–π inter­actions to symmetry equivalents [centroid–centroid distances = 3.725 (3) and 4.059 (3) Å]

Dinuclear iron(II) complex, [(TPyA)FeII(THBQ 2-)FeII(TPyA)](BF4)2 [TPyA = tris(2-pyridylmethyl)amine; THBQ2- = 2,3,5,6-tetrahydroxy-1,4- benzoquinonate] exhibiting both spin crossover with hysteresis and ferromagnetic exchange

Journal ArticleDinuclear [(TPyA)FeII(THBQ22)FeII(TPyA)](BF4)2 (1) possesses hydrogen bonding interactions that form a 1-D chain, and p-p interactions between the 1-D chains that give rise to a 2-D supramolecular-layered structure, inducing hysteresis in the spin crossover behavior; 1 has shown spin crossover behavior around 250 K with thermal hysteresis and ferromagnetic interactions at low temperature