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

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

Positivity Bounds on Higgs-Portal Dark Matter

We consider the positivity bounds for WIMP scalar dark matter with effective Higgs-portal couplings up to dimension-8 operators. Taking the superposed states for Standard Model Higgs and scalar dark matter, we show that the part of the parameter space for the effective couplings, otherwise unconstrained by phenomenological bounds, is ruled out by the positivity bounds on the dimension-8 derivative operators. We find that dark matter relic density, direct and indirect detection and LHC constraints are complementary to the positivity bounds in constraining the effective Higgs-portal couplings. In the effective theory obtained from massive graviton or radion, there appears a correlation between dimension-8 operators and other effective Higgs-portal couplings for which the strong constraint from direct detection can be evaded. Nailing down the parameter space mainly by relic density, direct detection and positivity bounds, we find that there are observable cosmic ray signals coming from the dark matter annihilations into a pair of Higgs bosons, $WW$ or $ZZ$.Comment: 31 pages, 6 figures, v2: one-loop corrections to the positivity bounds added, version to be published in JHE

The smallest quaternary ammonium salts with ether groups for high-performance electrochemical double layer capacitors

Electrochemical double layer capacitors (EDLCs) are energy storage devices that have been used for a wide range of electronic applications. In particular, the electrolyte is one of the important components, directly related to the capacitance and stability. Herein, we first report a series of the smallest quaternary ammonium salts (QASs), with ether groups on tails and tetrafluoroborate (BF4) as an anion, for use in EDLCs. To find the optimal structure, various QASs with different sized head groups and ether-containing tail groups were systematically compared. Comparing two nearly identical structures with and without ether groups, QASs with oxygen atoms showed improved capacitance, proving that ions with oxygen atoms move more easily than their counterparts at lower electric fields. Moreover, the ether containing QASs showed low activation energy values of conductivities, leading to smaller IR drops during the charge and discharge processes, resulting in an overall higher capacitance

Short Term Effect and Safety of Antidiuretic Hormone in the Patients with Nocturia

Purpose To investigate the short-term safety of antidiuretic hormone in elderly patients with nocturnal polyuria, focus on hyponatremia and others electrolytes disturbances and to assess short-term effects on nocturnal urine output and number of nocturnal voids. Methods Between June 2005 and August 2006, a total of 34 patients with nocturnal polyuria were orally administered 0.2 mg desmopressin tablet at bedtime for two weeks. Serum sodium, others electrolytes, urine sodium and urine osmolarity were assessed in the third days, one week and two weeks after treatment with desmopressin and compared adult group (<65 years of age) with elderly group (≥65 years of age). We assessed the effect of desmopressin using a frequency-volume charts and analysed. Results In total 34 patients (20 adult, 14 elderly) were analyzed. Desmopressin treatment did not significantly change serum and urine electrolytes include soduim concentration in elderly patients comparied with adult patients. Serum sodium concentration below normal range was recorded in 2 patients in elderly group, but no serious adverse events occurred and recovered without sequelae. The mean number of nocturnal voids decresed (54% reduction) and nocturnal urine output decreased (57% reduction) after using desmopressin. Conclusions Desmopressin was well tolerated and effective in elderly patients with nocturnal polyuria without clinically significant hyponatremia

Combined Analysis of the Time-Resolved Transcriptome and Proteome of Plant Pathogen Xanthomonas oryzae pv. oryzae

Xanthomonas oryzae pv. oryzae (Xoo) is a plant pathogen responsible for causing bacterial blight in rice. The immediate alterations in Xoo upon initial contact with rice are essential for pathogenesis. We studied time-resolved genome-wide gene expression in pathogenicity-activated Xoo cells at the transcriptome and proteome levels. The early response genes of Xoo include genes related to cell motility, inorganic ion transport, and effectors. The alteration of gene expression is initiated as early as few minutes after the initial interaction and changes with time. The time-resolved comparison of the transcriptome and proteome shows the differences between transcriptional and translational expression peaks in many genes, although the overall expression pattern of mRNAs and proteins is conserved. The discrepancy suggests an important role of translational regulation in Xoo at the early stages of pathogenesis. The gene expression analysis using time-resolved transcriptome and proteome provides unprecedented valuable information regarding Xoo pathogenesis

Expression and functional role of formyl peptide receptor in human bone marrow-derived mesenchymal stem cells

AbstractWe investigated the expression of formyl peptide receptor (FPR) and its functional role in human bone marrow-derived mesenchymal stem cells (MSCs). We analyzed the expression of FPR by using ligand-binding assay with radio-labeled N-formyl-met-leu-phe (fMLF), and found that MSCs express FPR. FMLF stimulated intracellular calcium increase, mitogen-activated protein kinases activation, and Akt activation, which were mediated by Gi proteins. MSCs were chemotactically migrated to fMLF. FMLF-induced MSC chemotaxis was also completely inhibited by pertussis toxin, LY294002, and PD98059, indicating the role of Gi proteins, phosphoinositide 3-kinase, and extracellular signal regulated protein kinase. N-terminal fragment of annexin-1, Anx-1(2–26), an endogenous agonist for FPR, also induced chemotactic migration of MSCs. Thus MSCs express functional FPR, suggesting a new (patho)physiological role of FPR and its ligands in regulating MSC trafficking during induction of injured tissue repair