Identification of mercury species in coal combustion by-products from power plants using thermal desorption-atomic fluorescence spectrometry on-line coupling system.

Along with the environmental protection policies becoming strict in China, the air pollution control devices (especially selective catalytic reduction (SCR)) are widely equipped in coal-fired power plants. The installation and run of these devices will inevitably affect mercury (Hg) species distribution in coal fired by-products such like fly ash (FA) and gypsum. In this work, a new on-line coupling system based on atomic fluorescence spectrometry (AFS) with a home-made chromatographic workstation was successfully developed to identify Hg species through thermal programmed desorption (TPD). The influences of matrix, furnace temperature, and carrier gas flow on analytical performance were investigated and the parameters were optimized. The FA and gypsum samples from coal-fired power plants equipped with SCR were collected and the mercury species were analyzed by the developed coupling system. HgCl2 and HgO were the main species in FA, while Hg2Cl2 and HgO were the main species in gypsum. All of Hg species in the studied FA and gypsum samples were released below 400 °C. A sequential extraction procedure was applied to further verify the operational Hg species including mobile and non-mobile fractions in FA and gypsum samples. This study demonstrated that AFS coupled with TPD procedure was an effective method to analyze Hg species in coal combustion by-products from power plants.

An immunomagnetic separation and bifunctional Au nanoparticle probe-based multiamplification electrochemical strategy.

A novel electrochemical magnetoimmunosensor for the rapid and sensitive detection of carcinoembryonic antigen (CEA) was fabricated based on a combination of high-efficiency immunomagnetic separation, bifunctional Au-nanoparticle (bi-AuNP) probes, and enzyme catalytic amplification. The reaction carrier magnetic beads (MBs) effectively reduced the toxicity of the complex sample to the working electrode, and the signal carrier bi-AuNP probes loaded a large amount of signal molecules, both of which enhanced the signal-to-noise ratio and further improved the detection sensitivity. A detection limit as low as 0.11 pg/mL was achieved for CEA detection based on the immunomagnetic separation and bi-AuNP probe-based multiamplification strategy, and the strategy was further successfully applied in human serum samples. The transducer was regenerated via a simple washing procedure, which enabled the detection of all samples on a single electrode with high reproducibility. The proposed strategy, which has the merits of high sensitivity, selectivity, and reproducibility exhibits great potential for detection in complex samples.

Discovery, Synthesis, and Evaluation of Oxynitidine Derivatives as Dual Inhibitors of DNA Topoisomerase IB (TOP1) and Tyrosyl-DNA Phosphodiesterase 1 (TDP1), and Potential Antitumor Agents.

Tyrosyl-DNA phosphodiesterase 1 (TDP1) is a recently discovered enzyme repairing DNA lesions resulting from stalled topoisomerase IB (TOP1)-DNA covalent complex. Inhibiting TDP1 in conjunction with TOP1 inhibitors can boost the action of the latter. Herein, we report the discovery of the natural product oxynitidine scaffold as a novel chemotype for the development of TOP1 and TDP1 inhibitors. Three kinds of analogues, benzophenanthridinone, dihydrobenzophenanthridine, and benzophenanthridine derivatives, were synthesized and evaluated for both TOP1 and TDP1 inhibition and cytotoxicity. Analogue 19a showed high TOP1 inhibition (+++) and induced the formation of cellular TOP1cc and DNA damage, resulting in cancer cells apoptosis at nanomolar concentration range. In vivo studies indicated that 19a exhibits antitumor efficiency in HCT116 xenograft model. 41a exhibited additional TDP1 inhibition with IC50 value of 7 µM and synergistic effect with camptothecin in MCF-7 cells. This work will facilitate future efforts for the discovery of natural product-based TOP1 and TDP1 inhibitors.

Synthesis and biological evaluation of 6-substituted indolizinoquinolinediones as catalytic DNA topoisomerase I inhibitors.

In our previous work, indolizinoquinolinedione derivative 1 was identified as a Top1 catalytic inhibitor. Herein, a series of 6-substituted indolizinoquinolinedione derivatives were synthesized through modification of the parent compound 1. Top1 cleavage and relaxation assays indicate that none of these novel compounds act as classical Top1 poison, and that the compounds with alkylamino terminus at C-6 side chain, including 8, 11-16, 18-21, 25, 26 and 28-30, are the most potent Top1 catalytic inhibitors. Top1-mediated unwinding assay demonstrated that 14, 22 and 26 were Top1 catalytic inhibitors without Top1-mediated unwinding effect. Moreover, MTT results showed that compounds 26, 28-30 exhibit significant cytotoxicity against human leukemia HL-60 cells, and that compound 26 exerts potent cytotoxicity against A549 lung cancer cells at nanomolar range.

Fluorescein-labeled "arch-like" DNA probes for electrochemical detection of DNA on gold nanoparticle-modified gold electrodes.

In the present study, a gold nanoparticle-modified gold electrode (nanogold electrode) was used to develop a novel fluorescein electrochemical DNA biosensor based on a target-induced conformational change. The nanogold electrode was obtained by electrodepositing gold nanoparticles onto a bare gold electrode. This modification not only immobilized probe oligonucleotides, but also adsorbed fluorescein onto the surface of the gold nanoparticles to form an "arch-like" structure. This article compares the electrochemical signal changes caused by the hybridization of "arch-like" DNA on nanogold electrode and linear DNA on bare gold electrode. The results showed that the adsorption effect of nanogold can enhance the sensitivity of the sensor. The linear range of target ssDNA is from 2.0 × 10(-9)M to 2.0 × 10(-8)M with a correlation coefficient of 0.9956 and detection limit (3σ) of 7.10 × 10(-10)M. Additionally, the specificity and hybridization response of this simple sensor were investigated.

3-Benzyl-sulfanyl-5-(4-phenyl-1H-1,2,3-triazol-1-ylmeth-yl)-4H-1,2,4-triazol-4-amine.

The mol-ecule of the title compound, C(18)H(17)N(7)S, is non-planar, with a dihedral angle of 71.4 (4)° between the two triazole rings, and an angle of 15.5 (3)° between the two phenyl rings. An intra-molecular N-H⋯S hydrogen bond forms a five-membered ring.

2-(4-Phenyl-1H-1,2,3-triazol-1-yl)-N-(p-tol-yl)acetamide.

In the title mol-ecule, C(17)H(16)N(4)O, the triazole ring makes dihedral angles of 29.00 (1) and 77.74 (1)°, respectively, with the phenyl and benzene rings. In the crystal structure, inter-molecular N-H⋯O hydrogen bonds link the mol-ecules into chains extending along the c axis.

[Hematoporphyrin derivative-mediated photodynamic therapy for human colon carcinoma: a comparative study with LoVo and CoLo205 cells in vitro].

OBJECTIVE: To investigate the killing effect of photodynamic therapy (PDT) mediated by hematoporphyrin derivative (HpD) on human colon carcinoma LoVo and CoLo205 cells in vitro. METHODS: LoVo and CoLo205 cells cultured in vitro were incubated in the presence of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0 microg/ml HpD for 4 h and exposed to different light doses delivered using a semiconductor laser at 630 nm with the energy density of 2, 5, 10, and 20 J/cm(2). After further culture for 24 h, the survival rate of LoVo and CoLo205 cells were analyzed by MTT assay, and the cellular fluorescence intensities of HpD were measured with a luminescence spectrometer. RESULTS: HpD-PDT resulted in effective cell killing to a comparable magnitude in LoVo and CoLo205 cells cultured in vitro (P>0.05). The killing effects were positively correlated with the concentration of HpD and the dosage of laser irradiation. Exposure to 20 J/cm(2) resulted in an IC(50) of LoVo and CoLo205 cells of 0.4 and 0.6 microg/ml respectively, which were not significantly different (P>0.05). The cellular HpD fluorescence intensities were also similar between the two cells. CONCLUSION: HpD-PDT may effectively kill LoVo and CoLo205 cells cultured in vitro.

The role of the glutathione antioxidant system in gut barrier failure in a rodent model of experimental necrotizing enterocolitis.

BACKGROUND: Evidence suggests that intestinal barrier failure in necrotizing enterocolitis results in part from overproduction of nitric oxide and other toxic oxidant species that result in enterocyte death and intestinal barrier failure. We hypothesize that the glutathione detoxifying system is important in maintaining intestinal barrier integrity by protecting against nitrosative stress. METHODS: Newborn rats were subjected to hypoxia (5% O2, tid) and fed formula by gavage (NEC), or were breast-fed without hypoxia (BF). Rats were killed and the distal ilea were harvested for RNA, protein, and morphologic studies. RNA underwent cDNA microarray analysis. To assess glutathione in protecting against nitrosative stress, IEC-6 cells were exposed to SIN-1 and/or L-buthionine-(S,R)-sulfoximine (BSO), a glutathione inhibitor. Cells were analyzed for glutathione-S-transferase activity, apoptosis and mitochondrial function. RESULTS: BF controls developed normal intestinal architecture, whereas NEC animals sustained damage to the intestinal epithelium. Microarray analysis demonstrated that 93 genes were overexpressed in NEC compared with controls. In the array, glutathione-S-transferase pi and alpha 2, GSH-dependent detoxifying enzymes, RNA were upregulated compared with BF controls. IEC-6 cells exposed to SIN-1/BSO produced an increase in apoptosis. Poly ADP-ribosylpolymerase cleavage and apoptosis-inducing factor (AIF) nuclear localization, markers of apoptosis, were seen in IEC-6 cells exposed to SIN-1/BSO as opposed to media controls. CONCLUSION: These data support the hypothesis that GSH antioxidant system plays a crucial role in gut barrier protection by attenuating enterocyte death.

Peroxynitrite inhibits enterocyte proliferation and modulates Src kinase activity in vitro.

Overproduction of nitric oxide (NO) or its toxic metabolite, peroxynitrite (ONOO-), after endotoxemia promotes gut barrier failure, in part, by inducing enterocyte apoptosis. We hypothesized that ONOO- may also inhibit enterocyte proliferation by disrupting the Src tyrosine kinase signaling pathway, thereby blunting repair of the damaged mucosa. We examined the effect of ONOO- on enterocyte proliferation and Src kinase activity. Sprague-Dawley rats were challenged with LPS or saline, whereas intestinal epithelial cell line cells were treated with ONOO- or decomposed ONOO- in vitro. Enterocyte proliferation in vivo and in vitro was measured by 5-bromo-2'-deoxyuridine (BrdU) or [3H]thymidine incorporation. Src kinase activity in cell lysates was determined at various times. LPS challenge in vivo and ONOO- treatment in vitro inhibited enterocyte proliferation. ONOO- treatment blunted the activity of Src and its downstream target, focal adhesion kinase, in a time-dependent manner. ONOO- blocked mitogen (FBS, EGF)-induced enterocyte proliferation and Src phosphorylation while increasing Src nitration. Thus ONOO- may promote gut barrier failure not only by inducing enterocyte apoptosis but also by disrupting signaling pathways involved in enterocyte proliferation.

Mechanism of intestinal-derived fungal sepsis by gliotoxin, a fungal metabolite.

BACKGROUND/PURPOSE: Gut barrier dysfunction resulting from fungal overgrowth may be caused by the interaction of gliotoxin (GT), a fungal metabolite, with enterocytes. The goal of this study was to determine the mechanisms by which gliotoxin (GT), a fungal metabolite, causes enterocyte apoptosis. METHODS: The authors measured enterocyte apoptosis, caspase-3 activity, pro-caspase-3, and poly (ADP-ribose) polymerase (PARP) cleavage in GT-exposed IEC-6 cells, a rat intestinal cell line. RESULTS: GT induced apoptosis in IEC-6 cells. The pan-caspase inhibitor ZVAD suppressed this GT-mediated apoptosis. GT induced a 15-fold increase in caspase-3 activity over media control. The authors detected PARP cleavage by after GT exposure. DTT pretreatment decreased apoptosis compared with GT alone. CONCLUSIONS: This study supports the concept that fungal overgrowth may lead to gut barrier dysfunction by the local release of gliotoxin and the induction enterocyte apoptosis.

NF-kappaB inhibition enhances peroxynitrite-induced enterocyte apoptosis.

BACKGROUND: Sustained overproduction of nitric oxide and peroxynitrite (ONOO(-)) in conditions such as necrotizing enterocolitis and inflammatory bowel disease may promote gut barrier failure by inducing enterocyte apoptosis. NF-kappaB is upregulated in the gut during inflammation and, in addition to its proinflammatory effects, may upregulate protective or antiapoptotic factors such as inhibitor of apoptosis proteins (IAPs). We have previously demonstrated that NF-kappaB inhibition increases cytokine-induced enterocyte apoptosis; however, the effect of NF-kappaB on ONOO(-)-induced enterocyte apoptosis is unknown. MATERIALS AND METHODS: Rat intestinal epithelial cells (IEC-6) were transfected with the adenoviral vector AdIkappaB or AdlacZ. AdIkappaB contains a mutated form of IkappaB which functions as a superrepressor of NF-kappaB. Cells were then treated with 50 microM ONOO(-) or decomposed ONOO(-). Apoptosis was then determined by flow cytometry with annexin V-FITC and propidium iodide staining. Caspase activation and IAP, Bcl-2, Bad, and Bax expression were examined using Western blot analysis, and NF-kappaB activation was determined via electrophoretic mobility shift assay (EMSA). RESULTS: Inhibition of NF-kappaB with AdIkappaB significantly enhanced ONOO(-)-induced apoptosis in IEC-6 cells. ONOO(-) treatment did not activate NF-kappaB in IEC-6 cells as determined by EMSA. There was no difference in IAP, Bcl-2, Bad, and Bax expression between nontransfected, AdlacZ-transfected, and AdIkappaB-transfected cells. Baseline procaspase 3 activation was increased in AdIkappaB-transfected cells. CONCLUSIONS: NF-kappaB inhibition enhances ONOO(-)-induced enterocyte apoptosis, suggesting that NF-kappaB upregulates a protective factor. This protective factor does not appear to be an IAP or Bcl-2 family member and may be expressed constitutively, since ONOO(-) did not activate NF-kappaB over baseline levels of activation.