Molecular basis of Toxoplasma gondii oryzalin resistance from a novel α-tubulin binding site model

Oryzalin (ORY) is a dinitroaniline derivative that inhibits the microtubule polymerization in plants and parasitic protozoa by selectively binding to the α-tubulin subunit. This herbicidal agent exhibits good antiprotozoal activity against major human parasites, such as Toxoplasma gondii (toxoplasmosis), Leishmania mexicana (leishmaniasis), and Plasmodium falciparum (malaria). Previous chemical mutagenesis assays on T. gondii α-tubulin (TgAT) have identified key mutations that lead to ORY resistance. Herein, we employed alchemical free energy methods and molecular dynamics simulations to determine if the ORY resistance mutations either decrease the TgAT's affinity of the compound or increase the protein stability. Our results here suggest that L136F and V202F mutations significantly decrease the affinity of ORY to TgAT, while T239I and V252L mutations diminish TgAT's flexibility. On the other hand, protein stability predictors determined that R243S mutation reduces TgAT stability due to the loss of its salt bridge interaction with E27. Interestingly, molecular dynamics simulations confirm that the loss of this key interaction leads to ORY binding site closure. Our study provides a better insight into the TgAT-ORY interaction, further supporting our recently proposed ORY-binding site.

A combination of Olea europaea leaf extract and Spirodela polyrhiza extract alleviates atopic dermatitis by modulating immune balance and skin barrier function in a 1-chloro-2,4-dinitrobenzene-induced murine model

BACKGROUND

Atopic dermatitis is a chronic inflammatory skin disease in humans. Although Olea europaea leaf extract (OLE) and Spirodela polyrhiza extract (SPE) have been used to protect against skin damage, the effects of their combined administration on atopic dermatitis have yet to studied.

PURPOSE

In this study, we evaluated the potential therapeutic effects of an OLE and SPE combination on the progression of atopic dermatitis and the possible mechanisms underlying these effects in 1-chloro-2,4-dinitrobenzene (DNCB)-treated NC/Nga mice.

METHODS

Atopic dermatitis was induced by topical application of 0.2% w/v DNCB prepared in an olive oil:acetone solution (1:3), and thereafter OLE, SPE and OLE + SPE were administered orally for 5 weeks. We determined atopic dermatitis symptoms, serum IgE levels, and levels of cytokine- and gene expression in the dorsal skin and splenocytes, and performed histological and immune cell subtype analyses. The expression of skin barrier-related proteins (filaggrin, sirtuin 1, and claudin 1) was also evaluated.

RESULTS

The OLE + SPE combination significantly ameliorated atopic dermatitis symptoms, including dermatitis scores, and reduced epidermal thickness and infiltration of different inflammatory cells in mice with DNCB-induced atopic dermatitis. It also significantly reduced the number of CD4⁺, CD8⁺, and CD4⁺/CD69⁺ T cells; immunoglobulin E-producing B cells (CD23⁺/B220⁺) in the axillary lymph nodes; CD3⁺ T-cell eosinophils (chemokine-chemokine receptor 3⁺/CD11b⁺) in the skin; and CD3⁺ T cells, immunoglobulin E-producing B cells (CD23⁺/B220⁺), and eosinophils in peripheral blood mononuclear cells. Additionally, the experimental combination lowered levels of serum immunoglobulin E and histamine, as well as Th2-mediated cytokines, and interleukin-4, -5, and -13, whereas it increased the levels of Th1-mediated cytokine interferon-γ in splenocytes. Furthermore, the preparation significantly restored expression of the skin barrier-related proteins filaggrin, sirtuin 1, and claudin 1, and also reduced the expression of the inflammatory cytokine interleukin-6 and chemokine-chemokine receptor 3, as well as the pruritus-related cytokine interleukin-31 and interleukin-31 receptor, in atopic dermatitis skin lesions.

CONCLUSION

Taken together, our findings indicate that administration of a combination of OLE and SPE can alleviate atopic dermatitis symptoms by regulating immune balance and skin barrier function and may be an effective therapeutic option for the treatment of atopic dermatitis.

Tetrahydro[5]helicene fused nitrobenzoxadiazole as a fluorescence probe for hydrogen sulfide, cysteine/homocysteine and glutathione

Biological thiols including homocysteine (Hcy), cysteine (Cys), hydrogen sulfide (H₂S) and glutathione (GSH) play crucial roles in various pathological and physiological processes. The development of optical probes for biothiols has been an active research area in recent years. Herein, a new turn-on fluorescence probe (HD-NBD) was designed and synthesized by fusing tetrahydro[5]helicene and 7-nitro-2,1,3-benzoxadiazole (NBD) for simultaneous discrimination of Hcy/Cys, H₂S and GSH in aqueous solution. This probe is able to show unique absorbance enhancement at 548 nm for H₂S and additional fluorescence enhancement at 536 nm only for Cys/Hcy, which can be used to discriminate H₂S, Cys/Hcy and GSH simultaneously. In addition, HD-NBD also shows low background without any self-fluorescence, as well as high selectivity toward common biothiols. The low detection limits of this probe are about 0.15 μM for Hcy with a wide linear range (1-80 μM), 0.36 μM for Cys (linear range: 1-45 μM), 0.79 μM for H₂S (linear range: 1-80 μM) and 4.44 μM for GSH (linear range: 1-60 μM). Moreover, HD-NBD can identify Hcy/Cys, H₂S from GSH and other amino acids with high sensitivity and selectivity, therefore it could be used for detecting endogenous and exogenous Hcy/Cys under biological condition.

Multiple Hydrogen Loss from [M + H]+ and [a]+ ions of Peptides in MALDI In-Source Decay Using a Dinitro-Substituted Matrix

The formation and radical-directed dissociation of multiple hydrogen-abstracted peptide cations [M + H - mH]·⁺ has been reported using MALDI-ISD with dinitro-substituted matrices. The MALDI-ISD of synthetic peptides using 3,5-dinitrosalicylic acid (3,5-DNSA) and 3,4-dinitrobenzoic acid (3,4-DNBA) as matrices resulted in multiple hydrogen abstraction from the analyte [M + H]⁺ and fragment [a]⁺ ions, i.e., [M + H - mH]⁺ and [a - mH]⁺ (m = 1-8). All of the ISD spectra showed unusually intense [a]⁺ ions originating from cleavage at the Cα-C bond of the Leu-Xxx residues when peptides without Phe/Tyr/His/Cys residues were used. The intensity of the [a_n]⁺ series ions generated using 3,5-DNSA and 3,4-DNBA rapidly decreased with increasing residue number n, suggesting cleavage at multiradical sites of [M + H - mH]^•+. It was suggested that multiple hydrogen abstraction from protonated peptides [M + H]⁺ mainly takes place from the backbone amide nitrogen.

Meptyldinocap and azoxystrobin residue behaviors in different ecosystems under open field conditions and distribution on processed cucumber

BACKGROUND

Several diseases and insects may cause damage to the normal growth of cucumber. Azoxystrobin and meptyldinocap, because of their novel mode of action, are effective against pathogens that have developed reduced sensitivity to other fungicides. Azoxystrobin is persistent in various crops and environments. However, there is a lack of research on the dissipation of these two pesticides, especially meptyldinocap.

RESULTS

Analytes could be quantified with decent recoveries of 90-101%, with relative standard deviations (RSDs) of 3.0-10.1%. The terminal residues of meptyldinocap and azoxystrobin in cucumber were all < limit of quantification (LOQ) (0.02 and 0.05 mg kg^-1 ). The half-lives of meptyldinocap and azoxystrobin were 0.8-1.1 and 1.2-2.8 days, respectively. The processing factors (PFs) for washing were all < 1, but the removal rate for washing was < 29.0%. Peeling had a significant effect on the removal of pesticide. The largest residue reductions were noticed through the pickling process, but special care should be taken regarding residues in the pickling solution as pesticides could transfer to them from cucumber. A more interesting finding was that the degradation of two pesticides was accelerated by the addition of calcium oxide.

CONCLUSION

Pesticide residues on cucumber decreased after these processes. These results enable the health-risks from dietary exposures to pesticide residues to be characterized. They enable maximum residue limits (MRLs) to be established for pesticide residues in food products. They also assist the optimization of food processing with regard to pesticide residue dissipation. © 2019 Society of Chemical Industry.

Cation-group interaction as the predominant force for adsorption of substituted dinitrobenzenes by smectite clays

Elucidation of the interaction between NACs and smectites is important to the understanding of the potential for transport of nitroaromatic compounds (NACs) in soils and to implementation of NAC-contaminated soil remediation. The adsorption of dinitrotoluene isomers (DNTs) and substituted dinitrobenzenes (SDNBs) by smectite was determined by batch equilibration and characterized by FTIR and XPS, along with molecular dynamics simulations. The adsorption of DNTs differed substantially among the isomers, attributed to the overall degree of nitro deflection relative to the aromatic ring plane. The substituents in SDNBs strengthened the electrostatic interaction between smectite K⁺ and nitro groups, facilitating SDNB adsorption to smectite. The competition between 2,4-DNT and 1,3-DNB, as well as the inclusion complexation of K⁺ by crown ether 18c6e, both reduced 2,4-DNT adsorption to smectite by weakening the K⁺-nitro interaction. All the results demonstrated that the electrostatic interaction between smectite K⁺ and nitro of NACs was the predominant force in mediating their adsorption. This was supported by FTIR spectra that the N-O bands shifted due to the weakening of N-O bonds and strengthening of C-N bonds via the electron transfer to cations. The XPS of smectite further manifested the cation-nitro interactions that the binding energies of K 2p 1/2, K 2p 3/2, and Si 2p shifted higher with 1,3-DNB adsorbed. Molecular dynamics simulations indicated the aromatic planes of 2,4-DNP and 2,4-DNAs were parallel to the basal plane of smectite and the oxygens of nitro groups in the molecules were directly coordinated with smectite K⁺.

Inhibition of C. albicans Dimorphic Switch by Cobalt(II) Complexes with Ligands Derived from Pyrazoles and Dinitrobenzoate: Synthesis, Characterization and Biological Activity

Seven cobalt(II) complexes of pyrazole derivatives and dinitrobenzoate ligands were synthesized and characterized. The single-crystal X-ray diffraction structure was determined for one of the ligands and one of the complexes. The analysis and spectral data showed that all the cobalt complexes had octahedral geometries, which was supported by DFT calculations. The complexes and their free ligands were evaluated against fungal strains of Candida albicans and emerging non-albicans species and epimastigotes of Trypanosoma cruzi. We obtained antifungal activity with a minimum inhibitory concentration (MIC) ranging from 31.3 to 250 µg mL-1. The complexes were more active against C. krusei, showing MIC values between 31.25 and 62.5 µg mL-1. In addition, some ligands (L1-L6) and complexes (5 and Co(OAc)2 · 4H2O) significantly reduced the yeast to hypha transition of C. albicans at 500 µg mL-1 (inhibition ranging from 30 to 54%). Finally, the complexes and ligands did not present trypanocidal activity and were not toxic to Vero cells. Our results suggest that complexes of cobalt(II) with ligands derived from pyrazoles and dinitrobenzoate may be an attractive alternative for the treatment of diseases caused by fungi, especially because they target one of the most important virulence factors of C. albicans.

Rapid and selective detection of biothiols by novel ruthenium(II) complex-based phosphorescence probes

Considering the excellent photochemical properties of ruthenium(II) complexes, two new ruthenium(II) complexes, RuL¹-DNBS and RuL²-DNBS, have been developed as phosphorescence probes for detection of biothiols in 100:1 (v/v) Hepes buffer (20 mM, pH = 7.2)/CH₃CN solution. The response rate was highly improved of these two probes toward biothiols because the steric interactions between 1H-imidazo [4, 5-f] [1,10] phenanthroline group and ortho-2, 4-dinitrobenzensulfonate resulted in a relatively rapid thiol-induced S_NAr substitution reaction. RuL¹-DNBS and RuL²-DNBS were weakly phosphorescent owing to the effectual photoinduced electron transfer from ruthenium(II) luminophore to the sensing group, 2,4-dinitrobenzenesulfonyl. After reacting with biothiols, the 2,4-dinitrobenzenesulfonyl group of RuL¹-DNBS and RuL²-DNBS were cleavaged and the RuL¹ and RuL² were obtained. Meanwhile, the phosphorescence were "turn-on". Both of these two probes can detect biothiols sensitively and selectively under physiological conditions with submicromolar detection limits. Furthermore, application of RuL²-DNBS for detecting of intracellular biothiols has been successfully performed in living Glioma cells.

Nanoscale Coordination Polymers for Synergistic NO and Chemodynamic Therapy of Liver Cancer

Nitric oxide (NO) induces a multitude of antitumor activities, encompassing the induction of apoptosis, sensitization to chemo-, radio-, or immune-therapy, and inhibition of metastasis, drug resistance, angiogenesis, and hypoxia, thus attracting much attention in the area of cancer intervention. To improve the precise targeting and treatment efficacy of NO, a glutathione (GSH)-sensitive NO donor (1,5-bis[(l-proline-1-yl)diazen-1-ium-1,2-diol- O²-yl]-2,4-dinitrobenzene, BPDB) coordinates with iron ions to form the nanoscale coordination polymer (NCP) via a simple precipitation and then partial ion exchange process. The obtained Fe(II)-BNCP shows desirable solubility, biocompatibility, and circulation stability. Quick NO release triggered by high concentrations of GSH in tumor cells improves the specificity of NO release in situ, thus avoiding side effects in other tissues. Meanwhile, under high concentrations of H₂O₂ in tumors, Fe²⁺ ions in BPDB-based NCP, named Fe(II)-BNCP, exert Fenton activity to generate hydroxyl radicals (·OH), which is the main contribution for chemodynamic therapy (CDT). In addition, ·O₂^- generated by the Haber-Weiss reaction of Fe²⁺ ions with H₂O₂ can quickly react with NO to produce peroxynitrite anion (ONOO^-) that is more cytotoxic than ·O₂^- or NO only. This synergistic NO-CDT effect has been proved to retard the tumor growth in Heps xenograft ICR mouse models. This work not only implements a synergistic effect of NO-CDT therapy but also offers a simple and efficient strategy to construct a coordination polymer nanomedicine via rationally designed prodrug molecules such as NO donors.

LC-MS/MS-Based Separation and Quantification of Marfey's Reagent Derivatized Proteinogenic Amino Acid DL-Stereoisomers

D-Amino acids are important biological molecules. Improved analytical methods for their resolution and quantification remain of keen interest. In this study, we investigated the use of Marfey's reagent (chiral) derivatization coupled with LC-MS/MS-based separation and detection of the resulting diastereomers for quantification of the 19 common L- and D-amino acids and glycine. Standard formic acid (pH 2)-based separations on reverse phase media were unable to separate all 19 amino acid DL pairs. In contrast, a water/acetonitrile/ammonium acetate (pH 6.5) solvent system allowed all 19 amino acid DL pairs to be chromatographically resolved on a 30 min gradient, with negative mode detection at pH 6.5 giving good sensitivity. Derivatization reaction rates between amino acids varied substantially, with overnight derivatization required for some amino acids. Chromatography at pH 6.5 combined with MS/MS quantification in negative mode demonstrated good linearity over a wide concentration range for all 20 amino acids. Matrix effects, assessed with an MRSA extract, were negligible. Marfey's derivatized analytes were stable for 24 h at room temperature. This method was demonstrated by determining the levels of these analytes in mid-log phase MRSA extracts. This approach provides for the chromatographic resolution and MS/MS-based quantification of all 20 common L- and D-amino acids in complex matrices. Graphical Abstract.

A fluorescent probe based on tetrahydro[5]helicene for highly selective recognition of hydrogen sulfide

Endogenous hydrogen sulfide plays an important role in various physiological and pathological processes and the convenient and selective recognition of hydrogen sulfide has become a research hotspot. We designed and synthesized a tetrahydro[5]helicene and 2,4-dinitrobenzene conjugate (HD-DNP) as an effective fluorescent probe for selective detection of H₂S. The selective deprotection of 2,4-dinitrophenyl ether group of HD-DNP by H₂S led to a dramatic fluorescent enhancement (101-fold) at 500 nm and colorimetric change in DMSO-PBS solution. HD-DNP displays many advantages including low background without any self-fluorescence, as well as high selectivity towards common bio-thiols such as Cysteine, Homocysteine and Glutathione. The detection limit of this probe for H₂S was found to be about 2.4 μM with a wide linear range (10-70 μM). The response mechanism of the probe with HS^- is confirmed to be thiolysis of the dinitrophenyl ether induced by HS^- through ¹H NMR comparison investigations.

Structure-activity investigation of the potentiating effect of cyano substitution on nitroaniline mutagenicity in the ames test

2,6-Dicyano-4-nitroaniline and 2-cyano-4-nitroaniline (CNNA; 2-amino-5-nitrobenzonitrile) are potent mutagens in the Ames test, even though unsubstituted nitroanilines (NAs) are no more than weak mutagens. These compounds are putative reduction products of many commercial azo dyes, including Disperse Blue 165, Disperse Blue 337, Disperse Red 73, Disperse Red 82, Disperse Violet 33, and Disperse Violet 63. We have examined the mutagenicity in strains TA98 and YG1024 of a series of commercially-available isomers of CNNA, and some related compounds, to probe the relationship between structure and genotoxic activity in this class of compounds. The potentiating effect of the cyano substituent is seen in many cases; e.g. 2-amino-4-nitrobenzonitrile is a much more potent mutagen than 3-NA. 2,4-Dinitrobenzonitrile is also highly mutagenic. Possible mechanisms for the "cyano effect" are considered, with respect to the likely structures of cyanonitroaniline-DNA adducts and the roles of the enzymes (nitroreductase and acetyl CoA:arylamine N-acetyltransferase) believed to be involved in the activation of nitroaromatic compounds. Environ. Mol. Mutagen. 59:114-122, 2018. © 2017 Wiley Periodicals, Inc.

Sorption and desorption kinetics of nitroglycerin and 2,4-dinitrotoluene in nitrocellulose and implications for residue-bound energetic materials

Energetic materials (EMs) bound to propellant residues can contribute to environmental risk and public health concerns. This work investigated how nitrocellulose, a common binding material in propellants, may control the release dynamics of nitroglycerin (NG) and 2,4-dinitrotoluene (2,4-DNT) from propellant residues. Batch adsorption/desorption experiments on nitrocellulose and re-interpretation on results from past leaching studies involving propellant-bound EMs were conducted. Mechanistic modeling of adsorption/desorption kinetics based on intra-particle diffusion (IPD) predicted aqueous intrinsic diffusivities (D_iw) to within a factor of 2 of expected values. Furthermore, the IPD model was able to predict effective diffusivities (D_eff) during the early leaching of NG from propellant residues to within a factor of 2 over a 3-log unit range. Prediction of leaching D_eff's associated with fired residues was less successful probably due to the neglect of compositional and morphological heterogeneity within the residues. Close correlations were found between the early and late D_eff's of residue-bound NG and between the fast- and slow-domain rate constants for both EMs, suggesting that the late leaching kinetics of bound-EMs may be empirically assessed from the early kinetics. This work illustrates that, in addition to dissolution, retarded diffusion through nitrocellulose matrix may also limit the overall release and transformation of residue-bound EMs in the field. Implications and limitations of the current study, and the steps forward are also presented.

Insights into the attenuated sorption of organic compounds on black carbon aged in soil

Sorption of organic compounds on fresh black carbons (BCs) can be greatly attenuated in soil over time. We examined herein the changes in surface properties of maize straw-derived BCs (biochars) after aged in a black soil and their effects on the sorptive behaviors of naphthalene, phenanthrene and 1,3-dinitrobenzene. Dissolved fulvic and humic acids extracted from the soil were used to explore the role of dissolved organic carbon (DOC) in the aging of biochars. Chromatography analysis indicated that DOC molecules with relatively large molecular weight were preferentially adsorbed on the biochars during the aging processes. DOC sorption led to blockage of the biochar's micropores according to N₂ and CO₂ adsorption analyses. Surface chemistry of the biochars was also substantially modified, with more O-rich functional groups on the aged biochars compared to the original biochars, as evidenced by Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses. The changes in both the physical and chemical surface properties of biochars by DOC led to significant attenuation of the sorption capacity and nonlinearity of the nonionic organic compounds on the aged biochars. Among the tested organic compounds, phenanthrene was the most attenuated in its sorption by the aging treatments, possibly because of its relatively large molecular size and hydrophobicity. The information can help gain a mechanistic understanding of interactions between BCs and organic compounds in soil environment.

Development of cyanine probes with dinitrobenzene quencher for rapid fluorogenic protein labelling

A multicolour protein labelling technique using a protein tag and fluorogenic probes is a powerful approach for spatio-temporal analyses of proteins in living cells. Since cyanine fluorophores have attractive properties for multicolour imaging of proteins, there is a huge demand to develop fluorogenic cyanine probes for specific protein labelling in living cells. Herein, we develop fluorogenic cyanine probes for labelling a protein tag by using a dinitrobenzene fluorescence quencher. The probes enhanced fluorescence intensity upon labelling reactions and emitted orange or far-red fluorescence. Intramolecular interactions between the cyanine fluorophores and the dinitrobenzene quencher led not only to fluorescence quenching of the probes in the free state but also to promotion of labelling reactions. Furthermore, the probes successfully imaged cell-surface proteins without a washing process. These findings offer valuable information on the design of fluorogenic cyanine probes and indicate that the probes are useful as novel live-cell imaging tools.This article is part of the themed issue 'Challenges for chemistry in molecular imaging'.

1,3-Dinitrobenzene reductive degradation by alkaline ascorbic acid - Reaction mechanisms, degradation pathways and reagent optimization

Nitro-aromatic compounds (NACs) such as 1,3-dinitrobenzene (1,3-DNB) contain the nitrogroup (-NO₂), in which the N with a +III oxidation state accepts electrons. Water soluble ascorbic acid (AsA) at elevated pH produces electron transfer and governs the electron-donating pathway. The influence of the NaOH/AsA molar ratio on the degradation of 1,3-DNB was investigated. Using 0.21-2 M NaOH and 20-100 mM AsA, nearly complete 1,3-DNB removals (90-100%) were achieved within 0.5 h. On the basis of intermediates identified using GC/MS, the reduction pathways of 1,3-DNB can be categorized into step-by-step electron transfer, and condensation routes. A higher NaOH/AsA molar ratio would result in relatively higher AsA decomposition, promote the condensation route into the formation of azo- and azoxy-compounds, and ultimately reduce 1,3-DNB to 1,3-phenylenediamine. Contaminated soil flushing using 500 mM NaOH/100 mM AsA revealed that 1,3-DNB was completely degraded within 2 h. Based on these test results, the alkaline AsA treatment method is a potential remediation process for NACs contaminated soils.

Polymer/biomass-derived biochar for use as a sorbent and electron transfer mediator in environmental applications

Co-pyrolysis of polymer and biomass wastes was investigated as a novel method for waste treatment and synthesis of enhanced biochar. Co-pyrolysis of rice straw (RS) with polypropylene (PP), polyethylene (PE) or polystyrene (PS) increased the carbon content, cation exchange capacity (CEC), surface area and pH of the biochar. As a result, the sorption of 2,4-dinitrotoluene (DNT) and Pb to polymer/RS-derived biochar was markedly enhanced. The increased aromaticity and hydrophobicity may be responsible for enhancing the DNT sorption to the polymer/RS-derived biochar. In contrast, increasing CEC, higher pH, and the newly developed surface area may account for the enhancement in Pb sorption. The addition of polymer to RS did not significantly change the catalytic role of biochar during the reduction of DNT by dithiothreitol. Our results suggest that co-pyrolysis of RS and polymer can improve the biochar properties to enhance the sorption of DNT and Pb.

Reductive removal of 2,4-dinitrotoluene and 2,4-dichlorophenol with zero-valent iron-included biochar

In order to remediate organic contaminants in natural waters and soils, a novel zero-valent iron [Fe(0)]-included biochar was synthesized via slow pyrolysis. 2,4-Dinitrotoluene (DNT) and 2,4-dichlorophenol (DCP) were removed in water via sorption to the Fe(0)-included biochar. Compared to sorption control without Fe(0), the sorbed DNT and DCP were further transformed to reduction products by Fe(0)-included biochar. Compared to the reduction control with Fe(0), the presence of biochar promoted the reductive transformation of DNT and DCP. Increasing the pyrolysis temperature resulted in enhancing the removal of DNT and DCP, suggesting that the aromaticity of biochar may be responsible for the removal. The yields of the reduction products also indicated that unlike the direct reduction by Fe(0), different reduction pathways existed in the reduction of DNT and DCP with Fe(0)-included biochar. The results suggest that Fe(0)-included biochar is a viable option to immobilize and transform redox-sensitive organic contaminants in natural environments.

Photodegradation of Oryzalin in aqueous isopropanol and acetonitrile

The phototransformation of Oryzalin was studied under UV light (λmax ≥ 290 nm) and sunlight (λmax ≥ 250 nm) in aqueous isopropanol and acetonitrile solution in absence and presence of TiO2 as sensitizer. The rate of photodegradation of Oryzalin in different solvent system followed first-order kinetics, and calculated half-lives were found to be in the range of 23.52-53.75 h for UV light and 41.23-61.43 h for sunlight. From this study, total 12 photoproducts were identified and characterized on the basis of column chromatography and Q-Tof micromass spectral data. The plausible mechanism of phototransformation involved was hydrolysis, breaking of sulfonic bond, and loss of amino and sulfonic acid group.

Highly narrow nanogap-containing Au@Au core-shell SERS nanoparticles: size-dependent Raman enhancement and applications in cancer cell imaging

Cellular imaging technologies employing metallic surface-enhanced Raman scattering (SERS) tags have gained much interest toward clinical diagnostics, but they are still suffering from poor controlled distribution of hot spots and reproducibility of SERS signals. Here, we report the fabrication and characterization of high narrow nanogap-containing Au@Au core-shell SERS nanoparticles (GCNPs) for the identification and imaging of proteins overexpressed on the surface of cancer cells. First, plasmonic nanostructures are made of gold nanoparticles (∼15 nm) coated with gold shells, between which a highly narrow and uniform nanogap (∼1.1 nm) is formed owing to polyA anchored on the Au cores. The well controlled distribution of Raman reporter molecules, such as 4,4'-dipyridyl (44DP) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), are readily encoded in the nanogap and can generate strong, reproducible SERS signals. In addition, we have investigated the size-dependent SERS activity of GCNPs and found that with the same laser wavelength, the Raman enhancement discriminated between particle sizes. The maximum Raman enhancement was achieved at a certain threshold of particle size (∼76 nm). High narrow nanogap-containing Au@Au core-shell SERS tags (GCTs) were prepared via the functionalization of hyaluronic acid (HA) on GCNPs, which recognized the CD44 receptor, a tumor-associated surface biomarker. And it was shown that GCTs have a good targeting ability to tumour cells and promising prospects for multiplex biomarker detection.

Enhanced Photoreduction of Nitro-aromatic Compounds by Hydrated Electrons Derived from Indole on Natural Montmorillonite

A new photoreduction pathway for nitro-aromatic compounds (NACs) and the underlying degradation mechanism are described. 1,3-Dinitrobenzene was reduced to 3-nitroaniline by the widely distributed aromatic molecule indole; the reaction is facilitated by montmorillonite clay mineral under both simulated and natural sunlight irradiation. The novel chemical reaction is strongly affected by the type of exchangeable cation present on montmorillonite. The photoreduction reaction is initiated by the adsorption of 1,3-dinitrobenzene and indole in clay interlayers. Under light irradiation, the excited indole molecule generates a hydrated electron and the indole radical cation. The structural negative charge of montmorillonite plausibly stabilizes the radical cation hence preventing charge recombination. This promotes the release of reactive hydrated electrons for further reductive reactions. Similar results were observed for the photoreduction of nitrobenzene. In situ irradiation time-resolved electron paramagnetic resonance and Fourier transform infrared spectroscopies provided direct evidence for the generation of hydrated electrons and the indole radical cations, which supported the proposed degradation mechanism. In the photoreduction process, the role of clay mineral is to both enhance the generation of hydrated electrons and to provide a constrained reaction environment in the galley regions, which increases the probability of contact between NACs and hydrated electrons.

Effects of operational parameters and common ions on the reduction of 2,4-dinitrotoluene by scrap copper-modified cast iron

Scrap Cu-modified cast iron (CMCI) is a potent material for the reduction of 2,4-dinitrotoluene (2,4-DNT) by a surface-mediated reaction. However, the effects of operational parameters and common ions on its reduction and final rate are unknown. Results show that the 2,4-DNT reduction was significantly affected by Cu:Fe mass ratio and the optimum m(Cu:Fe) was 0.25%. The slight pH-dependent trend of 2,4-DNT reduction by CMCI was observed at pH 3 to 11, and the maximum end product, 2,4-diaminotoluene (2,4-DAT), was generated at pH 7. Dissolved oxygen (DO) in the water reduced the 2,4-DNT degradation and the formation of 2,4-DAT. CMCI effectively treated high concentrations of 2,4-DNT (60 to 150 mg L(-1)). In addition, varying the concentration of (NH4)2SO4 from 0.001 to 0.1 mol L(-1) improved the efficiency of the reduction process. The green rust-like corrosion products (GR-SO4 (2-)) were also effective for 2,4-DNT reduction, in which Na2CO3 (0.01 to 0.2 mol L(-1)) significantly inhibited this reduction. The repeated-use efficiency of CMCI was also inhibited. Moreover, 2,4-DNT and its products, such as 4A2NT, 2A4NT, and 2,4-DAT, produced mass imbalance (<35%). Hydrolysis of Fe(3+) and CO3 (2-) leading to the generation of Fe(OH)3 and conversion to FeOOH that precipitated on the surface and strongly adsorbed the products of reduction caused the inhibition of CO3 (2-). The 2,4-DNT reduction by CMCI could be described by pseudo-first-order kinetics. The operational conditions and common ions affected the 2,4-DNT reduction and its products by enhancing the corrosion of iron or accumulating a passive oxide film on the reactivity sites.

Liposomes versus lipid nanoparticles: comparative study of lipid-based systems as oryzalin carriers for the treatment of leishmaniasis

Main-stay in treatment of leishmaniasis relies on chemotherapy but none of the current drugs combines high activity and low toxicity at affordable costs. Dinitroanilines are a new class of drugs with proved in vitro antileishmanial activity. However the development of their pharmaceutical formulations has been compromised by low water solubility and low accumulation in diseased organs. These limitations can be overcome by incorporation in lipid-based nanoformulations such as liposomes and solid lipid nanoparticles. In previous work this strategy was already followed with the incorporation of a dinitroaniline, oryzalin, resulting in the improvement of the biodistribution profile. The present work aims at demonstrating the in vitro and in vivo therapeutic activity of these oryzalin nanoformulations, and establishing a systematic comparison of both systems. After oryzalin incorporation suitable physicochemical properties for parenteral administration were obtained. Nanoformulations revealed reduced cytotoxicity and haemolytic activity when compared with free-oryzalin, while retaining the in vitro intracellular activity. Therapeutic activity, assessed in a murine model of visceral leishmaniasis, was evaluated in terms of number of administrations, dose-response and influence of the lipid excipient. Results demonstrate the superiority of both oryzalin nanoformulations on the reduction of parasitic burden in liver and spleen as compared to the control group (84 to 91%) and similar to Glucantime. A strong reduction in ED50 values (3 to 65 fold) as compared to free-oryzalin was also obtained, depending on the organ and nanoformulation used. Both oryzalin nanoformulations are potential candidates as therapeutic agents against visceral leishmaniasis.

Synthesis, characterization, biological evaluation and docking studies of macrocyclic binuclear manganese(II) complexes containing 3,5-dinitrobenzoyl pendant arms

A series of bis(phenoxo) bridged binuclear manganese(II) complexes of the type [Mn2L(1-3)](ClO4)2 (1-3) containing 3,5-dinitrobenzoyl pendant-arms have been synthesized by cyclocondensation of 2,6-diformyl-4-R-phenols (where R=CH3, C(CH3)3 or Br) with 2,2'-3,5-dinitrobenzoyliminodi(ethylamine) trihydrochloride in the presence of manganese(II) perchlorate. The IR spectra of complexes indicate the presence of uncoordinated perchlorate anions. The UV-Vis spectra of complexes suggest the distorted octahedral geometry around manganese(II) nuclei. The EPR spectra of Mn(II) complexes show a broad signal with g value 2.03-2.04, which is characteristic for octahedral high spin Mn(2+) complex. The observed room temperature magnetic moment values of the Mn(II) complexes (5.60-5.62B.M.) are less than the normal value (5.92B.M.), indicating weak antiferromagnetic coupling interaction between the two metal ions. Electrochemical studies of the complexes show two distinct quasi-reversible one electron transfer processes in the cathodic (E(1)pc=-0.73 to -0.76V, E(2)pc=-1.30 to -1.36V), and anodic (E(1)pa=1.02-1.11V, E(2)pa=1.32-1.79V) potential regions. Antibacterial efficacy of complexes have been screened against four Gram (-ve) and two Gram (+ve) bacterial strains. The DNA interaction studies suggest that these complexes bind with CT-DNA by intercalation, giving the binding affinity in the order 1>2>3. All the complexes display significant cleavage activity against circular plasmid pBR322 DNA. Docking simulation was performed to insert complexes into the crystal structure of EGFR tyrosine kinase and B-DNA at active site to determine the probable binding mode.

Altering the regioselectivity of a nitroreductase in the synthesis of arylhydroxylamines by structure-based engineering

Nitroreductases have great potential for the highly efficient reduction of aryl nitro compounds to arylhydroxylamines. However, regioselective reduction of the desired nitro group in polynitroarenes is still a challenge. Here, we describe the structure-based engineering of Escherichia coli nitroreductase NfsB to alter its regioselectivity, in order to achieve reduction of a target nitro group. When 2,4-dinitrotoluene was used as the substrate, the wild-type enzyme regioselectively reduced the 4-NO2 group, but the T41L/N71S/F124W mutant primarily reduced the 2-NO2 group, without loss of activity. The crystal structure of T41L/N71S/F124W and docking experiments indicated that the regioselectivity change (from 4-NO2 to 2-NO2 ) might result from the increased hydrophobicity of residues 41 and 124 (proximal to FMN) and conformational changes in residues 70 and 124.

DAMP, an acidotropic pH indicator, can be used as a tool to visualize non-esterified cholesterol in cells

Cholesterol-rich regions are attractive targets for studying metabolic disorders that involve accumulation of cholesterol. Despite efforts to develop probes for labelling cholesterol-rich regions in cells, few of these reagents have a low molecular weight. Previous studies have shown that the acidotropic pH indicator, N-{3-[(2,4-dinitrophenyl)amino]propyl}-N-(3-aminopropyl)methylamine dihydrochloride (DAMP), reacts with cholesterol-rich organelles, such as endocrine secretary granules from endocrine cells. In this study, we demonstrated that DAMP could react with free cholesterol in a dose-dependent manner, and DAMP was able to detect cholesterol-rich subcellular organelles. DAMP was sufficiently potent to detect free cholesterol-enriched organs, but was unable to detect atherosclerotic plaques primarily composed of esterified cholesterol. Taken together, these results demonstrate that DAMP facilitates the study of cholesterol-enriched lipid rafts and disorders which involve cholesterol accumulation.

Enhanced Photocatalytic Activity of as-Prepared Sodium Titanates for m-Dinitrobenzene Reduction and Sulfosulfuron Oxidation

This paper demonstrates the preparation and photocatalytic activity of sodium titanate nanorods and nanotubes prepared by hydrothermal method using P25-TiO2 as the precursor. XRD results confirmed the monoclinic structure of sodium titanate nanorods obtained after calcinations of orthorhombic sodium titanate nanotubes at 800 °C for 2 h. The BET surface area of sodium titanate nanotubes (176 m2 g-1) was significantly reduced for sodium titanate nanorods (21 m2 g-1) formation because of the collapsing of the hollow interior of the former during its high temperature sintering. The selective formation of m-diaminobenzene by the photoreduction of the m-dinitrobenzene was found to be comparable by sodium titanate nanorods (89.5 ± 0.5%) and P25-TiO2 (98.2 ± 0.8%), whereas Au-deposition (0.5 and 2 wt%) onto sodium titanate nanorods notably altered the products (m-nitroaniline and m-diaminobenzene) distribution after 8 h of UV-light irradiation and which was confirmed later by GC-MS analysis. This high photoactivity of as-prepared nanorods could be credited to better delocalization and longer relaxation lifetime (68 µs) of photoexcited e-/h+ pairs along the length of crystalline sodium titanate nanorods than P25-TiO2 (45 µs) as measured from Time-resolved spectroscopy. The photooxidation of sulfosulfuron herbicide (1000 ppm) and corresponding CO2 formation was found to be highest with sodium titanate nanotubes due to the presence of more hydroxyl groups over the largest surface area that dominates over its least relaxation lifetime (41 µs).

π(+)-π interactions between (hetero)aromatic amine cations and the graphitic surfaces of pyrogenic carbonaceous materials

Many organic compounds of environmental concern contain amine groups that are positively charged at environmental pH. Here we present evidence that (hetero)aromatic amine cations can act as π acceptors in forming π(+)–π electron donor–acceptor (EDA) interactions with the π electron-rich, polyaromatic surface of pyrogenic carbonaceous materials (PCMs) (i.e., biochar, black carbon, and graphene). The π(+)–π EDA interactions combine a cation−π force with a π–π EDA force resulting from charge polarization of the ring’s quadrupole. Adsorption on a biochar and reference adsorbent graphite was conducted of triazine herbicides, substituted anilines, heterocyclic aromatic amines, and other amines whose charge is insulated from the aromatic ring. When normalized for the hydrophobic effect, the adsorption increased with decreasing pH as the amines became ionized, even on graphite that had no significant fixed or variable charge. The cationic π acceptor (quinolinium ion) was competitively displaced more effectively by the π acceptor 2,4-dinitrobenzene than by the π donor naphthalene. The maximum electrostatic potential of organocations computed with density functional theory was found to be a strong predictor of the π(+)–π EDA interaction. The π(+)–π EDA interaction was disfavored by electropositive alkyl substituents and by charge delocalization into additional rings. Amines whose charge was insulated from the ring fell far out of the correlation (more positive free energy of adsorption). Identifying and characterizing this novel π(+)–π EDA interaction on PCMs will help in predicting the fate of organocations in both natural and engineered systems.

Differentiation of isomeric dinitrotoluenes and aminodinitrotoluenes using electrospray high resolution mass spectrometry

Explosive detection and identification play an important role in the environmental and forensic sciences. However, accurate identification of isomeric compounds remains a challenging task for current analytical methods. The combination of electrospray multistage mass spectrometry (ESI-MS(n) ) and high resolution mass spectrometry (HRMS) is a powerful tool for the structure characterization of isomeric compounds. We show herein that resonant ion activation performed in a linear quadrupole ion trap allows the differentiation of dinitrotoluene isomers as well as aminodinitrotoluene isomers. The explosive-related compounds: 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), 2-amino-4,6-dinitrotoluene (2A-4,6-DNT) and 4-amino-2,6-dinitrotoluene (4A-2,6-DNT) were analyzed by ESI-MS in the negative ion mode; they produced mainly deprotonated molecules [M - H](-) . Subsequent low resolution MS(n) experiments provided support for fragment ion assignments and determination of consecutive dissociation pathways. Resonant activation of deprotonated dinitrotoluene isomers gave different fragment ions according to the position of the nitro and amino groups on the toluene backbone. Fragment ion identification was bolstered by accurate mass measurements performed using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS). Notably, unexpected results were found from accurate mass measurements performed at high resolution for 2,6-DNT where a 30-Da loss was observed that corresponds to CH2 O departure instead of the expected isobaric NO(•) loss. Moreover, 2,4-DNT showed a diagnostic fragment ion at m/z 116, allowing the unambiguous distinction between 2,4- and 2,6-DNT isomers. Here, CH2 O loss is hindered by the presence of an amino group in both 2A-4,6-DNT and 4A-2,6-DNT isomers, but nevertheless, these isomers showed significant differences in their fragmentation sequences, thus allowing their differentiation. DFT calculations were also performed to support experimental observations.

Comprehensive investigations of kinetics of alkaline hydrolysis of TNT (2,4,6-trinitrotoluene), DNT (2,4-dinitrotoluene), and DNAN (2,4-dinitroanisole)

Combined experimental and computational techniques were used to analyze multistep chemical reactions in the alkaline hydrolysis of three nitroaromatic compounds: 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), and 2,4-dinitroanisole (DNAN). The study reveals common features and differences in the kinetic behavior of these compounds. The analysis of the predicted pathways includes modeling of the reactions, along with simulation of UV-vis spectra, experimental monitoring of reactions using LC/MS techniques, development of the kinetic model by designing and solving the system of differential equations, and obtaining computationally predicted kinetics for decay and accumulation of reactants and products. Obtained results suggest that DNT and DNAN are more resistant to alkaline hydrolysis than TNT. The direct substitution of a nitro group by a hydroxide represents the most favorable pathway for all considered compounds. The formation of Meisenheimer complexes leads to the kinetic first-step intermediates in the hydrolysis of TNT. Janovsky complexes can also be formed during hydrolysis of TNT and DNT but in small quantities. Methyl group abstraction is one of the suggested pathways of DNAN transformation during alkaline hydrolysis.

Rapid quantitative chiral amphetamines liquid chromatography-tandem mass spectrometry: method in plasma and oral fluid with a cost-effective chiral derivatizing reagent

Methamphetamine is a widely abused psychostimulant containing a chiral center. Consumption of over-the-counter and prescription medications may yield positive amphetamines results, but chiral separation of l- and d-methamphetamine and its metabolite amphetamine can help determine whether the source was licit or illicit. We present the first LC-MS/MS method with precolumn derivatization for methamphetamine and amphetamine chiral resolution in plasma and oral fluid collected with the Oral-Eze(®) and Quantisal™ devices. To 0.5mL plasma, 0.75mL Oral-Eze, or 1mL Quantisal specimen racemic d11-methamphetamine and amphetamine internal standards were added, followed by protein precipitation. Samples were centrifuged and supernatants loaded onto pre-conditioned Phenomenex(®) Strata™-XC Polymeric Strong Cation solid phase extraction columns. After washing, analytes were eluted with 5% ammonium hydroxide in methanol. The eluate was evaporated to dryness and reconstituted in water. Derivatization was performed with 1-fluoro-2,4-dinitrophenyl-5-l-alanineamide (Marfey's reagent) and heating at 45°C for 1h. Derivatized enantiomer separations were performed under isocratic conditions (methanol:water, 60:40) with a Phenomenex(®) Kinetex(®) 2.6μm C18 column. Analytes were identified and quantified by two MRM transitions and their ratio on a 3200 QTrap (AB Sciex) mass spectrometer in ESI negative mode. In all three matrices, the method was linear for all enantiomers from 1 to 500μg/L, with imprecision and accuracy of ≤11.3% and 85.3-108%, respectively. Extraction efficiencies ranged from 67.4 to 117% and matrix effects from -17.0 to 468%, with variation always ≤19.1%. Authentic plasma and OF specimens were collected from an IRB-approved study that included controlled Vicks(®) VapoInhaler™ administration. The present method is sensitive, selective, economic and rapid (separations accomplished in <10min), and improves methamphetamine result interpretation.

Mobility and bioavailability reduction of soil TNT via sorption enhancement using monopotassium phosphate

In this study, the effect of monopotassium phosphate (MKP) on the reduction in mobility and bioavailability of 2,4,6-trinitrotoluene (TNT) was tested. In the test soil, collected from an active firing range, of which cation binding sites were mostly exchanged with H(+) or Al(3+), potassium ions in MKP exchanged the existing cations and hence significantly increased TNT sorption. In addition, a competitive sorption experiment with hexafluorobenzene and 2,4-dinitrotoluene suggests that TNT was specifically sorbed through cation-polar interaction in the test soil. The unit-equivalent Freundlich sorption coefficient of TNT in MKP-amended soil (1370.96 mg-TNT/kg-soil) was about 13 times higher than that in untreated soil (106.23 mg-TNT/kg-soil). Finally, modified synthetic precipitation leaching procedure and hydroxypropyl-β-cyclodextrin extraction result revealed that MKP application could reduce both the leachability and bioavailability of soil TNT. The leachable and extractable fraction of TNT in untreated soil were 87.63% and 94.47% of the initial TNT, respectively, whereas these fractions decreased to 49.15% and 54.85% of the initial TNT in the presence of MKP, respectively. MKP application can be a benign technology which can reduce both mobility and bioavailability of TNT in soil.

Conformational stability, molecular orbital studies (chemical hardness and potential), vibrational investigation and theoretical NBO analysis of 4-tert-butyl-3-methoxy-2,6-dinitrotoluene

The FT-IR and FT-Raman spectra of 4-tert-butyl-3-methoxy-2,6-dinitrotoluene (musk ambrette) have been recorded in the regions 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The total energy calculations of musk ambrette were tried for the possible conformers. The molecular structure, geometry optimization, vibrational frequencies were obtained by the density functional theory (DFT) using B3LYP and LSDA method with 6-311G(d,p) basis set for the most stable conformer "C1". The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated and the scaled values were compared with experimental FT-IR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The stability of the molecule arising from hyper conjugate interactions and the charge delocalization has been analyzed using bond orbital (NBO) analysis. The HOMO and LUMO energy gap reveals that the energy gap reflects the chemical activity of the molecule. The dipole moment (μ), polarizability (α), anisotropy polarizability (Δα) and first hyperpolarizability (βtot) of the molecule have been reported. The thermodynamic functions (heat capacity, entropy and enthalpy) were obtained for the range of temperature 100-1000 K. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecule has been obtained by mapping electron density isosurface with molecular electrostatic potential (MEP).

Molecular structure, vibrational investigation of 2-chloro-α-α-α-trifluoro-3,5-dinitrotoluene using DFT (LSDA, B3LYP, B3PW91 and MPW1PW91) and UV-Vis absorption spectra in organic solvents: a IEF-PCM/TD-DFT study

Theoretical Spectrograms (IR and Raman) have been constructed and compared with the experimental FT-IR and FT-Raman spectra. The effect of solvent polarity on the optimized structure is studied by the density functional theory calculation (LSDA, B3LYP, B3PW91 and MPW1PW91 with 6-311++G(d,p)) in gas phase and selected solvents benzene (non-polar solvent), tetrahydrofuran THF (polar aprotic solvent), DMSO, Methanol (polar solvent) and water (protic solvent). In addition variation of dipole moment and charges on atoms in the solvents are studied. With the help of TD-DFT study, the electrostatic effects of different solvents and the energy difference between the excited electronic states noticeably depends on the size of the solute cavity used in the PCM calculations. On the basis of the thermodynamic properties of the title compound at different temperatures have been calculated in gas phase, reverling the correlations between standard heat capacities (C), standard entropies (S), standard enthalpy (H) and vibrational and rotational temperatures. The solvation influence on the geometrical parameters, atomic charges and HOMO-LUMO energies was estimated with the use of PCM method. The presence of solvent did not alter these parameters, but affected the orbital energies. The aggregation phenomena were studied with dimer and trimer structure of the title compound.

Expression, purification and substrate specificities of 3-nitrotoluene dioxygenase from Diaphorobacter sp. strain DS2

3-Nitotoluene dioxygenase (3-NTDO) is the first enzyme in the degradation pathway of 3-nitrotoluene (3-NT) by Diaphorobacter sp. strain DS2. The complete gene sequences of 3-NTDO were PCR amplified from genomic DNA of Diaphorobacter sp., cloned, sequenced and expressed. The 3-NTDO gene revealed a multi component structure having a reductase, a ferredoxin and two oxygenase subunits. Clones expressing the different subunits were constructed in pET21a expression vector system and overexpressed in E. coli BL21(DE3) host. Each subunit was individually purified separately to homogeneity. The active recombinant enzyme was reconstituted in vitro by mixing all three purified subunits. The reconstituted recombinant enzyme could catalyse biotransformations on a variety of organic aromatics.

Microfluidic based immunosensor for detection and purification of carbonylated proteins

A microchip has been developed on the basis of immno-precipitation approach for fast and sensitive enrichment of low abundant carbonylated proteins. This microfluidic method could enrich molecular biomarkers, which could be further analyzed in the proteomic study of age-related diseases and therapeutic development. In this study, an immunoaffinity-based PDMS micro-device was designed, fabricated, and chemically modified to specifically trap DNP-labeled PTM proteins of low abundance from a complex protein mixture. Carbonylated protein is selected as a representative PTM protein to illustrate the wide application of this immuno-based microchip for other PTMs which could be readily labeled by different antibody groups. Surface characterization methods such as atomic force microscopy and fluorescence microscopy were used to evaluate the construction of glutaraldehyde- and antibody- terminated PDMS substrates in the device fabrication. Quantitative study was also applied to study the target protein capture and elution efficiency of the device. In a testing mixture consisting of smaller amount of test model-In Vitro oxidized cytochrome c and large blocking protein BSA, a high sensitivity and specificity for only carbonylated protein biomarkers was demonstrated using this on-chip immnuoaffinity based extraction/enrichment. For this highly dense 193-post arrays μ-chip, a low abundance of 159 ng of standard in vitro test model- cytochrome c was enriched at flow speed of 5 μL/min within 110 min. We demonstrated that this nascent micro-immunoprecipitation (μ-IP) method is capable for enrichment of biomarkers in protein post-translation modification related diseases and promise great advance in early disease detection.

Structural and spectral characterization of novel non-centrosymmetric 2,4-dintrobenzene derivative

A novel organic compound 9-(2,4-dinitrophenyloxy)-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxepino[5,6-c]pyridine (DNPAP) has been synthesized and a nonlinear optical (NLO) crystal has been grown by slow evaporation method. Compound was subjected to different characterization analyses in order to find out its suitability for optoelectronic applications. Single crystal and powder X-ray diffraction analyses show that DNPAP crystallizes in the orthorhombic space group Pca21. The range of optical absorption was ascertained by recording UV–Vis spectrum. The second harmonic generation (SHG) test has shown that DNPAP possesses 6.4-times higher NLO efficiency compared to KDP.

Synergistic role of different soil components in slow sorption kinetics of polar organic contaminants

We observed that the sorption kinetics of nitrobenzene and 2,4-dinitrotoluene (two model polar compounds) was significantly slower than that of 1,4-dichlorobenzene and phenanthrene (two model apolar compounds). The difference was attributable to the strong non-hydrophobic interactions between the polar molecules and soil. Interestingly, sorption kinetics of the polar sorbates to the soil organic matter-free soil, humic/fulvic acid-free soil, and extracted humic acids was very fast, indicating that different soil components played a synergetic role in the observed slow kinetics. We propose that slow sorption kinetics of highly polar sorbates stems mainly from the strong specific interactions (H-bonding, electron donor-acceptor interactions, etc.) with humic/fulvic acids; such specific interactions occur when sorbate molecules diffuse through humic/fulvic acids coiled, in relatively compressed confirmations, within the complex, tortuous, and porous soil matrices formed by mineral grains/particles and soil organic matter.

Computational studies of molecular charge transfer complexes of heterocyclic 4-methylepyridine-2-azomethine-p-benzene derivatives with picric acid and m-dinitrobenzene

Charge transfer complexes of substituted aryl Schiff bases as donors with picric acid and m-dinitrobenzene as acceptors were investigated by using computational analysis calculated by Configuration Interaction Singles Hartree-Fock (CIS-HF) at standard 6-31G∗ basis set and Time-Dependent Density-Functional Theory (TD-DFT) levels of theory at standard 6-31G∗∗ basis set, infrared spectra, visible and nuclear magnetic resonance spectra are investigated. The optimized geometries and vibrational frequencies were evaluated. The energy and oscillator strength were calculated by Configuration Interaction Singles Hartree-Fock method (CIS-HF) and the Time-Dependent Density-Functional Theory (TD-DFT) results. Electronic properties, such as HOMO and LUMO energies and band gaps of CTCs set, were studied by the Time-Dependent density functional theory with Becke-Lee-Young-Parr (B3LYP) composite exchange correlation functional and by Configuration Interaction Singles Hartree-Fock method (CIS-HF). The ionization potential Ip and electron affinity EA were calculated by PM3, HF and DFT methods. The columbic force was calculated theoretically by using (CIS-HF and TD-DFT) methods. This study confirms that the theoretical calculation of vibrational frequencies for (aryl Schiff bases--(m-dinitrobenzene and picric acid)) complexes are quite useful for the vibrational assignment and for predicting new vibrational frequencies.

Analysis of Arabidopsis glutathione-transferases in yeast

The genome of Arabidopsis thaliana encodes 54 functional glutathione transferases (GSTs), classified in seven clades. Although plant GSTs have been implicated in the detoxification of xenobiotics, such as herbicides, extensive redundancy within this large gene family impedes a functional analysis in planta. In this study, a GST-deficient yeast strain was established as a system for analyzing plant GSTs that allows screening for GST substrates and identifying substrate preferences within the plant GST family. To this end, five yeast genes encoding GSTs and GST-related proteins were simultaneously disrupted. The resulting yeast quintuple mutant showed a strongly reduced conjugation of the GST substrates 1-chloro-2,4-dinitrobenzene (CDNB) and 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl). Consistently, the quintuple mutant was hypersensitive to CDNB, and this phenotype was complemented by the inducible expression of Arabidopsis GSTs. The conjugating activity of the plant GSTs was assessed by in vitro enzymatic assays and via analysis of exposed yeast cells. The formation of glutathione adducts with dinitrobenzene was unequivocally verified by stable isotope labeling and subsequent accurate ultrahigh-resolution mass spectrometry (ICR-FTMS). Analysis of Arabidopsis GSTs encompassing six clades and 42 members demonstrated functional expression in yeast by using CDNB and NBD-Cl as model substrates. Subsequently, the established yeast system was explored for its potential to screen the Arabidopsis GST family for conjugation of the fungicide anilazine. Thirty Arabidopsis GSTs were identified that conferred increased levels of glutathionylated anilazine. Efficient anilazine conjugation was observed in the presence of the phi, tau, and theta clade GSTs including AtGSTF2, AtGSTF4, AtGSTF6, AtGSTF8, AtGSTF10, and AtGSTT2, none of which had previously been known to contribute to fungicide detoxification. ICR-FTMS analysis of yeast extracts allowed the simultaneous detection and semiquantification of anilazine conjugates as well as catabolites.

Biochar-mediated reductive transformation of nitro herbicides and explosives

Biochar, a subset of black carbon produced via pyrolysis of biomass, has received much attention in recent years due to its potential to address many important issues, from energy and climate to agriculture and environmental quality. Biochar is known to influence the fate and transport of organic contaminants, although its role has been generally assumed to be as an adsorbent. In this study, the authors investigated the ability of biochar to catalyze the reductive reactions of nitro herbicides and explosives. Two biochars, derived from poultry litter and wastewater biosolids, were found to promote the reductive removal of the dinitro herbicides pendimethalin and trifluralin and the explosives 2,4-dinitrotoluene and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by dithiothreitol. Parallel experiments using another black carbon material, graphite powder or granular activated carbon, in place of a biochar resulted in comparable rate enhancement to show reduction products, such as 2,4-diaminotoluene and formaldehyde. A cyclization product of trifluralin and reduction products of dinitrotoluene and RDX were detected only when biochar and dithiothreitol were both present, supporting the ability of biochar to promote redox reactions. Three possible catalysts, including graphene moieties, surface functional groups, and redox-active metals, in biochar may be responsible for the biochar-mediated reactions. The environmental significance, implications, and applications of this previously unrecognized role of biochar are discussed.

Bisolute sorption and thermodynamic behavior of organic pollutants to biomass-derived biochars at two pyrolytic temperatures

The bisolute sorption and thermodynamic behavior of organic pollutants on low temperature biochars (LTB) at 300 °C and high temperature biochars (HTB) at 700 °C were determined to elucidate sorptive properties of biochar changed with pyrolytic temperatures. The structural characteristics and isotherms shape of the biochar were more dependent on the pyrolytic temperature than on the biomass feedstocks, which included orange peel, pine needle, and sugar cane bagasse. For LTB, the thermally altered organic matter colocalized with the carbonized matter, and the visible fine pores of the fixed carbons were plugged by the remaining volatile carbon. For HTB, most of the volatile matter was gone and the fixed matter was composed of fully carbonized adsorptive sites. Monolayer adsorption of 1-naphthol to HTB was dominant but was suppressed by phenol. In comparison, LTB displayed exceptional sorption behavior where partition and adsorption were concurrently promoted by a cosolute and elevated temperature. In addition to monolayer surface coverage, pore-filling mechanisms may contribute to the increase of adsorption fraction. Moreover, the entropy gain was a dominant force driving the partition and adsorption processes in LTB. Thus, the colocalizing partition phase and adsorptive sites in LTB are proposed to be in interencased states rather than in physical separation.

Reduction of dinitrotoluene sulfonates in TNT red water using nanoscale zerovalent iron particles

PURPOSE

This research was designed to investigate the feasibility of converting the dinitrotoluene sulfonates (DNTS) in TNT red water into the corresponding aromatic amino compounds using nanoscale zerovalent iron (NZVI).

METHODS

NZVI particles were simultaneously synthesized and stabilized by sodium borohydride reduction in a nondeoxygenated system. The morphology, elemental content, specific surface area, and crystal properties of the NZVI were characterized before and after the reaction by environmental scanning electron microscope; energy dispersive X-ray; Brunauer, Emmett, and Teller; and X-ray diffraction, respectively. The reduction process was conducted at pH = 6.3 at ambient temperature. The efficiency of the NZVI-mediated DNTS reduction process was monitored by HPLC, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses.

RESULTS

The properties of the NZVI particles prepared were found to be similar to those obtained through oxygen-free preparation and inert stabilization processes. Both 2,4-DNT-3-sulfonate (2,220 mg L(-1)) and 2,4-DNT-5-sulfonate (3,270 mg L(-1)) in TNT red water underwent a pseudo-first-order transformation when mixed with NZVI at room temperature and near-neutral pH. Their observed rate constants were 0.11 and 0.30 min(-1), respectively. Within 1 h of processing, more than 99% of DNTS was converted by NZVI-mediated reduction into the corresponding diaminotoluene sulfonates.

CONCLUSIONS

NZVI can be simultaneously prepared and stabilized in a nondeoxygenated system. NZVI reduction is a highly efficient method for the conversion of DNTS into the corresponding diaminotoluene sulfonates under near-neutral pH conditions. Therefore, NZVI reduction may be useful in the treatment of TNT red water and subsequent recovery of diaminotoluene from explosive wastewater.

Removal of dinitrotoluenes in wastewater by sono-activated persulfate

Oxidative degradation of dinitrotoluenes (DNTs) in wastewater was performed using persulfate anions combined with ultrasonic irradiation, wherein a synergistic effect is observed. The batch-wise experiments were carried out to elucidate the influence of various operating parameters on sono-activated persulfate oxidation, including ultrasonic power intensity, persulfate anion concentration, reaction temperature and acidity of wastewater. It is noteworthy that the nitrotoluene contaminants could be almost completely eliminated by virtue of sono-activated persulfate oxidation, wherein sulfate radicals serve as principal oxidants, of which amounts are significantly enhanced via addition of sodium sulfate. Based on the results given by gas chromatograph-mass spectrometer (GC-MS), it is postulated that the methyl group of DNTs preliminarily underwent oxidation pathway into dinitrobenzoic acid, followed by decarboxylation to form 1,3-dinitrobenzene (DNB). In sum, the sono-activated persulfate oxidation is a promising method for treatment of nitrotoluenes in wastewater.

Molecular structure, heteronuclear resonance assisted hydrogen bond analysis, chemical reactivity and first hyperpolarizability of a novel ethyl-4-{[(2,4-dinitrophenyl)-hydrazono]-ethyl}-3,5-dimethyl-1H-pyrrole-2-carboxylate: a combined DFT and AIM approach

A new ethyl-4-{[(2,4-dinitrophenyl)-hydrazono]-ethyl}-3,5-dimethyl-1H-pyrrole-2-carboxylate (EDPHEDPC) has been synthesized and characterized by FT-IR, (1)H NMR, UV-vis, DART-Mass spectroscopy and elemental analysis. Quantum chemical calculations have been performed by DFT level of theory using B3LYP functional and 6-31G(d,p) as basis set. The (1)H NMR chemical shifts are calculated using gauge including atomic orbitals (GIAO) approach in DMSO as solvent. The time dependent density functional theory (TD-DFT) is used to find the various electronic transitions and their nature within molecule. A combined theoretical and experimental wavenumber analysis confirms the existence of dimer. Topological parameters such as electron density (ρ(BCP)), Laplacian of electron density (nabla(2)ρ(BCP)), kinetic electron energy density (G(BCP)), potential electron density (V(BCP)) and the total electron energy density (H(BCP)) at bond critical points (BCP) have been analyzed by Bader's 'Atoms in molecules' AIM theory in detail. The intermolecular hydrogen bond energy of dimer is calculated as -12.51 kcal/mol using AIM calculations. AIM ellipticity analysis is carried out to confirm the presence of resonance assisted intra and intermolecular hydrogen bonds in dimer. The calculated thermodynamic parameters show that reaction is exothermic and non-spontaneous at room temperature. The local reactivity descriptors such as Fukui functions (f(k)(+), f(k)(-)), local softnesses (s(k)(-), s(k)(+)) and electrophilicity indices (ω(k)(+), ω(k)(-)) analyses are performed to determine the reactive sites within molecule. Nonlinear optical (NLO) behavior of title compound is investigated by the computed value of first hyperpolarizability (β(0)).

Comment on: "Comparative vibrational analysis of 1,2-dinitrobenzene and 1-fluoro-3-nitrobenzene" by S Ramalingam, S. Periandy et al. [Spectrochim. Acta A 84 (2011) 86-98]

The title paper reports, inter alia, the ab initio calculated structure and vibrational spectra of 1,2-dinitrobenzene. The calculated structure of the dinitrobenzene is wrong. We have recalculated the ab initio structure and assigned the spectra in agreement with previously published work.

Preparation of SRN1-Type Coupling Adducts from Aliphatic gem-Dinitro Compounds in Ionic Liquids

S_RN1-type coupling adducts are readily prepared by the reaction between α-sulfonylesters or α-cyanosulfones and gem-dinitro compounds in ionic liquids. The reactions progress smoothly and recovered ionic liquids can be used for several iterations, as long as they are washed with water to remove alkali metallic salts. The reaction rate is slower than the corresponding S_RN1 reaction in DMSO, but no acceleration on irradiation or no inhibition in the presence of m-DNB are observed.

Natural flavonoids interact with dinitrobenzene system in aprotic media: an electrochemical probing

Three structurally related natural flavonoids (FlOH), quercetin (Q), rutin (R) and morin (M), were investigated by cyclic voltammetry to probe their interactions with hazardous 1,4-dinitrobenzene (1,4-DNB) using a glassy carbon electrode. Scavenging of 1,4-DNB by FlOH was inferred from a positive shift in reduction potential, decrease in anodic peak current, and irreversible electrochemical behavior of 1,4-DNB on increasing the flavonoid concentration. The homogeneous bi-molecular rate constant (k2) was determined using the Nicholson-Shain equation and found to be higher for the dianion. Morin posed a comparatively higher k2 value for its interaction with the 1,4-DNB electrochemical system owing to its more acidic nature and least intramolecular hydrogen bonding. The cyclic voltammetric (CV) results were further supported by HyperchemPM3 quantum mechanical semi-empirical calculations, which point towards E(r)C(i) interactions between flavonoids and 1,4-DNB. The present investigation is biologically significant in terms of natural flavonoidal scavenging activity toward toxins such as dinitroaromatics.

The role of black carbon as a catalyst for environmental redox transformation

Black carbon (BC) is an important class of geosorbents that control the fate and transport of organic pollutants in soil and sediment. We previously demonstrated a new role of BC as an electron transfer mediator in the abiotic reduction of nitroaromatic and nitramine compounds by Oh and Chiu (Environ Sci Technol 43:6983-6988, 2009). We proposed that BC can catalyze the reduction of nitro compounds because it contains microscopic graphitic (graphene) domains, which facilitate both sorption and electron transfer. In this study, we assessed the ability of different types of BC--graphite, activated carbon, and diesel soot--to mediate the reduction of 2,4-dinitrotoluene (DNT) and 2,4-dibromophenol (DBP) by H(2)S. All three types of BC enhanced DNT and DBP reduction. H(2)S supported BC-mediated reduction, as was observed previously with a thiol reductant. The results suggest that BC may influence the fate of organic pollutants in reducing subsurface environments through redox transformation in addition to sorption.