Determination of diflubenzuron and chlorbenzuron in fruits by combining acetonitrile-based extraction with dispersive liquid-liquid microextraction followed by high-performance liquid chromatography.

In this study, a simple and low-organic-solvent-consuming method combining an acetonitrile-partitioning extraction procedure followed by "quick, easy, cheap, effective, rugged and safe" cleanup with ionic-liquid-based dispersive liquid-liquid microextraction and high-performance liquid chromatography with diode array detection was developed for the determination of diflubenzuron and chlorbenzuron in grapes and pears. Ionic-liquid-based dispersive liquid-liquid microextraction was performed using the ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate as the extractive solvent and acetonitrile extract as the dispersive solvent. The main factors influencing the efficiency of the dispersive liquid-liquid microextraction were evaluated, including the extractive solvent type and volume and the dispersive solvent volume. The validation parameters indicated the suitability of the method for routine analyses of benzoylurea insecticides in a large number of samples. The relative recoveries at three spiked levels ranged between 98.6 and 109.3% with relative standard deviations of less than 5.2%. The limit of detection was 0.005 mg/kg for the two insecticides. The proposed method was successfully used for the rapid determination of diflubenzuron and chlorbenzuron residues in real fruit samples.

An amphiphilic perylene imido diester for selective cellular imaging.

A new amphiphilic membrane marker based on a water-soluble dendritic polyglycerol perylene imido dialkylester has been designed, synthesized, and its optical properties characterized. In water it forms fluorescently quenched micellar self-aggregates, but when incorporated into a lipophilic environment, it monomerizes, and the highly fluorescent properties of the perylene core are recovered. These properties make it an ideal candidate for the imaging of artificial and cellular membranes as demonstrated by biophysical studies.

Identification of polyimide materials using quantitative CE with UV and QTOF-MS detection.

Polyimides (PIs) are a group of widely used synthetic materials that service a variety of different purposes including microelectronics, insulating films and aerospace applications. Depending on the requirements (defined by the particular final product), the actual composition of PIs may show substantial chemical variation. To study this variation in chemical structure, CE-MS can be employed for the determination of PI composition following chemical degradation of the polymer sample. PI is chemically decomposed to corresponding aromatic diamine and carboxylic acid components using an alkali fusion reaction. Solid polymer samples are fused in a potassium hydroxide melt yielding reaction products that are diluted in acid and can be immediately analysed by CE coupled to a Q/TOF-MS with quantification performed using conventional UV detection. This approach involves a simple and rapid sample preparation yielding both qualitative and quantitative information regarding the chemical composition of the polymer. Application of the CE-MS approach is shown for a range of commercially available PI and poly(amide-imide) materials and the results are used to infer the respective chemical compositions.

CE-ESI-MS analysis of singly charged inorganic and organic anions using a dicationic reagent as a complexing agent.

A dicationic ion-pairing reagent, N,N'-dibutyl 1,1'-pentylenedipyrrolidinium, was used to form complexes with singly charged anions for their subsequent analysis by CE-ESI-MS in positive ion mode. This methodology offers the advantages of greater versatility and sensitivity relative to direct detection of the anions in negative ion mode, and it can be realized by a number of possible complexation strategies, including pre-column, on-column, and post-column modes. Four model anions, perfluorooctanoate, benzenesulfonate (BZSN), monochloroacetate (MCA), and trifluoromethanesulfonimide were amenable to complexation with the dicationic reagent, yielding singly charged cations with greater m/z. By optimizing various parameters, including the CE separation buffer composition and pH, the concentration of the dicationic reagent, the mode of complexation, the nebulizing gas pressure, and the sheath liquid composition, it was possible to develop a robust CE-ESI-MS method appropriate for the analysis of anions in a tap water sample. By this method, LODs were found to be 20.9 and 1.31 ng/mL for MCA and BZSN, respectively.

Temperature-controlled ionic liquid-dispersive liquid-phase microextraction for preconcentration of chlorotoluron, diethofencarb and chlorbenzuron in water samples.

This article describes a new, rapid and sensitive method for the determination of chlorotoluron, diethofencarb and chlorbenzuron from water samples with temperature-controlled ionic liquid-dispersive liquid-phase microextraction. In the preconcentration procedure, ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate [C(6)MIM] [PF(6)] was employed as the extraction solvent. The parameters, such as volume of [C(6)MIM] [PF(6)], sample pH, extraction time, centrifuging time, temperature and salting-out effect, were investigated in detail. Under the optimal extraction conditions, it has been found that three analytes had excellent LODs (S/N=3) in the range of 0.04-0.43 microg/L. The RSDs (n=6) were in the range of 1.3-4.7%. The proposed method was evaluated with lake water, tap water and melted snow water samples. The experimental results indicated that the proposed method had excellent prospect and would be widely used in the future.

A small-molecule compound identified through a cell-based screening inhibits JAK/STAT pathway signaling in human cancer cells.

Inappropriate activation of JAK/STAT signaling occurs with high frequency in human cancers and is associated with cancer cell survival and proliferation. Therefore, the development of pharmacologic STAT signaling inhibitors has therapeutic potential in the treatment of human cancers. Here, we report 2-[(3,5-bis-trifluoromethyl-phenyl)-hydroxy-methyl]-1-(4-nitro-phenylamino)-6-phenyl-1,2,4a,7a-tetrahydro-pyrrolo[3,4-b]-pyridine-5,7-dione (AUH-6-96) as a novel small-molecule inhibitor of JAK/STAT signaling that we initially identified through a cell-based high-throughput screening using cultured Drosophila cells. Treatment of Drosophila cells with AUH-6-96 resulted in a reduction of Unpaired-induced transcriptional activity and tyrosine phosphorylation of STAT92E, the sole Drosophila STAT homologue. In human cancer cell lines, AUH-6-96 inhibited both constitutive and interleukin-6-induced STAT3 phosphorylation. Specifically, in Hodgkin lymphoma L540 cells, treatment with AUH-6-96 resulted in reduced levels of tyrosine phosphorylated STAT3 and of the STAT3 downstream target gene SOCS3 in a dose- and time-dependent manner. In addition, AUH-6-96-treated L540 cells showed decreased expression of persistently activated JAK3, suggesting that AUH-6-96 inhibits the JAK/STAT pathway signaling in L540 cells by affecting JAK3 activity and subsequently blocking STAT3 signaling. Importantly, AUH-6-96 selectively affected cell viability only of cancer cells harboring aberrant JAK/STAT signaling. In support of the specificity of AUH-6-96 for inhibition of JAK/STAT signaling, treatment with AUH-6-96 decreased cancer cell survival by inducing programmed cell death by down-regulating the expression of STAT3 downstream target antiapoptotic genes, such as Bcl-xL. In summary, this study shows that AUH-6-96 is a novel small-molecule inhibitor of JAK/STAT signaling and may have therapeutic potential in the treatment of human cancers harboring aberrant JAK/STAT signaling.

[Analysis of 2, 3-pyridinedicarboximide and its products conversed by engineering strain with high performance liquid chromatography].

A high performance liquid chromatography (HPLC) method was established for the detection of 2, 3-pyridinedicarboximide (PDI) and its enzyme reaction products, 3-carbamoyl-α-picolinic acid (α-3CP), using an engineering strain containing the D-hydantoinase gene expression box.The strain pET3a-hyd/BL21(DE3) was collected after induction and added to a PDI saturated aqueous solution.After reacting at 37℃ for 30 min with constant stirring, the supernatant was separated by centrifugation at 13000 r/min and detected by HPLC.The chromatographic conditions were as follows:HypersilTM GOLD C18 column (250 mm×4.6 mm, 5 µm), H2O-acetonitrile (90:10, v/v) containing 0.1%(v/v) trifluoroacetic acid as the mobile phase with a flow rate of 1 mL/min and a detection wavelength of 254 nm.The specific activity of pET3a-hyd/BL21(DE3) was found to be 0.61 U/(mL·10OD600 nm).This study provides a theoretical basis for the preparation of complicated half-amides using biological methods.

A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes.

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic nature of the monomer is conserved. The resulting polymer, polynorbornene, has a very high glass transition temperature, Tg, and interesting optical and electrical properties. However, the polymerization of functional norbornenes by this mechanism is complicated by the fact that the endo substituted norbornene monomer has, in general, a very low reactivity. Furthermore, the separation of the endo substituted monomer from the exo monomer is a tedious task. Here, we present a simple protocol for the polymerization of substituted norbornenes (endo:exo ca. 80:20) bearing either a carboxylic acid or a pendant double bond. The process does not require that both isomers be separated, and proceeds with low catalyst loadings (0.01 to 0.02 mol%). The polymer bearing pendant double bonds can be further transformed in high yield, to afford a polymer bearing pendant epoxy groups. These simple procedures can be applied to prepare polynorbornenes with a variety of functional groups, such as esters, alcohols, imides, double bonds, carboxylic acids, bromo-alkyls, aldehydes and anhydrides.

Helical aromatic imide based enantiomers with full-color circularly polarized luminescence.

Five pairs of enantiomers based on helical aromatic imides were synthesized, and their absolute configurations were determined using X-ray crystal structures. It was found that the enantiomers not only exhibited large Stokes shifts and high quantum yields, but also showed mirror image CD signals and full-color CPL properties.

Application of toxicity identification evaluation procedure to toxic industrial effluent in South Korea.

Toxicity identification evaluation (TIE) was applied to the effluent from a pharmaceutical industrial complex, following the US EPA TIE guidelines. The whole effluent toxicity (WET) test found toxicity greater than 16toxic units (TU) in the effluent. Dissolved non-polar organic compounds were identified as the major contributor to the observed toxicity in the TIE manipulations in phases I and II. Among the 48 organic compounds identified, three compounds (i.e., acetophenone, benzoimide, and benzothiazole) were related to the pharmaceutical production procedure; however, no contribution to toxicity was predicted in the compounds. The results of the ECOSAR model, which predicts toxicity, indicated that the alkane compounds caused significant toxicity in the effluent. The toxicity test and heavy metal analysis, which used IC and ICP/MS, identified that particulate and heavy metals, such as Cu and Zn, contributed to the remaining toxicity, except dissolved organics. The results showed the applicability of the TIE method for predicting regional effluents produced by the industrial pharmaceutical complex in this study. Although the location was assumed to be affected by discharge of pharmaceutical related compounds in the river, no correlations were observed in the study. Based on the results, advanced treatment processes, such as activated carbon adsorption, are recommended for the wastewater treatment process in this location.

A fluorescence method for estimation of toxemia: binding capacity of lipoproteins and albumin in plasma.

The hazard of toxemia, a condition resulting from the spread of toxins by the bloodstream, is regulated by plasma proteins capable of binding with free toxins. As toxin binding results in a reduction of available binding sites, measuring the proteins' binding capacity can be used to estimate toxemia severity. Suggested by this approach, a novel fluorescence method was developed to determine lipoprotein and albumin binding capacities in whole plasma. The method entails two steps: specific binding of N(n-carboxy)phenylimide-4-dimethyl-aminonaphthalic acid with albumin followed by addition of 12-(9-anthroyloxy)stearic acid which, under these conditions, binds mostly with lipoprotein. Reduced fluorescence intensity of the probes in plasma of patients compared to that of healthy donors reflected saturation of binding sites by toxins, thereby estimating toxemia severity. Poor correlation was found between the lipoprotein and albumin binding abilities, suggesting their independent diagnostic values. The simplicity and rapidity of this method are advantageous for its clinical application.

Gas chromatographic-mass spectrometric separation, identification and determination of C6-C12 cyclic imides in thermally treated epoxy and alkyd resins to locate hot spots inside large electricity generators.

A simple and rapid GC-MS method for separation, identification and quantitative determination of long-chain cyclic imides in the 300 degrees C thermally treated epoxy and alkyd resins has been developed. The method provides a positive means of identifying C6-C12 cyclic imide derivatives by GC-MS and enables the specific area of overheating to be identified, thereby averting catastrophic failures of power generators in service.

Gas chromatographic analysis of norcantharidin and related compounds using derivatization to imides.

Derivatization to imides has been studied for determining alpha,beta-diacids or corresponding anhydrides (e.g. norcantharidin) as well as for analysing primary amines by gas chromatography. 2-Naphthylaniline, n-heptylamine, cyclohexamine, 2,5-dimethoxyaniline, 2,4,5-trichloroaniline, 3,5-dichloroaniline, aniline and benzylaniline were used as derivatization reagents. 1H-nuclear magnetic resonance and mass spectrometry data were obtained for the norcantharidin N-imides synthesized. Factors such as derivatization yields, linearity, reproducibility and sensitivity were evaluated. The influences of reaction temperature and solvent were investigated.

Isolation and identification of cyclic imide and deamidation products in heat stressed pramlintide injection drug product.

This report summarizes the identification of six cyclic imide [Asu] and two deamidation products from a sample of pramlintide final drug product that had been stressed at 40 degrees C for 45 days. The pramlintide degradation products were isolated by cation exchange high-performance liquid chromatography (HPLC) followed by reversed-phase HPLC. The isolated components were characterized by mass spectrometry (MS), tandem MS (MS/MS) and when necessary, by enzymatic (thermolysin) digestion followed by liquid chromatography/mass spectrometry (LC/MS) and sequence analysis. The isolated products were identified as [Asu14]-pramlintide, [Asu21]-pramlintide, [Asu22]-pramlintide, [Asu35]-pramlintide, [1-21]-succinimide-pramlintide, and [1-22]-succinimide-pramlintide. Also identified were [Asp35]-pramlintide, the deamidation product of pramlintide at Asn35, and [Tyr37-OH]-pramlintide, the deamidation product of the pramlintide amidated C-terminal Tyr. Together these data support those presented earlier (C. Hekman et al., Isolation and identification of peptide degradation products of heat stressed pramlintide injection drug product. Pharm Res 1998;15:650-9) indicating that the primary mechanism of degradation for pramlintide in this pH 4.0 formulation is deamidation, with six of the eight possible deamidation sites observed to undergo deamidation. Gln-10 and Asn-31 are the only two residues subject to deamidation for which none is observed. The data indicate that the cyclic imide products account for approximately 20% of the total thermal degradation while the deamidation products account for 64%. The remaining degradation is due to peptide backbone hydrolysis.

The isolation and identification of a toxic impurity in XP315 drug substance.

In early safety assessment studies with the experimental anti-neoplastic drug XP315, a toxic reaction was observed in dogs immediately after intravenous (iv) infusion. The reaction was characterized by severe erythema around the ears, eyes, face and body; ocular hyperemia; head shaking; swelling around the eyes, face, paws, head, neck and legs; scratching; and reddened gums, which lasted several hours after dosing. By fractionating the drug substance using preparative HPLC and then infusing the residues into dogs by iv, this reaction was traced to an impurity in the drug substance. Following the preparative isolation of the toxic impurity, characterization was performed using a combination of NMR and mass spectral methods. The proposed impurity was found to be structurally related and nearly twice the molecular weight of XP315, resulting from a dimerization by ring fusion of two 3-aminonaphthalene fragments during the synthetic process. This paper details the steps taken to isolate the toxic impurity and characterize its structure using off-line methods.

Sequential thin-layer chromatography of phosfolan, mephosfolan and related compounds.

A sequential thin-layer chromatographic method (STLC) has been developed to analyze the two organophosphorus insecticides phosfolan (O,O-diethyl 1,3-dithiolan-2-ylidenephosphoramidate) and mephospholan (O,O-diethyl 4-methyl-1,3-dithiolan-2-ylidenephosphoramidate) and some of their possible degradation products. Gelman type SA, Instant Thin Layer Chromatography (ITLC) silicic acid-impregnated glass fiber sheets were first developed up to 6 cm with the primary solvent 2-butanone-1-butanol-water (9:3:1), then after drying, to 16 cm with the secondary solvent acetonitrile-n-hexane-benzene-acetic acid (80:40:40:1). This two-solvent sequential system separated each insecticide from its corresponding metabolites. The R1 values were: phosfolan, 0.69; ethylene dithioimido-carbonate hydrochloride, 0.08; ethylene dithiocarbonate, 0.90; potassium thiocyanate, 0.40; mephosfolan, 0.76; O,O-diethyl 4-hydroxymethyl-1,3-dithiolan-2-amidate, 0.83; propylene dithioimidocarbonate hydrochloride; 0.15 and propylene dithiocarbonate, 0.87.

Identification of drugs and other toxic compounds from their ultraviolet spectra. Part II: Ultraviolet absorption properties of thirteen structural groups.

The ultraviolet absorption spectra of 13 different chemical classes of drugs and toxic organic compounds were studied. A classification system has been developed in which compounds with the same conjugated molecular system and auxochrome substituents are grouped together. Each of these groups has characteristic absorption spectra, showing similarities in the number of major bands, position of maximum absorbance, pH effects, and solvent effects. The absorption maxima and molecular absorptivities are tabulated for approximately 100 compounds, and characteristic spectra of each designated group are illustrated. Classes of drugs included in this study are pyridine derivatives, hydrazines, pyridylamine derivatives, variously substituted phenols, barbiturates, ureides, imides, hydantoins, and conjugted ketones (enones).

Impact of local compressive stress on the optical transitions of single organic dye molecules.

The ability to mechanically control the optical properties of individual molecules is a grand challenge in nanoscience and could enable the manipulation of chemical reactivity at the single-molecule level. In the past, light has been used to alter the emission wavelength of individual molecules or modulate the energy transfer quantum yield between them. Furthermore, tensile stress has been applied to study the force dependence of protein folding/unfolding and of the chemistry and photochemistry of single molecules, although in these mechanical experiments the strength of the weakest bond limits the amount of applicable force. Here, we show that compressive stress modifies the photophysical properties of individual dye molecules. We use an atomic force microscope tip to prod individual molecules adsorbed on a surface and follow the effect of the applied force on the electronic states of the molecule by fluorescence spectroscopy. Applying a localized compressive force on an isolated molecule induces a stress that is redistributed throughout the structure. Accordingly, we observe reversible spectral shifts and even shifts that persist after retracting the microscope tip, which we attribute to transitions to metastable states. Using quantum-mechanical calculations, we show that these photophysical changes can be associated with transitions among the different possible conformers of the adsorbed molecule.

Detection of parasitic plant suicide germination compounds using a high-throughput Arabidopsis HTL/KAI2 strigolactone perception system.

Strigolactones are terpenoid-based plant hormones that act as communication signals within a plant, between plants and fungi, and between parasitic plants and their hosts. Here we show that an active enantiomer form of the strigolactone GR24, the germination stimulant karrikin, and a number of structurally related small molecules called cotylimides all bind the HTL/KAI2 α/ß hydrolase in Arabidopsis. Strigolactones and cotylimides also promoted an interaction between HTL/KAI2 and the F-box protein MAX2 in yeast. Identification of this chemically dependent protein-protein interaction prompted the development of a yeast-based, high-throughput chemical screen for potential strigolactone mimics. Of the 40 lead compounds identified, three were found to have in planta strigolactone activity using Arabidopsis-based assays. More importantly, these three compounds were all found to stimulate suicide germination of the obligate parasitic plant Striga hermonthica. These results suggest that screening strategies involving yeast/Arabidopsis models may be useful in combating parasitic plant infestations.

Extraction of imide fungicides in water and juice samples using magnetic graphene nanoparticles as adsorbent followed by their determination with gas chromatography and electron capture detection.

In this paper, a sensitive analytical method for four fungicides (procymidone, folpet, vinclozolin and ditalimfos) in environmental water and juice samples was developed by using magnetic solid-phase extraction (MSPE) with magnetic graphene nanocomposite (G-Fe3O4) as the adsorbent, followed by determination with gas chromatography and electron capture detection. Parameters such as the amount of G-Fe3O4, extraction time, ionic strength and pH of the sample solution, desorption solvent and desorption time were optimized. Under the optimum conditions, the enrichment factors of the method for the analytes were in the range from 1495 to 1849. The limits of detection for the fungicides ranged from 1.0 to 7.0 ng L(-1). The recoveries of the method for the analytes were in the range from 79.2 to 102.4%. The developed G-Fe3O4-MSPE method was simple and efficient for the extraction and determination of the four fungicides in water and grape juice samples.