Resonance light‐scattering enhancement effect of the protein–Y3+–TTA–SLS system and its analytical application

In this paper, a sensitive resonance light scattering (RLS) method for the determination of protein is reported. In the Tris–HCl (pH 7.50) buffer, protein enhanced the RLS intensity of the Y³⁺–2‐thenoyltrifluoroacetone (TTA)–sodium dodecyl sulphate (SLS) system. The enhanced RLS intensities were in proportion to the concentrations of proteins in the range 8.0 × 10^?9–1.0 × 10^?5 g/mL for BSA, 1.0 × 10^–8–1.0 × 10^?5 g/mL for HSA and 1.0 × 10^–8–1.0 × 10^?6 g/mL for EA, and their detection limits were 5.0, 5.4 and 6.7 ng/mL, respectively. Actual samples were satisfactorily determined. The interaction mechanism was also studied. Copyright © 2008 John Wiley & Sons, Ltd.     

Exposure to polychlorinated biphenyls causes endothelial cell dysfunction

Environmental chemicals, such as polychlorinated biphenyls (PCBs), may be atherogenic by disrupting normal functions of the vascular endothelium. To investigate this hypothesis, porcine pulmonary artery-derived endothelial cells were exposed to 3,3′,4,4′-tetrachlorobiphenyl (PCB 77), 2,3,4,4′,5-pentachlorobiphenyl (PCB 114), or 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153) for up to 24 hours. These PCBs were selected for their varying binding avidities with the aryl hydrocarbon (Ah) receptor and differences in their induction of cytochrome P450. PCB 77 and PCB 114 significantly disrupted, in a dose-dependent manner, endothelial barrier function by allowing an increase in albumin transfer across endothelial monolayers. These PCBs also contributed markedly to cellular oxidative stress, as measured by 2,7-dichlorofluorescin (DCF) fluorescence and lipid hydroperoxides, and caused a significant increase in intracellular calcium ([Ca²⁺]_i) levels. Enhanced oxidative stress and [Ca²⁺]_i in PCB 77- and PCB 114-treated cells were accompanied by increased activity and content of cytochrome P450 1A and by a decrease in the vitamin E content in the culture medium. In contrast to the effects of PCB 77 and PCB 114, cell exposure to PCB 153 had no effect on cellular oxidation, [Ca²⁺]_i, or endothelial barrier function. These results suggest that certain PCBs may play a role in the development of atherosclerosis by causing endothelial cell dysfunction and a decrease in the barrier function of the vascular endothelium. It is possible that interaction of PCBs with the Ah receptor and activation of the cytochrome P450 1A subfamily are involved in this pathology. © 1995 John Wiley & Sons, Inc.     

Extracts and phenolic compounds from Zuccagnia punctata as fungicide seed protectants for corn

The ethanolic leaf extract (TZP) of Zuccagnia punctata, its ethereal fraction (Eet), 2′,4′‐dihydroxychalcone (DC), 2′,4′‐dihydroxy‐3′‐methoxychalcone (DMC) and 7‐hydroxy‐3′,4′‐dimethoxyflavone (HF) were evaluated as fungicide seed protectants on corn. Microdilution assays on a set of Fusarium strains showed minimum inhibitory concentrations (MICs) of 400–800 μg mL^?1 (TZP), 50–100 μg mL^?1 (Eet), 25–50 μg mL^?1 (DC), 50–100 μg mL^?1 (DMC) and 200–400 μg mL^?1 (HF), with minimum fungicidal concentration (MFC)/MIC = 1. Suspensions of TZP, Eet, DC and DMC at MIC × 20 incorporated to the grains at rates of 1920, 240, 120 and 240 mg dry matter kg^?1 of grain, respectively, increased the elongation of the primary roots (24–44%) and the number of seminal roots (44–50%). TZP also increased the number of secondary roots. HF was phytotoxic. Suspensions of TZP, Eet, DC and DMC suppressed the endogenous grain mycoflora at levels similar to those recorded for a thiram + carbendazim‐based fungicide. Grains treated with TZP (1920 mg kg^?1), Eet (240 mg kg^?1), DC (120 mg kg^?1) and DMC (240 mg kg^?1) stimulated the growth of the seedling root system both because of fungal suppression and hormetic effects in greenhouse curative and preventive assays against Fusarium verticillioides on a sand/soil substrate. Eet and its chalcones also reduced the severity of seedling blight more than the thiram + carbendazim‐based fungicide in preventive assays and led to the same disease severity observed for the fungicide treatment in the curative assays. Our results show that Eet and its chalcones not only were effective seed protectants against F. verticillioides and other seedborne fungi, but also improved the early performance of maize seedlings.     

Capillary electrophoresis analysis of isoniazid using luminol-periodate potassium chemiluminescence system

A rapid and simple capillary electrophoresis method coupled with chemiluminescent (CL) detection was proposed for analysis of isoniazid (ISO) based on the enhancement effect of ISO to CL emission of luminol‐periodate potassium reaction. Under the optimal conditions, ISO can be assayed in the range of 7.0 × 10^?7 to 3.0 × 10^?5 g mL^?1 (R² = 0.9990) with a limit of detection of 3.0 × 10^?7 g mL^?1 (signal‐to‐noise ratio of 3). The whole analysis process can be completed within 2.5 min with a theoretical plate number of 6258. The relative standard deviations of the signal intensity and the migration time were 3.1 and 1.4% for a standard sample at 1.0 × 10^?5 g mL^?1 (n = 5), respectively. The presented novel strategy was successfully applied to the determination of ISO in commercial pharmaceutical preparations and spiked human serum samples. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of the rotational barriers of atropisomeric polychlorinated biphenyls (PCBs) by a novel stopped-flow multidimensional gas chromatographic technique

The rotational barriers ΔG^‡ (T) of the four atropisomeric polychlorinated biphenyls (PCBs) 2,2′,3,5′,6-pentachlorobiphenyl (PCB 95), 2,2′3,3′,4,6′-hexachlorobiphenyl (PCB 132), 2,2′,3,3′,6,6′-hexachlorobiphenyl (PCB 136), and 2,2′,3,4′,5′,6-hexachlorobiphenyl (PCB 149) were determined via on-line enantiomerization kinetics by a new stopped-flow multidimensional gas chromatographic technique (stopped-flow MDGC) employing Chirasil-Dex as chiral stationary phase for enantiomer separation. The calculated rotational barriers ΔG^‡ (T) of the trichloro-ortho-substituted atropisomers are 184 ± 2 kJ/mol for PCB 95, 189 ± 4 kJ/mol for PCB 132, and 184 ± 1 kJ/mol for PCB 149 at 300°C. The rotational barrier ΔG^‡ (T) of tetrachloro-ortho-substituted PCB 136 is at least (or higher than) 210 kJ/mol at 320°C. Chirality 10:316–320, 1998. © 1998 Wiley-Liss, Inc.     

A flow injection chemiluminescence method for the determination of lincomycin in serum using a diperiodato-cuprate (III)-luminol system

In this paper, the novel trivalent copper–periodate complex {K₅[Cu(HIO₆)₂], DPC} has been applied in a luminol‐based chemiluminescence (CL) reaction. Coupled with flow injection (FI) technology, the FI‐CL method was proposed for the determination of lincomycin hydrochloride. The CL reaction between luminol and DPC occurred in an alkaline medium. The CL intensity could be greatly enhanced by lincomycin hydrochloride. The relative CL intensity was proportional to the concentration of lincomycin hydrochloride in the range of 1 × 10^?8 to 5 × 10^?6 g mL^?1 and the detection limit was at the 3.5 × 10^?9 g mL^?1 level. The relative standard deviation at 5 × 10^?8 g mL^?1 was 1.7% (n = 9). The sensitive method was successfully applied to the direct determination of lincomycin hydrochloride (ng mL^?1) in serum. A possible mechanism of the lumonol–DPC CL reaction was discussed by the study of the CL kinetic characteristics and the spectra of CL reaction. The oxidability of DPC was studied by means of its electrochemical response. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of dipyridamole using TCPO–H2O2 chemiluminescence in the presence of silver nanoparticles

The method is based on the fact that dipyridamole can enhance the chemiluminescence (CL) emission from the redox reaction of bis (2,4,6‐tricholorophenyl) oxalate (TCPO) with H₂O₂ in the presence of silver nanoparticles (AgNPs). The CL reaction mechanism was discussed. The effect of concentrations of TCPO, H₂O₂, AgNPs and pH value on the CL reaction were investigated. Under the optimum conditions, the linear dynamic range was 1.0–1000 × 10^?9 g/mL and the detection limit (3σ) was 9 × 10^?10 g/mL. The relative standard deviation (RSD) was 4.8% for 1.0 × 10^?9 g/mL dipyridamole (n = 7). The proposed method has been successfully applied to the determination of dipyridamole tablets and the recovery was 99–103%. Copyright © 2011 John Wiley & Sons, Ltd.     

Batch‐to‐Batch Variation of Polymeric Photovoltaic Materials: its Origin and Impacts on Charge Carrier Transport and Device Performances

A detailed investigation of the impact of molecular weight distribution of a photoactive polymer, poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] (PCDTBT), on photovoltaic device performance and carrier transport properties is reported. It is found that different batches of as‐received polymers have substantial differences in their molecular weight distribution. As revealed by gel permeation chromatography (GPC), two peaks can generally be observed. One of the peaks corresponds to a high molecular weight component and the other peak corresponds to a low molecular weight component. Photovoltaic devices fabricated with a higher proportion of low molecular weight component have power conversion efficiencies (PCEs) reduced from 5.7% to 2.5%. The corresponding charge carrier mobility at the short‐circuit region is also significantly reduced from 2.7 × 10^?5 to 1.6 × 10^?8 cm² V^?1 s^?1. The carrier transport properties of the polymers at various temperatures are further analyzed by the Gaussian disorder model (GDM). All polymers have similar energetic disorders. However, they appear to have significant differences in carrier hopping distances. This result provides insight into the origin of the molecular weight effect on carrier transport in polymeric semiconducting materials.     

NaCS‐PDMDAAC immobilized cultivation of recombinant Dictyostelium discoideum for soluble human Fas ligand production

Dictyostelium discoideum is a promising eukaryotic host for the expression of heterologous proteins requiring post‐translational modifications. However, the dilute nature of D. discoideum cell culture limits applications for high value proteins production. D. discoideum cells, entrapped in sodium cellulose sulfate/poly‐dimethyl‐diallyl‐ammonium chloride (NaCS‐PDMDAAC) capsules were used for biosynthesis of the heterologous protein, soluble human Fas ligand (hFasL). Semi‐continuous cultivations with capsules recycling were carried out in shake flasks. Also, a scaled‐up cultivation of immobilized D. discoideum for hFasL production in a customized vitreous airlift bioreactor was conducted. The results show that NaCS‐PDMDAAC capsules have desirable biophysical properties including biocompatibility with the D. discoideum cells and good mechanical stability throughout the duration of cultivation. A maximum cell density of 2.02 × 10⁷ cells mL^?1 (equivalent to a maximum cell density of 2.22 × 10⁸ cells mL^?1 in capsules) and a hFasL concentration of 130.40 μg L^?1 (equivalent to a hFasL concentration of 1434.40 μg L^?1 in capsules) were obtained in shake flask cultivation with capsules recycling. Also, a maximum cell density of 1.72 × 10⁷cells mL^?1 (equivalent to a maximum cell density of 1.89 × 10⁸ cells mL^?1 in capsules) and a hFasL concentration of 106.10 μg L^?1 (equivalent to a hFasL concentration of 1167.10 μg L^?1 in capsules) were obtained after ～170 h cultivation in the airlift bioreactor (with a working volume of 200 mL in a 315 mL bioreactor). As the article presents a premier work in the application of NaCS‐PDMDAAC immobilized D. discoideum cells for the production of hFasL, more work is required to further optimize the system to generate higher cell densities and hFasL titers for large‐scale applications. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 31:424–430, 2015     

Reconstituted human breast milk PCBs as potent inducers of aryl hydrocarbon hydroxylase

The major polychlorinated biphenyl (PCB) components identified in human breast milk have been synthesized and a reconstituted breast milk PCB mixture representing the average levels determined in the Osaka Prefecture in Japan has been prepared. The dose effecting the half-maximal (ED₅₀) induction of rat hepatic microsomal aryl hydrocarbon hydroxylase (AHH) for the reconstituted breast milk PCBs (ED₅₀ ～12 μmol·kg^?1) was approximately seven times less than the ED₅₀ for the commercial PCB mixture, Kanechlor 500. The increased biological potency of the former mixture reflects the preferential bioconcentration of the toxic PCB congeners, 2,3,3′,4,4′-penta-, 2,3′,4,4′,5-penta- and 2,3,3′,4,4′,5-hexachlorobiphenyl.     

Diazepinone Nucleosides as Inhibitors of Cytidine Deaminase.

Abstract

The synthesis of 2′-deoxy and 2′,3′-dideoxy derivatives of 1-ß-D-ribofuranosyl-1,3,4,7-tetrahydro-2H-1,3-diazepin-2-one (2) was undertaken in order to find new cytidine deaminase (CDA) inhibitors and potential adjuvants in anticancer chemotherapy. Replacement of ribose by a 2-deoxyribose moiety led to compound 9 that appeared slightly more potent than 2 (Ki = 2.5 × 10^?8 M). Remarkably, the corresponding α-2′-deoxynucleoside 10 acted as a very potent inhibitor of human placenta CDA, with a Ki = 7.5 × 10^?8 M. Attempt to synthesize the 2′,3′-dideoxy derivative of 2 led to N-[4,5-dihydroxy-1-(2-oxo-2,3,4,7-tetrahydro[1,3] diazepin-1-yl)-pentyl]-2,2,2-trifluoroacetamide (13), which is devoid of CDA inhibitory activity.     

Flow injection chemiluminescence determination of 6‐mercaptopurine based on a new system of potassium permanganate–thioacetamide–sodium hexametaphosphate

A novel chemiluminescence method for the determination of 6‐mercaptopurine was established based on 6‐mercaptopurine inhibition of the chemiluminescence emission of potassium permanganate–thioacetamide–sodium hexametaphosphate system. The peak height was proportional to log 6‐mercaptopurine concentration in the range 7.0 × 10^?10 to 1.0 × 10^?7 g/mL and the detection limit was 1.9 × 10^?11 g/mL (S/N = 3). The relative standard deviation was 1.5% for the determination of 8.0 × 10^?8 g/mL 6‐mercaptopurine (n = 11). The proposed sensor was successfully applied to the analysis of 6‐mercaptopurine in human serum samples. Copyright © 2009 John Wiley & Sons, Ltd.     

pH effects on growth and lipid accumulation of the biofuel microalgae Nannochloropsis salina and invading organisms

Biofuels derived from non-crop sources, such as microalgae, offer their own advantages and limitations. Despite high growth rates and lipid accumulation, microalgae cultivation still requires more energy than it produces. Furthermore, invading organisms can lower efficiency of algae production. Simple environmental changes might be able to increase algae productivity while minimizing undesired organisms like competitive algae or predatory algae grazers. Microalgae are susceptible to pH changes. In many production systems, pH is kept below 8 by CO₂ addition. Here, we uncouple the effects of pH and CO₂ input, by using chemical pH buffers and investigate how pH influences Nannochloropsis salina growth and lipid accumulation as well as invading organisms. We used a wide range of pH levels (5, 6, 7, 8, 9, and 10). N. salina showed highest growth rates at pH 8 and 9 (0.19?±?0.008 and 0.19?±?0.011, respectively; mean ± SD). Maximum cell densities in these treatments were reached around 21 days into the experiment (95.6?×?10⁶?±?9?×?10⁶ cells mL^?1 for pH 8 and 92.8?×?10⁶?±?24?×?10⁶ cells mL^?1 for pH 9). Lipid accumulation of unbuffered controls were 21.8?±?5.8 % fatty acid methyl esters content by mass, and we were unable to trigger additional significant lipid accumulation by manipulating pH levels at the beginning of stationary phase. Ciliates (grazing predators) occurred in significant higher densities at pH 6 (56.9?±?39.6?×?10⁴ organisms mL^?1) than higher pH treatments (0.1–6.8?×?10⁴ organisms mL^?1). Furthermore, the addition of buffers themselves seemed to negatively impact diatoms (algal competitors). They were more abundant in an unbuffered control (12.7?±?5.1?×?10⁴ organisms mL^?1) than any of the pH treatments (3.6–4.7?×?10⁴ organisms mL^?1). In general, pH values of 8 to 9 might be most conducive to increasing algae production and minimizing invading organisms. CO₂ addition seems more valuable to algae as an inorganic carbon source and not as an essential mechanism to reduce pH.     

Quantum‐dots‐based fluoroimmunoassay for the rapid and sensitive detection of avian influenza virus subtype H5N1

The continuous spread of highly pathogenic avian influenza virus (AIV) subtype H5N1 is threatening the poultry industry and human health worldwide. Rapid and sensitive diagnostic methods are required for the H5N1 surveillance. In this study, the fluorescent (FL) probe of CdTe quantum dots (QDs) was designed using covalently linked rabbit anti‐AIV H5N1 antibody. Based on these QD–antibody conjugates, a novel sandwich FL‐linked immunosorbent assay (sFLISA) was developed for H5N1 viral antigen detection. The sFLISA allowed for H5N1 viral antigen determination in a linear range of 8.0 × 10^?3 to 5.1 × 10^?1 μg mL^?1 with the limit of detection (LOD) of 1.5 × 10^?4 μg mL^?1. In comparison with virus isolation for 103 clinic samples, the sensitivity and specificity of sFLISA were found to be 93.6 and 91.1% respectively. The sFLISA supplied a novel approach to rapid and sensitive detection of AIV subtype H5N1 and showed great potential for biological applications in immunoassays. Copyright © 2009 John Wiley & Sons, Ltd.     

Selective signaling of fluoride anion based on imidazole moieties

The imidazole ring unit in both 2‐(2′‐hydroxyphenyl)‐benzimidazole (ligand a) and a europium(III) complex exhibited specific luminescent responses in the presence of fluoride anions. UV‐visible and ¹H‐nuclear magnetic resonance spectra showed that the NH bond of the imidazole ring can form a hydrogen bond with added fluoride anions. The detection limits are 5 × 10^?6 m for organic ligand and 1.0 × 10^?6 m for the europium complex respectively. The response times are less than 3 s. The europium complex exhibits a linear response in a concentration range lower than 1.0 × 10^?6 m (Y = ?666.86X + 730.1). Copyright © 2011 John Wiley & Sons, Ltd.     

Highly selective determination of phenolphthalein by flow injection chemiluminescence method based on a molecular imprinting polymer

The phenolphthalein‐imprinted polymer was prepared with methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross‐linker. Taking advantage of the quenching effect of phenolphthalein on the potassium permanganate–HCl–anhydrous alcohol chemiluminescence system, a new model was established to determine phenolphthalein by a highly selective flow injection chemiluminescence method. The traditional flow‐though cell was replaced with a novel flow path using a Y‐shaped polymethyl methacrylate column, through which the three reactants were injected simultaneously. The linear range of this assay was from 1.0 × 10^?8 to 1.0 × 10^?6 g/mL (r = 0.9978). The limit of detection was 8.9 × 10^?9 g/mL. The relative standard deviation for the determination of 1.0 × 10^?8 g/mL phenolphthalein solution was below 2.9% (n = 11). The proposed method was applied to the determination of phenolphthalein in real samples with satisfactory results. Copyright © 2009 John Wiley & Sons, Ltd.     

Spectrophotometric and spectrofluorimetric determination of indacaterol maleate in pure form and pharmaceutical preparations: application to content uniformity

Two simple, rapid, sensitive and precise spectrophotometric and spectrofluorimetric methods were developed for the determination of indacaterol maleate in bulk powder and capsules. Both methods were based on the direct measurement of the drug in methanol. In the spectrophotometric merthod (Method I) the absorbance was measured at 259 nm. The absorbance‐concentration plot was rectilinear over the range 1.0–10.0 µg mL^?1 with a lower detection limit (LOD) of 0.078 µg mL^?1 and lower quantification limit (LOQ) of 0.238 µg mL^?1. Meanwhile in the spectrofluorimetric method (Method II) the native fluorescence was measured at 358 nm after excitation at 258 nm. The fluorescence‐concentration plot was rectilinear over the range of 1.0–40.0 ng mL^?1 with an LOD of 0.075 ng mL^?1and an LOQ of 0.226 ng mL^?1. The proposed methods were successfully applied to the determination of indacaterol maleate in capsules with average percent recoveries ± RSD% of 99.94 ± 0.96 for Method I and 99.97 ± 0.81 for Method II. In addition, the proposed methods were extended to a content uniformity test according to the United States Pharmacopoeia (USP) guidelines and were accurate, precise for the capsules studied with acceptance value 3.98 for Method I and 2.616 for Method II. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of ketotifen fumarate by capillary electrophoresis with tris(2,2′‐bipyridyl) ruthenium(II) electrochemiluminescence detection

On the basis of an europium (III)‐doped Prussian blue analog film modifying platinum electrode as the working electrode, a Ru(bpy)₃²⁺‐based electrochemiluminescence (ECL) assay coupled with capillary electrophoresis has been first established for the determination of ketotifen fumarate (KTF). Analytes were injected onto a separation capillary of 50 cm length (50 μm i.d., 360 μm o.d.) by electrokinetic injection for 10 s at 10 kV. Parameters related to the separation and detection were discussed and optimized. It was proved that 15 mm phosphate buffer at pH 8.0 could achieve the most favorable resolution, and the highest sensitivity of detection was obtained using the detection potential at 1.25 V and 5 mm Ru(bpy)₃²⁺ in 100 mm phosphate buffer at pH 8.0 in the detection reservoir. Under the optimized conditions, the ECL intensity was in proportion to KTF concentration over the range from 3.0 × 10^?8 to 5.0 × 10^?6 g mL^?1 with a detection limit of 2.1 × 10^?8 g mL^?1 (3σ). The relative standard deviations of the ECL intensity and the migration time were 0.95 and 0.26%, respectively. The developed method was successfully applied to determine KTF contents in pharmaceuticals and human urine with recoveries between 99.5 and 107.0%. Copyright © 2010 John Wiley & Sons, Ltd.     

The influence of low and high doses of theophylline on spontaneous motility and cyclic 3',5' AMP content in isolated rat uterus

It was found in isolated rat uterus that 5 × 10^?4 N theophylline inhibited spontaneous contractions which were restituted by increasing extracellular calcium 4-fold. Tissue level of cyclic 3′, 5′ AMP was not affected. On the other hand, 10^?2 M theophylline elevated cyclic 3′, 5′ AMP by 170 % for at least 60 minutes. The concomitant inhibition of spontaneous uterine motility could neither be restituted by increasing calcium up to 40-fold nor by washing. It was suggested that cyclic 3′, 5′ AMP was involved in theophylline-induced uterine relaxation when the drug was administrated in high amounts able to inhibit phosphodiesterase. Small doses of theophylline (5 × 10^?4 M) were supposed to initiate relaxing effects by a calcium-antagonistic intrinsic activity.