Detection of Exposure to Environmental Pesticides During Pregnancy by the Analysis of Maternal Hair Using GC–MS

Several classes of pesticides were extracted from maternal hair by solid-liquid extraction. Analysis of their selected metabolites involved a methanolic/hydrochloric acid methyl ester derivatization and liquid-liquid extraction. Gas chromatography electron impact mass spectrometry was used to detect and quantify the pesticides and metabolites. Recovery of parent compounds and metabolites from the analysis of spiked hair ranged from 87 to 112% with coefficients of variation less than 11%. Limits of detection ranged from 0.031 to 5.88 μg g(-1). Analysis of hair samples from pregnant women in the Philippines showed maternal exposure during pregnancy to bioallethrin, propoxur, chlorpyrifos, pretilachlor and malathion.     

Expression of hepatitis C virus nonstructural 4B in transgenic mice

Hepatitis C virus (HCV) is a pathogen that is of great medical significance in chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma worldwide. Although the HCV proteins have been intensively investigated over the past decade, the biochemical functions of the NS4B protein are still largely unknown. To investigate NS4B as a potential causative agent of liver disease, transgenic mice expressing the NS4B protein in liver tissue were produced. The transgenic animals were phenotypically similar to their normal littermates for up to 18 months of age. Our results suggest that the HCV NS4B protein is not directly cytopathic or oncogenic in our transgenic mice model.     

Syntheses and structures of half-sandwich iridium(III) and rhodium(III) complexes with organochalcogen (S, Se) ligands bearing N-methylimidazole and their use as catalysts for norbornene polymerization

The organochalcogen ligands derived from 3-methyl-imidazole-2-thione/selone groups, Mbit, Mbis, Ebit and Ebis [Mbit = 1,1'-methylenebis(3-methyl-imidazole-2-thione); Mbis = 1,1'-methylenebis(3-methyl-imidazole-2-selone), Ebit = 1,1'-(1,2-ethanediyl)bis(3-methyl-imidazole-2-thione), Ebis = 1,1'-(1,2-ethanediyl)bis(3-methyl-imidazole-2-selone)] have been synthesized and characterized. Reactions of [Cp*Ir(micro-Cl)Cl]2 and [Cp*Rh(micro-Cl)Cl]2 (Cp* = eta5-pentamethylcyclopentadienyl) with Mbit, Mbis, Ebit and Ebis result in the formation of the complexes [Cp*Ir(Mbit)Cl]Cl 1a x Cl), [Cp*Ir(Mbis)Cl]Cl (3a x Cl), [Cp*Ir(Ebit)Cl]Cl (1b x Cl), [Cp*Ir(Ebis)Cl]Cl (2a x Cl), [Cp*Rh(Mbit)Cl]Cl (2b x Cl), Cp*Rh(Mbis)Cl][Cp*RhCl(3)] (3b x[Cp*RhCl(3)]), [Cp*Rh(Ebit)Cl]Cl (4a x Cl) and [Cp*Rh(Ebis)Cl]Cl (4b x Cl), respectively. All compounds have been characterized by elemental analysis, NMR and IR spectra. The molecular structures of 1b, 2b, 3a, 3b and 4a have been determined by X-ray crystallography. After activation with methylaluminoxane (MAO), the iridium complexes exhibit moderate activities for the vinyl polymerization of norbornene.     

Electrochemical origin of voltage-controlled molecular conductance switching

We have studied electron transport in bipyridyl-dinitro oligophenylene-ethynelene dithiol (BPDN) molecules both in an inert environment and in aqueous electrolyte under potential control, using scanning tunneling microscopy. Current-voltage (IV) data obtained in an inert environment were similar to previously reported results showing conductance switching near 1.6 V. Similar measurements taken in electrolyte under potential control showed a linear dependence of the bias for switching on the electrochemical potential. Extrapolation of the potentials to zero switching bias coincided with the potentials of redox processes on these molecules. Thus switching is caused by a change in the oxidation state of the molecules.     

Ultrafast spectroscopic study of the photochemistry and photophysics of arylhalodiazirines: direct observation of carbene and zwitterion formation

Ultrafast photolysis (lambdaex = 270, 350, or 360 nm) of bromophenyl, chlorophenyl, fluorophenyl, and fluoro-para-trifluoromethylphenyl diazirines produces transient species which absorb broadly in the UV and visible regions. Transient decay can be fit to either mono- or biexponential functions (tau1 approximately 0.3-10 ps, tau2 approximately 10-350 ps; dependent on solvent and halogen). Fluoro- and chlorophenylcarbene are formed within the time resolution of the spectrometer (300 fs, 270 nm excitation). Bromophenyl diazirine decay (270 nm excitation) correlates with the growth of bromophenylcarbene. Solvent and substituent effects on the slower decays of the transient absorptions are consistent with assigning the carriers of transient absorption in the visible region to ring-opened zwitterionic species.     

The toxicosis and detoxifcation of anionic/cationic surfactants targeted to bovine serum albumin

By using the techniques of resonance light scattering (RLS) and absorption spectra, we studied the toxicosis and detoxifcation mechanism of anionic surfactant SDBS and cationic surfactant CTMAB targeted to bovine serum albumin (BSA). Small quantity of CTMAB combines with SDBS-BSA complex to form SDBS-BSA-CTMAB complex and the IRLS of system enhanced greatly. With the cumulation of quantity, CTMAB captures SDBS from SDBS-BSA complex by electrostatic attraction and CTMAB-SDBS complex forms, meanwhile BSA automatically frees, which is corresponding to the toxicosis and detoxifcation process. Absorption experiment validates that SDBS induces the denaturalization of BSA and CTMAB facilitates the refolding of this protein.     

A fluorescent chemosensor for cobalt ions based on a multi-substituted phenol-ruthenium(II) tris(bipyridine) complex

An amide-linked 2,6-bis{[(2-hydroxy-5-tert-butylbenzyl)(pyridyl-2-methyl)-amino]-methyl}-4-methylphenol-ruthenium(II) tris(bipyridine) 2PF₆⁻ complex, 1, was first used to recognize Co(II) in EtOH/H₂O (1:1, v/v) solution, with the ruthenium(II) tris(bipyridine) moiety selected as a fluorophore and the multi-substituted phenol unit chosen as a receptor. The fluorescence quenching of 1 was attributed to the formation of an inclusion complex between multi-substituted phenol unit and Co(II) by 1:1 complex ratio (K = 2.5 × 10⁵), which has been utilized as the basis of the fabrication of the Co(II)-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Co(II)-sensitive chemosensor were investigated. The sensor can be applied to the quantification of Co(II) with a linear range covering from 1.0 × 10⁻⁷ to 5.0 × 10⁻⁵ M and a detection limit of 5 × 10⁻⁸ M. The experiment results show that the response behavior of 1 to Co(II) is pH-independent in medium condition (pH 4.5–9.5) and show excellent selectivity for Co(II) over transition metal cations except Cu(II). The chemosensor has been used for determination of Co(II) in water samples.     

Development of core–shell structure Fe3O4@Ta2O5 microspheres for selective enrichment of phosphopeptides for mass spectrometry analysis

Protein phosphorylation is one of the most important post-translational modifications. Due to the dynamic nature and low stoichiometry of the protein phosphorylation, enrichment of phosphopeptides from proteolytic mixtures is often necessary prior to their characterization by mass spectrometry. Many metal oxides such as titanium dioxide and zirconium dioxide have been successfully applied to isolation and enrichment of phosphopeptides. Recently, niobium pentoxide was proved to have the ability for selective enrichment of phosphopeptides. Considering the proximity of tantalum to niobium, we supposed that Ta₂O₅ can be used as affinity probes for phosphopeptide enrichment. In the work, we synthesized Fe₃O₄@Ta₂O₅ magnetic microspheres with core–shell structure for selective enrichment of phosphopeptides. To demonstrate its ability for selective enrichment of phosphopeptides, we applied Fe₃O₄@Ta₂O₅ magnetic microspheres to isolation and enrichment of the phosphopeptides from tryptic digestion of standard proteins and real samples, and then the enriched peptides were analyzed by matrix-assisted laser desorption mass spectrometry analysis (MALDI-MS) or liquid chromatography coupled to electrospray ionization mass spectrometry (LC–ESI-MS). Experiment results demonstrate that Ta₂O₅ coated-magnetic microspheres show the excellent potential for selective enrichment of phosphopeptides.     

Prevention of UV radiation-induced premature skin aging in hairless mice by the novel compound Melanocin A

Repetitive exposure of the skin to UV radiation induces various harmful changes, such as thickening, wrinkle formation, inflammation and carcinogenesis. A variety of natural compounds and synthetic compounds have been studied to determine whether they can prevent UV-induced harmful effects. In this study, we investigated the effect of a novel compound, Melanocin A, which was isolated from Eupenicillium shearii F80695, on UV-induced premature skin aging. First, we studied the effect of Melanocin A on UV-induced matrix metalloproteinase (MMP)-9 expression in an immortalized human keratinocyte cell line, HaCaT, in vitro. Acute UV irradiation induced MMP-9 expression at both the mRNA and protein levels and Melanocin A suppressed this expression in a dose-dependent manner. We then investigated the effect of Melanocin A on UV-induced skin changes in hairless mice in vivo. Chronic exposure of hairless mouse dorsal skin to UV increased skin thickness and induced wrinkle formation and the gelatinase activities of MMP-2 and MMP-9. Moreover, Melanocin A significantly suppressed UV-induced morphologic skin changes and MMP-2 and MMP-9 expression. Taken together, these results show that Melanocin A can prevent the harmful effects of UV that lead to skin aging. Therefore, we suggest that Melanocin A should be viewed as a potential therapeutic agent for preventing and/or treating premature skin aging.