Study of Inhibition,Reactivation and Aging Processes of Pesticides Using Graphene Nanosheets/Gold Nanoparticles‐Based Acetylcholinesterase Biosensor

Organophosphate (OP) and carbamate pesticides exert their toxicity via attacking the hydroxyl moiety of serine in the ‘active site’ of acetylcholinesterase (AChE). In this paper we developed a stable AChE biosensor based on self‐assembling AChE to graphene nanosheet (GN)‐gold nanoparticles (AuNPs) nanocomposite electrode for investigation of inhibition, reactivation and aging processes of different pesticides. It is confirmed that pesticides can inhibit AChE in a short time. OPs poisoning is treatable with oximes while carbarmates exposure is insensitive to oximes. The proposed electrochemical approach thus provides a new simple tool for comparison of pesticide sensitivity and guide of therapeutic intervention.     

A chiral polymer‐based turn‐on fluorescent sensor for specific recognition of hydrogen sulfate

A new kind of polymeric chemosensor containing chiral naphthaldimine moiety in the side chain was synthesized by the reversible addition‐fragmentation chain transfer polymerization of N‐{[2‐(4‐vinylbenzyloxy)‐1‐naphthyl]‐methylene}‐(S)‐2‐phenylglycinol (VNP). The resulting polymers (PVNP) showed high selectivity for hydrogen sulfate relative to other anions including F^?, Cl^?, Br^?, H₂PO, CH₃CO, and NO in tetrahydrofuran (THF) solution as judged from UV?vis, fluorescence, and circular dichroism spectrophotometric titrations. Compared with its monomer, the polymer has proven to be more attractive for detection of HSO in terms of sensitivity and reproducibility. Upon addition of the anion it gives remarkable spectral responses concomitant with detectable color change from colorless to pale yellow. Furthermore, the HSO‐induced CD or fluorescence signal can be totally reversed with addition of base and eventually recovered the initial state, leading to a reproducible molecular switch with two distinguished “on” and “off” states. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Urinary metabonomic study using a CUMS rat model of depression

Chronic unpredictable mild stress (CUMS) is a well‐validated model of depression. In this study, a urinary metabonomics method based on the NMR spectrometry was used to study the metabolic perturbation in CUMS‐induced rat depression model. With pattern recognition analysis, a clear separation of CUMS rats and healthy controls was achieved, and nine endogenous metabolites contributing to the separation were identified. CUMS‐treated rats were characterized by the increase of glycine, pyruvate, glutamine, and asparagines, as well as the decrease of 2‐oxoglutarate, dimethylglycine, citrate, succinate, and acetate. The urinary biochemical changes related to the metabolic disturbance in CUMS induced depression, and the possible correlations with live qi stagnation in traditional Chinese medicine are discussed. The work shows that CUMS is a reliable model for studying depression, and the noninvasive urinary metabolomic method is a valuable tool to investigate the biochemical pertubations in depression as an early diagnostic means. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of poly(arylene disulfide)-vermiculite nanocomposites via in situ ring-opening reaction of cyclic oligomers

An exfoliated poly(4,4^′-oxybis(benzene)disulfide) (POBDS)/vermiculite (VMT) nanocomposite was prepared by using cyclo(4,4^′-oxybis(benzene)disulfide) (COBDS) oligomers and cetyltrimethyl ammonium bromide exchanged VMT. The POBDS/VMT nanocomposites were fabricated in two steps. First, the COBDS oligomers were used to swell and exfoliate organo VMT to afford COBDS-VMT nanocomposite precursor. Subsequently, the exfoliated POBDS-VMT nanocomposite can be made via in situ and instant melt ring-opening polymerization of the COBDS-VMT nanocomposite precursor. High molecular weight POBDS polymer can be formed in a few minutes. The nano scale dispersion of VMT layers within POBDS polymer was confirmed by both the X-ray diffraction patterns and TEM examinations. This methodology provides a potential approach to synthesize high performance polymer nanocomposite.     

Organic/inorganic hybrid vesicles based on a reactive block copolymer

Presented in this communication is a novel hybrid vesicle with a cross-linked polyorganosiloxane wall based on a new reactive block copolymer, poly(ethylene oxide)-block-poly(3-(trimethoxysilyl)propyl methacrylate) (PEO-b-PTMSPMA), which was synthesized by atom transfer radical polymerization. The vesicles were prepared first by self-assembly of the block copolymer in a selective solvent, and then the PTMSPMA block was subjected to hydrolysis and polycondensation reaction to fix vesicle wall in the presence of triethylamine as a catalyst. Transmission electron microscopy, scanning electron microscopy, NMR, and light scattering have been used to characterize the vesicles.     

Bonding, structure, and energetics of gaseous E8(2+) and of solid E8(AsF6)2 (E = S, Se)

The attempt to prepare hitherto unknown homopolyatomic cations of sulfur by the reaction of elemental sulfur with blue S8(AsF6)2 in liquid SO2/SO2ClF, led to red (in transmitted light) crystals identified crystallographically as S8(AsF6)2. The X-ray structure of this salt was redetermined with improved resolution and corrected for librational motion: monoclinic, space group P2(1)/c (No. 14), Z = 8, a = 14.986(2) A, b = 13.396(2) A, c = 16.351(2) A, beta = 108.12(1) degrees. The gas phase structures of E8(2+) and neutral E8 (E = S, Se) were examined by ab initio methods (B3PW91, MPW1PW91) leading to delta fH theta[S8(2+), g] = 2151 kJ/mol and delta fH theta[Se8(2+), g] = 2071 kJ/mol. The observed solid state structures of S8(2+) and Se8(2+) with the unusually long transannular bonds of 2.8-2.9 A were reproduced computationally for the first time, and the E8(2+) dications were shown to be unstable toward all stoichiometrically possible dissociation products En+ and/or E4(2+) [n = 2-7, exothermic by 21-207 kJ/mol (E = S), 6-151 kJ/mol (E = Se)]. Lattice potential energies of the hexafluoroarsenate salts of the latter cations were estimated showing that S8(AsF6)2 [Se8(AsF6)2] is lattice stabilized in the solid state relative to the corresponding AsF6- salts of the stoichiometrically possible dissociation products by at least 116 [204] kJ/mol. The fluoride ion affinity of AsF5(g) was calculated to be 430.5 +/- 5.5 kJ/mol [average B3PW91 and MPW1PW91 with the 6-311 + G(3df) basis set]. The experimental and calculated FT-Raman spectra of E8(AsF6)2 are in good agreement and show the presence of a cross ring vibration with an experimental (calculated, scaled) stretching frequency of 282 (292) cm-1 for S8(2+) and 130 (133) cm-1 for Se8(2+). An atoms in molecules analysis (AIM) of E8(2+) (E = S, Se) gave eight bond critical points between ring atoms and a ninth transannular (E3-E7) bond critical point, as well as three ring and one cage critical points. The cage bonding was supported by a natural bond orbital (NBO) analysis which showed, in addition to the E8 sigma-bonded framework, weak pi bonding around the ring as well as numerous other weak interactions, the strongest of which is the weak transannular E3-E7 [2.86 A (S8(2+), 2.91 A (Se8(2+)] bond. The positive charge is delocalized over all atoms, decreasing the Coulombic repulsion between positively charged atoms relative to that in the less stable S8-like exo-exo E8(2+) isomer. The overall geometry was accounted for by the Wade-Mingos rules, further supporting the case for cage bonding. The bonding in Te8(2+) is similar, but with a stronger transannular E3-E7 (E = Te) bonding. The bonding in E8(2+) (E = S, Se, Te) can also be understood in terms of a sigma-bonded E8 framework with additional bonding and charge delocalization occurring by a combination of transannular n pi *-n pi * (n = 3, 4, 5), and np2-->n sigma * bonding. The classically bonded S8(2+) (Se8(2+) dication containing a short transannular S(+)-S+ (Se(+)-Se+) bond of 2.20 (2.57) A is 29 (6) kJ/mol higher in energy than the observed structure in which the positive charge is delocalized over all eight chalcogen atoms.     

Geissoschizine methyl ether, a corynanthean-type indole alkaloid from Uncaria rhynchophylla as a potential acetylcholinesterase inhibitor

Geissoschizine methyl ether (1), a newly discovered strong acetylcholinesterase (AChE) inhibitor, along with six weakly active alkaloids, vallesiachotamine (2), hisuteine (3), hirsutine (4), isorhynchophylline (5), cisocorynoxeine (6) and corynoxeine (7) have been isolated from Uncaria rhynchophylla. Geissoschizine methyl ether (1) inhibited 50% of AChE activity at concentrations of 3.7?±?0.3?μg?mL(-1) while the IC(50) value of physostigmine as a standard was 0.013?±?0.002?μg?mL(-1). The mode of AChE inhibition by 1 was reversible and non-competitive. In addition, molecular modelling was performed to explore the binding mode of inhibitor 1 at the active site of AChE.     

Comparative spectroscopic and electrochemical properties of bis(octakis(dodecylthio)naphthalocyaninato)europium(III) and bis(tetra-tert-butylnaphthalocyaninato)europium(III) complexes

Bis(substituted-2,3-naphthalocyaninato)europium(III) complexes: bis(octakis(dodecylthio)-2,3-naphthalocyaninato)europium(III) (Eu[2,3-Nc(SC12H25)8]2, 1) and bis(tetra-tert-butyl-2,3- naphthalocyaninato)europium(III) (Eu[2,3-Nc(t-Bu)4]2, 2) have been synthesized by cyclic tetramerization of naphthalonitriles with Eu(acac)3.H2O in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in refluxing n-octanol. These compounds were characterized by UV-visible, magnetic circular dichroism (MCD), near-IR, IR, EPR, and mass spectroscopies. The absorption and MCD spectra of 1 showed splitting of the Q band, with peaks at 700 and 784 nm, red shifted from the Q band of 2 at 763 nm. The absorption and MCD spectral band deconvolution calculations of complex 1 gave two A terms in the Q-band region. The A terms are assigned to 2A2-->2E1 transitions. Cyclic voltammograms of 1 and 2 showed reversible oxidation couples at E1/2 = -0.28 V (for 2) and -0.25 V (for 1) vs ferrocenium/ferrocene (Fc+/Fc). The second oxidation exhibited a complicated behavior for both complexes. The reduction couples for 2 were observed at E1/2 = -0.61, -1.64, -1.97, and -2.42 V, and for 1 they were observed at E1/2 = -0.62, -1.60, -1.86, and -2.27 V vs Fc+/Fc. Spectral changes observed on chemical oxidation and reduction of the complexes are presented, and the behaviors of 1 and 2 are compared.     

The preparation and characterization of novel cocylic(arylene disulfide) oligomers

A series of homo‐ and cocyclic(arylene disulfide) oligomers were synthesized under high dilution conditions by the catalytic oxidation of arylenedithiols with oxygen in the presence of a copper‐amine catalyst in DMAc. The aryl groups contained moieties such as sulfone, ether, and ketone. The free radical ring‐opening polymerization of these cyclic(arylene disulfide) oligomers led to the formation of linear poly(thio arylene)s. The homo‐ and cocyclic(arylene disulfide) oligomers were characterized by gradient high pressure liquid chromatography (HPLC), get permeation chromatography (GPC), ¹H‐NMR, and differential scanning calorimetry (DSC) methods. These cocyclic(arylene disulfide) oligomers except those containing sulfone moiety had lower melt flow temperature as low as 140 °C and therefore could readily undergo free radical ring‐opening polymerization under mild conditions. The glass transition temperatures of these cocyclics ranged from 72.3 to 190.0 °C, while the glass transition temperatures of the polydisulfides derived from these cocyclics ranged from 78.4 to 194.5 °C. In this article, a new method of preparing arylene dithiols 4,4′‐oxybis(benzenethiol) and diphenylmethane‐4,4′‐dithiol is reported. Copyright © 2003 John Wiley & Sons, Ltd.     

Complete Quenching of the Pd3(dppm)3(CO)2+ Cluster Emission Via Electrostatic Host–Guest Assemblies with Carboxylate-Containing Tetraphenylporphyrins of Ni(II) and Fe(III)

The title cluster is luminescent at 77?K and exhibits an unsaturated site for binding anions when the counter ion is PF₆ ^?. A series of five non-luminescent metalloporphyrins exhibiting carboxylate anchoring groups were synthesized and characterized. These are the sodium salts of the 5-carboxyphenyl-tri-10,15,20-tolyl-, trans-di-5,10-carboxyphenyl-di-15,20-tolyl-, and tetra-5,10,15,20-carboxyphenyl(metallo)porphyrin (metallo?=?chloroiron(III), nickel(II)) anions. Evidence for supramolecular assemblies between the carboxylates and the cluster is provided by ³¹P NMR and UV?Cvis spectroscopy. The binding constant, K_1n, extracted from the UV?Cvis data via Benesi-Hildebrand, Scott and Scatchard plots are approximately 21,000?±?5,000?M^?1 for the nickel(II) species, in agreement with the previously reported zinc(II) ones (K₁₁?=?20,000?±?2,000?M^?1), but those for the chloroiron(III) are measured to be lower (12,500?±?3,500?M^?1). This association is accompanied by a complete quenching of the luminescence of the cluster which can only be due to an efficient energy transfer to the d?Cd states of the chloroiron(III) and nickel(II) species but an electron transfer from the nickel(II)-containing chromophore to the cluster is also possible. This work demonstrates the profound effect that supramolecular interactions may have on the photophysical properties despite the long donor?Cacceptor separation.