Development of a single-chain variable fragment-alkaline phosphatase fusion protein and a sensitive direct competitive chemiluminescent enzyme immunoassay for detection of ractopamine in pork

A rapid, sensitive chemiluminescent enzyme immunoassay (CLEIA) for ractopamine (RAC) based on a single-chain variable fragment (scFv)-alkaline phosphatase (AP) fusion protein was developed. The scFv gene was prepared by cloning the heavy- and light-chain variable region genes (V_H and V_L) from hybridoma cell line AC2, which secretes antibodies against RAC, and assembling V_H and V_L genes with a linker by means of splicing overlap extension polymerase chain reaction. The resulting scFv gene was inserted into the expression vector pLIP6/GN containing AP to produce the fusion protein in Escherichia coli strain BL21. The purified scFv-AP fusion protein was used to develop a direct competitive CLEIA (dcCLEIA) protocol for detection of RAC. The average concentration required for 50% inhibition of binding and the limit of detection of the assay were 0.25 ± 0.03 and 0.02 ± 0.004 ng mL⁻¹, respectively, and the linear response range extended from 0.05 to 1.45 ng mL⁻¹. The assay was 10 times as sensitive as the corresponding enzyme-linked immunosorbent assay based on the same fusion protein. Cross-reactivity studies showed that the fusion protein did not cross react with RAC analogs. DcCLEIA was used to analyze RAC spiked pork samples, and the validation was confirmed by high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS). The results showed a good correlation between the data of dc-CLEIA and HPLC–MS (R² > 0.99), indicating that the assay was an efficient analytical method for monitoring food safety.     

New Benzofuranylpropanoids from the Roots of Codonopsis lanceolata

Three new benzofuranylpropanoids, lanceolunes A–C ( 1 – 3 ), were isolated from the roots of Codonopsis lanceolata. Their structures were determined by means of HR‐ESI‐MS, extensive 1D‐ and 2D‐NMR spectroscopic, and chemical evidence.     

Green Synthesis of 3‐Hydroxynaphthalene‐1,4‐dione Derivatives via Microwave‐Assisted Three‐Component Reactions in Neat Water

A novel and efficient access to 2‐(argio(3‐methyl‐5‐oxo‐1‐phenyl‐4,5‐dihydro‐1H‐pyrazol‐4‐yl)methyl)‐3‐hydroxynaphthalene‐1,4‐dione derivatives from readily available substrates in neat water is described with aid of microwave irradiation. The results of our study provide a green, simple and practical one‐pot approach to the synthesis of 3‐hydroxynaphthalene‐1,4‐dione analogs in excellent yields without further purification.     

Synthesis, characterization of bridged bis(amidinate) lanthanide amides and their application as catalysts for addition of amines to nitriles for monosubstituted N-arylamidines

A series of lanthanide amide complexes supported by bridged bis(amidinate) ligand L, LLnNHAr(1)(DME) (L = [Me(3)SiNC(Ph)N(CH(2))(3)NC(Ph)NSiMe(3)], Ar(1) = 2,6-(i)Pr(2)C(6)H(3), DME = dimethoxyethane, Ln = Y (1), Pr (2), Nd (3), Gd (4), Yb (5)), [Yb(μ(2)-NHPh)](2)(μ(2)-L)(2) (6) and [LYb](2)(μ(2)-NHAr(2))(2) (7) (Ar(2) = (o-OMe)C(6)H(4)), were synthesized by reaction of LLnCl(THF)(2) with the corresponding lithium amide in good yields and structurally characterized by X-ray crystal structure analyses. All complexes were found to be precatalysts for the catalytic addition of aromatic amines to aromatic nitriles to give monosubstituted N-arylamidines. The catalytic activity was influenced by lanthanide metals and the amido groups with the active sequence of Y (1) < Gd (4) < Nd (3) < Pr (2) ～ Yb (5) for the lanthanide metals and -NHAr(2) < -NHPh < -NHAr(1) for the amido groups. The catalytic addition reaction with complex 5 showed a good scope of aromatic amines. Some key reaction intermediates were isolated and structurally characterized, including the amidinate complexes LLn[NPhCNAr(1)](PhCN) (Ln = Y (8), Ln = Yb (9)), LYb[NAr(2)CNAr(1)](Ar(2)CN) (10), and amide complex 5 prepared by protonation of 9 by Ar(1)NH(2). Reactivity studies of these complexes suggest that the present catalytic formation of monosubstituted N-arylamidines proceeds through nucleophilic addition of an amido species to a nitrile, followed by amine protonolysis of the resultant amidinate species.     

Growth and characterization of a new langasite‐type single crystal Sr3NbAl1.5Ga1.5Si2O14

Single crystals of Sr₃NbAl_1.5Ga_1.5Si₂O₁₄ (SNAGS) with langasite structure have been successfully grown by Czochralski method. The X‐ray diffraction (XRD) verified that the as‐grown crystal was isostructural with A₃BC₃D₂O₁₄ structure and the lattice parameters were calculated as follows: a = 8.242 Å, c = 5.041 Å, V = 296.6 ų. The piezoelectric coefficient d₁₁ was 5.7pC/N, which was 2.47 times of α‐quartz (d₁₁=2.31pC/N). The electric resistivity was up to 3.04×10⁶ Ωcm at 700 °C for X‐cut sample. In addition, the transmission spectrum of the SNAGS crystal showed that it had a high transmittance (>80%) in the range of 350‐800 nm and exceeded 90% above 520 nm. These results suggest that the SNAGS crystals have potential applications in high‐temperature piezoelectric sensors and optical techniques. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Raman spectroscopy of seized drugs and density functional theory interpretation

Abstract

The demand for a hand-held Raman spectrometer in the fast and accurate detection and identification of seized drugs is much higher than before, especially when facing unknown suspicious drugs. However, Raman spectra for the different drugs are less reported due to the inaccessibility of them. Here, we reported the experimental Raman spectra in detail of four typical drugs (such as methamphetamine, ketamine, caffeine, and magu). The Raman vibrational frequencies were also calculated by the method of density functional theory (DFT) at Becke-3-Lee-Yang-Parr (B3LYP) level with the 6-31?G and 6-31G(d,p) basis set. The results show that the experimental Raman spectra of these typical drugs are consistent with the theoretical Raman spectra. Using the potential energy distribution (PED) calculation with the GAR2PED program, the assignments of the observed Raman bands to the vibrational modes were presented. Further, methamphetamine and its camouflage N-benzylisopropylamine were analyzed by Raman spectroscopy and DFT calculations, and the result showed that the obvious differences of the Raman characteristic bands for these two samples could be found so that Raman technique could be used to identify the authenticity of methamphetamine. All the above results confirm the potential of the approach involving Raman spectroscopy combined with DFT calculations in the characterization of drugs. Based on this, the experimental spectra of seized drugs measured directly through a plastic package were studied. Raman spectroscopy has the advantage of being performed through packaging without disturbing the samples. Polypropylene transparent packaging does not alter the spectra of the drugs but will mask the corresponding bands if the Raman spectrum has a strong autofluorescence interference.     

Flame atomic absorption spectrometric determination of copper,lead, and cadmium in Gastrodiae rhizoma samples after preconcentration using magnetic solid-phase extraction

In this research, ferroferric oxide nanoparticles were coated with silicon dioxide and further functionalized with alizarin complexone as the adsorbent of magnetic solid-phase extraction, thus aiming for extraction and preconcentration of heavy metals in Gastrodiae rhizoma samples. The determination of heavy metals was carried out by flame atomic absorption spectrometry. The results showed that the functionalized magnetic nanoparticles demonstrated higher extraction efficiency for copper, lead, and cadmium. The synthesized magnetic sorbents were characterized by transmission electron microscope, X-ray diffraction, and Fourier-transformed infrared spectra. Different parameters influencing the extraction efficiency including the amount of sorbent, sample pH, sorption time, solution volume, elution solvent, and reuse times were optimized. Under the optimal conditions, the method detection limit was 0.18, 0.25, and 0.12 µg/L for copper, lead, and cadmium, respectively. The proposed method was successfully applied to extract copper, lead, and cadmium in Gastrodiae rhizoma samples, and the recoveries of the samples ranged from 90.0 to 102.0% and relative standard deviations (n = 5) were in the range of 1.93–3.82%.     

Analysis of circular bends in planar optical waveguides

Waveguides with circular bends are analyzed by means of a conformal transformation in conjunction with the WKB method of dealing with the nonuniform refractive index that results from the transformation. The result is a prediction of the operational parameters of the bent guide, including the loss. The transformation makes possible an intuitive understanding of the cause of the loss.     

Raman spectroscopic investigation on femtosecond laser induced residual stress and element distribution in bismuth germanate glasses

Localized microstructure and elemental redistribution were induced in bismuth germanate glasses by irradiation with high repetition rate 800 nm femtosecond laser pulses. The confocal Raman spectra were examined to study the redistribution of elements and residual thermal stress. The microscopic Raman spectra indicated that the residual thermal stress increases from the unmodified region to the center of the laser modified region, while Bi is enriched at the boundary area of the inner structure of the laser modified region relative to Ge. Electron microprobe analysis further confirmed the elemental redistribution of Bi and Ge, which agrees well with the Raman spectral analysis. Copyright © 2012 John Wiley & Sons, Ltd.     

Critical theories of phase transition between symmetry protected topological states and their relation to the gapless boundary theories

Symmetry protected topological states (SPTs) have the same symmetry and the phase transition between them are beyond Landau?s symmetry breaking formalism. In this paper we study (1) the critical theory of phase transition between trivial and non-trivial SPTs, and (2) the relation between such critical theory and the gapless boundary theory of SPTs. Based on examples of SO(3)$\mathrm{SO}(3)$ and SU(2)$\mathrm{SU}(2)$ SPTs, we propose that under appropriate boundary condition the critical theory contains the delocalized version of the boundary excitations. In addition, we prove that the boundary theory is the critical theory spatially confined between two SPTs. We expect these conclusions to hold in general and, in particular, for discrete symmetry groups as well.