[QuEChERS-liquid chromatography-tandem mass spectrometry for determination of 22 triazole pesticide residues in Chinese herbal medicines].

Eight well-known herbals in Zhejiang Province, Zhebawei, are commonly used as traditional Chinese herbal medicines owing to their rich active ingredients. However, the unavoidable use of pesticides during agricultural production has led to pesticide residue problems in these herbs. In this study, a simple, rapid, and accurate method was established to determine 22 triazole pesticide residues in Zhebawei. An improved QuEChERS method was used for sample pretreatment, and Rhizoma Atractylodis Macrocephalae was used as a representative sample. The sample was extracted with acetonitrile to eliminate some polar and nonpolar compounds, pigments, and other impurities, and the purification effects of multiwalled carbon nanotubes (MWCNTs), amino-modified multiwalled carbon nanotubes (MWCNTs-NH2), carboxylated multiwalled carbon nanotubes (MWCNTs-COOH), crosslinked polyvinylpyrrolidone (PVPP), zirconium dioxide (ZrO2), 3-(N,N-diethylamino)-propyltrimethoxysilane (PSA), octadecyl (C18), and graphitized carbon black (GCB) were compared. MWCNTs-COOH and C18 were selected as the purification adsorbents, and their dosages were systematically optimized. The combination of 10 mg of MWCNTs-COOH and 20 mg of C18 was eventually selected as the purification adsorbents. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for analysis, and box graphs were plotted to present the dispersion of each group of recoveries, thus enabling the identification of the data outliers, dispersion distribution, and data symmetry. The established method was systematically verified and showed good linearity over the concentration range of 1-200 µg/L (except for bromuconazole, epoxiconazole, and etaconazole) with correlation coefficients >0.99. The average recoveries of the 22 pesticides at spiked levels of 10, 20, 100, and 200 µg/kg were in the range of 77.0%-115% with relative standard deviations (RSDs) <9.4%. The limits of detection and quantification were 1-2.5 µg/kg and 10-20 µg/kg, respectively. The applicability of the developed method to other herbals was investigated at 100 µg/kg, and the average recoveries of the target pesticides in different matrices ranged from 76.4% to 123% with RSDs <12.2%. Finally, the method established was used to detect triazole pesticide residues in 30 actual Zhebawei samples. The results showed that triazole pesticides were present in Bulbus Fritillariae Thunbergii and Dendranthema Morifolium. Difenoconazole was detected in Bulbus Fritillariae Thunbergii at contents ranging from 41.4 µg/kg to 110 µg/kg, while difenoconazole, myclobutanil, triadimenol and propiconazole were detected in Dendranthema Morifolium at contents ranging from 16.1 µg/kg to 250 µg/kg. The established method can meet the requirements for the accurate quantitative analysis of triazole fungicides in Zhebawei.

ALDH5A1 acts as a tumour promoter and has a prognostic impact in papillary thyroid carcinoma.

Thyroid cancer is the most common endocrine carcinoma, with papillary thyroid carcinoma (PTC) accounting for 80%-90% of thyroid cancers. Accumulating studies reported that mitochondria plays an important role in the regulation of cell proliferation. ALDH5A1, may function as an oncogene or tumour suppressor in various human cancers, and the role of ALDH5A1 in PTC is still unclear. The aim of this study was to investigate the clinical significance of ALDH5A1 expression and its functions in PTC. In this present study, we studied ALDH5A1 expression on primary papillary thyroid carcinoma (PTC) in The Cancer Genome Atlas (TCGA) database. Results showed that the levels of ALDH5A1 were found positively correlated with tumour stage, metastasis, lymph node stage, and higher levels of ALDH5A1 demonstrated poor disease-free survival (DFS). Immunohistochemistry (IHC) revealed that significantly higher expression of ALDH5A1 was found in PTC tissues. On the other hand, knockdown of ALDH5A1 significantly inhibited PTC cell proliferation, migration and invasion detection found the migration and invasion of cells also were hindered when ALDH5A1 level was reduced. The knockdown of ALDH5A1 inhibited the expression of Vimentin and promoted the expression of E-cadherin. In brief, knockdown of ALDH5A1may act as a novel molecular target for the prevention and treatment of PTC. SIGNIFICANCE OF THE STUDY: The present study focused on the role and the potential mechanism of ALDH5A1 in papillary thyroid carcinoma. We demonstrated that reduced expression of ALDH5A1 might inhibit the progression of TC by inhibiting cell proliferation, migration and invasion and reversing epithelial-mesenchymal transition (EMT). The findings ensured the interaction relation between ALDH5A1 and EMT in PTC, providing a novel biological marker for PTC and enriching the potential strategies for TC treatment.

Magnetic covalent organic framework as a solid-phase extraction absorbent for sensitive determination of trace organophosphorus pesticides in fatty milk.

A simple and efficient magnetic solid-phase extraction (MSPE) method was established with magnetic covalent organic framework (COF) as adsorbent to enrich organophosphorus pesticides from fatty milk samples, followed by the sensitive determination via LC-MS/MS. The key parameters influencing the MSPE efficiency were comprehensively investigated to afford an optimized procedure. All the target analytes could be captured directly by magnetic COF from milk without protein precipitation, making the pretreatment rapid and convenient. Systematic method validation demonstrated its satisfactory linearity, recoveries (80.0-105 %), and precision (RSDs <12.3 %). The method limits of quantification were 0.2-0.5 µg L-1. A comparison experiment to the reported solid-phase extraction fully verified the present MSPE more rapid, accurate, and environment-friendly. Furthermore, FT-IR and XPS analysis were performed to reveal the adsorption mechanisms of magnetic COF to organophosphorus pesticides, which could offer guidance on the rational design of COF adsorbent for various target analytes.

High-throughput determination of fungicides in grapes using thin-film microextraction coupled with liquid chromatography-tandem mass spectrometry.

A high-throughput and environmentally friendly method based on 96-well plate thin-film microextraction was established to determine 14 fungicides in grapes and grape juice using liquid chromatography-tandem mass spectrometry. The thin-film microextraction optimized method consisted of 60 min of extraction at pH 6.0 with the addition of sodium chloride (2-5%). Acetonitrile/water in the ratio of 8:2 was used for desorption analytes for 60 min. Evaluation of different extractive phases showed that polyacrylonitrile-polystyrene-divinylbenzene was the optimum coating. The linearity of the method was good in the range of 0.01-0.5 µg/mL for 14 fungicides with determination coefficients (R2 ) from 0.990 to 0.999, which indicated good linearity for both the grape juice and grape matrixes. The limit of detection was in the range of 0.002-0.01 µg/mL. The limit of quantitation was in the range of 0.01 mg/kg according to the minimum fortified level. The average absolute recoveries of the 14 fungicides ranged from 75.0 to 118.3%. The intraday relative standard deviation (n = 4) and interday relative standard deviation (n = 4) were 5.6-13.0% and 1.6-6.4%, respectively. This study showed that this method can be used for analyzing 96 samples in parallel, and the sample preparation time was approximately 2.0 min per sample. In addition, this approach offers a green and low-cost sample pretreatment technique for future analyses.

K6 carbon: a metallic carbon allotrope in sp3 bonding networks.

We identify by first-principles calculations a new cubic carbon phase in I4132 (O(8)) symmetry, named K6 carbon, which has a six atom primitive cell comprising sp(3) hybridized C3 triangle rings. The structural stability is verified by phonon mode analysis. The calculated elastic constants show that the K6 carbon is a high ductile material with a density even lower than graphite. Electronic band and density of states calculations reveal that it is a metallic carbon allotrope with a high electronic density of states of ∼0.10 states/eV per atom at the Fermi level. These results broaden our understanding of the structural and electronic properties of carbon allotropes.

Hydrogenated K4 carbon: a new stable cubic gauche structure of carbon hydride.

The structural and electronic properties of hydrogenated K(4) carbon as a new cubic gauche structure in I2(1)3 symmetry are investigated using first-principles calculations. The total energy for this carbon hydride (labeled by K(4)-CH) is 0.47 eV per CH unit lower than that of solid molecular cubane, suggesting its energetic stability. Based on the calculated phonon dispersion curves and electronic band structure obtained by hybrid density functional method, we find that K(4)-CH is dynamically stable and exhibits as an insulator with an indirect band gap of 6.07 eV, which is close to 6.10 eV of cubic gauche nitrogen (cg-N). To study the doping effect of nitrogen, we have also investigated N-doped K(4)-CH with a composition of C(4)H(4)N(4) in P2(1)3 symmetry. The phonon and electronic band structures show that it is dynamically stable and behaves as an insulator with an indirect band gap of 5.39 eV, smaller than that of both K(4)-CH and cg-N. These results broaden our understanding of the cubic gauche structure.

Prediction of a new two-dimensional metallic carbon allotrope.

By means of the first-principles calculations, we predict a new metallic two-dimensional carbon allotrope named net W with Cmmm (D(2h)(19)) symmetry. This new carbon phase consists of squares C(4), hexagons C(6), and octagons C(8), its dynamical stability is validated based on phonon-mode analysis and it is energetically more favored over previously proposed two-dimensional carbon forms such as net C, planar C(4), biphenylene, graphyne, and the recently prepared graphdiyne. On the other hand, we find that net W possesses strong metallicity due to its rather large density of states across the Fermi level contributed by the carbon p(z) orbital. Through first-principles molecular dynamics simulations, we theoretically demonstrate that selective dehydrogenation of the parallel-laid narrowest angular polycyclic aromatic hydrocarbons (4-AGNRs) would lead to a spontaneous interconversion to such a net W carbon phase, the possible synthetic routes are also addressed. Of particular interest, semiconductivity could be introduced when a net W carbon sheet is cut into ribbons of certain widths. Our work shows that the net W carbon sheet and its nanoribbons have great potential for future nanoelectronics.

Structural stabilities and electronic properties of planar C4 carbon sheet and nanoribbons.

By means of first-principles calculations, we theoretically studied the structural stabilities and electronic properties of a pure-carbon 2D covalent metal named planar C(4) in P4/mmm (D(1)(4h)) symmetry. Planar C(4) is confirmed to be dynamically stable in the ground state based on phonon-mode analysis, and it is more stable than graphyne and the recently prepared graphdiyne. Moreover, it has a higher density of states (DOS) at the Fermi level than any plausible metallic carbon nanotube. Of particular interest, there exist two distinct types of planar C(4) nanoribbons (NRs): type I is predicted to be uniformly metallic regardless of the width change, while type II exhibits remarkable odd-even metal-semiconductor oscillating behavior depending on the width. The edge structure of type II NRs is revealed to be energetically more favored since its formation energy is about 0.45 eV per edge atom lower than that of type I NRs. Our work shows that planar C(4) carbon sheet and its NRs could serve as potential materials for future functional nanodevices.

Induced ferromagnetism in one-side semihydrogenated silicene and germanene.

The intriguing electronic and magnetic properties of one-side semihydrogenated silicene and germanene are investigated by means of first-principles calculations. Both one-side semihydrogenated silicene and germanene are confirmed as dynamically stable in the ground state based on phonon-mode analysis. Moreover, we find that semihydrogenation from only one side causes localized and unpaired 3p (4p) electrons in the unhydrogenated Si (Ge) sites and then introduces ferromagnetism to silicene (germanene) sheet with no need for doping, cutting, or etching. One-side semihydrogenated silicene and germanene are both identified as semiconductors with direct energy gaps: their gap values obtained from the HSE06 functional are estimated to be 1.74 eV and 1.32 eV, much greater than the PBE-GGA results of 0.94 eV and 0.41 eV, respectively. From pristine to one-side semihydrogenated and then to fully hydrogenated systems, silicene and germanene change from metallic to magnetic semiconducting and then to nonmagnetic semiconducting. The hydrogenation process provides a novel method to tune the properties of silicene and germanene with unprecedented potentials for future nanoelectronics.

[Advance in imaging spectropolarimeter].

Imaging spectropolarimeter (ISP) is a type of novel photoelectric sensor which integrated the functions of imaging, spectrometry and polarimetry. In the present paper, the concept of the ISP is introduced, and the advances in ISP at home and abroad in recent years is reviewed. The principles of ISPs based on novel devices, such as acousto-optic tunable filter (AOTF) and liquid crystal tunable filter (LCTF), are illustrated. In addition, the principles of ISPs developed by adding polarized components to the dispersing-type imaging spectrometer, spatially modulated Fourier transform imaging spectrometer, and computer tomography imaging spectrometer are introduced. Moreover, the trends of ISP are discussed too.

[Study and simulation of the intensity modulation-Fourier transform spectropolarimeter].

Intensity modulation-Fourier transform spectropolarimetry (IMFTSP) is a novel technology that combines the intensity modulation spectropolarimetry and Fourier transform spectroscopy. The IMFTSP can obtain full Stokes spectropolarimetric parameters simultaneously, and maintains the throughput (Jacquinot) and multiplex (Fellgett) advantages. Yet aside from this, the IMFTSP has the advantage of reducing the complexity of data processing. The data collecting and spectropolarimetric parameters reconstruction processes were analyzed theoretically in this paper, the theoretical formulas are presented, and a whole process mathematical simulation for the IMFTSP system is introduced. The theory analysis and simulation results proved the feasibility of the IMFTSP.

[Developments and trends of the computed tomography imaging spectrometers].

The present paper reviews the computed tomography imaging spectrometer (CTIS) measurement systems at home and abroad from the aspects of technological characterizations and research focuses. The developments of computed tomography imaging spectrometers are described, involving the adding new abilities by improving systematic structure and by incorporating other elements or systems, the study and applications of novel grating elements, detectors or apparatus, the optimizations and improvements of the system calibration methods and reconstruction algorithms. In addition, based on the classification of application scope, the extension status of probing spectral bands and application fields towards computed tomography imaging spectrometers and related systems are summarized. The principles of non-scanning computed tomography imaging spectrometer and high-throughput computed tomography imaging spectrometer are introduced. Moreover, the trends of computed tomography imaging spectrometers are discussed too.

Crystal structure of human dynein light chain Dnlc2A: structural insights into the interaction with IC74.

The human light chain of the motor protein dynein, Dnlc2A, is also a novel TGF-beta-signaling component, which is altered with high frequency in epithelial ovarian cancer. It is an important mediator of dynein and the development of cancer, owing to its ability to bind to the dynein intermediate light chain (DIC) IC74 and to regulate TGF-beta-dependent transcriptional events. Here we report the 2.1-A crystal structure of Dnlc2A using single anomalous diffraction. The proteins form a homodimer in solution and interact mainly through the helix alpha(2), strand beta(3), and the loop following this strand in each protein to generate a 10-stranded beta-sheet core. The surface of the beta-sheet core is mainly positively charged and predicted (by software PPI-Pred) to be the site that interacts with other partners. At the same time, the residues 79-82, 88, and 90 of each molecule formed two holes in the core. Residue 89 of each molecule, which is crucial for the DIC binding function of Dnlc2A, is within the holes. On the basis of these observations, we propose that the homodimer is the structural and functional unit maintained by hydrogen bonding interactions and hydrophobic packing, and that the patch of the surface of the beta-sheet core is the main area of interaction with other partners. Furthermore, the two holes would be the key sites to interact with IC74.

Crystal structure of KD93, a novel protein expressed in human hematopoietic stem/progenitor cells.

The crystal structure of a novel hypothetical protein, KD93, expressed in human hematopoietic stem/progenitor cells, was determined at 1.9A resolution using the multiple-wavelength anomalous dispersion (MAD) method. The protein KD93, which is encoded by the open reading frame HSPC031, is a NIP7 homologue and belongs to the UPF0113 family. The structural and functional information for the group of homologues has not yet been determined. Crystallographic analysis revealed that the overall fold of KD93 consists of two interlinked alpha/beta domains. Structure-based homology analysis with DALI revealed that the C domain of KD93 matches the PUA domain of some RNA modification enzymes, especially that of archaeosine tRNA-ribosyltransferase (ArcTGT), which suggests that its possible molecular function is related to RNA binding. The difference between the RNA binding regions of KD93 and ArcTGT in amino acid constitution and surface electrostatic potential indicate that they may have different RNA binding modes. The N domain of KD93 is a unique structure with no obvious similarity to other proteins with known three-dimensional structures. The high-resolution structure of KD93 provides a first view of a member of the family of hypothetical proteins. And the structure provides a framework to deduce and assay the molecular function of other proteins of the UPF0113 family.