A highly stable electrochemical acetylcholinesterase (AChE) biosensor for detection of organophosphorus pesticides (OPs) was developed simply by adsorption of AChE on chitosan (CS), TiO2 sol-gel, and ...reduced graphene oxide (rGO) based multi-layered immobilization matrix (denoted as CS@TiO2-CS/rGO). The biosensor fabrication conditions were optimized, and the fabrication process was probed and confirmed by scanning electron microscopy and electrochemical techniques. The matrix has a mesoporous nanostructure. Incorporation of CS and electrodeposition of a CS layer into/on the TiO2 sol-gel makes the gel become mechanically strong. The catalytic activity of the AChE immobilized CS@TiO2-CS/rGO/glassy carbon electrode to acetylthiocholine is significantly higher than those missing any one of the component in the matrix. The detection linear range of the biosensor to dichlorvos, a model OP compound, is from 0.036μM (7.9 ppb) to 22.6μM, with a limit of detection of 29nM (6.4 ppb) and a total detection time of about 25min. The biosensor is very reproducibly and stable both in detection and in storage, and can accurately detect the dichlorvos levels in cabbage juice samples, providing an efficient platform for immobilization of AChE, and a promisingly applicable OPs biosensor with high reliability, simplicity, and rapidness.
•Chitosan (CS) was electrodeposited on and also incorporated in TiO2 sol-gel.•The TiO2 sol-gel was layered on rGO film modified GC electrode.•AChE was efficiently immobilized into the matrix.•The CS@TiO2-CS/rGO matrix is mechanically strong.•The biosensor is stable, sensitive, reproducible and accurate in detection OP.
Recently semi-supervised fuzzy clustering with pairwise constraints was developed, in which the disagreement on the magnitude order between penalty cost function and the basic objective function will ...cause over adjustment of membership values and their deviation from the normal range. In order to solve this problem, an improved semi-supervised fuzzy clustering algorithm with pairwise constraints (SCAPC) was proposed based on a redefined objective function. The new penalty cost function in SCAPC theoretically conforms to the methodology of classical fuzzy clustering, which is expressed as the violation cost incurred by the pairs, and has the same magnitude order as the basic objective function. Experimental results on benchmark datasets and images showed that SCAPC can produce more accurate clustering by moderately enhancing or reducing the ambiguous memberships. Research indicates that constraint term of the proposed algorithm can achieve a good agreement and cooperation with the basic objective function.
Abstract Although it is well documented that mountains tend to exhibit high biodiversity, how geological processes affect the assemblage of montane floras is a matter of ongoing research. Here, we ...explore landform-specific differences among montane floras based on a dataset comprising 17,576 angiosperm species representing 140 Chinese mountain floras, which we define as the collection of all angiosperm species growing on a specific mountain. Our results show that igneous bedrock (granitic and karst-granitic landforms) is correlated with higher species richness and phylogenetic overdispersion, while the opposite is true for sedimentary bedrock (karst, Danxia, and desert landforms), which is correlated with phylogenetic clustering. Furthermore, we show that landform type was the primary determinant of the assembly of evolutionarily older species within floras, while climate was a greater determinant for younger species. Our study indicates that landform type not only affects montane species richness, but also contributes to the composition of montane floras. To explain the assembly and differentiation of mountain floras, we propose the ‘floristic geo-lithology hypothesis’, which highlights the role of bedrock and landform processes in montane floristic assembly and provides insights for future research on speciation, migration, and biodiversity in montane regions.
Floral scent is an important vehicle of communication between plants and their pollinators. In an obligate mutualism between fig and fig wasps, the chemical regulation plays a crucial role in their ...encounter. Pollinating wasps mainly rely on their olfactory sensation to the volatile organic compounds (VOCs) emitted by their host plants to localize their hosts.
In this study, we collected the VOCs from male and female figs of Ficus pumila var. pumila by in vivo dynamic headspace adsorption (VDHA) before and after pollination, and analyzed the VOCs using gas chromatography–mass spectrometry (GC–MS). We examined the Wiebesia pumilae pollinators' behavior in response to the VOCs at different developmental phases in Y-tube experiments.
The results: (1) The fig volatiles of F. pumila var. pumila contained a variety of compounds, in which Linalool appears to be the dominant one to pollinating wasps, suggesting that Linalool may be used for the long-range localization while the short-range localization may rely on the chemical profile containing specific compositions and concentrations. (2) Although the quality and quantity of VOCs were different between receptive male and female syconia, they shared a few compounds which account for >50% of total volatiles. In addition, the proportion of the three classes of compounds including terpenes, benzenoids, and fatty acid derivatives was similar, suggesting that a simulating interaction occurs between the VOCs of receptive male and female syconia. Furthermore, the Y-tube experiments showed no preference of pollinating wasps to the male and female syconia. Therefore a pollinator is unlikely to discriminate male and female figs via the VOC variations. (3) The VOCs of syconia were changed after pollination or oviposition, with some compounds decreased (e.g. Linalool) or even disappeared, while some increased (e.g. Longifolene) or new compounds formed. In terms of the chemical composition, terpenes and fatty acid derivatives are decreased, while benzenoids are increased, and nitrogens arisen. The results derived from Y-tube experiments showed that the VOCs of receptive male and female figs played a very significant role in attracting pollinating wasps. In contrast, the fig volatiles of inter-floral phase (5days after pollination or oviposition) were significantly repellent to the wasps. Figs may thus express their flower developmental and pollinating or ovipositing status by changing their VOC quantity and composition in order for pollinating wasps to receive the chemical signals, choose the right hosts, and recognize the right developmental phases of their hosts.
Three‐membered cyclic structures are widely existing in natural products and serve as enabling intermediates in organic synthesis. However, the efficient and straightforward access to such structures ...with diversity remains a formidable challenge. Herein, a general and practical protocol to aziridines and cyclopropanes synthesis using free XH2 (X=C or N) with alkenes by thianthrenation is presented. This metal‐free protocol features the direct aziridination and cyclopropanation with unprotected XH2. Free sulfonamides, amides, carbamates, amines, and methylene with acidic protons, are good precursors, providing an attractive alternative for straightforward synthesis of aziridines and cyclopropanes from easily available starting materials.
Herein, a general and practical protocol to aziridines and cyclopropanes using free XH2 (X=C or N) with alkenes by thianthrenation is presented under mild conditions. Free sulfonamides, amides, carbamates, amines, and acidic methylene with protons, are good precursors for three‐membered ring formation, providing an attractive alternative for straightforward synthesis of aziridines and cyclopropanes from easily available starting materials.
High-altitude pulmonary edema (HAPE) can develop in unacclimatized persons after acute ascent to high altitude and is associated with fibrinolytic and coagulation abnormalities. The authors ...investigated whether fibrinolytic and coagulation abnormalities were associated with the severity of HAPE.
Sixty-one patients who developed HAPE after acute ascent to altitudes above 3600 m were recruited. Twenty unacclimatized controls who acutely ascended to the same altitude and 20 acclimatized inhabitants served as controls. Tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) levels were measured using chromogenic substrate assays. Plasma fibrinogen concentration was determined by the sodium sulphite fractionation method. The concentrations of fibrin/fibrinogen degradation products (FDP) and D-dimer were measured by enzyme linked immunosorbent assay.
The plasma concentrations of D-dimer, fibrinogen, FDP and t-PA and PAI-1 were significantly higher in patients with HAPE than controls. In addition, these abnormalities were correlated with the severity of HAPE. The plasma concentrations of D-dimer and fibrinogen recovered to normal upon recovery from HAPE while t-PA, PAI-1 and FDP levels in HAPE patients still remained significantly increased over those of unacclimatized controls.
The development of HAPE is associated with abnormalities in the fibrinolysis and coagulation system, and these abnormalities correlate with the severity of HAPE.
Radiotherapy is the main locoregional control modality for many types of unresectable tumors, including gastric cancer. However, many patients fail radiotherapy due to intrinsic radioresistance of ...cancer cells, which has been found to be strongly associated with cancer stem cell (CSC)-like properties. In this study, we developed a nanoparticle formulation to deliver miR-200c, which is reported to inhibit CSC-like properties, and then evaluated its potential activity as a radiosensitizer. miR-200c nanoparticles significantly augmented radiosensitivity in three gastric cancer cell lines (sensitization enhancement ratio 1.13-1.25), but only slightly in GES-1 cells (1.06). In addition to radioenhancement, miR-200c nanoparticles reduced the expression of CD44, a putative CSC marker, and the percentage of CD44(+) BGC823 cells. Meanwhile, other CSC-like properties, including invasiveness and resistance to apoptosis, could be suppressed by miR-200c nanoparticles. CSC-associated radioresistance mechanisms, involving reactive oxygen species levels and DNA repair capacity, were also attenuated. We have demonstrated that miR-200c nanoparticles are an effective radiosensitizer in gastric cancer cells and induce little radiosensitization in normal cells, which suggests that they are as a promising candidate for further preclinical and clinical evaluation.
Loading hyaluronidase (Hyal) in a nanocarrier is a potent strategy to degrade the tumor extracellular matrix for tumor deep penetration and enhanced tumor therapy. Herein, a pH-sensitive biomimicking ...nanosystem with high Hyal loading, effective tumor targeting, and controllable release is constructed. Specifically, cationic mesoporous silica nanoparticles (CMSNs) with large pores 13.52 nm in diameter were synthesized in a one-pot manner by adding N-3-trimethoxysilylpropyl-N,N,N-trimethylammonium to a reversed microemulsion reaction system. The Hyal loading rate was as high as 19.47% owing to matched pore size and the cationic surface charge. Subsequently, a pH-sensitive biomimetic hybrid membrane (pHH) composed of pH-sensitive liposome (pHL), red blood cell membrane, and pancreatic cancer cell membrane was camouflaged on the pHL-coated and doxorubicin/Hyal-loaded CMSNs (shortened as DHCM). The DHCM@pHL@pHH is stable at neutral pH while it releases the payloads smoothly in the tumor acidic microenvironment. Consequently, it can escape from macrophage clearance, be specifically taken up by pancreatic cancer cells, and efficiently accumulate at the tumor site. More importantly, it can penetrate deeply in pancreatic tumors with a tumor growth inhibition ratio of 80.46%. The nanosystem is biocompatible and has potential for clinical transformation, and the nanocarrier is promisingly applicable as a platform for encapsulation of various macromolecules for smart and tumor-targeted delivery.
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