Inhibitory effect of α-cyclodextrin on α-amylase activity

Purpose: To explore the effect of α-cyclodextrin on the activity of α-amylase with a view to expanding its application range.Methods: The concentration of α-cyclodextrin, temperature, pH and interaction time were used as single factors to explore the influence of α-cyclodextrin on the activity of α-amylase and endogenous fluorescence in the enzyme system.Results: The results showed that the concentration, time, pH and temperature affect the interaction of them. The most obvious conditions for inhibition of α-amylase activity are as follows: 10 mmol/L concentration of α-cyclodextrin, pH 6.9, duration of 120 min and temperature at 55 oC. In addition, the fluorescence intensity of α-amylase changed as a result of the addition of α-cyclodextrin.Conclusion: The activity of α-amylase can be inhibited by α-cyclodextrin. At the same time, the addition of α-cyclodextrin will lead to the transfer of tryptophan group in α-amylase, which cause the change of microenvironment and changes the endogenous fluorescence intensity of α-amylase.Keywords: α-Cyclodextrin, α-Amylase, Fluorescence intensity, Inhibitio

Cyclotrimerization of alkynes catalyzed by a self-supported cyclic tri-nuclear nickel(0) complex with α-diimine ligands

A cyclic tri-nuclear α-diimine nickel(0) complex [{Ni(μ-L Me-2,4 )} 3 ] (2) was synthesized from a “pre-organized”, trimerized trigonal LNiBr 2 -type precursor [Ni 3 (μ 2 -Br) 3 (μ 3 -Br) 2 (L Me-2,4 ) 3 ]·Br (1; L Me-2,4 = [(2,4-Me 2 C 6 H 3 )NC(Me)] 2 ). In complex 2, the α-diimine ligands not only exhibit the normal N,N′-chelating mode, but they also act as bridges between the Ni atoms through an unusual π-coordination of a C═N bond to Ni. Complex 2 is able to catalyze the cyclotrimerization of alkynes to form substituted benzenes in good yield and regio-selectivity for the 1,3,5-isomers, which is found to vary with the nature of the alkyne employed. This complex represents a convenient self-supported nickel(0) catalyst with no need for additional ligands and reducing agent

Synthesis, crystal structure and bioactivity of phenazine-1-carboxylic acylhydrazone derivatives

A phenazine-1-carboxylic acid intermediate was synthesized from the reaction of aniline and 2-bromo-3-nitro-benzoic acid. It was then esterified and reacted with hydrazine hydrate to afford phenazine-1-carboxylic hydrazine. Finally, 10 new hydrazone compounds 3a–3j were obtained by the condensation reaction of phenazine-1-carboxylic acid hydrazide and the respective aldehyde-containing compound. The structures were characterized by 1H and 13C NMR spectroscopy, MS and single crystal X-ray diffraction. The antitumor activity of the target compounds in vitro (HeLa and A549) was determined by thiazolyl blue tetrazolium bromide. The results showed that compound (E)-N′-(2-hydroxy-4-(2-(piperidine-1-yl) ethoxy) benzyl) phenazine-1-carbonyl hydrazide 3d exhibited good cytotoxic activity

A Turn-On Fluorescent Chemosensor for Cyanide Ion Detection in Real Water Samples

We have designed and synthesized a novel simple colorimetric fluorescent probe with aggregation-induced emission (AIE) properties. Probe 5-(4-(diphenylamine)phenyl) thiophen-2-formaldehyde W exhibited a turn-on fluorescent response to cyanide ion (CN−), which induces distinct visual color changes. Probe W exhibited a highly selective and sensitive ratiometric fluorescence response for the detection of CN− over a wide pH range (4–11) and in the presence of common interferents. The linear detection of CN− over the concentration range of 4.00–38.00 µM (R2 = 0.9916, RSD = 0.02) was monitored by UV-Vis absorption spectrometry (UV-Vis) with the limit of detection determined to be 0.48 µM. The linear detection of CN− over the concentration range of 8.00–38.00 µM was examined by fluorescence spectrophotometry (R2 = 0.99086, RSD = 0.031), and the detection limit was found to be 68.00 nM. The sensing mechanisms were confirmed by 1H NMR spectroscopic titrations, X-ray crystallographic analysis, and HRMS. Importantly, probe W was found to show rapid response, high selectivity, and sensitivity for cyanide anions in real water samples, over the range of 100.17∼100.86% in artificial lake water and 100.54∼101.64% in running water by UV-Vis absorption spectrometry, and over the range of 99.42∼100.71% in artificial lake water and 100.59∼101.17% in running water by fluorescence spectrophotometry. Importantly, this work provides a simple and effective approach which uses an economically cheap and uncomplicated synthetic route for the selective, sensitive, and quantitative detection of CN− ions in systems relevant to the environment and health

3% diquafosol sodium eye drops in Chinese patients with dry eye: a phase IV study

IntroductionThe efficacy and safety of 3% diquafosol sodium eye drops in Chinese patients with dry eye in the real-world setting remains unclear.Methods3099 patients with dry eye symptoms were screened according to Asia Dry Eye Society latest recommendation. Among them, 3000 patients were enrolled for a phase IV study. We followed up with multiple clinical characteristics including corneal fluorescein staining, tear break up time, Schirmer’s tests, visual acuity, intraocular pressure, and others. The follow ups were performed at baseline, 2 weeks and 4 weeks after treatment.ResultsBased on the results of corneal fluorescein staining and tear break up time, all age and gender subgroups exhibited obvious alleviation of the symptoms among the patients with dry eye, and the data in elderly group showed the most significant alleviation. All the adverse drug reactions (ADRs, 6.17%) were recorded, among which 6% local ocular ADRs were included. Meanwhile, mild ADRs (91.8%) accounted for the most. Most of the ADRs (89.75%) got a quick and full recovery, with an average time at 15.6 days. 1.37% of patients dropped out of the study due to ADRs.DiscussionThe use of 3% diquafosol sodium eye drop is effective and safe in the treatment of dry eye, with a low incidence of ADRs showing mild symptoms. This trial was registered at Chinese Clinical Trial Registry ID: ChiCTR1900021999 (Registration Date: 19/03/2019)

Research on Resilience Evaluation and Enhancement of Deep Foundation Pit Construction Safety System

Deep foundation pit (DFP) projects have been a high incidence area of safety accidents because of their own high danger and complexity. Therefore, it is necessary to study the resilience of their construction safety system. This paper systematically identifies the key factors affecting the resilience of deep foundation pit construction based on the analysis of the composition of the deep foundation pit construction safety system (DFPCTSS), the synergistic relationship of its subsystems in the face of the interference and impact of internal and external disaster-causing factors, and the causal mechanism of typical accidents in DFP accidents and the emergent process of system resilience. A resilience evaluation indicator system based on four capacity dimensions of prevention absorption, resistance, recovery, and learning adaptation was constructed by using the fuzzy Delphi method, which is characterized by the resilience emergence process. Then the correlation and weight of evaluation indexes were analyzed based on the DEMATEL–ANP method, the boundary cloud parameters of the resilience evaluation grade were set according to the normal extension cloud model, and the membership degree of the resilience evaluation level was calculated to complete the evaluation of the resilience level. Finally, taking a DFP project of a metro station as an example, the above model was used to evaluate the resilience level of its construction safety system, and suggestions for resilience enhancement were put forward. The results show that the evaluation results are consistent with the actual situation of the project, and the evaluation model is conducive to providing a systematic analysis method and improvement countermeasures for deep foundation pit construction safety management from the perspective of resilience

Research on Resilience Evaluation and Enhancement of Deep Foundation Pit Construction Safety System

Deep foundation pit (DFP) projects have been a high incidence area of safety accidents because of their own high danger and complexity. Therefore, it is necessary to study the resilience of their construction safety system. This paper systematically identifies the key factors affecting the resilience of deep foundation pit construction based on the analysis of the composition of the deep foundation pit construction safety system (DFPCTSS), the synergistic relationship of its subsystems in the face of the interference and impact of internal and external disaster-causing factors, and the causal mechanism of typical accidents in DFP accidents and the emergent process of system resilience. A resilience evaluation indicator system based on four capacity dimensions of prevention absorption, resistance, recovery, and learning adaptation was constructed by using the fuzzy Delphi method, which is characterized by the resilience emergence process. Then the correlation and weight of evaluation indexes were analyzed based on the DEMATEL–ANP method, the boundary cloud parameters of the resilience evaluation grade were set according to the normal extension cloud model, and the membership degree of the resilience evaluation level was calculated to complete the evaluation of the resilience level. Finally, taking a DFP project of a metro station as an example, the above model was used to evaluate the resilience level of its construction safety system, and suggestions for resilience enhancement were put forward. The results show that the evaluation results are consistent with the actual situation of the project, and the evaluation model is conducive to providing a systematic analysis method and improvement countermeasures for deep foundation pit construction safety management from the perspective of resilience

Double Cross-Linked Hydrogel Dressings Based on Triblock Copolymers Bearing Antifreezing, Antidrying, and Inherent Antibacterial Properties

Bacterial infections typically invade the living tissue of wounds, thereby aggravating the inflammatory response, delaying wound healing, or causing further complications. In this paper, the antibacterial hydrogel (PNVBA) with antifreezing and antidrying properties was prepared by a two-step method using N-isopropylacrylamide (NIPAM), 1-butyl-3-vinylimidazolium bromide (VBIMBr), and 3-acrylamidophenylboronic acid (AAPBA). PNVBA hydrogels exhibited a high adsorption capacity of 280 mg·g-1 for bovine serum albumin (BSA) and can adhere to the surface of different materials through ion-dipole or hydrogen-bonding interactions. Meanwhile, the PNVBA hydrogels exhibited high viscoelasticity and good adhesion after freezing at −20 °C or heating at 70 °C for 24 h with a sterilizing rate of up to 98% against multidrug-resistant (MDR) Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). Moreover, a survival rate of up to 90% after incubation with L929 cells over 24 h was observed. Therefore, this inherent antibacterial hydrogel can be used as an excellent alternative material for wound dressings