Molecular Structural Characteristics and 3D Model Reconstruction of Organic Matter in Longmaxi Formation Shale.

The establishment of molecular structure modeling is an important means to study the pore characteristics of shale organic matter and is significant for molecular-level simulations of gas storage and diffusion. Using 13C NMR, FTIR, and XPS combined with the split-peak fitting technique, the structural characteristics of the aromatic structure, aliphatic structure, and oxygen functional groups of kerogen from the shale of the Longmaxi Formation, Wuxi County, Chongqing Municipality, were quantitatively characterized. A macromolecular structure model of the kerogen was also constructed by using the 2D macromolecular structure model construction method in combination with elemental analysis experiments. The results showed that the 2D single-molecule structural model of the sample consisted of 2 benzenes, 2 naphthalenes, 1 anthracene, 5 pyrenes, 1 pyridine, and 1 pyrrole. The C skeleton types were 93 protonated arylons, 39 bridged arylons, 6 carboxylons, 5 alkyl-substituted carbons, 2 oxygen-substituted carbons, 4 methylene carbons, and 3 methylons. The established 2D molecular structure formula was C152H82O12N2. The final 3D macromolecular structure model consisted of 14 2D molecular structures (structural formula C2128H1148O168N28), with the density set to 1.77 cm3/g, compressed in a cubic cell with an edge length of 3.05 nm. Finally, the adsorption results showed that the experimental adsorption of CO2 adsorption was less than the simulated adsorption, completing the validation of the model. The above study provides a method for determining the molecular structure of kerogen in the Longmaxi Formation shale, which can guide the study of the pore structure characteristics of the Longmaxi Formation shale.

Effect of Pore Structure Heterogeneity of Sandstone Reservoirs on Porosity-Permeability Variation by Using Single-Multi-Fractal Models.

Pore structure heterogeneity affects sandstone porosity and permeability and thus sandstone gas productivity. A total of 17 sandstone samples collected from the northwestern margin of the Junggar Basin in Xinjiang Province are investigated in this study. The pore-fracture system distribution of target sandstones is studied by high-pressure mercury injection tests. On this basis, single- and multi-fractal models are used to characterize pore structure heterogeneity, and the applicability of four models (Menger model, Sierpinski model, Thermodynamic model, multifractal model) to characterize pore and fracture distribution heterogeneity are discussed. Moreover, a correlation between fractal dimension, pore structure parameters, and variation coefficient of porosity-permeability is discussed based on overburden permeability test results. The results are as follows. (1) D S (fractal dimension of Sierpinski model) shows a significant correlation with pore volume percentage, so the Sierpinski model could better characterize fracture distribution heterogeneity quantitatively. Multifractal dimensions are consistent with those of Sierpinski and Thermodynamic models, which indicates that the single- and multiple-fractal models are consistent. (2) The porosity and permeability decrease as a power function with higher confining pressure. The porosity and permeability behavior changes at a critical conversion pressure value. For a confining pressure lower than this critical value, the porosity and permeability decrease largely. For confining pressures higher than this critical value, the porosity and permeability vary less. In contrast, permeability has a larger variation rate and is more obviously affected by confining pressure. (3) Pore compression space is affected by the permeability variation coefficient. Compressibility, porosity, and permeability variation coefficient have no relationship with pore structure parameters since compressibility is affected by pore structure, mineral composition, and other factors in sandstone samples.

Correction: Immunoassay-aptasensor for the determination of tumor-derived exosomes based on the combination of magnetic nanoparticles and hybridization chain reaction.

[This corrects the article DOI: 10.1039/D0RA10159A.].

Identification and quantification of nine compounds in Fangwen Jiuwei decoction by liquid chromatography-mass spectrometry.

Fangwen Jiuwei Decoction is a traditional Chinese medicine preparation for the treatment of pneumonia developed by Shenzhen Bao'an Chinese Medicine Hospital, which shows remarkable clinical responses. Qualitative and quantitative analyses of the main active compounds are crucial for the quality control of traditional Chinese medicine prescription in clinical application. In this study, we identified nine active compounds essential for the pharmacological effects of Fangwen Jiuwei Decoction based on the analysis of the Network Pharmacology and relevant literature. Moreover, these compounds can interact with several crucial drug targets in pneumonia based on molecular docking. We applied high-performance liquid chromatography-tandem mass spectrometry method was established these nine active ingredients' qualitative and quantitative detections. The possible cleavage pathways of nine active components were determined based on secondary ions mass spectrometry. The results of high-performance liquid chromatography-tandem mass spectrometry were further validated, which show a satisfactory correlation coefficient (r > 0.99), recovery rate (≥93.31%), repeatability rate (≤5.62%), stability (≤7.95%), intra-day precision (≤6.68%), and inter-day precision (≤9.78%). The limit of detection was as low as 0.01 ng/ml. In this study, we established a high-performance liquid chromatography-tandem mass spectrometry method to qualitatively and quantitatively analyze the chemical components in the Fangwen Jiuwei Decoction extract.

Determination of six core components from Mahuang Xuanfei Zhike syrup in rat plasma and tissues by UPLC-MS/MS: Application to a pharmacokinetics and tissue distribution study.

Mahuang Xuanfei Zhike (MXZ) syrup, a Chinese patent medicine, has been widely used in the clinical treatment of cough. However, there is no reported method for the quantitative analysis of the effective components of MXZ syrup in biological samples. In this study, the effective components of MXZ syrup were screened by network pharmacology and molecular docking technology. A sensitive and rapid ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was established to test the active components of MXZ syrup in rat plasma and tissue homogenates, including ephedrine, amygdalin, chlorogenic acid, harpagoside, forsythin and forsythoside A. Chromatographic separation was performed on a Waters Acquity UPLC HSS T3 column (2.1 × 50 mm, 1.8 µm) and the mass analysis was conducted using a Waters Xevo TQ mass spectrometer using multiple reaction positive and negative ion simultaneous monitoring mode. The results showed that the linearity ranged from 0.3 to 409.4 ng/ml. The extraction recoveries were all <8.33%, and the matrix effects were all <8.45, which met the requirements. The pharmacokinetic and tissue distribution results indicated that the main active components of MXZ syrup were absorbed quickly and eliminated slowly in vivo, and there may be a reabsorption process.

Highly sensitive electrochemical determination of rutin based on the synergistic effect of 3D porous carbon and cobalt tungstate nanosheets.

Rutin, a flavonoid found in fruits and vegetables, is a potential anticancer compound with strong anticancer activity. Therefore, electrochemical sensor was developed for the detection of rutin. In this study, CoWO4 nanosheets were synthesized via a hydrothermal method, and porous carbon (PC) was prepared via high-temperature pyrolysis. Successful preparation of the materials was confirmed, and characterization was performed by transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. A mixture of PC and CoWO4 nanosheets was used as an electrode modifier to fabricate the electrochemical sensor for the electrochemical determination of rutin. The 3D CoWO4 nanosheets exhibited high electrocatalytic activity and good stability. PC has a high surface-to-volume ratio and superior conductivity. Moreover, the hydrophobicity of PC allows large amounts of rutin to be adsorbed, thereby increasing the concentration of rutin at the electrode surface. Owing to the synergistic effect of the 3D CoWO4 nanosheets and PC, the developed electrochemical sensor was employed to quantitively determine rutin with high stability and sensitivity. The sensor showed a good linear range (5-5000 ng/mL) with a detection limit of 0.45 ng/mL. The developed sensor was successfully applied to the determination of rutin in crushed tablets and human serum samples.

Highly sensitive electrochemical determination of rutin based on the synergistic effect of 3D porous carbon and cobalt tungstate nanosheets / 药物分析学报

Rutin,a flavonoid found in fruits and vegetables,is a potential anticancer compound with strong anti-cancer activity.Therefore,electrochemical sensor was developed for the detection of rutin.In this study,CoWO4 nanosheets were synthesized via a hydrothermal method,and porous carbon(PC)was prepared via high-temperature pyrolysis.Successful preparation of the materials was confirmed,and character-ization was performed by transmission electron microscopy,scanning electron microscopy,and X-ray photoelectron spectroscopy.A mixture of PC and CoWO4 nanosheets was used as an electrode modifier to fabricate the electrochemical sensor for the electrochemical determination of rutin.The 3D CoWO4 nanosheets exhibited high electrocatalytic activity and good stability.PC has a high surface-to-volume ratio and superior conductivity.Moreover,the hydrophobicity of PC allows large amounts of rutin to be adsorbed,thereby increasing the concentration of rutin at the electrode surface.Owing to the syn-ergistic effect of the 3D CoWO4 nanosheets and PC,the developed electrochemical sensor was employed to quantitively determine rutin with high stability and sensitivity.The sensor showed a good linear range(5-5000 ng/mL)with a detection limit of O.45 ng/mL.The developed sensor was successfully applied to the determination of rutin in crushed tablets and human serum samples.

A highly sensitive electrochemical aptasensor for vascular endothelial growth factor detection based on toehold-mediated strand displacement reaction.

An electrochemical aptasensor with high sensitivity, specificity, and good intra-day reproducibility is reported to meet the detection needs of vascular endothelial growth factor (VEGF). The toehold-mediated strand displacement recycling amplification and VEGF aptamer are integrated in the biosensor. The probe A is hybridized with the VEGF aptamer to form the probe A-aptamer complex. When VEGF is introduced, the aptamer specifically binds with VEGF, and probe A can be liberated. Then, the free probe A captures the toehold region of the Hp1, leading the exposure of the toehold region on the other end of Hp1. Similarly, Hp2 and Hp3 are also immobilized on the surface of the electrode; thus, the methylene blue labelled on Hp2 and Hp3 causes the current response. With the signal transduction mechanism, the expression level of VEGF can be detected quantitatively. With a series of optimizations of sensor parameters, high sensitivity and specificity of the VEGF detection sensor can be achieved with a detection limit as low as 10 pg mL-1. This significant performance has good intra-day reproducibility, and it can be applied to human biological samples such as serum, urine, and saliva to detect the VEGF content.

Immunoassay-aptasensor for the determination of tumor-derived exosomes based on the combination of magnetic nanoparticles and hybridization chain reaction.

The detection of tumor-related exosomes is of great significance. In this work, a fluorescence aptasensor was designed for the determination of tumor-related exosomes based on the capture of magnetic nanoparticles (MNPs) and specific recognition of an aptamer. MNPs were used as substrates to capture the exosomes by modifying the CD63 antibody on the MNP surface. Probe 1 consists of PDL-1 aptamer sequence and a section of other sequences. PDL-1 expression was observed on the surface of exosomes; the aptamer of PDL-1 could combine with PDL-1 with high affinity. Thus, the immunoassay-type compounds of "MNPs-exosomes-probe 1" were formed. The other section of probe 1 triggered the HCR with probe 2 and probe 3 and formed the super-long dsDNA. The addition of GelRed resulted in the generation of an amplified fluorescence signal. The proposed design demonstrated a good linearity with the exosome concentration ranging from 300 to 107 particles per mL and with a low detection limit of 100 particles per mL. This aptasensor also exhibited high specificity for tumor-related exosomes, and was successfully applied in biological samples.

An ultrasensitive electrochemical sensing platform for the detection of cTnI based on aptamer recognition and signal amplification assisted by TdT.

We have developed an ultrasensitive and highly specific electrochemical sensing platform for the detection of cardiac troponin I (cTnI), a recognized biomarker for the diagnosis of acute myocardial infarction (AMI) and related cardiovascular diseases (CVDs). This strategy is based on the assists of terminal deoxynucleotidyl transferase (TdT)-mediated signal amplification and the specific recognition between cTnI and the aptamer of cTnI. In this experiment, we prepared a gold electrode that modified with probe 2 (P2), in the presence of cTnI, the aptamer of cTnI that in probe 1 (P1)/aptamer complexes bond with cTnI specifically and release the free P1. P1 would bind with P2, resulting in the formation of 3'-OH of DNA. In the presence of terminal deoxynucleotidyl transferase (TdT) and dTTP, TdT mediated P1 to extend and formed the structure of poly T. Methylene blue (MB)-poly A hybridized with the extended poly T and generated an electrochemical signal. The detection limit can be as low as 40 pg mL-1. This sensor was also successfully applied to the detection of cTnI in numerous spiked biological samples, and it can be a great reference for the clinical diagnosis, prognosis, and treatment of CVDs and AMI.

[Study of anticoagulant activity of ethanol extracts from leech in vitro].

OBJECTIVE: To study the anticoagulant activity of different portions of leech ethanol extracts (LEEs). METHODS: Anticoagulant activity was determined by measuring prothrombin time(PT), thrombin time (TT), activated partial throboplstin time (APTT) and fibrinogen coagulation time (FCT). RESULTS: PT, TT, APTT and FCT were remarkably prolonged by ethyl acetate portion of LEEs. Portions of petroleum ethrer, n-butanol and water extracted from LEEs was much weaker on anticoagulant activity. CONCLUSION: The anticoagulant effect of ethyl acetate extract portion of LEEs is the strongest among the four portions, and this results may be from its inhibitory effect on thrombin-catalyzed fibrinogen hydrolysis.