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2020 Volume 48 Issue 8
2020, 48(8): 969-980
doi: 10.19756/j.issn.0253-3820.201128
Abstract:
The heterogeneity among individual cells is of great importance for organisms to achieve different biological functions. Investigations deep into the mechanism of some biological phenomena rely on the analysis of the chemical compositions of single cells. Unfortunately, the successful analysis of single cells is technically difficult to achieve due to the complex composition of single cells, the very limited amount of materials in single cells and the huge difference among different metabolites in their concentrations. Mass spectrometry (MS) has been widely used in single cell analysis in recent years due to its high sensitivity, high specificity and capability for structure identification. Methods based on MS have been developed for the analysis of different metabolites in single cells. From the perspective of ionization techniques, there are mainly three single cell analysis methods, including nano-electrospray ionization (Nano-ESI) based method, laser desorption ionization (LDI) based method and secondary ion MS (SIMS) based method. This review summarizes the up-to-date developments of these methods and their future trends.
The heterogeneity among individual cells is of great importance for organisms to achieve different biological functions. Investigations deep into the mechanism of some biological phenomena rely on the analysis of the chemical compositions of single cells. Unfortunately, the successful analysis of single cells is technically difficult to achieve due to the complex composition of single cells, the very limited amount of materials in single cells and the huge difference among different metabolites in their concentrations. Mass spectrometry (MS) has been widely used in single cell analysis in recent years due to its high sensitivity, high specificity and capability for structure identification. Methods based on MS have been developed for the analysis of different metabolites in single cells. From the perspective of ionization techniques, there are mainly three single cell analysis methods, including nano-electrospray ionization (Nano-ESI) based method, laser desorption ionization (LDI) based method and secondary ion MS (SIMS) based method. This review summarizes the up-to-date developments of these methods and their future trends.
2020, 48(8): 981-989
doi: 10.19756/j.issn.0253-3820.201165
Abstract:
Surface-enhanced Raman scattering (SERS) spectroscopy technology can be used to detect volatile organic pollutants with many advantages such as fast detection speed, high sensitivity and fingerprint recognition. However, the pre-processing equipment in conventional SERS is bulky and has insufficient human-computer interaction and inconvenient operation. All these issues limit its applications to onsite tests. In this work, a portable detection system was developed for onsite and real-time detections. This system provided a miniaturized portable purge and trap device for the enrichment of volatile samples in pretreatment. It had the characteristics of low consumption of samples and short consumption of time. Meanwhile, it was also equipped with a miniaturized Raman optical detection module that adopted ARM + CPLD (Advanced RISC Machine & Complex Programmable Logic Device) dual-core control mode and Android operating system. These features enabled the device realizing the real-time quantitative detection of volatile and harmful substances onsite in human-machine direct interaction mode. For example, by using thiophenol in the soil as the detection target and gold nanoparticles as the enhanced substrate, the developed system was used to quantitatively analyze the thiophenol level in the soil, with detection limit of 0.104 μg/g and RSD of 4.2%-6.2%. The result showed that the experimental data were reproducible.
Surface-enhanced Raman scattering (SERS) spectroscopy technology can be used to detect volatile organic pollutants with many advantages such as fast detection speed, high sensitivity and fingerprint recognition. However, the pre-processing equipment in conventional SERS is bulky and has insufficient human-computer interaction and inconvenient operation. All these issues limit its applications to onsite tests. In this work, a portable detection system was developed for onsite and real-time detections. This system provided a miniaturized portable purge and trap device for the enrichment of volatile samples in pretreatment. It had the characteristics of low consumption of samples and short consumption of time. Meanwhile, it was also equipped with a miniaturized Raman optical detection module that adopted ARM + CPLD (Advanced RISC Machine & Complex Programmable Logic Device) dual-core control mode and Android operating system. These features enabled the device realizing the real-time quantitative detection of volatile and harmful substances onsite in human-machine direct interaction mode. For example, by using thiophenol in the soil as the detection target and gold nanoparticles as the enhanced substrate, the developed system was used to quantitatively analyze the thiophenol level in the soil, with detection limit of 0.104 μg/g and RSD of 4.2%-6.2%. The result showed that the experimental data were reproducible.
2020, 48(8): 990-996
doi: 10.19756/j.issn.0253-3820.191737
Abstract:
Digital filtering is one of the most important methods to improve the signal-to-noise ratio of quadrupole mass spectrometer. Aiming at the insufficient data processing capacity of the control system in miniature quadrupole mass spectrometers, one solution of digital filtering which based on FPGA was proposed in this work. The FPGA program instead of the general processor program was used to perform digital filtering operations, which improved the data processing capability of the instrument control system and completed high-order digital filtering. In miniature quadrupole mass spectrometer developed by our team, the solution here was used to achieve 130-order digital filtering. The high frequency noise attenuation of the perfluorotributylamine standard sample was more than -50 dB. The power consumption was only increased about 190 mW, which accounted for about 1.7% of the total power consumption of the control system. Meanwhile, it solved the problem of easy data loss caused by general processors for digital filtering, and provided design reference for other low-power control systems to complete high-performance data processing.
Digital filtering is one of the most important methods to improve the signal-to-noise ratio of quadrupole mass spectrometer. Aiming at the insufficient data processing capacity of the control system in miniature quadrupole mass spectrometers, one solution of digital filtering which based on FPGA was proposed in this work. The FPGA program instead of the general processor program was used to perform digital filtering operations, which improved the data processing capability of the instrument control system and completed high-order digital filtering. In miniature quadrupole mass spectrometer developed by our team, the solution here was used to achieve 130-order digital filtering. The high frequency noise attenuation of the perfluorotributylamine standard sample was more than -50 dB. The power consumption was only increased about 190 mW, which accounted for about 1.7% of the total power consumption of the control system. Meanwhile, it solved the problem of easy data loss caused by general processors for digital filtering, and provided design reference for other low-power control systems to complete high-performance data processing.
2020, 48(8): 997-1003
doi: 10.19756/j.issn.0253-3820.191623
Abstract:
A simple and highly sensitive colorimetric assay method for ascorbic acid (AA) detection was developed based on the high catalytic activity of metal-organic polyhedron (MOP) and the reducibility of ascorbic acid. Copper metal-organic polyhedra nanorods (Cu-MOP) exhibited high peroxidase-mimicking activity, which were capable of catalyzing the oxidation of the 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2. The presence of AA in detection solution triggered the decomposition of Cu-MOP by reducing Cu2+, which weakened peroxidase-mimicking activity of Cu-MOP dramatically. As a result, the catalytic oxidation reaction of TMB by Cu-MOP in the presence of H2O2 was inhibited, and AA could be detected specifically by detecting the solution color and its absorbance. The calibration graph for the determination of AA was linear in the range of 1.0-30.0 μmol/L and 40.0-200 μmol/L, and the detection limit (S/N=3) was 0.68 μmol/L. The sensor showed many advantage such as simple, fast and without the need of complicated instruments, and could be applied to the determination of AA in drugs with satisfactory results.
A simple and highly sensitive colorimetric assay method for ascorbic acid (AA) detection was developed based on the high catalytic activity of metal-organic polyhedron (MOP) and the reducibility of ascorbic acid. Copper metal-organic polyhedra nanorods (Cu-MOP) exhibited high peroxidase-mimicking activity, which were capable of catalyzing the oxidation of the 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2. The presence of AA in detection solution triggered the decomposition of Cu-MOP by reducing Cu2+, which weakened peroxidase-mimicking activity of Cu-MOP dramatically. As a result, the catalytic oxidation reaction of TMB by Cu-MOP in the presence of H2O2 was inhibited, and AA could be detected specifically by detecting the solution color and its absorbance. The calibration graph for the determination of AA was linear in the range of 1.0-30.0 μmol/L and 40.0-200 μmol/L, and the detection limit (S/N=3) was 0.68 μmol/L. The sensor showed many advantage such as simple, fast and without the need of complicated instruments, and could be applied to the determination of AA in drugs with satisfactory results.
2020, 48(8): 1004-1011
doi: 10.19756/j.issn.0253-3820.201251
Abstract:
Molecular imaging (MI) techniques have extremely significant effect on the diagnosis and prognosis of diseases, such as gastrointestinal (GI) tract-related diseases. Furthermore, nanomaterials as contrast agents have attracted a great deal of research attention due to their rational fabrication and biomedical application. Herein, a facile process to synthesis PEGylated BaGdF5 nanoparticles via a one-pot solvothermal route was reported as CT/MRI dual-modal contrast agents for in vivo imaging of GI tract. Compared to the commercially used iodine contrast agents, the well-prepared nanoparticles exhibited enhancement in computed tomography (CT) imaging. In the presence of Gd, nanoparticles could also be used in magnetic resonance imaging (MRI). PEGylated BaGdF5 nanoparticles were characterized by transmission electron microscopy (TEM), X-ray powder diffraction analysis (XRD), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). Besides, MTT assay revealed that the obtained PEGylated BaGdF5 nanoparticles proved to be low toxicity for Hela cells. Hemolytic assay illustrated that nanoparticles possessed favorable hemocompatibility. H & E histological staining assessed long-term toxicity of oral PEGylated BaGdF5 nanoparticles and the results showed that nanoparticles had overall safety for GI tissue with comparatively high biocompatibility. PEGylated BaGdF5 nanoparticles were admired multi-functional contrast agents to apply in CT and MRI imaging with prominent prospects.
Molecular imaging (MI) techniques have extremely significant effect on the diagnosis and prognosis of diseases, such as gastrointestinal (GI) tract-related diseases. Furthermore, nanomaterials as contrast agents have attracted a great deal of research attention due to their rational fabrication and biomedical application. Herein, a facile process to synthesis PEGylated BaGdF5 nanoparticles via a one-pot solvothermal route was reported as CT/MRI dual-modal contrast agents for in vivo imaging of GI tract. Compared to the commercially used iodine contrast agents, the well-prepared nanoparticles exhibited enhancement in computed tomography (CT) imaging. In the presence of Gd, nanoparticles could also be used in magnetic resonance imaging (MRI). PEGylated BaGdF5 nanoparticles were characterized by transmission electron microscopy (TEM), X-ray powder diffraction analysis (XRD), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). Besides, MTT assay revealed that the obtained PEGylated BaGdF5 nanoparticles proved to be low toxicity for Hela cells. Hemolytic assay illustrated that nanoparticles possessed favorable hemocompatibility. H & E histological staining assessed long-term toxicity of oral PEGylated BaGdF5 nanoparticles and the results showed that nanoparticles had overall safety for GI tissue with comparatively high biocompatibility. PEGylated BaGdF5 nanoparticles were admired multi-functional contrast agents to apply in CT and MRI imaging with prominent prospects.
2020, 48(8): 1012-1017
doi: 10.19756/j.issn.0253-3820.201083
Abstract:
Random forest algorithm (RF) is a machine learning algorithm based on decision trees. Due to the good performance of classification and variables selection, it has been widely used in biomedical high-dimensional data analysis. In order to fast and accurately distinguish human lung cancer from adjacent normal tissues, a model for direct ambient mass spectrometric analysis of lung cancer tissue sections based on random forest algorithm was developed. The purpose of this study was to establish a liquid assisted surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS) platform, combined with the random forest algorithm, to directly identify and differentiate the untreated human lung squamous cell carcinoma tissue sections under normal temperature and pressure, as well as obtaining the biomarkers of lung cancer for differentiation from normal tissue. The results showed that when the number of decision trees ntree=100, the accuracy of distinguishing human lung squamous cell carcinoma from adjacent normal tissues reached 100%. Compared with other methods, this model had higher robustness, better classification effect and stronger generalization ability. This study provided a more accurate and reliable classification model for rapid differentiation of human lung cancer tissues from adjacent normal tissues in complex matrix.
Random forest algorithm (RF) is a machine learning algorithm based on decision trees. Due to the good performance of classification and variables selection, it has been widely used in biomedical high-dimensional data analysis. In order to fast and accurately distinguish human lung cancer from adjacent normal tissues, a model for direct ambient mass spectrometric analysis of lung cancer tissue sections based on random forest algorithm was developed. The purpose of this study was to establish a liquid assisted surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS) platform, combined with the random forest algorithm, to directly identify and differentiate the untreated human lung squamous cell carcinoma tissue sections under normal temperature and pressure, as well as obtaining the biomarkers of lung cancer for differentiation from normal tissue. The results showed that when the number of decision trees ntree=100, the accuracy of distinguishing human lung squamous cell carcinoma from adjacent normal tissues reached 100%. Compared with other methods, this model had higher robustness, better classification effect and stronger generalization ability. This study provided a more accurate and reliable classification model for rapid differentiation of human lung cancer tissues from adjacent normal tissues in complex matrix.
2020, 48(8): 1018-1024
doi: 10.19756/j.issn.0253-3820.201130
Abstract:
A gold nanorod (GNR)-based immunochromatographic strip was developed for rapid and quantitative detection of prostate specific antigen (PSA). GNR was used as the labeled probe and coated with sodium polyacrylate. Then the anti-PSA monoclonal antibody (dAb) was immobilized on the surface of GNR through covalent attachment to form the GNR-dAb conjugates. The mouse anti-PSA monoclonal antibody and the goat anti-mouse IgG were sprayed onto the nitrocellulose membrane as test line and control line, respectively. The resultant GNR-dAb conjugates were introduced to construct the immunochromatographic strip for the quantitative detection of PSA by a sandwich method. The proposed GNR-based immunochromatographic strip exhibited good specificity, high stability and high sensitivity. The experimental results indicated that GNR-based immunochromatographic strip showed a good linear range from 0.1 ng/mL to 50 ng/mL with a limit of detection of 0.1 ng/mL, and the relative standard deviation was less than 10%. The established assay could be successfully applied for PSA detection in serum, which was beneficial for early diagnosis, treatment and prognosis of prostate cancer.
A gold nanorod (GNR)-based immunochromatographic strip was developed for rapid and quantitative detection of prostate specific antigen (PSA). GNR was used as the labeled probe and coated with sodium polyacrylate. Then the anti-PSA monoclonal antibody (dAb) was immobilized on the surface of GNR through covalent attachment to form the GNR-dAb conjugates. The mouse anti-PSA monoclonal antibody and the goat anti-mouse IgG were sprayed onto the nitrocellulose membrane as test line and control line, respectively. The resultant GNR-dAb conjugates were introduced to construct the immunochromatographic strip for the quantitative detection of PSA by a sandwich method. The proposed GNR-based immunochromatographic strip exhibited good specificity, high stability and high sensitivity. The experimental results indicated that GNR-based immunochromatographic strip showed a good linear range from 0.1 ng/mL to 50 ng/mL with a limit of detection of 0.1 ng/mL, and the relative standard deviation was less than 10%. The established assay could be successfully applied for PSA detection in serum, which was beneficial for early diagnosis, treatment and prognosis of prostate cancer.
2020, 48(8): 1025-1032
doi: 10.19756/j.issn.0253-3820.201163
Abstract:
Fluorescent metal nanoclusters usually do not have specific selectivity, which limits their sensing application. Herein, the gold nanoclusters/zeolitic imidazolate framework-8 (AuNCs/ZIF-8) nanocomposites were developed for specific detection of MnO4-. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) characterization showed that AuNCs were immobilized on the outer surface of ZIF-8 via the coordinative interaction. Compared with individual AuNCs solution, the photoluminescence intensity of AuNCs on AuNCs/ZIF-8 nanocomposites was increased, eliminating the interference of Cu2+ and Hg2+ ions, and demonstrating a better selectivity toward MnO4-. UV-Vis absorption spectra and TEM images showed that the sensing mechanism of MnO4- resulted from inner filter effect. In addition, a good linearity between photoluminescence intensity of AuNCs/ZIF-8 nanocomposites and MnO4- concentration in the range of 1-30 -μmol/L was obtained, with a detection limit of 0.64 -μmol/L.
Fluorescent metal nanoclusters usually do not have specific selectivity, which limits their sensing application. Herein, the gold nanoclusters/zeolitic imidazolate framework-8 (AuNCs/ZIF-8) nanocomposites were developed for specific detection of MnO4-. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) characterization showed that AuNCs were immobilized on the outer surface of ZIF-8 via the coordinative interaction. Compared with individual AuNCs solution, the photoluminescence intensity of AuNCs on AuNCs/ZIF-8 nanocomposites was increased, eliminating the interference of Cu2+ and Hg2+ ions, and demonstrating a better selectivity toward MnO4-. UV-Vis absorption spectra and TEM images showed that the sensing mechanism of MnO4- resulted from inner filter effect. In addition, a good linearity between photoluminescence intensity of AuNCs/ZIF-8 nanocomposites and MnO4- concentration in the range of 1-30 -μmol/L was obtained, with a detection limit of 0.64 -μmol/L.
2020, 48(8): 1033-1040
doi: 10.19756/j.issn.0253-3820.191686
Abstract:
A highly selective and sensitive fluorescent probe 2-(2-furyl)-7-methoxychromone-3-acrylate (HFAC) was designed and synthesized with paeonol and furfural as raw material, 3-hydroxyflavone as fluorophore and acrylate group as recognition unit. The probe HFAC was characterized by 1H NMR, 13C NMR and HRMS-ESI. The results of absorption and fluorescence spectral analysis indicated that the probe had high sensitivity and selectivity towards cysteine (Cys), and the detection was not affected by other biothiols such as homocysteine, glutathione and others. Meanwhile, it was confirmed that HFAC was a reaction type "off-on" fluorescent probe, the fluorescence intensity at 525 nm had a high linear relationship with Cys concentration in the range of 20-400 μmol/L with a regression equation of y=0.4608x + 3.994 (R2=0.9987) and a detection limit of 37.9 nmol/L, and the color of the reaction solution changed from colorless to bright green at UV light of 365 nm. Fluorescence bioimaging experiment proved that probe HFAC had excellent cell membrane permeability, low cytotoxicity and biocompatibility, which was desirable for fast detection and visualization of both endogenous and exogenous Cys in A549 cells.
A highly selective and sensitive fluorescent probe 2-(2-furyl)-7-methoxychromone-3-acrylate (HFAC) was designed and synthesized with paeonol and furfural as raw material, 3-hydroxyflavone as fluorophore and acrylate group as recognition unit. The probe HFAC was characterized by 1H NMR, 13C NMR and HRMS-ESI. The results of absorption and fluorescence spectral analysis indicated that the probe had high sensitivity and selectivity towards cysteine (Cys), and the detection was not affected by other biothiols such as homocysteine, glutathione and others. Meanwhile, it was confirmed that HFAC was a reaction type "off-on" fluorescent probe, the fluorescence intensity at 525 nm had a high linear relationship with Cys concentration in the range of 20-400 μmol/L with a regression equation of y=0.4608x + 3.994 (R2=0.9987) and a detection limit of 37.9 nmol/L, and the color of the reaction solution changed from colorless to bright green at UV light of 365 nm. Fluorescence bioimaging experiment proved that probe HFAC had excellent cell membrane permeability, low cytotoxicity and biocompatibility, which was desirable for fast detection and visualization of both endogenous and exogenous Cys in A549 cells.
2020, 48(8): 1041-1049
doi: 10.19756/j.issn.0253-3820.201054
Abstract:
Gold nanoparticles (AuNPs) were prepared by reducing HAuCl4 with pear juice as reducing and protecting agent, which was rapid and environmentally friendly. AuNPs were characterized by scanning electron microscopy (SEM), Fourier Transform Infra-Red (FT-IR) and ultraviolet-visible (UV-Vis) spectroscopy. Compared with AuNPs prepared using citrate sodium as reducing agent, AuNPs synthesized by pear juice were more stable. AuNPs were used for colorimetric detection of vitamin C. When this as-prepared AuNPs mixed with AgNO3 and vitamin C, AgNO3 was reduced to Ag by vitamin C and deposited on the surface of AuNPs to form Ag/AuNPs, which was accompanied by a color change, as well as the increase of the Ag/AuNPs peak absorbance at 432 nm monitored by UV-Vis detection. Vitamin C could be analyzed qualitatively by the naked eyes according to the color change and quantitatively by UV-Vis detection. The main factors influencing detection of vitamin C were investigated in detail, including the volume of AgNO3, the pH value and the incubate time. When the concentration of vitamin C was 0.8 mg/L, the solution could be observed from red to brown with naked eyes. The linear range of vitamin C was from 0.4 mg/L to 40 mg/L and from 40 mg/L to 80 mg/L, the relative standard deviation (RSD) was 1.6% (n=8, CVc=8 mg/L) and the limit of detection (LOD) was 0.17 mg/L. This method had good selectivity and specificity and was applied to detect vitamin C in vitamin C tablets with recoveries ranging from 89.5% to 110.0%.
Gold nanoparticles (AuNPs) were prepared by reducing HAuCl4 with pear juice as reducing and protecting agent, which was rapid and environmentally friendly. AuNPs were characterized by scanning electron microscopy (SEM), Fourier Transform Infra-Red (FT-IR) and ultraviolet-visible (UV-Vis) spectroscopy. Compared with AuNPs prepared using citrate sodium as reducing agent, AuNPs synthesized by pear juice were more stable. AuNPs were used for colorimetric detection of vitamin C. When this as-prepared AuNPs mixed with AgNO3 and vitamin C, AgNO3 was reduced to Ag by vitamin C and deposited on the surface of AuNPs to form Ag/AuNPs, which was accompanied by a color change, as well as the increase of the Ag/AuNPs peak absorbance at 432 nm monitored by UV-Vis detection. Vitamin C could be analyzed qualitatively by the naked eyes according to the color change and quantitatively by UV-Vis detection. The main factors influencing detection of vitamin C were investigated in detail, including the volume of AgNO3, the pH value and the incubate time. When the concentration of vitamin C was 0.8 mg/L, the solution could be observed from red to brown with naked eyes. The linear range of vitamin C was from 0.4 mg/L to 40 mg/L and from 40 mg/L to 80 mg/L, the relative standard deviation (RSD) was 1.6% (n=8, CVc=8 mg/L) and the limit of detection (LOD) was 0.17 mg/L. This method had good selectivity and specificity and was applied to detect vitamin C in vitamin C tablets with recoveries ranging from 89.5% to 110.0%.
2020, 48(8): 1050-1057
doi: 10.19756/j.issn.0253-3820.201135
Abstract:
Kinetic studies of the reactions between ·OH and alkanes were performed with laser-flash photolysis and Faraday rotation spectrometer (LFP-FRS). The ·OH was generated by flash photolysis of ozone with a 266 nm pulsed laser, the decay of the ·OH concentration was directly measured with a time-resolved FRS spectrometer at 2.8 μm under the pseudo-first-order, and the reaction rate constant of methane with ·OH at 5 kPa was measured to be 6.59×10-15 cm3/(molecule·s). Meanwhile, the rate constants of methane, ethane and propane reacted with ·OH under different pressure conditions were compared. The reaction process was simulated by implementing several existed reaction channels into a chemical kinetic model, which provided a basis for studying the important atmospheric chemical mechanism and reaction process of ·OH radical.
Kinetic studies of the reactions between ·OH and alkanes were performed with laser-flash photolysis and Faraday rotation spectrometer (LFP-FRS). The ·OH was generated by flash photolysis of ozone with a 266 nm pulsed laser, the decay of the ·OH concentration was directly measured with a time-resolved FRS spectrometer at 2.8 μm under the pseudo-first-order, and the reaction rate constant of methane with ·OH at 5 kPa was measured to be 6.59×10-15 cm3/(molecule·s). Meanwhile, the rate constants of methane, ethane and propane reacted with ·OH under different pressure conditions were compared. The reaction process was simulated by implementing several existed reaction channels into a chemical kinetic model, which provided a basis for studying the important atmospheric chemical mechanism and reaction process of ·OH radical.
2020, 48(8): 1058-1066
doi: 10.19756/j.issn.0253-3820.191732
Abstract:
The terahertz (THz) spectra of hypoxanthine and allopurinol samples were measured by THz time-domain spectroscopy (THz-TDS) in the range of 0.1-2 THz at room temperature. The geometry structures of these two samples were optimized using density functional theory (DFT). The low frequency vibrations of molecular group for these two samples were assigned using the potential energy distribution (PED) analysis. The spectral dispersion characteristics of samples were qualitatively analyzed by the energy decomposition analysis based on molecular forcefield (EDA-FF) method. PED analysis results showed that the vibration modes of the hypoxanthine cluster were all dihedral angle torsion, while allopurinol cluster were bond angle bending and dihedral angle torsion. EDA-FF data and atomic coloring diagrams indicated that the weak interaction types of the two clusters were dominated by electrostatic, while the amount of hydrogen bonds in allopurinol system were double compared with hypoxanthine, and the dispersion was mainly reflected on the donor and acceptor atoms that directly interacted with hydrogen bonds. The combination of DFT, PED and EDA-FF methods provided a valuable reference for the further study of intermolecular non-bonded interaction and biomolecules with structural similaritield
The terahertz (THz) spectra of hypoxanthine and allopurinol samples were measured by THz time-domain spectroscopy (THz-TDS) in the range of 0.1-2 THz at room temperature. The geometry structures of these two samples were optimized using density functional theory (DFT). The low frequency vibrations of molecular group for these two samples were assigned using the potential energy distribution (PED) analysis. The spectral dispersion characteristics of samples were qualitatively analyzed by the energy decomposition analysis based on molecular forcefield (EDA-FF) method. PED analysis results showed that the vibration modes of the hypoxanthine cluster were all dihedral angle torsion, while allopurinol cluster were bond angle bending and dihedral angle torsion. EDA-FF data and atomic coloring diagrams indicated that the weak interaction types of the two clusters were dominated by electrostatic, while the amount of hydrogen bonds in allopurinol system were double compared with hypoxanthine, and the dispersion was mainly reflected on the donor and acceptor atoms that directly interacted with hydrogen bonds. The combination of DFT, PED and EDA-FF methods provided a valuable reference for the further study of intermolecular non-bonded interaction and biomolecules with structural similaritield
2020, 48(8): 1067-1074
doi: 10.19756/j.issn.0253-3820.191528
Abstract:
A novel carbon dots (CDs) fluorescent probe was prepared by pyrolyzing the mixture of ascorbic acid (Vc) and polyethyleneimine (PEI) aqueous solution through hydrothermal method for rapid, simple and on-site detection of mercuric ion. The particle size of CDs was characterized by TEM to be 3 nm with a good dispersivity. The fluorescence of the CDs could be quenched by Hg2+, while remained nearly constant when exposed to other metal ions including Na+, K+, Ca2+, Mg2+, Mn2+, Fe3+, Co2+, Ni2+, Zn2+, Cd2+, Ag+, Ba2+ and Pb2+, implying its good selectivity. A good linear relationship between the fluorescence quenching degree (F0-F)/F0 of probe and Hg2+ concentration was obtained with correlation coefficient (R2) of 0.9878, and the detection limit (S/N=3) for Hg2+ was 22 nmol/L in aqueous solution. In addition, the probe was used to determine Hg2+ in real water samples, and the recoveries ranged from 94.0% to 105.5% in river water, tap water and mineral water samples, proving its good practical applicability for detection of Hg2+ in complex water samples.
A novel carbon dots (CDs) fluorescent probe was prepared by pyrolyzing the mixture of ascorbic acid (Vc) and polyethyleneimine (PEI) aqueous solution through hydrothermal method for rapid, simple and on-site detection of mercuric ion. The particle size of CDs was characterized by TEM to be 3 nm with a good dispersivity. The fluorescence of the CDs could be quenched by Hg2+, while remained nearly constant when exposed to other metal ions including Na+, K+, Ca2+, Mg2+, Mn2+, Fe3+, Co2+, Ni2+, Zn2+, Cd2+, Ag+, Ba2+ and Pb2+, implying its good selectivity. A good linear relationship between the fluorescence quenching degree (F0-F)/F0 of probe and Hg2+ concentration was obtained with correlation coefficient (R2) of 0.9878, and the detection limit (S/N=3) for Hg2+ was 22 nmol/L in aqueous solution. In addition, the probe was used to determine Hg2+ in real water samples, and the recoveries ranged from 94.0% to 105.5% in river water, tap water and mineral water samples, proving its good practical applicability for detection of Hg2+ in complex water samples.
2020, 48(8): 1075-1083
doi: 10.19756/j.issn.0253-3820.191650
Abstract:
An efficient, fast and green ionic liquid-liquid liquid microextraction on the basis of solid phase clean-up combined with temperature controlled method was established for the extraction of six triazine and phenylurea herbicides (monuron, chlorotoluron, atrazine, monolinuron, propazine and prometryn) from soy product samples. The impurities such as protein and fat in the samples were removed by solid phase clean-up. Hydrophobic low-density solidified ionic liquid ([P4 4 4 12]BF4) was used as extraction solvent, which was dispersed into the samples solution and formed fine droplets with the help of water-bath and vortex method. Finally, to achieve the purpose of extracting the analytes, the solidified ionic liquid enriched with the target was separated from the sample solution by changing temperature. Some extraction conditions, such as type and amount of ionic liquid, type and amount of absorbent, ionic strength of sample solution, vortex time and pH value were investigated. The experimental results showed that the target analytes exhibited good correlation coefficients (R2 ≥ 0.9994) in the linear range. The limits of detection (LODs) and quantification (LOQs) were in the range of 0.52-2.59 μg/L and 1.72-8.63 μg/L, respectively. The spiked recoveries were in the range of 82.6%-118.2%. The proposed method showed many advantages such as simplicity, high efficiency, green and low reagent consumption, and could be successfully applied to the extraction of triazine and phenylurea herbicide residues form soy product samples.
An efficient, fast and green ionic liquid-liquid liquid microextraction on the basis of solid phase clean-up combined with temperature controlled method was established for the extraction of six triazine and phenylurea herbicides (monuron, chlorotoluron, atrazine, monolinuron, propazine and prometryn) from soy product samples. The impurities such as protein and fat in the samples were removed by solid phase clean-up. Hydrophobic low-density solidified ionic liquid ([P4 4 4 12]BF4) was used as extraction solvent, which was dispersed into the samples solution and formed fine droplets with the help of water-bath and vortex method. Finally, to achieve the purpose of extracting the analytes, the solidified ionic liquid enriched with the target was separated from the sample solution by changing temperature. Some extraction conditions, such as type and amount of ionic liquid, type and amount of absorbent, ionic strength of sample solution, vortex time and pH value were investigated. The experimental results showed that the target analytes exhibited good correlation coefficients (R2 ≥ 0.9994) in the linear range. The limits of detection (LODs) and quantification (LOQs) were in the range of 0.52-2.59 μg/L and 1.72-8.63 μg/L, respectively. The spiked recoveries were in the range of 82.6%-118.2%. The proposed method showed many advantages such as simplicity, high efficiency, green and low reagent consumption, and could be successfully applied to the extraction of triazine and phenylurea herbicide residues form soy product samples.
2020, 48(8): 1084-1095
doi: 10.19756/j.issn.0253-3820.201009
Abstract:
High performance liquid chromatography with porous graphite carbon (PGC) columns and a n-octane-isopropanol mobile phase was used to separate triacylglycerols (TAGs) in edible oils. The samples were separated by a Hypercarb column (2.1 mm×100 mm, 5 μm) with n-octane-isopropanol (70:30, V/V) as mobile phase at a flow rate of 0.25 mL/min and column temperature of 60℃, with detection wavelength of 215 nm. The experimental conditions were optimized. Then, TAGs in 7 vegetable oils and 5 animal fats were separated under the selected experimental conditions. A total of 14 TAGs in corn oil, 9 TAGs in olive oil, and 14 TAGs in sunflower oil, 14 TAGs in soybean oil, 15 TAGs in sesame oil, 18 TAGs in peanut oil, 16 TAGs in rapeseed oil, 19 TAGs in chicken fat, 19 TAGs in lard, 12 TAGs in sheep fat, 13 TAGs in beef tallow and 16 TAGs in goose fat were identified by combining with mass spectrometry. By means of analysis of chicken fat and beef tallow, it was found that the SLP and SOP could be all separated with their respective isomers, which indicated that the system could separate the TAG isomers. The method was validated and applied to determine LLL in corn oil, rapeseed oil, sunflower seed oil, soybean oil, peanut oil, sesame oil and olive oil. The practical method used less-polluting mobile phase to provide a valuable method for the analysis of triacylglycerols and its isomers in edible oil.
High performance liquid chromatography with porous graphite carbon (PGC) columns and a n-octane-isopropanol mobile phase was used to separate triacylglycerols (TAGs) in edible oils. The samples were separated by a Hypercarb column (2.1 mm×100 mm, 5 μm) with n-octane-isopropanol (70:30, V/V) as mobile phase at a flow rate of 0.25 mL/min and column temperature of 60℃, with detection wavelength of 215 nm. The experimental conditions were optimized. Then, TAGs in 7 vegetable oils and 5 animal fats were separated under the selected experimental conditions. A total of 14 TAGs in corn oil, 9 TAGs in olive oil, and 14 TAGs in sunflower oil, 14 TAGs in soybean oil, 15 TAGs in sesame oil, 18 TAGs in peanut oil, 16 TAGs in rapeseed oil, 19 TAGs in chicken fat, 19 TAGs in lard, 12 TAGs in sheep fat, 13 TAGs in beef tallow and 16 TAGs in goose fat were identified by combining with mass spectrometry. By means of analysis of chicken fat and beef tallow, it was found that the SLP and SOP could be all separated with their respective isomers, which indicated that the system could separate the TAG isomers. The method was validated and applied to determine LLL in corn oil, rapeseed oil, sunflower seed oil, soybean oil, peanut oil, sesame oil and olive oil. The practical method used less-polluting mobile phase to provide a valuable method for the analysis of triacylglycerols and its isomers in edible oil.
2020, 48(8): 1096-1103
doi: 10.19756/j.issn.0253-3820.191770
Abstract:
Mass spectrometry is a rapid, sensitive and accurate approach for the direct monitoring of enzyme-catalyzed reaction that does not require chromophore or radiolabeling, and thus provides a viable alternative to existing analytical techniques. Herein, a simple and efficient assay for characterization of E. coli O77 O-unit biosynthetic pathway by using matrix-assisted laser desorption-ionization (MALDI) mass spectrometry with collision-induced dissociation (CID) was demonstrated by WbaD and WbaC (two glycosyltransferases from E. coli O77 O antigen) lipooligosacharide enzymatic products, respectively. The rapid and direct monitoring of the enzymatic reaction was achieved by subjecting a small amount (0.3 μL) of the reaction mixture to MS analysis without chromatographic separation or desalting steps, and subsequent MS-MS analyses of their lipooligosacharide enzymatic products via collision-induced dissociation enabled the structure of the products of enzyme-catalyzed reaction to be determined. The results demonstrated that WbaD catalyzed the transfer of the first Man residue to GlcNAc-PP-PhU and formed Man-GlcNAc-PP-PhU, and WbaC acted actted after WbaD, adding two Man residues to the growing polymer. Furthermore, the model for E. coli O77 O-unit biosynthesis was studied with the help of time-lapse analysis, and it was proposed that WbaC and WbaD acted in both cooperative and alternating fashion to form the repeat unit and WbaC did not act in tandem with WbaD. Collectively, these data demonstrated that a high-energy CID MALDI-TOF/TOF MS-based platform was applicable to the facile characterization of biosynthetic pathways of O-unit and offered significant advantages over current methods in terms of speed, sensitivity, reproducibility, automation and reagent costs, which would open new way for the future mechanistic study of O-unit biosynthesis and exploitation of these fascinating glycocatalysts.
Mass spectrometry is a rapid, sensitive and accurate approach for the direct monitoring of enzyme-catalyzed reaction that does not require chromophore or radiolabeling, and thus provides a viable alternative to existing analytical techniques. Herein, a simple and efficient assay for characterization of E. coli O77 O-unit biosynthetic pathway by using matrix-assisted laser desorption-ionization (MALDI) mass spectrometry with collision-induced dissociation (CID) was demonstrated by WbaD and WbaC (two glycosyltransferases from E. coli O77 O antigen) lipooligosacharide enzymatic products, respectively. The rapid and direct monitoring of the enzymatic reaction was achieved by subjecting a small amount (0.3 μL) of the reaction mixture to MS analysis without chromatographic separation or desalting steps, and subsequent MS-MS analyses of their lipooligosacharide enzymatic products via collision-induced dissociation enabled the structure of the products of enzyme-catalyzed reaction to be determined. The results demonstrated that WbaD catalyzed the transfer of the first Man residue to GlcNAc-PP-PhU and formed Man-GlcNAc-PP-PhU, and WbaC acted actted after WbaD, adding two Man residues to the growing polymer. Furthermore, the model for E. coli O77 O-unit biosynthesis was studied with the help of time-lapse analysis, and it was proposed that WbaC and WbaD acted in both cooperative and alternating fashion to form the repeat unit and WbaC did not act in tandem with WbaD. Collectively, these data demonstrated that a high-energy CID MALDI-TOF/TOF MS-based platform was applicable to the facile characterization of biosynthetic pathways of O-unit and offered significant advantages over current methods in terms of speed, sensitivity, reproducibility, automation and reagent costs, which would open new way for the future mechanistic study of O-unit biosynthesis and exploitation of these fascinating glycocatalysts.
2020, 48(8): 1104-1110
doi: 10.19756/j.issn.0253-3820.201138
Abstract:
The "top-down" high-resolution tandem mass spectrometry method was used for the first time to comprehensively analyze the amino acid sequence of insulin degludec and the non-protein modification sequence of C-terminal side chain of B-chain. The reduction conditions of insulin degludec and the collision conditions of tandem mass spectrometry were optimized. The results indicated that insulin degludec could be fully reduced to two independent peptide chains when tris(2-carboxyethyl) phosphine (50 mmol/L) and guanidine hydrochloride (6 mol/L) were used in combination and reacted for 40 min at 45℃. The reduction products were separated by Accucore C18 column and analyzed by orbitrap high resolution tandem mass spectrometry. When the higher energy collision induced dissociation was 20 for Chain A and 25 for Chain B, the most abundant fragment information could be obtained, which not only met the basic requirements of 100% peptide coverage in biotechnology drug evaluation, but also provided more comprehensive sequence analysis for the problem samples. This method eliminated the costly enzymatic hydrolysis step in the traditional sequence analysis, limited the risk of introducing artifactual modification to obtain better sequence information, thus saved the cost and significantly improved work efficiency, and provided a new solution for sequence analysis of insulin analogs such as insulin degludec.
The "top-down" high-resolution tandem mass spectrometry method was used for the first time to comprehensively analyze the amino acid sequence of insulin degludec and the non-protein modification sequence of C-terminal side chain of B-chain. The reduction conditions of insulin degludec and the collision conditions of tandem mass spectrometry were optimized. The results indicated that insulin degludec could be fully reduced to two independent peptide chains when tris(2-carboxyethyl) phosphine (50 mmol/L) and guanidine hydrochloride (6 mol/L) were used in combination and reacted for 40 min at 45℃. The reduction products were separated by Accucore C18 column and analyzed by orbitrap high resolution tandem mass spectrometry. When the higher energy collision induced dissociation was 20 for Chain A and 25 for Chain B, the most abundant fragment information could be obtained, which not only met the basic requirements of 100% peptide coverage in biotechnology drug evaluation, but also provided more comprehensive sequence analysis for the problem samples. This method eliminated the costly enzymatic hydrolysis step in the traditional sequence analysis, limited the risk of introducing artifactual modification to obtain better sequence information, thus saved the cost and significantly improved work efficiency, and provided a new solution for sequence analysis of insulin analogs such as insulin degludec.
2020, 48(8): 1111-1119
doi: 10.19756/j.issn.0253-3820.201040
Abstract:
Laser ablation-atmospheric pressure glow discharge atomic emission spectrometry (LA-APGD-AES) was utilized to investigate the effect of matrix effects on the detection results of Cd and Pb in soil samples. Actual soil samples from different regions with large differences in major substances were selected. Under the laser energy of 60 mJ and laser pulse number of 20, the stable signal intensity and high sensitivity were obtained when the discharge distance was 14 mm, the gas flow rate was 130 mL/min, and the discharge current was 27 mA. This method was combined with the univariate calibration model to quantitatively detect Cd and Pb in four different matrix soils. The linear correlation coefficients (R2) of Cd and Pb were ≥ 0.99 and >0.97, respectively. The relative errors of Cd and Pb measurement were 0.4%-11.8%. When the detection results were combined in the same calibration curve for analysis, the R2 of Cd and Pb had slight change, and the relative errors of measurement were 3.0%-13.2%. Moreover, the limits of detection (LODs) for Cd and Pb in different matrix soils had not change significantly. The detection results of all the verification values were agreement with values of inductively coupled plasma-optical emission spectroscopy (ICP-AES). Overall, the detection results of Cd and Pb in complex matrix soils were less affected by matrix effects.
Laser ablation-atmospheric pressure glow discharge atomic emission spectrometry (LA-APGD-AES) was utilized to investigate the effect of matrix effects on the detection results of Cd and Pb in soil samples. Actual soil samples from different regions with large differences in major substances were selected. Under the laser energy of 60 mJ and laser pulse number of 20, the stable signal intensity and high sensitivity were obtained when the discharge distance was 14 mm, the gas flow rate was 130 mL/min, and the discharge current was 27 mA. This method was combined with the univariate calibration model to quantitatively detect Cd and Pb in four different matrix soils. The linear correlation coefficients (R2) of Cd and Pb were ≥ 0.99 and >0.97, respectively. The relative errors of Cd and Pb measurement were 0.4%-11.8%. When the detection results were combined in the same calibration curve for analysis, the R2 of Cd and Pb had slight change, and the relative errors of measurement were 3.0%-13.2%. Moreover, the limits of detection (LODs) for Cd and Pb in different matrix soils had not change significantly. The detection results of all the verification values were agreement with values of inductively coupled plasma-optical emission spectroscopy (ICP-AES). Overall, the detection results of Cd and Pb in complex matrix soils were less affected by matrix effects.
