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2021 Volume 49 Issue 8
2021, 49(8): 1247-1257
doi: 10.19756/j.issn.0253-3820.211135
Abstract:
The route of electron transfer between photoactive semiconductors has great impact on the photoelectric performance of photoelectrochemical (PEC) sensor. Thus, an effective electron transfer pathway is of great significance for enhancing the photoelectric conversion efficiency and improving the sensitivity of the sensor. Z-scheme mechanism can improve the migration efficiency of photogenerated carriers while retaining maximized redox capacity of the photoactive semiconductor. Therefore, the construction and design of the Z-scheme-based PEC sensing system has attracted the attention of many researchers. In this review, the construction and recent progress of Z-scheme-based PEC sensor are summarized in view of the electron transfer mechanism and sensing strategies. Firstly, we present the configuration of Z-scheme-based PEC sensor system by summarizing the two electron transfer paths of Z-scheme system with electronic mediator and direct Z-scheme system. Then, the as-reported sensing strategies regarding Z-scheme system are systematically summarized into four aspects, including steric resistance effect, introduction of new energy level, target inhibition of carrier recombination/migration, and target-induced of Z-scheme system formation/transformation. Finally, future outlooks toward Z-scheme PEC sensor are highlighted.
The route of electron transfer between photoactive semiconductors has great impact on the photoelectric performance of photoelectrochemical (PEC) sensor. Thus, an effective electron transfer pathway is of great significance for enhancing the photoelectric conversion efficiency and improving the sensitivity of the sensor. Z-scheme mechanism can improve the migration efficiency of photogenerated carriers while retaining maximized redox capacity of the photoactive semiconductor. Therefore, the construction and design of the Z-scheme-based PEC sensing system has attracted the attention of many researchers. In this review, the construction and recent progress of Z-scheme-based PEC sensor are summarized in view of the electron transfer mechanism and sensing strategies. Firstly, we present the configuration of Z-scheme-based PEC sensor system by summarizing the two electron transfer paths of Z-scheme system with electronic mediator and direct Z-scheme system. Then, the as-reported sensing strategies regarding Z-scheme system are systematically summarized into four aspects, including steric resistance effect, introduction of new energy level, target inhibition of carrier recombination/migration, and target-induced of Z-scheme system formation/transformation. Finally, future outlooks toward Z-scheme PEC sensor are highlighted.
2021, 49(8): 1258-1269
doi: 10.19756/j.issn.0253-3820.201797
Abstract:
G-quadruplex is a kind of secondary structure of nucleic acids that is formed by the stacking of guanine-rich oligonucleotides. It has been reported that G-quadruplexes widely locate in the human genome (Telomere, gene promoter and so on) and play important roles in regulation of gene transcription and expression, stabilization of gene and synthesis of telomere. This indicates that the structure, quantity and distribution of G-quadruplex in organism are related to the occurrence and development of various diseases to some extent. Therefore, the real-time monitoring of G-quadruplex in organism has great significance for the diagnosis and treatment of diseases. Fluorescence spectrometry technique shows many advantages such as high sensitivity and convenience in practice, and has become one of the main tools for detection and identification of G-quadruplex. Herein, the recent development of G-quadruplex fluorescent probes (including porphyrins, thiazole orange, Thioflavin T, etc.) and the research progress of biosensors and fluorescence cell imaging based on the specific recognition reaction between G-quadruplex and probes are reviewed.
G-quadruplex is a kind of secondary structure of nucleic acids that is formed by the stacking of guanine-rich oligonucleotides. It has been reported that G-quadruplexes widely locate in the human genome (Telomere, gene promoter and so on) and play important roles in regulation of gene transcription and expression, stabilization of gene and synthesis of telomere. This indicates that the structure, quantity and distribution of G-quadruplex in organism are related to the occurrence and development of various diseases to some extent. Therefore, the real-time monitoring of G-quadruplex in organism has great significance for the diagnosis and treatment of diseases. Fluorescence spectrometry technique shows many advantages such as high sensitivity and convenience in practice, and has become one of the main tools for detection and identification of G-quadruplex. Herein, the recent development of G-quadruplex fluorescent probes (including porphyrins, thiazole orange, Thioflavin T, etc.) and the research progress of biosensors and fluorescence cell imaging based on the specific recognition reaction between G-quadruplex and probes are reviewed.
2021, 49(8): 1270-1281
doi: 10.19756/j.issn.0253-3820.201679
Abstract:
The baseline drift is common in the measurement process of Raman spectroscopy, middle infrared (MIR) spectroscopy, near infrared (NIR) spectroscopy, laser-induced breakdown spectroscopy (LIBS) and other spectral instrumentation, which will seriously deteriorate the result of subsequent qualitative and quantitative analysis of spectra. To obtain accurate and clear results, some effective baseline correction algorithms have been implemented to correct the baseline of spectra before subsequent qualitative and quantitative analysis, especially combined with chemometric methods. Baseline correction algorithms are mainly derivative method, iterative polynomial fitting, piecewise fitting, moving window smoothing, wavelet transform (WT), penalized least squares and robust baseline estimation (RBE). These algorithms can eliminate the adverse effects of baseline drift on quantitative and qualitative analysis to a large extent, but each of them has some shortcomings in certain aspects. In recent years, in response to the drawbacks of the aforementioned algorithms, some improved and novel algorithms for baseline correction have been proposed one after another. Improved algorithms are mainly adaptive minmax polynomial fitting fluorescence background subtraction algorithms, interval linear fitting based on subspace vector angle, dynamic moving Savitzky-Golay algorithms, selection method of optimum decomposition in wavelet transform based on energy distribution, adaptive iteratively reweighted penalized least squares (airPLS), etc. Novel algorithms include fluorescence photo-bleaching difference approach (FBDA), algorithms based on morphological operators, synchronous fitting algorithms of pure spectrum and baseline based on sparse representation, etc. These algorithms have not only improved the quality of spectra but also further enhanced the accuracy and robustness of subsequent quantitative and qualitative analysis based on spectra. This article systematically reviews basic algorithms, improved algorithms and novel algorithms for spectral baseline correction, as well as their application research progress, and the development prospect of algorithms for spectral baseline correction is discussed.
The baseline drift is common in the measurement process of Raman spectroscopy, middle infrared (MIR) spectroscopy, near infrared (NIR) spectroscopy, laser-induced breakdown spectroscopy (LIBS) and other spectral instrumentation, which will seriously deteriorate the result of subsequent qualitative and quantitative analysis of spectra. To obtain accurate and clear results, some effective baseline correction algorithms have been implemented to correct the baseline of spectra before subsequent qualitative and quantitative analysis, especially combined with chemometric methods. Baseline correction algorithms are mainly derivative method, iterative polynomial fitting, piecewise fitting, moving window smoothing, wavelet transform (WT), penalized least squares and robust baseline estimation (RBE). These algorithms can eliminate the adverse effects of baseline drift on quantitative and qualitative analysis to a large extent, but each of them has some shortcomings in certain aspects. In recent years, in response to the drawbacks of the aforementioned algorithms, some improved and novel algorithms for baseline correction have been proposed one after another. Improved algorithms are mainly adaptive minmax polynomial fitting fluorescence background subtraction algorithms, interval linear fitting based on subspace vector angle, dynamic moving Savitzky-Golay algorithms, selection method of optimum decomposition in wavelet transform based on energy distribution, adaptive iteratively reweighted penalized least squares (airPLS), etc. Novel algorithms include fluorescence photo-bleaching difference approach (FBDA), algorithms based on morphological operators, synchronous fitting algorithms of pure spectrum and baseline based on sparse representation, etc. These algorithms have not only improved the quality of spectra but also further enhanced the accuracy and robustness of subsequent quantitative and qualitative analysis based on spectra. This article systematically reviews basic algorithms, improved algorithms and novel algorithms for spectral baseline correction, as well as their application research progress, and the development prospect of algorithms for spectral baseline correction is discussed.
2021, 49(8): 1282-1288
doi: 10.19756/j.issn.0253-3820.201580
Abstract:
For the simplified linear ion traps (LITs), the use of non-hyperbolic electrodes might produce even greater proportions of higher-order field components. Different higher-order fields will have different effects on the ion trap performance. In this work, the performances of semi-circular rod electrode LITs with different dodecapole electric field components were investigated by theoretical simulations and experiments. Different amplitude dodecapole field (A6) components were added to the quadrupole field (A2) by changing the ratio between the circular electrode radii and the electric field radii. In theoretical simulation calculations and experimental research, the mass resolution gradually improved to a maximum of 1250 (full-width at half-maximum=0.14) at m/z 175 Da when A6/A2 decreased from 1.91% to 0.03%, but when A6/A2 was negative, the mass resolution was seriously degraded. The experimental results coincided with those of the theoretical calculation. The collision-induced dissociation (CID) efficiency was also affected by the amount of higher-order field A6, and as a result, when A6/A2=0.03%, the highest CID efficiency was obtained.
For the simplified linear ion traps (LITs), the use of non-hyperbolic electrodes might produce even greater proportions of higher-order field components. Different higher-order fields will have different effects on the ion trap performance. In this work, the performances of semi-circular rod electrode LITs with different dodecapole electric field components were investigated by theoretical simulations and experiments. Different amplitude dodecapole field (A6) components were added to the quadrupole field (A2) by changing the ratio between the circular electrode radii and the electric field radii. In theoretical simulation calculations and experimental research, the mass resolution gradually improved to a maximum of 1250 (full-width at half-maximum=0.14) at m/z 175 Da when A6/A2 decreased from 1.91% to 0.03%, but when A6/A2 was negative, the mass resolution was seriously degraded. The experimental results coincided with those of the theoretical calculation. The collision-induced dissociation (CID) efficiency was also affected by the amount of higher-order field A6, and as a result, when A6/A2=0.03%, the highest CID efficiency was obtained.
2021, 49(8): 1289-1299
doi: 10.19756/j.issn.0253-3820.211148
Abstract:
Salmonella typhimurium (S.typhimurium) is one of the most widespread pathogens causing foodborne diseases. In this work, S.typhimurium was used as the model bacteria. An aptasensor based on aldehyde magnetic beads (Mbs), enzyme digestion and terminal deoxynucleotidyl transferase-mediated signal amplification technique for simple colorimetric detection of S.typhimurium was developed. The Mbs@dsDNA hybrid complex was first prepared using the capture probe (CP) and aptamer. In the presence of S.typhimurium, the aptamer specifically bound to it, and released from the Mbs, which was then removed by magnetic separation. Subsequently, CP on Mbs folded back on itself owing to partially complementary bases and formed enzyme digestion recognition sites. 3'-OH terminal ends were obtained by EcoR I enzyme digestion. Deoxynucleotides were catalyzed to the 3'-OH end under the action of terminal deoxynucleotidyl transferase (TdT) to obtain products of single-stranded DNA (ssDNA). In the process, signal reporter molecules were embedded in the chain of ssDNA, thus obtaining amplified signals. In the absence of S.typhimurium, TdT signal amplification reaction could not be initiated because no released aptamer and blocked 3'-OH end CP. The aptasensor had a good response performance to S.typhimurium in the concentration range of 101-105 CFU/mL, and the detection limit was as low as 21 CFU/mL, showing high sensitivity and specificity. Moreover, the recovery of S.typhimurium in milk samples was 92.2%-112.7% (RSD<3%). The aptasensor showed potential application prospect in the food safety detection and supervision of other foodborne pathogenic microorganisms and other pollutants.
Salmonella typhimurium (S.typhimurium) is one of the most widespread pathogens causing foodborne diseases. In this work, S.typhimurium was used as the model bacteria. An aptasensor based on aldehyde magnetic beads (Mbs), enzyme digestion and terminal deoxynucleotidyl transferase-mediated signal amplification technique for simple colorimetric detection of S.typhimurium was developed. The Mbs@dsDNA hybrid complex was first prepared using the capture probe (CP) and aptamer. In the presence of S.typhimurium, the aptamer specifically bound to it, and released from the Mbs, which was then removed by magnetic separation. Subsequently, CP on Mbs folded back on itself owing to partially complementary bases and formed enzyme digestion recognition sites. 3'-OH terminal ends were obtained by EcoR I enzyme digestion. Deoxynucleotides were catalyzed to the 3'-OH end under the action of terminal deoxynucleotidyl transferase (TdT) to obtain products of single-stranded DNA (ssDNA). In the process, signal reporter molecules were embedded in the chain of ssDNA, thus obtaining amplified signals. In the absence of S.typhimurium, TdT signal amplification reaction could not be initiated because no released aptamer and blocked 3'-OH end CP. The aptasensor had a good response performance to S.typhimurium in the concentration range of 101-105 CFU/mL, and the detection limit was as low as 21 CFU/mL, showing high sensitivity and specificity. Moreover, the recovery of S.typhimurium in milk samples was 92.2%-112.7% (RSD<3%). The aptasensor showed potential application prospect in the food safety detection and supervision of other foodborne pathogenic microorganisms and other pollutants.
2021, 49(8): 1300-1307
doi: 10.19756/j.issn.0253-3820.201742
Abstract:
By using 3-mercaptopropionic acid (MPA) as a reductant and protective agent, fluorescent copper nanoclusters (MPA-CuNCs) were prepared by one-pot reaction method, and Cu2+@MPA-CuNCs was further synthesized based on that Cu2+ could induce aggregation-induced emission effect of MPA-CuNCs. The synthesized Cu2+@MPA-CuNCs nanocomposite was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, etc. The experimental results showed that Cu2+@MPA-CuNCs nanocomposite was successfully synthesized. Pyrophosphate can combine with Cu2+, which lead to the fluorescence quenching of Cu2+@MPA-CuNCs system. Based on this, a new fluorescent sensor was thus constructed for sensitive detection of pyrophosphate, with a good linear relationship in the concentration rang of 5-100 μmol/L. The limit of detection was 0.65 μmol/L (3σ). This method had high selectivity in detection of pyrophosphate.
By using 3-mercaptopropionic acid (MPA) as a reductant and protective agent, fluorescent copper nanoclusters (MPA-CuNCs) were prepared by one-pot reaction method, and Cu2+@MPA-CuNCs was further synthesized based on that Cu2+ could induce aggregation-induced emission effect of MPA-CuNCs. The synthesized Cu2+@MPA-CuNCs nanocomposite was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, etc. The experimental results showed that Cu2+@MPA-CuNCs nanocomposite was successfully synthesized. Pyrophosphate can combine with Cu2+, which lead to the fluorescence quenching of Cu2+@MPA-CuNCs system. Based on this, a new fluorescent sensor was thus constructed for sensitive detection of pyrophosphate, with a good linear relationship in the concentration rang of 5-100 μmol/L. The limit of detection was 0.65 μmol/L (3σ). This method had high selectivity in detection of pyrophosphate.
2021, 49(8): 1308-1317
doi: 10.19756/j.issn.0253-3820.201678
Abstract:
A novel porous titanium dioxide (P-TiO2) was successfully synthesized via calcination of metal-organic framework MIL-125(Ti). Then P-TiO2 was coated with massive polyethyleneimine films and further bound covalently with 3-mercaptopropionic acid stabilized cadmium sulfide quantum dots (CdS QDs) to prepare P-TiO2/CdS QDs composites. The as-prepared P-TiO2/CdS QDs was modified on the surface of glassy carbon electrode to develop a sensitive electrochemiluminescence (ECL) sensor for detection of Cu2+. The morphology, microstructure and element composition of different materials were characterized by scanning electron microscope, X-ray powder diffraction, energy disperse spectroscopy, ultraviolet-visible absorption spectrometry, fluorescence spectrometry and infrared spectrometry, respectively. The electrochemical behavior and ECL performance of the sensor were also studied by cyclic voltammetry, electrochemical impedance and ECL technique. Under the optimized conditions, the proposed sensor demonstrated excellent analytical performance with a wide linear detection range from 3 nmol/L to 530 nmol/L (R2=0.9989) and a detection limit of 0.01 nmol/L (S/N=3) for Cu2+. This method exhibited excellent stability, reproducibility and selectivity. In addition, the detection results of Cu2+ in water samples were similar to that of inductively coupled plasma-atomic emission spectrometry method (ICP-AES) with recovery rates of 96.9%-105.8%.
A novel porous titanium dioxide (P-TiO2) was successfully synthesized via calcination of metal-organic framework MIL-125(Ti). Then P-TiO2 was coated with massive polyethyleneimine films and further bound covalently with 3-mercaptopropionic acid stabilized cadmium sulfide quantum dots (CdS QDs) to prepare P-TiO2/CdS QDs composites. The as-prepared P-TiO2/CdS QDs was modified on the surface of glassy carbon electrode to develop a sensitive electrochemiluminescence (ECL) sensor for detection of Cu2+. The morphology, microstructure and element composition of different materials were characterized by scanning electron microscope, X-ray powder diffraction, energy disperse spectroscopy, ultraviolet-visible absorption spectrometry, fluorescence spectrometry and infrared spectrometry, respectively. The electrochemical behavior and ECL performance of the sensor were also studied by cyclic voltammetry, electrochemical impedance and ECL technique. Under the optimized conditions, the proposed sensor demonstrated excellent analytical performance with a wide linear detection range from 3 nmol/L to 530 nmol/L (R2=0.9989) and a detection limit of 0.01 nmol/L (S/N=3) for Cu2+. This method exhibited excellent stability, reproducibility and selectivity. In addition, the detection results of Cu2+ in water samples were similar to that of inductively coupled plasma-atomic emission spectrometry method (ICP-AES) with recovery rates of 96.9%-105.8%.
2021, 49(8): 1318-1326
doi: 10.19756/j.issn.0253-3820.201624
Abstract:
Diesel fuel is one of ignitable liquid with complex components. Different crude oil source and production process would cause differences in its components and content. To select feature components of diesel fuel based on the regional information, 36 samples of 0# diesel fuel, collected from different refineries in China, were taken as the research objects in this work. Comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS) was used to test diesel fuel, which could greatly reduce the co-elution of diesel fuel components. Additionally, under the experimental conditions such as direct injection and using polar-nonpolar column system, the peak capacity was calculated. The contour plots that were suitable for fingerprinting analysis were obtained, and the family distribution of diesel fuel was qualitatively analyzed. The preprocessing and chemometric methods of pixel-based F-ratio and peak table-based partial least squares-discrimination analysis (PLS-DA) were used to select the comprehensive two-dimensional gas chromatography data of diesel fuel. Finally, the results showed that C16-C20 alkanes and C7-C12 monocyclic aromatic hydrocarbons differed greatly among diesel fuel samples in different regions. By comparing the process and the results of two methods, the characteristics of the pixel-based method for processing comprehensive two-dimensional gas chromatography data matrix was introduced. The feature selection methods could be taken as a reference for processing experimental data of GC×GC-MS.
Diesel fuel is one of ignitable liquid with complex components. Different crude oil source and production process would cause differences in its components and content. To select feature components of diesel fuel based on the regional information, 36 samples of 0# diesel fuel, collected from different refineries in China, were taken as the research objects in this work. Comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS) was used to test diesel fuel, which could greatly reduce the co-elution of diesel fuel components. Additionally, under the experimental conditions such as direct injection and using polar-nonpolar column system, the peak capacity was calculated. The contour plots that were suitable for fingerprinting analysis were obtained, and the family distribution of diesel fuel was qualitatively analyzed. The preprocessing and chemometric methods of pixel-based F-ratio and peak table-based partial least squares-discrimination analysis (PLS-DA) were used to select the comprehensive two-dimensional gas chromatography data of diesel fuel. Finally, the results showed that C16-C20 alkanes and C7-C12 monocyclic aromatic hydrocarbons differed greatly among diesel fuel samples in different regions. By comparing the process and the results of two methods, the characteristics of the pixel-based method for processing comprehensive two-dimensional gas chromatography data matrix was introduced. The feature selection methods could be taken as a reference for processing experimental data of GC×GC-MS.
2021, 49(8): 1327-1334
doi: 10.19756/j.issn.0253-3820.211168
Abstract:
Based on the highly specific recognition ability of aptamers, and the combination with an exonuclease Ⅲ (Exo Ⅲ)-assisted nucleic acid signal amplification strategy and the time resolved fluorescence measurement technology, a label-free and ultra-sensitive aptamer fluorescent biosensor (aptasensor) was constructed to detect aflatoxin B1 (AFB1). Two label-free functional nucleic acid hairpins were designed. The hairpin H1 containing AFB1 aptamer sequence was used as the identification element, and the G-rich sequence-containing hairpin H2 of the stem acted as the signal response element. AFB1 could specifically bind to the aptamer sequence in H1, leading to the unfolding of H1 and its complementary paring with H2 to form an AFB1-H1-H2 complex, which consequently triggered the exonuclease Ⅲ (Exo Ⅲ) enzyme digestion. The 3' blunt end of H2 in the complex was digested to release the G-rich sequence in H2, which could significantly enhance the emission of terbium ions (Tb3+). Meanwhile, the released AFB1-H1 could freely bind to the next H2 to start Exo Ⅲ-assisted target cyclic amplification, causing the release of considerable G-rich single strands into the system and realizing signal amplification. As the concentration of AFB1 was increased, the relative fluorescence intensity of the system increased. AFB1 could be detected by time-resolved luminescence spectroscopy. The linear detection range was from 0.001 to 0.1 ng/mL, and the detection limit (3σ) was as low as 0.9 pg/mL. This method was used to detect AFB1 in corn samples, with the recoveries of 98.5%-103.5%, showing a good application potential in detection of AFB1 in food and agricultural products.
Based on the highly specific recognition ability of aptamers, and the combination with an exonuclease Ⅲ (Exo Ⅲ)-assisted nucleic acid signal amplification strategy and the time resolved fluorescence measurement technology, a label-free and ultra-sensitive aptamer fluorescent biosensor (aptasensor) was constructed to detect aflatoxin B1 (AFB1). Two label-free functional nucleic acid hairpins were designed. The hairpin H1 containing AFB1 aptamer sequence was used as the identification element, and the G-rich sequence-containing hairpin H2 of the stem acted as the signal response element. AFB1 could specifically bind to the aptamer sequence in H1, leading to the unfolding of H1 and its complementary paring with H2 to form an AFB1-H1-H2 complex, which consequently triggered the exonuclease Ⅲ (Exo Ⅲ) enzyme digestion. The 3' blunt end of H2 in the complex was digested to release the G-rich sequence in H2, which could significantly enhance the emission of terbium ions (Tb3+). Meanwhile, the released AFB1-H1 could freely bind to the next H2 to start Exo Ⅲ-assisted target cyclic amplification, causing the release of considerable G-rich single strands into the system and realizing signal amplification. As the concentration of AFB1 was increased, the relative fluorescence intensity of the system increased. AFB1 could be detected by time-resolved luminescence spectroscopy. The linear detection range was from 0.001 to 0.1 ng/mL, and the detection limit (3σ) was as low as 0.9 pg/mL. This method was used to detect AFB1 in corn samples, with the recoveries of 98.5%-103.5%, showing a good application potential in detection of AFB1 in food and agricultural products.
2021, 49(8): 1335-1341
doi: 10.19756/j.issn.0253-3820.211021
Abstract:
Protein, as one of the important biomolecules, plays important roles in many biological processes. Studies have shown that the function of the protein is closely related to its structure. Therefore, elucidating the structure changes of the protein in a given biological environment is one of the main ways to understand its biological function in a specific process. In this work, a high resolution mass spectrometry (MS) combined with ion mobility spectrometry (IMS) was used to study the conformation changes of hemoglobin under different conditions, such as different pH values and different solvents. The result showed that the structure of hemoglobin changed significantly at pH=4 with observed heme drop. Moreover, the ion mobility of the hemoglobin ions increased as the decrease of pH values, indicating the unfolding of the protein under the acidic solution conditions. By measuring the change of ion mobility, the unfolding of hemoglobin at different pH values was determined. Also the structural changes of hemoglobin ions as the change of the charge states at the same pH values were investigated and it was found that the structure of the hemoglobin became more extended as the increase of the protein charge state. In addition, it was found that the structure of the hemoglobin was also significantly affected by the type and the concentration of alcohol in the solvent. Specifically, the structure of hemoglobin in 50% methanol in water was about the same as the structure in 40% of ethanol aqueous solution. It was also found that the structure of hemoglobin collapsed in high concentration of alcohol solution, which made the structure of hemoglobin in high concentration of alcohol solution more compact.
Protein, as one of the important biomolecules, plays important roles in many biological processes. Studies have shown that the function of the protein is closely related to its structure. Therefore, elucidating the structure changes of the protein in a given biological environment is one of the main ways to understand its biological function in a specific process. In this work, a high resolution mass spectrometry (MS) combined with ion mobility spectrometry (IMS) was used to study the conformation changes of hemoglobin under different conditions, such as different pH values and different solvents. The result showed that the structure of hemoglobin changed significantly at pH=4 with observed heme drop. Moreover, the ion mobility of the hemoglobin ions increased as the decrease of pH values, indicating the unfolding of the protein under the acidic solution conditions. By measuring the change of ion mobility, the unfolding of hemoglobin at different pH values was determined. Also the structural changes of hemoglobin ions as the change of the charge states at the same pH values were investigated and it was found that the structure of the hemoglobin became more extended as the increase of the protein charge state. In addition, it was found that the structure of the hemoglobin was also significantly affected by the type and the concentration of alcohol in the solvent. Specifically, the structure of hemoglobin in 50% methanol in water was about the same as the structure in 40% of ethanol aqueous solution. It was also found that the structure of hemoglobin collapsed in high concentration of alcohol solution, which made the structure of hemoglobin in high concentration of alcohol solution more compact.
2021, 49(8): 1342-1349
doi: 10.19756/j.issn.0253-3820.211124
Abstract:
To meet the needs of rapid detection of nitrate in soil, a field rapid detection system for nitrate in soil was designed, which integrated the functions of soil leaching solution acquisition and nitrate detection. Nano palladium and gold modified ultramicro interdigital sensing electrode was used for nitrate detection. The sensing electrode was fabricated using micro-electro-mechanical systems (MEMS) technique, and the integrated structure was interdigital array of working electrode and counter electrode. Palladium and gold were modified on the surface of the working electrode by potentiostatic method to form a palladium-gold composite sensitive film. Through the optimization of the preparation parameters of the sensor electrode, the linear response range of the sensor electrode to nitrate was 0.5-100 mg/L (as N), the detection limit was 0.13 mg/L (3σ), the sensitivity was 1.8 μA·L/mg, and the relative deviation was less than 10% after 70 times of continuous repeated measurement. Furthermore, the developed sensor electrode had certain anti-interference ability against common ions in soil including Cl-, CO32-, SO42- and Si42-. The soil leaching solution was obtained by the developed soil nitrate detection system, and the nitrate in the leaching solution was detected. The detection results correlated with the detection results of the standard method.
To meet the needs of rapid detection of nitrate in soil, a field rapid detection system for nitrate in soil was designed, which integrated the functions of soil leaching solution acquisition and nitrate detection. Nano palladium and gold modified ultramicro interdigital sensing electrode was used for nitrate detection. The sensing electrode was fabricated using micro-electro-mechanical systems (MEMS) technique, and the integrated structure was interdigital array of working electrode and counter electrode. Palladium and gold were modified on the surface of the working electrode by potentiostatic method to form a palladium-gold composite sensitive film. Through the optimization of the preparation parameters of the sensor electrode, the linear response range of the sensor electrode to nitrate was 0.5-100 mg/L (as N), the detection limit was 0.13 mg/L (3σ), the sensitivity was 1.8 μA·L/mg, and the relative deviation was less than 10% after 70 times of continuous repeated measurement. Furthermore, the developed sensor electrode had certain anti-interference ability against common ions in soil including Cl-, CO32-, SO42- and Si42-. The soil leaching solution was obtained by the developed soil nitrate detection system, and the nitrate in the leaching solution was detected. The detection results correlated with the detection results of the standard method.
2021, 49(8): 1350-1356
doi: 10.19756/j.issn.0253-3820.201579
Abstract:
A new ratiometric fluorescence probe (HBT-CN) was developed with familiar excited state intramolecular proton transfer (ESIPT) fluorophore 2-(2'-hydroxyphenyl)-benzothiazole (HBT) as framework and diaminomeleonitrile (DMN) group as reactive site. The performance of this probe to monitor HOCl was further investigated. This probe possessed good sensitivity and with the ability to rapidly detect HOCl within seconds with a detection limit as low as 1.1×10-7 mol/L. Furthermore, this probe displayed high specificity for sensing HOCl over other relevant analytes including reactive oxygen species (H2O2, tBuO, ROO·) and reactive nitrogen species (NO2-, NO3-, ONOO-, NO·). Importantly, the cell experiments demonstrated that the probe HBT-CN had good cell membrane permeability and could monitor HOCl in live cells by dual-channel.
A new ratiometric fluorescence probe (HBT-CN) was developed with familiar excited state intramolecular proton transfer (ESIPT) fluorophore 2-(2'-hydroxyphenyl)-benzothiazole (HBT) as framework and diaminomeleonitrile (DMN) group as reactive site. The performance of this probe to monitor HOCl was further investigated. This probe possessed good sensitivity and with the ability to rapidly detect HOCl within seconds with a detection limit as low as 1.1×10-7 mol/L. Furthermore, this probe displayed high specificity for sensing HOCl over other relevant analytes including reactive oxygen species (H2O2, tBuO, ROO·) and reactive nitrogen species (NO2-, NO3-, ONOO-, NO·). Importantly, the cell experiments demonstrated that the probe HBT-CN had good cell membrane permeability and could monitor HOCl in live cells by dual-channel.
2021, 49(8): 1357-1365
doi: 10.19756/j.issn.0253-3820.201598
Abstract:
A method for determination of the number of active polycyclic aromatic hydrocarbons (PAHs)-degrading bacteria using flow cytometry was developed. PAHs degrading bacteria suspension (1×103-1×105 cells/mL) was prepared by using ultra-pure water as dilution. After stained using SG/PI and incubated at 35 ℃ for 10 min in the dark, the number of PAHs-degrading bacteria was determined using flow cytometry. The parameters of flow cytometry were set as follows: the green (FL1) and red (FL3) fluorescent acted as detector and the threshold value was 600; the flow rate of bacteria suspension was 33 mL/min and the counting rate kept below 1000 cells/s. Experimental results showed that there was a good correlation relationship between the results of flow cytometry and the plate counting determination, and the correlation coefficients were 0.9742-0.9962. To determine PAH-active bacteria, the bacteria during the growth phase were sterilized using NaClO that acted as negative control, and the activated bacteria were used as positive control. Both negative and positive bacteria were determined using flow cytometry after stained using SYBR Green I and propidium iodide, and the active and inactive cells regions were respectively classified. Compared to the plate counting method, the flow cytometry for counting bacteria number could greatly reduce determination time and improve the accuracy. This study provided a fast and efficiency method for determination of active bacteria in pollutant degrading systems.
A method for determination of the number of active polycyclic aromatic hydrocarbons (PAHs)-degrading bacteria using flow cytometry was developed. PAHs degrading bacteria suspension (1×103-1×105 cells/mL) was prepared by using ultra-pure water as dilution. After stained using SG/PI and incubated at 35 ℃ for 10 min in the dark, the number of PAHs-degrading bacteria was determined using flow cytometry. The parameters of flow cytometry were set as follows: the green (FL1) and red (FL3) fluorescent acted as detector and the threshold value was 600; the flow rate of bacteria suspension was 33 mL/min and the counting rate kept below 1000 cells/s. Experimental results showed that there was a good correlation relationship between the results of flow cytometry and the plate counting determination, and the correlation coefficients were 0.9742-0.9962. To determine PAH-active bacteria, the bacteria during the growth phase were sterilized using NaClO that acted as negative control, and the activated bacteria were used as positive control. Both negative and positive bacteria were determined using flow cytometry after stained using SYBR Green I and propidium iodide, and the active and inactive cells regions were respectively classified. Compared to the plate counting method, the flow cytometry for counting bacteria number could greatly reduce determination time and improve the accuracy. This study provided a fast and efficiency method for determination of active bacteria in pollutant degrading systems.
2021, 49(8): 1366-1374
doi: 10.19756/j.issn.0253-3820.201403
Abstract:
A high performance liquid chromatography-tandem quadrupole-time of flight-mass spectrometry (HPLC-Q-TOF/MS) method for determination of residues of indaziflam and its four metabolites (1-fluoroethyl triazinediamine, indaziflam-carboxylic acid, triazine-indanone and indaziflam-olefin) in cereal samples was developed. The samples were extracted by acetonitrile, and the supernatant was collected for purification after salting-out and centrifugation. Under the optimized chromatographic and mass spectrometric conditions, the data were collected by electrospray ionization (ESI) sources in positive ion mode. The calibration curves of five compounds showed good linearity in concentration range of 2.0-200 μg/L (R2>0.9987). The average recoveries were 79.3%-108.0% at three spiked levels (10, 20 and 100 μg/kg), while the relative standard deviations (RSD) were 1.2%-6.0%. The limits of detection and limits of quantification ranged from 0.05 to 0.60 μg/kg and 0.15 to 2.00 μg/kg, respectively. This method was a simple and efficient method with high sensitivity and precision, and had practical value for the rapid detection of residues of indaziflam and its four metabolites in cereals.
A high performance liquid chromatography-tandem quadrupole-time of flight-mass spectrometry (HPLC-Q-TOF/MS) method for determination of residues of indaziflam and its four metabolites (1-fluoroethyl triazinediamine, indaziflam-carboxylic acid, triazine-indanone and indaziflam-olefin) in cereal samples was developed. The samples were extracted by acetonitrile, and the supernatant was collected for purification after salting-out and centrifugation. Under the optimized chromatographic and mass spectrometric conditions, the data were collected by electrospray ionization (ESI) sources in positive ion mode. The calibration curves of five compounds showed good linearity in concentration range of 2.0-200 μg/L (R2>0.9987). The average recoveries were 79.3%-108.0% at three spiked levels (10, 20 and 100 μg/kg), while the relative standard deviations (RSD) were 1.2%-6.0%. The limits of detection and limits of quantification ranged from 0.05 to 0.60 μg/kg and 0.15 to 2.00 μg/kg, respectively. This method was a simple and efficient method with high sensitivity and precision, and had practical value for the rapid detection of residues of indaziflam and its four metabolites in cereals.
2021, 49(8): 1375-1383
doi: 10.19756/j.issn.0253-3820.211072
Abstract:
Aldehydes and ketones in breath can reflect the oxidative stress response of the cells in the body. A better understanding of the aldehydes and ketones emitted from the cells is the key to revealing the mechanism of breath test for the diagnosis of oxidative stress-related diseases. In this study, a quantitative method was developed for 22 typical aldehyde and ketone metabolites. Standard compounds were transformed into stable DNPH-carbonyl adducts by using 2,4-dinitrophenylhydrazine (DNPH) impregnated cartridge. These adducts were further eluted and analyzed by ultra high performance liquid chromatography coupled with high resolution mass spectrometry. The standard curves of 22 DNPH-carbonyl adducts showed linearity at high (40-1000 μg/L), medium (8-400 μg/L) and low (0.08-8 μg/L) levels, respectively. The coefficient of correlation (R2) was >0.998 and the detection limits were 0.003-0.09 μg/L. The method demonstrated good precision, e.g. intra-day RSD <3.92% and inter-day RSD <5.3%, as well as satisfactory recoveries of 95.1%-109.6% (RSD<5.9%). The method was further applied to the analysis of aldehydes and ketones in the headspace of A549 cells and influenza A (H1N1) infected A549 cells. The experimental data were analyzed by using orthogonal partial least squares discriminant analysis, and a total of 19 aldehydes and ketones were quantified and 11 potential biomarkers were screened for the diagnosis of IAV infection.
Aldehydes and ketones in breath can reflect the oxidative stress response of the cells in the body. A better understanding of the aldehydes and ketones emitted from the cells is the key to revealing the mechanism of breath test for the diagnosis of oxidative stress-related diseases. In this study, a quantitative method was developed for 22 typical aldehyde and ketone metabolites. Standard compounds were transformed into stable DNPH-carbonyl adducts by using 2,4-dinitrophenylhydrazine (DNPH) impregnated cartridge. These adducts were further eluted and analyzed by ultra high performance liquid chromatography coupled with high resolution mass spectrometry. The standard curves of 22 DNPH-carbonyl adducts showed linearity at high (40-1000 μg/L), medium (8-400 μg/L) and low (0.08-8 μg/L) levels, respectively. The coefficient of correlation (R2) was >0.998 and the detection limits were 0.003-0.09 μg/L. The method demonstrated good precision, e.g. intra-day RSD <3.92% and inter-day RSD <5.3%, as well as satisfactory recoveries of 95.1%-109.6% (RSD<5.9%). The method was further applied to the analysis of aldehydes and ketones in the headspace of A549 cells and influenza A (H1N1) infected A549 cells. The experimental data were analyzed by using orthogonal partial least squares discriminant analysis, and a total of 19 aldehydes and ketones were quantified and 11 potential biomarkers were screened for the diagnosis of IAV infection.
2021, 49(8): 1384-1392
doi: 10.19756/j.issn.0253-3820.201541
Abstract:
A method for rapid and simultaneous determination of organophosphate triesters (triphenyl phosphate (TPHP), triethyl phosphate (TEP), tri-n-butylphosphate (TnBP), tri(2-chloroethyl) phosphate (TCEP)) and diesters (diethyl phosphate (DEP) and diphenyl phosphate (DPHP)) in human serum by ultra-high performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-MS/MS) was developed. Serum sample (400 μL) was extracted using 1.2 mL of ethyl acetate with 60 μL of formic acid, followed by concentrating the extracts with freeze vacuum centrifugation technology. The sample was separated on a Phenomenex Kinetex 2.6 μm F5 LC column with formic acid aqueous solution and methanol as the mobile phase, and then detected in turn under electrospray ionization (ESI) positive and negative ion multiple reactive monitoring (MRM) mode. Stable isotope-labeled internal standards were used to improve the assay performance of UPLC-MS/MS. The analytical parameters involving sample pretreatment, chromatographic separation and mass determination were optimized. Under the optimal conditions, low limits of detection (0.002-0.01 ng/mL), wide linearity (0.05-50 ng/mL) and good recovery (56.1%-112.2%) were achieved. The intra-day and inter-day precisions were expressed as variation coefficients within 15%. The proposed method was successfully applied to the determination of six target compounds in 30 serum specimens collected from residents living in Shanghai city. This method provided a reliable alternative for large-scale monitoring trace level of organophosphate triesters and diesters in human exposure measurement and risk assessment.
A method for rapid and simultaneous determination of organophosphate triesters (triphenyl phosphate (TPHP), triethyl phosphate (TEP), tri-n-butylphosphate (TnBP), tri(2-chloroethyl) phosphate (TCEP)) and diesters (diethyl phosphate (DEP) and diphenyl phosphate (DPHP)) in human serum by ultra-high performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-MS/MS) was developed. Serum sample (400 μL) was extracted using 1.2 mL of ethyl acetate with 60 μL of formic acid, followed by concentrating the extracts with freeze vacuum centrifugation technology. The sample was separated on a Phenomenex Kinetex 2.6 μm F5 LC column with formic acid aqueous solution and methanol as the mobile phase, and then detected in turn under electrospray ionization (ESI) positive and negative ion multiple reactive monitoring (MRM) mode. Stable isotope-labeled internal standards were used to improve the assay performance of UPLC-MS/MS. The analytical parameters involving sample pretreatment, chromatographic separation and mass determination were optimized. Under the optimal conditions, low limits of detection (0.002-0.01 ng/mL), wide linearity (0.05-50 ng/mL) and good recovery (56.1%-112.2%) were achieved. The intra-day and inter-day precisions were expressed as variation coefficients within 15%. The proposed method was successfully applied to the determination of six target compounds in 30 serum specimens collected from residents living in Shanghai city. This method provided a reliable alternative for large-scale monitoring trace level of organophosphate triesters and diesters in human exposure measurement and risk assessment.
2021, 49(8): 1393-1401
doi: 10.19756/j.issn.0253-3820.211133
Abstract:
A new and portable method for extraction, enrichment and detection of trace total mercury in water by a headspace solid phase microextraction probe loaded with gold and wood stickswas developed. The surface morphology and elemental composition of the gold-loaded probe were characterized by scanning electron microscopy and energy dispersive analysis (SEM-EDS). The effects of solution pH, salinity, dissolved organic matter (DOM) concentration and co-existing metal ions on SnCl2 reduction of different forms of mercury (inorganic mercury, methyl mercury and ethyl mercury) were investigated. The results showed that the pH, salinity and DOM concentration of the solution had only weak effect on the reduction of different forms of mercury by SnCl2. Except for Cu2+, low concentration of metal ions (≤1 mg/L) had little effect on reduction of different forms of mercuryby SnCl2. High concentrations (100 mg/L) of Fe3+, Zn2+, Ni2+, As3+, Cr3+, Cu2+, V5+ and Pb2+ inhibited the reduction of organic mercury to different degrees by SnCl2, especially V5+ and Pb2+. The relative standard deviations (RSD, n=10) for reduction of inorganic mercury, MeHg and EtHg in solution by SnCl2 were 3.0 %, 3.7 % and 3.5 %, respectively, indicating that the stability of three forms of mercury in SnCl2 solution was good. The detection limit (LOD) of the method for total mercury in water was 0.03 μg/L, the RSD was less than 6.1% (n=6) and the standard recoveries was between 82.0% and 90.0%. This method was simple, less time-consuming and stable and could be applied to the detection of trace total mercury in surface water and tap water.
A new and portable method for extraction, enrichment and detection of trace total mercury in water by a headspace solid phase microextraction probe loaded with gold and wood stickswas developed. The surface morphology and elemental composition of the gold-loaded probe were characterized by scanning electron microscopy and energy dispersive analysis (SEM-EDS). The effects of solution pH, salinity, dissolved organic matter (DOM) concentration and co-existing metal ions on SnCl2 reduction of different forms of mercury (inorganic mercury, methyl mercury and ethyl mercury) were investigated. The results showed that the pH, salinity and DOM concentration of the solution had only weak effect on the reduction of different forms of mercury by SnCl2. Except for Cu2+, low concentration of metal ions (≤1 mg/L) had little effect on reduction of different forms of mercuryby SnCl2. High concentrations (100 mg/L) of Fe3+, Zn2+, Ni2+, As3+, Cr3+, Cu2+, V5+ and Pb2+ inhibited the reduction of organic mercury to different degrees by SnCl2, especially V5+ and Pb2+. The relative standard deviations (RSD, n=10) for reduction of inorganic mercury, MeHg and EtHg in solution by SnCl2 were 3.0 %, 3.7 % and 3.5 %, respectively, indicating that the stability of three forms of mercury in SnCl2 solution was good. The detection limit (LOD) of the method for total mercury in water was 0.03 μg/L, the RSD was less than 6.1% (n=6) and the standard recoveries was between 82.0% and 90.0%. This method was simple, less time-consuming and stable and could be applied to the detection of trace total mercury in surface water and tap water.
2021, 49(8): 1402-1409
doi: 10.19756/j.issn.0253-3820.201307
Abstract:
As a wavelength selection algorithm, successive projection algorithm (SPA) is used in the quantitative analysis of near infrared spectroscopy to simplify the model complexity and improve the prediction accuracy. According to the principle of SPA algorithm, SPA method can only ensure that there is low redundancy between the two wavelengths selected by two adjacent projections, but it does not guarantee that the selected variables must be effective variables, that is to say, the subset of variables screened by SPA may contain some uninformation variables or even interfering variables. We extract effective variables (i.e. strong and weak information variables) by iteratively retains informative variables (IRIV), and then select wavelength by SPA based on effective variables, so as to solve the problem that the selected variables by SPA may contain uninformation and interfering variables, and improve the prediction accuracy of the model. The improved IRIV-SPA is applied to processing of two groups of public NIR spectral data. After the wavelengths are selected, the MLR model is established and compared with the FULL-PLSR model and some other commonly used high-performance wavelength selection methods (SPA, IRIV, RF) to prove the effectiveness of the improved IRIV-SPA algorithm. The results show that the improved IRIV-SPA-MLR model has the best prediction accuracy under two opening test datasets, which greatly improves the prediction accuracy and simplifies the complexity of the model compared with other algorithms. The improved IRIV-SPA can achieve efficient dimensionality reduction and is an effective wavelength selection algorithm.
As a wavelength selection algorithm, successive projection algorithm (SPA) is used in the quantitative analysis of near infrared spectroscopy to simplify the model complexity and improve the prediction accuracy. According to the principle of SPA algorithm, SPA method can only ensure that there is low redundancy between the two wavelengths selected by two adjacent projections, but it does not guarantee that the selected variables must be effective variables, that is to say, the subset of variables screened by SPA may contain some uninformation variables or even interfering variables. We extract effective variables (i.e. strong and weak information variables) by iteratively retains informative variables (IRIV), and then select wavelength by SPA based on effective variables, so as to solve the problem that the selected variables by SPA may contain uninformation and interfering variables, and improve the prediction accuracy of the model. The improved IRIV-SPA is applied to processing of two groups of public NIR spectral data. After the wavelengths are selected, the MLR model is established and compared with the FULL-PLSR model and some other commonly used high-performance wavelength selection methods (SPA, IRIV, RF) to prove the effectiveness of the improved IRIV-SPA algorithm. The results show that the improved IRIV-SPA-MLR model has the best prediction accuracy under two opening test datasets, which greatly improves the prediction accuracy and simplifies the complexity of the model compared with other algorithms. The improved IRIV-SPA can achieve efficient dimensionality reduction and is an effective wavelength selection algorithm.
2021, 49(8): 1410-1418
doi: 10.19756/j.issn.0253-3820.211067
Abstract:
A rapid quantitative analysis method for heavy metals in soil based on laser-induced breakdown spectroscopy (LIBS) and random forest (RF) algorithm was developed. LIBS spectra of 22 soil samples were collected by LIBS spectrometer. The effects of different spectral pretreatment methods on the prediction performance of RF model based on LIBS spectra of soil samples were explored. With normalized LIBS spectral data as initial input variables, the RF calibration models based on full spectrum, characteristic band, variable importance and backward interval were constructed for the quantitative analysis of Cu, Cr, Pb and Ni in soil. The results showed that, compared with the RF calibration models based on full spectrum, characteristic band and variable importance, the RF calibration model based on backward interval (BiRF) had a better performance in quantitative analysis of Cu, Cr, Pb and Ni in soil. The optimal root mean square error (RMSE) values of Cu, Cr, Pb and Ni were 8.0221, 6.0120, 1.7382 and 1.2851 μg/g, respectively, and the optimal coefficient of determination (R2) values were 0.9610, 0.8985, 0.7021 and 0.9850, respectively. The results showed that the LIBS technology combined with BiRF algorithm was a feasible method for detection of heavy metals in soil.
A rapid quantitative analysis method for heavy metals in soil based on laser-induced breakdown spectroscopy (LIBS) and random forest (RF) algorithm was developed. LIBS spectra of 22 soil samples were collected by LIBS spectrometer. The effects of different spectral pretreatment methods on the prediction performance of RF model based on LIBS spectra of soil samples were explored. With normalized LIBS spectral data as initial input variables, the RF calibration models based on full spectrum, characteristic band, variable importance and backward interval were constructed for the quantitative analysis of Cu, Cr, Pb and Ni in soil. The results showed that, compared with the RF calibration models based on full spectrum, characteristic band and variable importance, the RF calibration model based on backward interval (BiRF) had a better performance in quantitative analysis of Cu, Cr, Pb and Ni in soil. The optimal root mean square error (RMSE) values of Cu, Cr, Pb and Ni were 8.0221, 6.0120, 1.7382 and 1.2851 μg/g, respectively, and the optimal coefficient of determination (R2) values were 0.9610, 0.8985, 0.7021 and 0.9850, respectively. The results showed that the LIBS technology combined with BiRF algorithm was a feasible method for detection of heavy metals in soil.
