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1.
Talanta ; 207: 120285, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31594625

RESUMO

Detection of microRNAs (miRNAs) in cells improves our understanding of their physiological functions and facilitates exploration of their roles diseases. The toehold-mediated strand displacement reaction initiates rolling circle amplification (RCA) to achieve signal amplification of the specific miRNA; This process is named as toehold-initiated RCA (TIRCA). The product of TIRCA was ligated to two DNA probes, which were modified with 6-carboxyfluorescein and carboxytetramethylrhodamine, respectively. Qualitative detection of miRNAs was successfully achieved by combining the fluorescence aggregation enhancement effect with fluorescence resonance energy transfer generated by the proximity of the two fluorescent dyes. Thus, this approach helps us analyze the roles of miRNAs in human disease more accurately.

2.
J Hazard Mater ; 382: 121041, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31470295

RESUMO

The high concentration of chloride (Cl-) ions in leachate often has negative effects in their harmless treatments, and the common treatments containing the ion exchange method consume excessive antichlors due to their large particle sizes and unfavorable morphologies. Herein, the antichlors of the Bi(III) containing oxides with quantum dots (QDs) or two-dimensional (2D) structures are first explored for the removal and recovery of Cl- ions in concentrated leachate. By using the QDs/2D flakes constructed antichlors of Bi2O3 and the magnetite Bi-Ti composite, the maximum Cl- removal rates of 61.8% and 66.1% are respectively achieved under the optimum conditions. The higher removal efficiency of the magnetite Bi-Ti composite is contributed by its less stable crystal phases of Bi25FeO40/Bi12TiO20, which can proceed more deeply in the removal of Cl- ions compared with that of Bi2O3. The recovered terminal magnetite Bi-Ti precipitate with Bi2O3/BiOCl heterostructure exhibits excellent photocatalytic activity in the degradation of the dechlorinated leachate, where a total organic carbon removal rate of 87.2% is achieved under UV-vis-near-infrared irradiation. Therefore, the selection of Bi(III) containing oxides opens a promising and high-value method for the removal and recovery of Cl- ions in leachate and other waste waters.

3.
J Hazard Mater ; 382: 121056, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31470305

RESUMO

We report a new 7-nitrobenzo-2-oxa-1, 3-diazolyl (NBD)-based chemosensor containing a piperazine derivative, NBDP, for detection of mercury ions in almost 100% aqueous medium. The chemosensor shows sensing exclusively toward Hg2+ with a switch-on fluorescence response at 543 nm, which could be attributed to the blocking of PET (photo-induced electron transfer) process upon complexation with mercury ions. The molar ratio of Hg(Ⅱ) to NBDP in the complex is 1:1 based on the Job's plot and HRMS studies. Optimized configurations of NBDP and NBDP-Hg2+ complexes were simulated by means of DFT calculations. The reversible fluorescence response with low detection limit (19.2 nM) in the pH range of 6.0-7.5 renders NBDP a promising candidate for Hg2+ detection in neutral aqueous environments. For the practical application of the chemosensor, test strips were successfully fabricated for rapid detection of Hg2+ ions. Moreover, the utility of NBDP showing the mercury recognition in Human liver cancer cells (SMMC-7721) and zebrafish as well as in live tissues of Arabidopsis thaliana has been demonstrated as monitored by fluorescence imaging.

4.
J Pharm Biomed Anal ; 177: 112868, 2020 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-31539713

RESUMO

Traditional Chinese Medicine Injection (TCMI) was restricted due to the batch-to-batch variability caused by the variable compositions of botanical raw materials and complexities of the current manufacturing process. To evaluate and control the quality of Kudiezi Injection (KDZI), a comprehensive and practical method based on multidimensional chromatographic fingerprint associated with multivariate statistical analysis was proposed. The multidimensional chromatographic fingerprint was established by integrating three kinds of chromatographic fingerprints, including High Performance Liquid Chromatography-Ultraviolet spectrum (HPLC-UV), Gas Chromatography-Mass Spectrometer (GC-MS) and High performance ion-exchange chromatography (HPIEC), which were used to detect flavones, nucleosides, organic acids, amino acids and saccharides in KDZI. In addition, four main multivariate statistical analyses were compared to assess the batch-to-batch consistency of samples. Results showed that the cosine method, which has been widely used in the quality evaluation of TCM, failed to distinguish the differences among batches based on neither chromatographic peaks' area nor contents information. t-test and Bayes' theorem could reveal the content difference among batches, while hierarchical clustering analysis could differentiate KDZI batches, and Luteolin-7-O-ß-D-glucuronopyranoside, Tau, Ser, guanine and allose were the main indicators. In conclusion, multidimensional chromatographic fingerprints could reflect the quality information of KDZI comprehensively and hierarchical clustering analysis was suitable to identify the differences among batches. This could provide an integrated method for consistency evaluation of TCMI, process improvement of TCMI and solving similar problems in TCMI.

5.
Food Chem ; 305: 125439, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31499287

RESUMO

Compared to the control longans, hydrogen peroxide (H2O2)-treated longans exhibited higher index of pulp breakdown, higher fruit respiration rate, higher activities of pulp phosphohexose isomerase (PGI), succinate dehydrogenase (SDH), cytochrome C oxidase (CCO), ascorbic acid oxidase (AAO) and polyphenol oxidase (PPO), but lower activity of pulp nicotinamide adenine dinucleotide kinase (NADK). H2O2-treated longans also exhibited lower total activities of pulp glucose-6-phosphate dehydrogenase (G-6-PDH) and 6-phosphogluconate dehydrogenase (6-PGDH), lower levels of pulp NADP(H), but higher levels of pulp NAD(H). These data indicated that H2O2-stimulated longan pulp breakdown was owing to a decreased proportion of pentose phosphate pathway (PPP), the increased proportions of Embden-Meyerhof-Parnas pathway (EMP), tricarboxylic acid (TCA) cycle and cytochrome pathway (CCP) in total respiratory pathways. These findings further revealed that H2O2 could enhance respiration rate, and thus accelerate pulp breakdown occurrence and shorten the shelf life of longan fruit.

6.
J Nanosci Nanotechnol ; 20(6): 3424-3431, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-31748035

RESUMO

The AgBrO3/few-layer g-C3N4 composite photocatalyst has been developed via an in-situ synthetic method. The structure, morphology, light response range, separation and migration efficiency of the photogenerated electron-hole pairs and element valence state of the as-obtained samples have been characterized. The tetracycline was used to discuss the photocatalytic activities of the samples. The photocatalytic degradation mechanism of the as-obtained composites was also researched. The analysis results show that the photocatalytic degradation property of the asobtained composite photocatalyst appears to the tendency of first increasing and then decreasing with increasing the amount of AgBrO3 under visible light illumination. When the mass ratio of AgBrO3 to g-C3N4 is 4:3, in 60 min, the photocatalytic degradation efficiency of the as-obtained composites reaches the maximum of 79%. It is 37% and 45% higher than that of pure AgBrO3 and g-C3N4, respectively. Moreover, the separation and migration efficiency of the photogenerated electron-hole pairs of the as-prepared composites are also enhanced. In addition, superoxide radicals and holes are the dominant active species during the photocatalytic degradation process.

7.
Waste Manag ; 101: 83-93, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31604161

RESUMO

The recycling of waste plastics is of considerable significance with environmental and economic benefits, while available separation approaches have been considered as a major bottleneck for its widespread application. Thus, we proposed a simple method, flotation along with surface modification, to separate waste acrylonitrile-butadienestyrene and polyvinylchloride mixtures. Single-factor experiment was conducted to determine the critical parameters in surface modification. Surface response methodology using Box-Behnken Design was performed to optimize separation performance. The quadratic models were generated to predict the floatability of acrylonitrile-butadienestyrene and the difference between the floatability of polyvinylchloride and acrylonitrile-butadienestyrene. The model was also utilized to determine optimized conditions by desirability approaches. The optimized conditions were: concentration = 0.18 M, temperature = 75.00 °C, treatment time = 11.50 min along with stirring rate = 200 rpm. The efficient separation of acrylonitrile-butadienestyrene and polyvinylchloride was achieved, yielding recovery of 98.40% and purity of 98.43%. The experimental responses well agreed with predicted values, demonstrating the accuracy of the prediction model. The formed hydrophilic groups, coated iron oxide, and signs of corrosion were confirmed as the major mechanism for the selective surface hydrophilization of acrylonitrile-butadienestyrene. Consequently, this method is feasible for separation of waste acrylonitrile-butadienestyrene and polyvinylchloride mixtures, and can be expected to promote the sustainable recycling of waste plastics.


Assuntos
Acrilonitrila , Eliminação de Resíduos , Butadienos , Ferro , Plásticos , Reciclagem , Estireno
8.
J Cell Physiol ; 235(2): 993-1000, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31332778

RESUMO

Cervical cancer is a tumor with the second highest morbidity and mortality in the world, and it is also the most common cancer and the eighth lethal factor among malignant tumors in Chinese female. This study aimed to identify long noncoding RNAs (lncRNAs) that related to diagnosis and prognosis in cervical cancer to improve early diagnosis and treatment. First, we extracted transcriptome profilings of cervical cancer samples from the cancer genome atlas (TCGA) database, and then extracted the lncRNAs and mRNAs expression profiles. Based on the lncRNAs expression profiles of test set, we screened lncRNAs that related to progression of cervical cancer tumors. We found six lncRNAs associated with tumor progression in cervical cancer patients, in which five lncRNAs have highly similar expression patterns but the other one has the opposite expression pattern. We found that these six lncRNAs might be related to keratinization and immunity by enrichment analysis, and two of them (AC126474 and C5orf66-AS1) were associated with prognosis in patients with cervical cancer. And these results were validated using the validation set. Overall, we identified six lncRNAs that played an important role in the development of cervical cancer, and two of them might be associated with the prognosis of cervical cancer, which provides new insight into the diagnosis and treatment of cervical cancer.

9.
J Cell Physiol ; 235(2): 1615-1623, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31347168

RESUMO

The incidence of gallbladder cancer (GBC) is relatively rare but a high degree of malignancy. The migration and invasion potential of GBC severely affects the prognosis of patients with GBC. Glycochenodeoxycholate (GCDC) is one of the most important components in GBC-associated microenvironment. However, the role of GCDC in the metastatic feature of GBC cells is not fully understood. First, the results of this study found that GCDC could effectively enhance the metastasis of GBC cells. Furthermore, GCDC could lead to the enhancement of epithelial to mesenchymal transition (EMT) phenotype in GBC cells, which is concerned to be an important mechanism of tumor metastasis. Further studies showed that GCDC treatment induced the upregulation of matrix metalloproteinase-3 (MMP3), MMP9, and SOCS3/JAK2/p-STAT3 signal pathway in GBC cells, which could regulate the level of EMT. Beside that, we also found the positive expression of farnesoid X receptor (FXR) in GBC cells and inhibition of FXR could significantly block the effect of GCDC on the metastasis of GBC cells. These results indicated that GCDC promoted GBC cells metastasis by enhancing the level of EMT and inhibition of FXR could significantly block the effect of GCDC. On one hand, FXR might be an indicator for predicting the metastasis of patient with GBC. On the other hand, FXR might serve as a potential antimetastasis target in GBC therapy.

10.
Meat Sci ; 159: 107938, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31520866

RESUMO

This study aimed to evaluate a novel three-step sous-vide (SV) method on bacterial growth and diversity, and its relationship to product storage life. Vacuum-packed naturally contaminated steaks were sequentially cooked at 39 °C (1 h), 49 °C (1 h), and 59 °C (4 h), then stored at -1.5 and 2 °C for 28 d, with a single-step SV at 59 °C for 4 h for comparison. None of the seven indicator bacteria tested proliferated (P > .05) after incubation at 39 or 49 °C; microbial diversity was also unaffected. Bacterial load was reduced (P < .05) by up to 5 log units with both (P > .05) SV methods. The odour of all steaks remained acceptable on d 28. Unexpectedly, during storage, Pseudomonas, not lactic acid bacteria, dominated the microbiota on steaks cooked by either SV method, likely due to the temperature shift-induced lag phase and/or heat sensitivity of psychrotrophic bacteria. In conclusion, the three-step SV did not lead to bacterial proliferation or compromise the storage life of cooked products.

11.
J Nanosci Nanotechnol ; 20(4): 2025-2031, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31492208

RESUMO

AS1411 Aptamer-functionalized liposome was successfully formulated and found to be nanosized. Flow cytometer and CLSM results demonstrated that Aptamer enhanced the targeting of carrier in the cancer cells via nucleolin-mediated transmembrane endocytosis pathway. The lipofectaminebased miR-29b showed a typical concentration-dependent cytotoxic effect in the cancer cells. LP-miR induced a significant reduction in the cell viability of A2780 cells compared to that of nontreated control, while LP-Mut (mutant loaded) did not have any effect on the cell viability indicating the importance of the specific gene sequencing. LP-miR induced a significant decrease in the green fluorescence which is indicative of the decrease in the cell viability. Simultaneously, higher PI positive cells were observed for LP-miR treated cancer cells in Live/Dead assay. Cells treated with LP-miR exhibited the brightest fluorescence indicating the presence of apoptotic cells. Significant increase in the Annexin-V+ cells and PI+ cells were observed for cell treated with LP-miR compared to that of non-treated control indicating the potential of miR-29b. This novel miR-29b-loaded Aptamer-directed liposome could potential serve as a new platform to improve the therapeutic outcome in ovarian cancers.

12.
J Hazard Mater ; 383: 121191, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31525689

RESUMO

In this study, we developed a highly enriched phenanthrene-degrading co-culture, PheN9, which uses nitrate as an electron acceptor under anaerobic conditions, and the processes mediating biodegradation were proposed. The dominant bacteria populations included Pseudomonas stutzeri (91.7% relative abundance), which shared 98% 16S rRNA-sequence similarity with the naphthalene-degrading, nitrate-reducing strain NAP-3-1, and Candidatus_Kuenenia (2.3% relative abundance), which is a type of anammox bacteria. Enrichment transformed 54% of the added phenanthrene, reduced nitrate, and generated significant amounts of nitrite. Enrichment also result in partial consumption of the produced nitrite by the anammox bacteria. The key initial steps of anaerobic phenanthrene biodegradation by PheN9 were methylation and carboxylation, which were identified for detection of metabolic products, as well as carboxylase and methyltransferase activities. The methylation product was then oxidized to 2-naphthoic acid and then underwent sequential biodegradation steps. Then, ring-system reducing occurred, and the metabolic products were identified as dihydro-, tetrahydro-, hexahydro-, and octahydro-2-phenanthroic acid. Downstream degradation proceeded via a substituted benzene series and cyclohexane derivatives. This study employed anaerobic phenanthrene-biodegradation processes with nitrate as an electron acceptor. These findings can improve our understanding of anaerobic polycyclic aromatic hydrocarbon (PAH) biodegradation processes and guide PAH bioremediation by adding nitrate to anaerobic environments.

13.
Chemosphere ; 239: 124734, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31494317

RESUMO

Dam construction and fish culture can change the biogeochemical processes in river, yet their impact on the spectral properties of particulate organic matter (POM) remains to be studied. This was investigated in a reservoir-type river (Minjiang river, SE China) using absorption spectroscopy and fluorescence excitation-emission matrices-parallel factor analysis (EEMs-PARAFAC). Five fluorescent components were identified from POM with PARAFAC. Four components C1-C4 were affected by the seasonal variations of rainfall and runoff, indicating the influences of hydrological condition and terrestrial inputs. The Chlorophyll a concentration (Chl a) correlated significantly with the humic-like C3 (p < 0.05) and the protein-like C4 (p < 0.01), indicating phytoplankton was an important source of C3 and C4. The Chl a and fluorescence intensities of C3-C4 were higher in the fish culture zones than in other areas, and the absorption coefficient a300 and C1-C4 were lower downstream the dam. These results indicated that fish farming in the reservoir probably promoted the production of POM. The a300 and C1 per unit mass of suspended particulate matter (a300/TSM and C1/TSM) correlated significantly with the median particle size (p < 0.01), which might be related to the contribution of micro-phytoplankton. The absorption spectra of POM showed a shoulder peak at ∼280 nm, and its intensity correlated significantly and positively with Chl a (p < 0.01). These results indicated that the peak was probably derived from phytoplankton production. Our results have implications for better understanding the influences of human activities on the dynamics of river POM.

14.
J Affect Disord ; 260: 214-221, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31505399

RESUMO

BACKGROUND: Evidence of the association between effort reward imbalance (ERI) and suicidal ideation is sparse. This study examined the influence of ERI at work on suicidal ideation and the mediating effect of depressive symptoms. METHODS: There were 4963 workers aged 50+ without suicidal ideation at baseline in the Survey of Health, Aging and Retirement in Europe, these workers were followed-up for 8-years to detect incident suicidal ideation. ERI was measured by a short ERI questionnaire. Suicidal ideation was evaluated by one item derived from the 12-item Europe-depression scale, and depressive symptoms were assessed by the remaining 11 items in the scale. Cox models were employed to explore the relationship adjusting for potential confounders. Mediation analysis was used to test the mediating effect of depressive symptoms. RESULTS: A significantly higher incidence of suicidal ideation was related with high effort (HR = 1.51) and low reward (HR = 1.42), respectively. A high effort-low reward imbalance was associated with even higher risk of suicidal ideation (HR = 1.96) as compared to low effort-high reward combination. The association was varied by gender, region, education and household income. Depressive symptoms mediated a modest proportion (natural indirect effect 14.4%) of the total association between ERI and suicidal ideation. LIMITATION: Suicidal ideation definition based on self-administered questionnaires which could lead to false negatives. And some unmeasured confounders might have biased the results. CONCLUSIONS: Efforts in promoting balanced effort-reward at work may reduce suicidal ideation among working population aged 50+. Avoiding depressive symptoms may further enhance such efforts.

15.
Nanotechnology ; 31(3): 035403, 2020 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-31557753

RESUMO

The development of low-cost electrocatalysts with high performance is important to provide sustainable hydrogen energy. In this work, via one-step sulfuration of [Formula: see text] intercalated NiFe-layered double hydroxide (abbr. NiFe-MoO4-LDH), hierarchical microspheres are assembled by intersecting nanoplates (15-30 nm in thickness) which are then decorated with MoS2 and (NiFe)S x nanoparticles (∼25 nm in size). The NiFe-MoO4-LDH is synthesized beforehand by a one-pot hydrothermal reaction. Under sulfuration at 300 °C, 400 °C and 600 °C, the NiFe-MoO4-LDH transforms into multi-metal sulfides of NiFeMoS-T (T is applied temperature). During sulfuration, the confinement effect of LDH limits the growth of metal sulfides, causing formation of nanoparticles of MoS2 and (NiFe)S x to expose more catalytic active sites. In an alkaline medium, NiFeMoS-400 depicts superior performance for hydrogen evolution reaction (HER), giving an overpotential of 210 mV at 10 mA cm-2. A Tafel slope of 88 mV dec-1 indicates a mixed Volmer-Heyrovsky rate-determining step. The electrode also maintains long-term electrochemical durability during 15 h electrolysis at 25 mA cm-2. The NiFe-MoO4-LDH precursor owns three metal elements (Ni, Fe and Mo), which ensure the formation of polymetallic sulfides, and maximum utilization of the LDH layer and interlayer metals contributes to the optimal electrocatalytic activity. The NiFeMoS nanoassembly is a potential low-cost and high-efficiency electrocatalyst.

16.
Food Chem ; 306: 125627, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31610328

RESUMO

Effects of various concentrations of Kadozan (chitosan) treatment on storability and quality properties of harvested 'Fuyan' longans were investigated. Compared to the control samples, Kadozan treated-longans displayed lower fruit respiration rate, lower pericarp cell membrane permeability, pericarp browning index, pulp breakdown index, fruit disease index, and weight loss, but higher rate of commercially acceptable fruit, higher levels of pericarp chlorophyll, carotenoid, anthocyanin, flavonoid and total phenolics, higher amounts of pulp total soluble sugar, sucrose, total soluble solids, and vitamin C. These results revealed Kadozan treatment could increase storability and retain better quality of harvested longan fruit. Among different concentrations of Kadozan, the dilution of 1:500 (VKadozan: VKadozan + Water) showed the best results in storability and maintained the best quality of longans during storage. These findings demonstrated that Kadozan could be a facile and eco-friendly postharvest handling approach for increasing storability and lengthening shelf-life of harvested 'Fuyan' longan fruit.

17.
Gait Posture ; 75: 66-71, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31605898

RESUMO

BACKGROUND: Walking on railroad ballast is a unique challenge for railroad workers and contributes to a large number of falls and slips. However, the characteristics of ground reaction force (GRF) when walking on ballast combined with a cross-slope condition are poorly understood. RESEARCH QUESTION: How does the magnitude and temporal distribution of GRF change during walking on railroad ballast combined with a cross-slope condition? METHODS: Eight experienced railroad workers walked with their self-selected speed on three surfaces (mainline ballast, walking ballast and no ballast) in both a level and cross-slope (7°) condition. The magnitude and time of occurrence of selected key features of the GRF were extracted from the force plate. A two-factor repeated measures ANOVA was used to determine the effect of surface and cross-slope condition. RESULTS: The minimum anteroposterior GRF and the first peak of the normal GRF occurred earlier on mainline ballast and walking ballast than no ballast. The maximum anteroposterior GRF was smaller, but the first peak of the normal GRF was larger on walking ballast compared with no ballast. Additionally, the asymmetrically mediolateral GRFs were observed between upslope limb and downslope limb in the cross-slope condition, which were also significantly different from the level condition. SIGNIFICANCE: Ballast combined with a cross-slope condition posed a higher requirement for dynamic control to prevent downslope slippage and body instability, which could increase the fall risk for railroad workers. Future studies should investigate interventions to improve dynamic balance and reduce foot slippage on ballast.

18.
Bioresour Technol ; 295: 122278, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31669867

RESUMO

This study explored the influences of peroxydisulfate (PDS) and peroxymonosulfate (PMS) activated with different catalysts on the anaerobic fermentation of waste activated sludge (WAS). All the treatments were effective in promoting short-chain fatty acids (SCFAs) production, particularly acetic acid, in the order of PMS/MnO2 > PMS/Zn > PDS/Zn > PMS/Fe > PDS/Fe > PDS/MnO2. Mechanistic investigations demonstrated that WAS disintegration was intensely induced by the free radicals (i.e., SO4- and OH) generated in PDS and PMS treating reactors. It significantly promoted the solubilization and hydrolysis processes and thereby provided sufficient bioavailable substrates for further acidogenic metabolisms. Additionally, it enlarged the abundance of functional bacteria responsible for SCFAs production. The simultaneous promotion of bioavailable substrates and fermentative microorganisms markedly contributed to the SCFAs enhancement. Moreover, the dewaterability and stabilization of fermented sludge were both improved with the PDS and PMS treatments, which were beneficial to the final disposal of WAS.


Assuntos
Compostos de Manganês , Esgotos , Ácidos Graxos Voláteis , Fermentação , Hidrólise , Óxidos
19.
J Biotechnol ; 307: 63-68, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31678458

RESUMO

Extensively modulating gene expression to achieve optimal flux is a critical step in metabolic engineering. Gene expression is usually modulated at the transcriptional level by controlling the strength of a promoter. However, this type of modulation is often hampered by its inability to fully sample the complete continuum of transcriptional control. In Escherichia coli, this limitation can be solved by constructing promoters with a wide range of strengths. In this study, a highly efficient method was developed to modulate a particular chromosomal gene of E. coli at a wide range of expression levels. This was achieved by combining highly efficient single-stranded oligonucleotide-mediated recombination and a stringent counter selection system kil. Using this strategy, a chromosomal library, with a range from 0.3% to 388% relative to the wild lac promoter, was easily obtained. The strength of our chromosomal promoter library was approximately 5-60 times wider in range than those of libraries reported before.

20.
Artigo em Inglês | MEDLINE | ID: mdl-31706150

RESUMO

The study is aimed to develop a rapid and efficient supercritical fluid chromatography coupled with diode-array detection (SFC-DAD) method for simultaneous quantification of six flavonoids in Citri Reticulatae Pericarpium (CRP). The chromatographic parameters including stationary phase, mobile phase composition, back pressure, temperature and flow rate, were systematically optimized with single-factor test. The results indicated that the six compounds were baseline separated on an Agilent Zorbax RX-SIL column using gradient elution within 10 min. The optimized mobile phase was constituted of carbon dioxide (CO2) and methanol. And the parameters were set as follows: backpressure, 95 bar; temperature, 45 °C; flow rate, 0.8 mL/min. The optimized method showed satisfactory retention and resolution for the analytes. The method was validated to demonstrate its selectivity, linearity, precision, accuracy and robustness. Thus, the verified SFC method was successfully applied to quantification of flavonoids present in CRP samples. The results indicated that SFC has the potential to become an excellent alternative for the analysis of flavonoids in herbal medicines, owning to its intrinsic features like high efficiency, separation speed and eco-friendly characteristics.

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