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A novel luminescent sensor for disaccharide detection in food: Synthesis and application of a water-soluble rod-coil ionic block copolymer
摘要： A simple and low cost method for detecting disaccharide in food product is important for people who need control the consumption of saccharides in daily life. In this study, a water soluble rod-coil ionic block copolymer poly[2,7-(9,9-dihexyl-fuorene)]-b-cationic quaternized-poly[2-(dimethylamino)ethyl methacrylate] (PF-b-PDI) was employed as luminescent sensor for detection of lactose, sucrose and maltose in food. It was found that the PF-b-PDI could emit vision fluorescence with the existence of hydroquinone (HQ) in aqueous, but would be quenched by the oxidization of hydrogen peroxide (H2O2). The glucose oxidase (GOx) could be used for catalyzing the glucose to generate the H2O2. And the sucrase, maltase and lactase could respectively catalyze sucrose, maltose and lactose to glucose. With the selectivity and catalyst of enzyme, the PF-b-PDI aqueous blend with HQ showed fluorescence sensitive to sucrose, maltose and lactose with detection limit value of 1.36 μM, 1.09 μM and 3.08 μM, respectively. Moreover, the detection of lactose in milk samples by this method just revealed 0.44% of average deviation compared to standard lactose solution, which mean this method was suitable for detecting lactose in milk.
关键词： maltose,rod-coil ionic block copolymer,lactose,sucrose,luminescent sensor
更新于2025-09-23 15:22:29
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A novel short-term high-lactose culture approach combined with a matrix-assisted laser desorption ionization-time of flight mass spectrometry assay for differentiating Escherichia coli and Shigella species using artificial neural networks
摘要： Background Escherichia coli is currently unable to be reliably differentiated from Shigella species by routine matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis. In the present study, a reliable and rapid identification method was established for Escherichia coli and Shigella species based on a short-term high-lactose culture using MALDI-TOF MS and artificial neural networks (ANN). Materials and methods The Escherichia coli and Shigella species colonies, treated with (Condition 1)/without (Condition 2) a short-term culture with an in-house developed high-lactose fluid medium, were prepared for MALDI-TOF MS assays. The MS spectra were acquired in linear positive mode, with a mass range from 2000 to 12000 Da and were then compared to discover new biomarkers for identification. Finally, MS spectra data sets 1 and 2, extracted from the two conditions, were used for ANN training to investigate the benefit on bacterial classification produced by the new biomarkers. Results Twenty-seven characteristic MS peaks from the Escherichia coli and Shigella species were summarized. Seven unreported MS peaks, with m/z 2330.745, m/z 2341.299, m/z 2371.581, m/z 2401.038, m/z 3794.851, m/z 3824.839 and m/z 3852.548, were discovered in only the spectra from the E. coli strains after a short-term high-lactose culture and were identified as belonging to acid shock protein. The prediction accuracies of the ANN models, based on data set 1 and 2, were 97.71±0.16% and 74.39±0.34% (n = 5), with an extremely remarkable difference (p < 0.001), and the areas under the curve of the receiver operating characteristic curve were 0.72 and 0.99, respectively. Conclusions In summary, adding a short-term high-lactose culture approach before the analysis enabled a reliable and easy differentiation of Escherichia coli from the Shigella species using MALDI-TOF MS and ANN.
关键词： MALDI-TOF MS,Escherichia coli,high-lactose culture,artificial neural networks,Shigella species
更新于2025-09-16 10:30:52
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Nitrogen Doped Carbon Quantum Dots Modified by Lens culinaris β-Galactosidase as a Fluorescent Probe for Detection of Lactose
摘要： Nitrogen doped carbon quantum dots (NCQDs) were synthesized via hydrothermal route. The NCQDs are thermally and optically stable with high flouresence yield. For the synthesis of NCQDs, citric acid and urea was taken as carbon and nitrogen sources, respectively. The Transmission Electron Microscopy (TEM) of these quantum dots revealed nearly spherical shape and average size of 1.5 nm, which was calculated using Image J software. The quantum dots were also well-characterized using spectroscopic techniques such as FTIR, UV-Visible absorption and fluorescence. These synthesized and characterized dots were utilized for selective detection of lactose in Milli Q water. The bioprobe provide a wide linear range varying from (10.00–77.41) μM with limit of detection 11.36 μM and sensitivity equal to (0.0065 ± 0.0002) μM?1.
关键词： Lens culinaris,β-Galactosidase,Biosensor,Fluorescence,Lactose
更新于2025-09-11 14:15:04
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Photoinactivation of the <b><i>Staphylococcus aureus</i></b> Lactose-Specific EIICB Phosphotransferase Component with <b><i>p</i></b>-azidophenyl-β-D-Galactoside and Phosphorylation of the Covalently Bound Substrate
摘要： Background: The phosphoenolpyruvate (PEP):lactose phosphotransferase system of Staphylococcus aureus transports and phosphorylates lactose and various phenylgalactosides. Their phosphorylation is catalyzed by the Cys476-phosphorylated EIIB domain of the lactose-specific permease enzyme IICB (EIICBLac). Phosphorylation causes the release of galactosides bound to the EIIC domain into the cytoplasm by a mechanism not yet understood. Results: Irradiation of a reaction mixture containing the photoactivatable p-azidophenyl-β-D-galactopyranoside and EIICBLac with UV light caused a loss of EIICBLac activity. Nevertheless, photoinactivated EIICBLac could still be phosphorylated with [32P] PEP. Proteolysis of photoinactivated [32P]P-EIICBLac with subtilisin provided an 11-kDa radioactive peptide. Only the sequence of its first three amino acids (-H-G-P-, position 245–247) could be determined. They are part of the substrate binding pocket in EIICs of the lactose/cellobiose PTS family. Surprisingly, while acid treatment caused hydrolysis of the phosphoryl group in active [32P]P EIICBLac, photoinactivated [32P]P-EIICBLac remained strongly phosphorylated. Conclusion: Phosphorylation of the –OH group at C6 of p-nitrenephenyl-β-D-galactopyranoside covalently bound to EIICLac by the histidyl-phosphorylated [32P]P EIIBLac domain is a likely explanation for the observed acid resistance. Placing p-nitrenephenyl-β-D-galactopyranoside into the active site of modelled EIICLac suggested that the nitrene binds to the -NH- group of Ser248, which would explain why no sequence data beyond Pro247could be obtained.
关键词： Staphylococcus aureus,Lactose transport,Photoinactivation,Phosphoenolpyruvate:carbohydrate phosphotransferase system,Azidophenyl-β-D-galactopyranoside
更新于2025-09-04 15:30:14