PubMed · 5244819
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M da G Lima, W C de Araujo, J de O Lima. [Studies on Snyder colorimetric method].. https://pubmed.ncbi.nlm.nih.gov/5244819/
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The development of colorimetric methods based on directly inhibiting nanozyme activity for pesticide detection has attracted considerable attention. In this study, we report a novel colorimetric sensing strategy utilizing BiO2-x/Bi2O2.75 nanosheets (BiO2-x/Bi2O2.75 NSs) with haloperoxidase (HPO)-like activity for the rapid and sensitive detection of carbosulfan (CBS) in foods. Oxygen-vacancy-rich BiO2-x/Bi2O2.75 NSs with HPO-like activity were rationally constructed. Kinetic studies revealed a remarkable Michaelis-Menten constant (Km) of 0.014 mM for I-, indicating a higher affinity for iodide ions than other reported HPO-like nanozymes, as evidenced by its lower Km. Under acidic conditions, CBS tends to be hydrolyzed to produce reductive sulfide species, which directly inhibit the iodoperoxidase-like activity of BiO2-x/Bi2O2.75 NSs, enabling selective detection with a limit of detection (LOD) of 0.18 μg/mL and a linear range of 0.20-100 μg/mL. When the concentration of interfering pesticides and substances was 5 times that of CBS, the sensor remained unaffected, exhibiting excellent stability and specificity. This work contributes to the detection of CBS in complex food matrices, bridging the application gap of HPO-like nanozymes in pesticide detection and providing a promising method for food safety detection.
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One of the key enzymes involved in the breakdown of reserve xyloglucan in seeds of some dicotyledonous plants during germination is the specific endo-beta-(1,4)-glucanase. The enzyme operates predominantly by a transglycosylic mechanism, i.e., by random splitting the beta-(1,4)-linked polyglucose backbone of xyloglucan molecules and rejoining the newly created reducing ends by beta-(1,4) glycosidic bonds to nonreducing ends of other xyloglucan molecules or xyloglucan subunit oligosaccharides. For this reason, the enzyme is regarded primarily as xyloglucan-endotransglycosylase (XET). Since almost no net formation of reducing ends occurs in the course of transglycosylation, the conventional reductometric methods used for the assessment of glycanase activities are not applicable for detection and determination of XET activity. The described colorimetric assay is based on the property of xyloglucan-derived subunit oligosaccharides (DP 5-10) to stimulate selectively the breakdown of xyloglucan by endotransglycosylation while serving as additional glycosyl acceptors. The depolymerization of xyloglucan in the course of reaction is followed colorimetrically by measuring the disappearance of the blue--green-colored iodine:xyloglucan complex. The transglycosylase activity is calculated as the difference of activities measured in the presence of stimulating xyloglucan-derived oligosaccharides and in their absence. The advantages of the described colorimetric method include its low cost, simplicity, speed, and the possibility to analyze multiple samples simultaneously.