PubMed · 5628295
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M Shirai. 1967. [Diphasic electricity].. https://pubmed.ncbi.nlm.nih.gov/5628295/
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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.
In vitro glycorandomization (IVG) technology is dependent upon the ability to rapidly synthesize sugar phosphates. Compared with chemical synthesis, enzymatic (kinase) routes to sugar phosphates would be attractive for this application. This work focuses upon the development of a high-throughput colorimetric galactokinase (GalK) assay and its application toward probing the substrate specificity and kinetic parameters of Escherichia coli GalK. The demonstrated dinitrosalicylic assay should also be generally applicable to a variety of sugar-processing enzymes. [reaction: see text]
Many assays for protein tyrosine phosphatases (PTPs) rely on colorimetric substrates or more recently developed fluorescent substrates. Enzyme activity is measured but no assessment of specific activity is made, which is important since these enzymes can exist in an enzymatically inactive form. In this study, we have directly compared the relative sensitivity of assays using either colorimetric or fluorescent substrates and show the latter to be considerably more sensitive with as few as 0.2 x 10(6) cells required compared to 3 x 10(6) cells for the colorimetric method. We then describe a quick and sensitive protocol that measures both the phosphatase activity and amount of CD45, allowing the calculation of the specific activity. CD45 is captured from cell lysates using anti-CD45 monoclonal antibody coated onto a 96-well plate, and the phosphatase activity is measured using the substrate fluorescein diphosphate (FDP). The amount of CD45 protein bound in the wells is measured against a standard curve using an anti-CD45-HRP conjugate, and this value is used to derive the specific activity. We used this assay to demonstrate that exposure of Jurkat T cells, and primary CD4(+) T cells to H(2)O(2) decreases the specific activity of their CD45, mimicking the changes seen in some diseases. The assay is applicable to other cell types and phosphatases, and so its use may help to identify the presence of inactive but intact enzyme in cells, which may play an important regulatory role in vivo.