| Assay Method Information | |
| | Inhibition Assay |
| Description: | Human carbonic anhydrase II (hCA-II) inhibition was measured by an absorbance method using 4-nitrophenyl acetate (4-NPA) as its substrate. 4-NPA can be catalyzed by active hCA II via a zinc-hydroxide mechanism. The nitrophenolate in the products can be ionized to generate a bright yellow anion with high absorbance at 348 to 400 nm, as reported in the literature (Armstrong et al., J. Biol. Chem. 1966, 241, 5137-5149). OD340 nm was chosen for detecting hCA II substrate conversion.Assay working solutions were made as follows:Assay buffer: 50 mM MOPS, 33 mM Na2SO4, 1 mM EDTA, 0.5 mg/ml BSA, pH 7.5;Enzyme solution: hCA-II (human, full length) stock solution (1.0 mg/mL in 20 mM HEPES, 50 mM NaCl, pH 7.4), diluted to 2133× final concentration in assay buffer;4-NPA substrate solution: 4-NPA substrate stock solution (250 mM in DMSO, stored at −20° C.), diluted to 50× final concentration in deionized water.Test compounds (10 mM stock in DMSO, 100 μL) were obtained in 96-well sample plates (Corning Costar #3655) and diluted to 0.5 mM. Column-wise serial dilutions were made by transferring 20 μL compound solutions to the next column, from column 3 up to 22. After this, 1.2 μL were transferred to 384 well assay plates (Corning Costar #3701). Then 30 μL of 16 nM hCA II solution was added (8 nM final concentration), mixed five times. 30 μL of 4-NPA substrate solution was added (2.5 mM final concentration), mixed five times. Absorbance at 340 nm was then measured immediately as time zero. The assay plates were incubated at room temperature for 1 hour and then measured as time 1 hour (Perkin Elmer EnVision 2103; Filter: Photometric 340; Light intensity 60%; Number of flashes: 10). IC50 values and Ki values were calculated from these readouts. |
| Affinity data for this assay | |
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