| Assay Method Information | |
| | SPR Binding Assay |
| Description: | The His-tagged SARS-CoV-2 PLpro enzyme was initially prepared in phosphate buffer and diluted to 50 pg/mL with 10 mM sodium acetate (pH 5.5) and immobilized on a CM5 sensor chip by standard amine-coupling with running buffer PBSP (10 mM phosphate, pH 7.4, 2.7 mM KCl, 137 mM NaCl, 0.05% Tween-20). The CM5 sensor chip surface was first activated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxy succinimide (NHS) mixture using a Biacore 8K instrument (Cytiva). SARS-CoV-2 PLpro enzyme was immobilized to flow channels 1 through 4 followed by ethanolamine blocking on the unoccupied surface area, and immobilization levels for all four channels were similar at 12,000 RU. Each flow channel has its own reference channel, and blank immobilization using EDC/NHS and ethanolamine was done for all reference channels. Compound solutions with a series of increasing concentrations (0.049-30 uM at 2.5-fold dilution) were applied to all active and reference channels in SPR binding buffer (10 mM HEPES, pH 7.4, 150 mM NaCl, and 0.05% Tween-20, 0.5 mM TCEP, and 2% DMSO) at a 30 uL/min flow rate at 25 C. The data were double referenced with a reference channel and zero concentration (2% DMSO) responses, and reference subtracted sensorgrams were fitted with 1 to 1 Langmuir kinetic model using a Biacore Insight evaluation software, producing two rate constants (ka and kd). |
| Affinity data for this assay | |
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