Irreversible enzyme inhibitors show time dependent behaviour characterized by the parameters KI and kinact which approximate the reversible binding component and rate of covalent bond formation. kinact/KI is the bimolecular rate constant to form inactivated enzyme under sub-saturating conditions. Medicinal chemistry utilizes these parameters to drive lead-optimization. Thorough biochemical characterization requires determination of a multitude of enzyme-activity measurements to yield inactivation rates against a compound serial dilution, repeated for each analog of interest. The SPT Labtech Dragonfly was programmed to generate assay plates for running 12 point serial dilutions x 16 timepoints x 8 compounds. Triplicate plates could efficiently be run in a single afternoon. Programming involved a simple procedure of specifying the reagent volumes and timed addition steps to the assay plate, all listed in a few .csv files easily created in Excel. An example method will be presented showing assay files, instrument setup, and resulting data. Techniques to optimize inactivation assay design will also be covered. In addition the utility of the Dragonfly for streamlining assay development to handle multiple reagents while minimizing errors, sample, and consumables will be highlighted.
