Assay Report Card

ID: ALA3887058

Type: Binding

Description: Cell Free Inhibition Assay: The inhibitory concentrations (IC50, [uM]) of the beta -lactamase inhibitors against purified TEM-1, SHV-1 and AmpC beta -lactamases are assessed by determining the concentration of inhibitor at which 50% of the nitrocefin hydrolysis is inhibited by the particular enzyme. Assays are performed with beta -lactamases expressed in the pET system (Novagen, San Diego, Calif.) without signal peptides. They contain an N-terminal hexa-Histidine tag that is used for purification on Ni-NTA (Qiagen, Hilden, Germany). The compounds are prepared as 50 mM stocks in DMSO and diluted into buffer P1 (50 mM phosphate, pH 7) to a final concentration of 10% DMSO. All further dilutions are done in P2 (P1 with 10% DMSO). Enzyme and compound dilutions are pre-incubated for 10 min at 37 C. and the reaction is started with the addition of pre-warmed (37 C.) nitrocefin at a final concentration of 50 mM. The change in absorption at 490 nm is followed at 37 C. for 10 min with 30 s intervals.