| Assay Method Information | |
| | Factor XIIa Assay |
| Description: | The effectiveness of a compound of the present invention as an inhibitor of Coagulation Factor XIIa can be determined using a relevant purified serine protease, and an appropriate synthetic substrate. The rate of hydrolysis of the chromogenic or fluorogenic substrate by the relevant serine protease was measured both in the absence and presence of compounds of the present invention. Assays were conducted at room temperature or at 37° C. Hydrolysis of the substrate resulted in release of amino trifluoromethylcoumarin (AFC), which was monitored spectrofluorometrically by measuring the increase in emission at 510 nm with excitation at 405 nm. A decrease in the rate of fluorescence change in the presence of inhibitor is indicative of enzyme inhibition. Such methods are known to one skilled in the art. The results of this assay are expressed as the IC50, the inhibitor concentration causing a 50% decrease in Factor XIIa protease activity.Factor XIIa activity determinations were made in 50 mM HEPES buffer containing 150 mM NaCl, 5 mM CaCl2, and 0.1% PEG 8000 (polyethylene glycol; JT Baker or Fisher Scientific) at pH 7.4. Determinations were made using purified human Factor XIIa at a final concentration of 500 pM (Sekisui Diagnostics) and the synthetic substrate, n-Acetyl-Lys-Pro-Arg-AFC, TFA salt (Sigma #C6608) at a concentration of 100 μM.Activity assays were performed by diluting a stock solution of substrate at least tenfold to a final concentration ≤0.1 Km into a solution containing enzyme or enzyme equilibrated with inhibitor. Times required to achieve equilibration between enzyme and inhibitor were determined in control experiments. Initial velocities of product formation in the absence (Vo) or presence of inhibitor (Vi) were measured. IC50 was determined as the concentration of I yielding Vi=Vo/2. |
| Affinity data for this assay | |
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