Assay Method Information

Assay Name:  LC-MS Based In Vitro Assay
Description:  hAC protein preparation (10 μg) was preincubated with inhibitors (final DMSO concentration 1%) in assay buffer (100 mM sodium phosphate, 0.1% Nonidet P-40, 150 mM NaCl, 3 mM DTT, 100 mM sodium citrate, pH 4.5) for 30 min at 37° C. Reactions were started by the addition of 50 μM N-lauroyl ceramide (Nu-Chek Prep, Elysian, Minn.) and carried on for 30 min at 37° C. Reactions were stopped by addition of a mixture of chloroform/methanol (2:1) containing 1 nmol 11-lauroleic acid (NuChek Prep). The organic phases were collected, dried under nitrogen and analyzed by UPLC/MS (Acquity, Waters). In the negative-ion mode monitoring the reaction product (lauric acid, m/z=199) using 11-lauroleic acid as internal standard.Lipids were eluted on an Acquity UPLC BEH C18 column (50×2.1 mmID, particle size 1.7 μm), column flow at 0.5 mL/min for 1.5 min with a gradient of acetonitrile and water, both containing 0.25% acetic acid and 5 mM ammonium acetate (70% to 100% acetonitrile in 0.5 min, 100% acetonitrile for 0.5 min, 70% acetonitrile for 0.4 min). The column temperature was 40° C. Electrospray ionization (ESI) was in the negative mode, capillary voltage was 1 kV and cone voltage was 50 V. N2 was used as drying gas at a flow rate of 500 L/h and at a temperature of 400° C.The [M-H]− ion was monitored in the selected-ion monitoring mode (m/z values: lauric acid 199, 11-lauroleic acid 197.35). Calibration curves were generated with authentic lauric acid (Nu Check Prep). Inhibition of AC activity was calculated as reduction of lauric acid in the samples compared to vehicle controls. IC50 values were calculated by non-linear regression analysis of log [concentration]/inhibition curves using GraphPad Prism 5 (GraphPad Software Inc., CA-USA) applying a standard slope curve fitting.
Affinity data for this assay
 

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