| Assay Method Information | |
| | LC-MS/MS-Based NSD2 Enzymatic Assay |
| Description: | This assay employed LC-MS/MS technology to monitor the SAH production from the NSD2 enzymatic reaction. The enzymatic reaction was performed in white proxiplate plus 384-well microplate (Perkin Elmer). The reaction mixture (10 μL) were composed of 8 nM NSD2 [1-1365], 1 M SAM (USB, 10601) and 400 nM nucleosome (purified from mouse liver) in reaction buffer (20 mM Tris-HCl, pH at 8.0, 0.01% Tween 20, 10 mM MgCl2, 50 mM NaCl, 1 mM DTT, 1 mM TCEP (pH7.5)). After 90 min incubation at room temperature, 3 μL quenching solution containing 2.5% TFA with 320 nM d4-SAH was added to stop the reaction.For the inhibition assay, compound solutions were transferred into the wells by Mosquito (TTP LabTech). The inhibition assays were carried out by preincubating various concentrations of the inhibitor with 5 uL reaction mixture containing 16 nM NSD2 [1-1365] and 2 uM SAM (USB, 10601) in reaction buffer. After 20 min preincubation, 5 uL solution containing 800 nM nucleosome (purified from mouse liver) in reaction buffer was added to initiate the reaction. The reaction was stopped by 3 μL quenching solution containing 2.5% TFA with 320 nM d4-SAH after 90 min.The SAH production from the enzymatic assays were monitored by LC-MS/MS on an API 4000 triple quadrupole mass spec with Turbolon Spray (Applied Biosystem) coupled with Prominenece UFLC(Shimazu). Liquid chromatography was performed on a Chromolith FastGradient HPLC column (RP-18e, 25-2 mm, from Merck) at a flow rate of 0.8 ml/min. The column was connected directly to the turbo ion electrospray operating in the positive-ion mode. Mobile phase A is 0.1% FA and 2% methanol in water and mobile phase B is 0.1% FA in ACN. Injection volume was 3 μl and the autosampler was kept at 4 degree. SAH and d4-SAH were simultaneously monitored. Data were acquired and processed by Analyst software.To quantify the formed SAH, d4-SAH was added as internal standard (IS). A series of SAH (Sigma, A9384) solution at varying concentration (1-500 nM in reaction buffer) was mixed with quenching solution mentioned above. Then LC-MS/MS was carried out on API 4000 LC/MS/MS system to detect both SAH and d4-SAH. The plot of SAH peak area/IS peak area vs SAH concentration was used to generate the normalization factor of SAH. The SAH production from real enzymatic reaction was derived from the standard curve of SAH. The down-limit of our system for the detection of SAH is around 1-2 nM, and the linear range can reach up to 500 nM. |
| Affinity data for this assay | |
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