Determination of OXA concentration by ICP-MS
We added 200 μL of HNO3 and 400 μL of H2O2 into the lysate of the collected cells, DRGs, or tumours; the mixture was incubated for 2 h at 80 ℃. Next, 200 μL of 25% ammonia solution was added, and the volume of the solution was adjusted to 4.0 mL with ddH20. Finally, the concentrations of OXA were determined by inductively coupled plasma mass spectrometry (ICP-MS, PerkinElmer Nexion 300X) after the solution was filtered using a film filter (0.22 μm). The OXA content was determined relative to the total protein content for cells or relative to the weight for tissues.