Topo II Buffer is supplied as a 10x Stock solution in two parts that must be mixed prior to use:
- 10X Incomplete Topo II Assay Buffer A contains the following: 0.5M Tris-HCl (pH8.0), 1.5M NaCl, 0.1M MgCl2, 5 mM dithiothreitol.
- 10X ATP Buffer B contains 20 mM ATP in water.
These two buffers must be mixed to prepare a final 5X working stock of assay buffer. Furthermore, the final 5X Complete Buffer contains both A and B and should be made fresh for each experiment. Do not freeze the 5X Complete Buffer; it is stable for 24 hours on ice. To Prepare the 5X Complete Buffer, mix equal volumes of A and B (0.1ml of A and 0.1ml of B) and place at 4° C or on ice.