Sometimes we find that one lot of kDNA may mot support topo II activity as well as another lot. Why is this?
KDNA must be purified from nuclear DNA using a density gradient of CsCl. One unfortunate characteristic of exposing KDNA catenanes to extremely high concentrations of CsCl is that contaminating heavy metals and undesirable ions can get trapped in the DNA ion atmosphere (estimated to be rich in counterions near the surface of the DNA helix). While this problem can result in very weak KDNA substrate activity with topo II, we screen each KDNA batch for this complication. We test 2 units of topo II with each new lot of KDNA; thus, the new lot must allow detection of 2 units at least. Some lots of kDNA that pass our screen may not be as robust as others and when trying to assay small amounts of topo II activity, any contamination problems may become more obvious. In these cases, please contact tecnnical support for assistance.
Related Questions
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- Sometimes we find that one lot of kDNA may mot support topo II activity as well as another lot. Why is this?
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