Improving transformation efficiencies- induce supercoiling?
Here is a report that shows significant increase in transformation efficiency for large plasmids (transformation was by electroporation. However the paper has been cited fewer than ten times so clearly the technique did not catch on.


  Zhixing, Y and Nahon, J-L (1995) DNA gyrase improves DNA transformation of E.coli cells with large recombinant plasmids. Nucleic Acids Res. 23:3353-3354