Can I use TOP10F' competent cells for transformation of my TOPO vector that contains the ccdB gene?
Strains that contain an F plasmid, such as TOP10F', are not recommended for transformation and selection of recombinant clones in any TOPO vector containing the ccdB gene. While the F plasmid does encode the CcdA protein, which acts as an inhibitor of the CcdB gyrase-toxin protein, the half-life of the CcdA protein is shorter than that of the CcdB protein. Overexpression of the CcdB protein causes cell death when its action is not prevented by sufficient CcdA.
Have you compared in vitro transcription levels between SP6 and T7 promoters in your pCRII vectors?
No, we have not done in-house comparisons of transcription levels. It is widely known though that T7 polymerase produces more RNA than SP6 (on the order of 10-fold higher).