Norfloxacin treatment causes formation of a sigma arc in undigested DNA. pBR322 DNA was isolated from JH39 under the following conditions:
A. Cleavage conditions (CLV) from untreated cells (UTR).
B. Cleavage conditions from norfloxacin-treated cells (NOR).
C. Resealing conditions (RSL) from norfloxacin-treated cells.
None of the samples were treated with restriction enzymes.
The illustrations indicate the various arcs, where B, bubble (blue); LM, linear monomer; LD, linear dimer; Y, simple-Y (green); TTC, two-tailed circle; S, sigma (red); OC, open circular monomer; CCC, covalently closed circle; CCC RI, covalently closed circle replication intermediate; TopCCC, topoisomers of CCCs; CCC2, dimer of CCC; and CCC/OC, CCC in first dimension, OC in second dimension.