We present a study of how kinks, flexible
bends, and flexible joints in the
DNA helix, induced by binding
cis-diamminedichloroplatinum(II) (cis-DDP), transdiamminedichloroplatinum(II) (
trans-DDP), and chlorodiethylenetriammineplatinum(II) (
dien-Pt) to the
DNA, affect the electrophoretic migration of
DNA in
agarose gels. For long
DNA the conformation oscillates between extended and compact states during the migration, as for native
DNA. The presence of flexible joints decreases both the length of time and the step length of the cycles, but in a compensatory manner so that there is no net effect on the mobility. This demonstrates that in some cases mobility alone cannot detect pertubations in the
DNA helix. Kinks and flexible
bends reduce the mobility because they both lead to longer time periods of the cycles. With kinks the reduction is strongest at low fields because at high fields the kinks are straightened out; the steps thus become even longer than for native
DNA. The results suggest that a combination of mobility and orientation measurements on reptating
DNA can be used for distinguishing different kinds of structural alterations in the
DNA.