LIGHT-SCATTERING OF DNA PLASMIDS CONTAINING REPEATED CURVED INSERTIONS - ANOMALOUS COMPACTION

The plasmid pUC18m containing the insertion of the curved sequence AluI, repeated from one to six times, has been studied by dynamic light scattering. The values of the translational diffusion coefficient D(t) for the whole series of inserted plasmids show oscillating behaviour versus the length of the insertion and two plasmids, those containing two and six AluI adjacent sequences, respectively, display a remarkable compaction. The occurrence of either an interwound linear structure or an interwound branched form for the inserted plasmids is discussed and tested by employing also a ''string of beads'' model that gives values of D(t) in agreement with the observations.