Visualisation of plasmid DNA molecules containing T15A15 repeat sequences by atomic force microscopy

P. C. Zhang, J. E. Mitchell, J. R. Smith, J. A. McClellan, S. A. Campbell, S. F. Newbury*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We have used atomic force microscopy to examine the conformations of a DNA plasmid which contains a repeated sequence that is able to form an unusual DNA structure. About 16.8% of plasmid molecules containing the sequence (T15A15)2 adopted a compacted rod-shaped form compared to 89.5% of control molecules without the repeated sequence. The secondary structure- forming sequence therefore changed the conformation of the supercoiled plasmid in the predicted manner. In about 40.2% of plasmids with the (T15A15)2 sequence a short, branched structure was visible. We speculate that this object may represent a non-standard local DNA conformation, and suggest an interpretation of the structure.

Original languageEnglish
Pages (from-to)303-311
Number of pages9
JournalProbe Microscopy
Issue number4
Publication statusPublished - 19 Oct 1999


  • Atomic force microscopy
  • Cruciforms
  • DNA structure
  • Supercoiling Repeated sequences


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