AFM and SFM images of proteins binding to a cruciform structure. A) AFM images of PARP-1 binding to supercoiled pUC8F14 plasmid DNA containing a 106 bp inverted repeat. PARP-1 binds to the end of the hairpin arm (white arrow). Images show 300 × 300 nm2 surface areas (reprinted with permission from . B) The interaction between p53CD and supercoiled DNA gives rise to cruciform structures. Shown is an SFM image of complex formed between p53CD and sc pXG(AT)34 plasmid DNA at a molar ratio of 2.5; the complexes were mounted in the presence of 10 mM MgAc2. The scale bars represent 200 nm (reprinted with permission from .