DNA structure: cations in charge?

Recent X-ray diffraction, NMR spectroscopy and molecular mechanics results suggest that monovalent cations selectively partition into the minor groove of AT-tracts in DNA. These observations are consistent with DNA deformation by electrostatic collapse around areas of uneven cation density. This model predicts the occurrence of known DNA deformations, such as AT-tract bending and changes in the minor-groove width.