Magnesium increases the curvature of duplex DNA that contains dA tracts.

Distinct structural features of DNA, such as the curvature of dA tracts, are important in the recognition, packaging, and regulation of DNA. Physiologically relevant concentrations of magnesium have been found to enhance the curvature of dA tract DNAs, as monitored by solution-state NMR, indicating that the structure of DNA depends on the cations present in solution. A model is presented which accounts for the sequence-dependent effects of magnesium on DNA curvature as well as for the previously known sequence-independent effect on DNA flexibility.