Figure 4.

Guanine–guanine overlap in GG=CC and GC dinucleotides influences divalent metal association (13,14). Simplified representation of the electrostatic potential around bases in GG and GC steps, adapted from ref. 42. The extensive electronegative zone (red) associated with the N7 and O6 atoms of guanine creates a general hotspot for cation association to the major groove. Bp step slide in the positive direction has opposite effects in GG versus GC steps, whereby guanine-guanine overlap is decreased and increased, respectively. The greater charge density for GG steps lacking large positive slide and GC steps having positive slide appears to promote divalent metal binding (green dumbbells).