Figure 2.

Energy-minimized models of BfPQ (a) or BQQ (b) intercalated in a triple helix made of Hoogsteen T⋅A×T base triplets. The planar ring system is shown stacked with the T⋅A×T base triplet on its 5′ side (with respect to the purine strand) (Upper) and on its 3′ side (Lower). The Watson strand (pyrimidine strand) is shown in blue, the Crick strand (purine strand) is in red, and the Hoogsteen strand (third strand) is in yellow. The intercalated molecule is colored using standard colors for each atom (C in green, H in white, N in blue, and O in red).