This is a short segment of H-DNA, that was solved by NMR. It is composed of a single strand of 30 nulceotides, that is folded to make a triple helix.
This is a spacefilling model, with the phospho-deoxyribose backbone colored blue and the bases colored red.
One triplet of bases is colored violet.
In this view the bases are colored gray, except for a triplet highlighted in black, which is examined in the next view. The direction of the strands can be followed by the changing colors of the backbone. The strand on the left with the dark blue is going "down", while the 2 strands that are green are going "up". The backbone is colored by group, which means that the colors change from blue to green to yellow to orange to red as the strand goes from 5' to 3'.
An isolated view of 3 base-pairing nucleotides. The upper center base is a G, which is making nearly normal hydrogen bonds with the C to the lower right. The third base is also a C, in the opposite orientation of the other C. It is making 2 hydrogen bonds with the central oxygen (red) of the G, resulting in a 4-center hydrogen bond.