Figure 4.
Succession of configurations illustrating the rigid-body motions that transform the associations of G and A between different pairing modes. Images of adenine oriented with respect to a common coordinate frame on guanine. Structures generated with 3DNA24 using the average rigid-body parameters reported in Table 1. Base pairs color-coded by interaction mode (Figures 1-3), with the minor (II) substates of m±W and m−M pairs noted by lighter hues. Pathways connecting (a) antiparallel m−m, m−WI, m−WII, W−W, m−MI, m−MII states; (b) parallel m+m, m+WII, m+WI, m+M states. Note the counterclockwise rotation of ribose C1′ atoms (darkened spheres) along the top-to-bottom transformation of antiparallel pairs and the clockwise rotation along the corresponding progression of parallel pairs. Hydrogen bonds between base atoms depicted by thin dashed lines.