Figure 3.

The repetitive units composed of four adenine bases in homo-(dA) duplexes. The arrows between base pairs indicate the ‘symmetry’ property of the H-bonds. Single arrows are non-symmetric H-bonds and double arrows are symmetric H-bonds, respectively. (The directions of the arrows are arbitrary.) ‘A’ indicates an anti base-sugar conformation and ‘S’ indicates a syn base-sugar conformation. The nomenclature chosen to denote each homo-(dA) duplex contains multiple pieces of information about the structure. The information is separated by hyphens, the first part denotes the type of the base pair, and the second and the third parts denote whether the base pairs are alternating and whether the base pairs are reversed, respectively. ^aBase-sugar conformation, ^bSymmetricity of the H-bond(s), ^cAlternating H-bond, ^dAlternating base-sugar conformation, ^eDuplexes belonging to the category.