Fig. 1. Structural properties of nucleic acids. (A) Adenine, guanine, thymine and cytosine bases are connected to the sugar-phosphate backbone via the 1′ sugar carbon. (B) Watson–Crick base pairing: complementary adenine and thymine bases form two hydrogen bonds, whereas guanine and cytosine bases form three hydrogen bonds. (C) π–π stacking interactions between the aromatic nucleobases result in the formation of a stable double-stranded helix.
