The purine structure consists of a pyrimidine ring (positions 1 to 6) fused to an imidazole ring (positions 7 to 9). Adenine and guanine, the two most common purines in DNA and RNA, share this core ...

The phosphate groups are closely packed about the axis of the molecule, with the pentose residues surrounding them, and the purine and pyrimidine groups projecting radially, their planes being ...

This diagram depicts the chemical structure of pyrimidine, a six-membered aromatic ring with two nitrogen atoms at positions 1 and 3 (highlighted in blue). The remaining positions are occupied by ...