Purine
From Eterna Wiki
A purine is an organic compound consisting of the fusion of two aromatic rings, an hexagonal one (pyrimidine) and a pentagonal one (imidazole).
There are many naturally occurring purines. Two of the five bases in nucleic acids, adenine and guanine, are purines. In RNA, these bases form hydrogen bonds with their complementary pyrimidines uracil and cytosine.
Other purines
Other notable purines are hypoxanthine, xanthine, theobromine, caffeine, uric acid and isoguanine.