kahe aromaatse tuumaga orgaaniline alus, mh. nukleiinhapetes esineva adeniini ja guaniini struktuurne osa
a crystalline base (...) composed of a pyrimidine ring fused with an imidazole ring (...)
a heterocyclic compound with a fused pyrimidine/imidazole ring. Planar and aromatic in character. The parent compound for the purine bases of nucleic acids.
