n. 1. A double-ringed, crystalline organic base, C5H4N4, that is the parent compound of a large group of biologically important compounds. 2. Any of a group of substituted derivatives of purine, including the nitrogen bases adenine and guanine, which are components of nucleic acids. Uric acid, caffeine, theobromine, and theophylline are also purines. [German Purin : blend of Latin pūrus, clean; see PURE, and New Latin ūricus, uric (from Greek ouron, urine) + -in, -in, -ine.] |
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