[too rz duh fawrs, -fohrs; French toor duh fawrs] /ËtÊÉrz dÉ ËfÉrs, -ËfoÊrs; French tur dÉ ËfÉrs/ (Show IPA) 1. an exceptional achievement by an artist, author, or the like, that is unlikely to be equaled by that person or anyone else; stroke of genius: Herman Melville's Moby Dick was a tour de force. 2. a particularly adroit maneuver or technique in handling a difficult situation:
edit Nucleobases. Purines make up two of the four nucleobases in DNA and RNA: adenine and guanine. Pyramidines make up the other bases in DNA and RNA: cytosine, thymine (in DNA) and uracil (in RNA).
â¢ Purine has a pyrimidine ring and an imidazole ring. â¢ Adenine and guanine are the purine derivative present in nucleic acids whereas cytosine, uracil and thymine are the pyrimidine derivatives present in the nucleic acids. â¢ Purines have more intermolecular interactions than pyrimidines.hey have the following structures. In nucleic acids, purine groups make hydrogen bonds with complementary pyrimidine bases. That is adenine makes hydrogen bonds with thymine and guanine makes hydrogen bonds with cytosine. IN RNA, since thymine is absent, adenine makes hydrogen bonds with uracil.