[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).
In addition to adenine and guanine, a group of chemical compounds called purine base include hypoxanthine (6-oxypurine), xanthine (2,6-dioxypurine), uric acid (2,6,8-trioxypurine), and theobromine (3,7-dimethyl xanthine). Theophylline and caffeine are a member of methylated purine family. Adenosine Triphosphate (ATP) : a nucleotide composed of adenine, the sugar ribose, and three phosphate groups; involved in energy metabolism and required for RNA synthesis.