Originally a combination of a (nucleic acid) purine or pyrimidine, one sugar (usually ribose or deoxyribose), and a phosphoric group; by extension, any compound containing a heterocyclic compound bound to a phosphorylated sugar by an N-glycosyl link (e.g., adenosine monophosphate, NAD+). For individual n.'s see specific names.mononucleotide;
cyclic n. a nucleoside monophosphate in which the phosphoryl group is linked twice to the sugar moiety; e.g., adenosine 3´,5´-cyclic monophosphate (cAMP).
flavin n. See flavin.
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