As noted in the 2'-deoxycytidine structure on the left, the numbering of the sugar carbons makes use of primed numbers to distinguish them from the heterocyclic base sites. The base components are colored green, and the sugar is black. Structures and names for these nucleosides will be displayed above by clicking on the heterocyclic base diagram. They are all polyfunctional bases, and may exist in tautomeric forms.īase-catalyzed hydrolysis of DNA gave four nucleoside products, which proved to be N-glycosides of 2'-deoxyribose combined with the heterocyclic amines. Each has at least one N-H site at which an organic substituent may be attached. The two monocyclic bases shown here are classified as pyrimidines, and the two bicyclic bases are purines. The acidic character of the nucleic acids was attributed to the phosphoric acid moiety. Analogous nucleic acids in which the sugar component is ribose are termed ribonucleic acids, abbreviated RNA. To reflect the unusual sugar component, chromosomal nucleic acids are called deoxyribonucleic acids, abbreviated DNA. Complete hydrolysis of chromosomal nucleic acids gave inorganic phosphate, 2-deoxyribose (a previously unknown sugar) and four different heterocyclic bases (shown in the following diagram). Unlike proteins, nucleic acids contained no sulfur. Elemental analysis of nucleic acids showed the presence of phosphorus, in addition to the usual C, H, N & O. In the 1920's nucleic acids were found to be major components of chromosomes, small gene-carrying bodies in the nuclei of complex cells. A few years later, Miescher separated nuclein into protein and nucleic acid components. He reported finding a weakly acidic substance of unknown function in the nuclei of human white blood cells, and named this material "nuclein". The first isolation of what we now refer to as DNA was accomplished by Johann Friedrich Miescher circa 1870.
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