title: Nonenzymatic template-directed synthesis on hairpin oligonucleotides.  2.  Templates containing cytidine and guanosine residues.
abstract: We have prepared hairpin oligonucleotides in which a 5'-terminal single-stranded segment contains cytidylate (C) and guanylate (G) residues.  When these hairpin substrates are incubated with a mixture of cytidine 5'-phosphoro(2-methly)imidazolide (2-MeImpC) and guanosine 5'-phosphoro(2-methyl)imidazolide (2-MeImpG), the 5'-terminal segment acts as a template to facilitate sequence-specific addition of G and C residues to the 3'-terminus of the hairpin.  If an isolated G residue is present at the 3'-end of the template strand, it is copied regiospecifically in the presence of 2-MeImpC and 2-MeImpG to give a product containing an isolated C residue linked to its G neighbors by 3'-5'-internucleotide bonds.  However, if only 2-MeImpC is present in the reaction mixture, very little reaction occurs.  Thus, the presence of 2-MeImpG catalyzes the incorporation of C.  If the template strand contains a short sequence of G residues, it is copied in the presence of a mixture of 2-MeImpC and 2-MeImpG.  If only 2-MeImpC is present in the reaction mixture, efficient synthesis occurs to give a final product containing one fewer C residue than the number of G residues in the template.
authors.affiliation: The Salk Institute for Biological Studies, San Diego, California 92186-5800, USA.
authors.forename: T
authors.initials: T
authors.lastname: Wu
authors.forename: L E
authors.initials: LE
authors.lastname: Orgel
mesh_terms: D001483:Base Sequence; D003562:Cytidine / Q000032:analysis*; D003568:Cytidine Monophosphate; D019020:Directed Molecular Evolution; D006151:Guanosine / Q000032:analysis*; D006157:Guanosine Monophosphate / Q000031:analogs & derivatives; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000032:analysis / Q000138:chemical synthesis* / Q000737:chemistry; D013698:Templates, Genetic
chemical_list: D009841:Oligonucleotides; D006151:Guanosine; D003562:Cytidine; C025339:guanosine 5'-phosphoimidazolide; D006157:Guanosine Monophosphate; D003568:Cytidine Monophosphate