inosinic-acid and cytidine-5--phospho-2-methylimidazolide

The template-directed oligomerization of nucleoside-5'-phosphoro-2-methyl imidazolides on standard oligonucleotide templates has been studied extensively. Here, we describe experiments with templates in which inosinic acid (I) is substituted for guanylic acid, or 2,6-diaminopurine nucleotide (D) for adenylic acid. We find that the substitution of I for G in a template is strongly inhibitory and prevents any incorporation of C into internal positions in the oligomeric products of the reaction. The substitution of D for A, on the contrary, leads to increased incorporation of U into the products. We found no evidence for the template-directed facilitation of oligomerization of A or I through A-I base pairing. The significance of these results for prebiotic chemistry is discussed.

Topics: 2-Aminopurine; Adenine; Adenosine; Adenosine Monophosphate; Base Pairing; Cytidine Monophosphate; Cytosine; DNA Primers; Evolution, Chemical; Evolution, Molecular; Exobiology; Guanine; Inosine Monophosphate; RNA; Templates, Genetic; Uracil; Uridine Monophosphate