Nonenzymatic oligomerization reactions on templates containing inosinic acid or diaminopurine nucleotide residues

The template-directed oligomerization of nucleoside-5'-phosphoro-2-methyl i midazolides on standard oligonucleotide templates has been studied extensiv ely. 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 s trongly inhibitory and prevents any incorporation of C into internal positi ons 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 oligomeriza tion of A or I through A-I base pairing. The significance of these results for prebiotic chemistry is discussed.