Substitution of Adenine by Purine-2,6-diamine Improves the Nonenzymatic Oligomerization of Ribonucleotides on Templates Containing Thymidine

Abstract

A standard DNA sequencer was used as a novel and highly efficient tool to study the template-controlled polymerization of RNA. When labeled with appropriate fluorescent dyes, primers and their extension products could be separated and quantified with excellent sensitivity, reproducibility, and speed. The new technique was applied to compare the template-controlled incorporation of adenosine mononucleotide 2 and its purine-2,6-diamine analogue 3, the latter being capable of forming three H-bonds with thymidine or uridine residues. The rates and yields of incorporation are similar when only one thymidine unit is available for pairing in the template (see template 6 and Table 2). However, on template 7 with two consecutive thymidine residues, purine-2,6-diamine is clearly ahead of adenine (see Table 3). This advantage is most pronounced when the template contains stretches of three and four thymidine moieties (see templates 8 and 9 and Tables 4 and 5, resp.).