Substitution of adenine by purine-2,6-diamine improves the nonenzymatic oligomerization of ribonucleotides on templates containing thymidine

A standard DNA sequencer was used as a novel and highly efficient tool to s tudy the template-controlled polymerization of RNA. When labeled with appro priate fluorescent dyes, primers and their extension products could be sepa rated and quantified with excellent sensitivity, reproducibility, and speed . The new technique was applied to compare the template-controlled incorpor ation 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 advantag e 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.).