Free-running enzymatic oligonucleotide synthesis for data storage applications

Here we present preliminary results for a method of oligodeoxynucleotide synthesis using terminal deoxynucleotidyl transferase (TdT) to generate mixed base homopolymer runs of defined sequence. In a process we have termed Free-Running Synthesis (FRS), we allow TdT to freely add multiple bases of a given monomer. With this method, homopolymeric runs can be used for writing DNA in a data storage capacity, where a stretch of As, for example, will be read as a single base, and the transitions between successive homopolymer runs encodes information. As a proof-of-concept, we demonstrate homopolymer additions of A, C and T onto the 3 end of a 22 base initiator strand.