Pseudoknots were designed using custom-made software, which ensued that the codon usage was appropriate for expression in E. coli and that the sequences were likely to fold into the correct structure as determined by pknotsRG (33) . Hence, the resulting sequences are artificial pseudoknot-like structures and there is always a risk that the structure does not fold as anticipated. The selected sequences were synthesized by GeneScript and were subsequently inserted into plasmid OFX302 [containing slippery sequence, spacer and pseudoknot (25) ] between HindIII and ApaI restriction sites.