Figure 5. Proof-of-principle chemical selection.

A degenerate library of DNA genes lacking one of the 1546 codons (C37) was mixed at 383 parts to 1 part with a short gene encoding C37 and missing one coding (VD) and one constant (ZD) position. The DNA solution was split over the C anticodon array and then blotted onto an anion-exchange chemistry array. The amine “synthetic nucleus” on the DNA in each well was acylated with chloroacetic acid. Propylamine was coupled to the DNA molecules in 383 of the wells, while the DNA in well G1 (corresponsing to the C37′ anticodon) was coupled to biotin hydrazide. The resulting peptoid-DNA conjugates were eluted, pooled and selected for binding to streptavidin-coated magnetic beads. The isolated material was amplified and analyzed on a 3% agarose gel, revealing a 13,000-fold enrichment of the sequence encoding the biotin monomer.