Visual evaluation of the library at different screening conditions, including
sequences identified from a 100 μM PLP reaction. (a) When incubated
with 10 mM PLP, the majority of the library members turned red, confirming
that at standard reaction conditions many sequences exhibit at least some
degree of conversion. (b) Using 1 mM PLP, fewer library members turned red,
and most showed a lighter color. (c) Using only 100 μM PLP, most of
the sequences showed no conversion (as evidenced by the colorless beads) but
a small number of red beads were still identified. (d) The sequences
corresponding to the red beads at 100 μM PLP revealed AXK and AKX as
the predominant N-terminal motifs.