Top: the amino acids Lysine (K), Ornithine (Orn) and Diaminobutyric acid (Dab) (top panels) have progressively shorter amino group side chains. Below: PAGE of primer extensions on template TI by the Z RPR over 3 days at 17°C, alone or with indicated peptides of different (a) lengths, (b) concentrations and (c) side chains and chirality. d, EMSA: The fluorescently labeled Z ribozyme (Z-Fluor 647) was incubated with K10 peptide at the indicated concentrations with 22 mM [Mg2+], and resolved on a non-denaturing agarose gel.