Peptide surrogates with RGG Box Sequences. Random peptide libraries were panned on four different mRNA targets. Isolated phage binders from rounds three and four of each pan, were sequenced. Several peptides from each pan showed the presence of the RGG box, a well-defined RNA-binding motif [8, 9]. RGG sequences in each surrogate is in bold and underlined. Peptide surrogate with KH Domain. Panning of the 20-mer random peptide library on target M1 isolated a phage clone containing the sequence VIGxxGxxF which is similar to an RNA-binding motif, the KH motif [8, 9]. The surrogate motif corresponding to the KH domain is in bold and underlined.