(A) Selections for hydrazide binding peptides included anti-selections with Boc-protected hydrazide resin to remove non-specific peptides (e.g., the red peptide), positive selections with hydrazide-derivatized resin to capture hydrazide interacting peptides (e.g., the blue peptide), and extensive wash steps to remove non-binding peptides (e.g., the purple peptide). (B) The sequences of peptides discussed in the text from selections of phage-displayed peptide libraries, spot synthesis, and chemical synthesis followed by mass spectrometry analysis.