Adsorbent selection by functional group interaction screening for peptide recovery

In order to selectively adsorb small peptides from complex aqueous feeds, selective adsorbents are required. The goal is to first find adsorbents with capacity for triglycine, as triglycine contains all groups common to small peptides. Selectivity studies will follow. Adsorbent selection was based on the interactions available to the triglycine groups and four types of interaction seemed theoretically suitable to provide adsorption of triglycine. These interaction types are hydrogen bonding, electrostatic interaction, π interaction and metal complex formation. This resulted in testing 16 different adsorbent functional groups for adsorption of triglycine under different solution conditions (triglycine only, with 0.2 M NaCl and at pH 8.2). Adsorbents using electrostatic interaction, such as zeolites, anion and cation exchangers, exhibit the strongest interaction, although in the presence of NaCl the distribution coefficient of triglycine is significantly lowered. The adsorbents, when loaded in the H+ form, interacting electrostatically with the peptide amino group show the highest selectivity. Regarding π interaction, several aromatic adsorbents show a weak interaction with triglycine, with low distribution coefficients. Transition metal complex adsorbents (copper(II) and vanadium(IV)oxide) show a weak interaction, limited by pH, or are stripped from the immobilizing ligand by triglycine. The hydrogen bonding adsorbents show no measurable adsorption of triglycine.