A comparison study between polymeric ligand and monomeric ligand for oligopeptide adsorption.

This work aimed to compare two types of affinity ligands, i.e. polymeric and monomeric ligands, by investigating their adsorption affinity, capacity and selectivity to oligopeptide. The peptide NH(2)-VVRGCTWW-COOH (VW-8) was chosen as the target adsorbate, while histidine (His), aspartic acid (Asp), and leucine (Leu) were selected as the ligands, respectively. For each kind of ligand, both monomeric (M) and polymeric (P) forms were introduced onto the Sepharose matrix respectively to obtain the corresponding adsorbents. Both affinity tests using isothermal titration calorimetry (ITC) and adsorption capacities using static adsorption experiments indicated that the adsorbents with polymeric ligands (MX-P) exhibited better adsorption ability for VW-8 than the adsorbents with monomeric ligands (MX-M). In particular, the MX-PHis exhibited its affinity constant of 2.39 × 10(6) M(-1) and its adsorption capacity of 77.4 mg/g for VW-8, which was approximately 8-10 times higher than that of MX-MHis. Such distinct adsorption abilities between polymeric and monomeric ligands were interpreted based on nuclear magnetic resonance (NMR) and ITC data, and the results indicated that such better characters of polymeric ligands were ascribed to their good flexibility which facilitated the cooperative effects as well as the accessibility of ligands to the peptide. Additionally, the selective adsorption experiments indicated that all the adsorbents with polymeric ligands exhibited good selectivity to the peptide VW-8.