Affinity adsorption mechanism studies of adsorbents for oligopeptides using model polymer

To understand the principle of designing efficient adsorbents toward specific peptides, adsorption mechanism between oligopeptide VVRGCTWW (VW-8) and alkylamine modified polyacrylamide adsorbents was studied in this article. Linear models of the adsorbents were used to facilitate various measurements except for adsorption experiment. 2D 1H NMR experiments reveal the main binding site of VW-8 to the adsorbents is C-terminal Trp. When peptide CTWW (CW-4) was introduced as the reference, the same binding site was found. However, in adsorption experiments, a remarkable difference was observed with the adsorption capacity of the two peptides. According to isothermal titration calorimetry (ITC) and surface plasmon resonance (SPR) experiments, which are in good agreement with the adsorption results, VW-8 has much higher affinity to the adsorbents than CW-4 and the main driving force in adsorption process is considered to be electrostatic force. However, the unusual affinity adsorption of two oligopeptides on the adsorbents contrasted to the traditional view of electrostatic interaction. With a comprehensive understanding of above experimental results along with computer-aided analysis, we conclude that the difference in conformation of the two peptides has a great impact on the interaction mode and further affects the affinity between the peptides and the adsorbents. This provides valuable information for the further design of synthetic affinity ligand for VW-8.