To exploit efficient adsorbents for removing middle molecular peptides containing DFLAE (DE5, a typical peptide sequence accumulated in uremic serum) sequence by hemoperfusion, we designed and synthesized three affinity adsorbents (C1-Zn^2+, C2-Zn^2+ and C3-Zn^2+) that could have high affinity to DE5. Subsequently, we evaluated the corresponding adsorption ability of each adsorbent by static adsorption experiments and isothermal titration calorimetry (ITC). The results showed that C1-Zn^2+ bad the best adsorption ability to DE5-containing peptides and the adsorption capacity for DE5 was 8.52 mg/g. By changing the adsorption conditions, the adsorption mechanism was elucidated. The main driving force of the adsorption is metal-carboxyl coordination and the hydrophobic force affords the cooperative effect. It is expected that our present work can provide basic understanding for the design of adsorbents with high affinity and selectivity towards oligopeptides.
LI PingLinFU LiXueQIAO YiTaoZHAO JianXinWANG Wei&YUAN Zhi
Linear polymers bearing the same functional groups as their corresponding adsorbents could be used as models to study the adsorption behaviors.However,the relationships between the data from model study and real adsorption have not been fully interpreted.In this work,three adsorbent(CP1-Zn2+,CP2-Zn2+ and CP3-Zn2+) and their corresponding linear models(P1-Zn2+,P2-Zn2+ and P3-Zn2+) were synthesized.The affinity constants(Ka) between these models and target peptide DFLAE(DE5) were obtained by isothermal titration calorimetry(ITC).Adsorption capacities and adsorption affinities were carried out by static adsorption and adsorption isotherm.The qualitative and quantitative relationships between affinity constants from model study and the real adsorption data were explored.This study was significant to bridge the model study with the real adsorption.
QIAO YiTao LI PingLin ZHAO JianXin WANG Wei YUAN Zhi
A surface plasmon resonance (SPR) technique was developed as an online screening method to identify effective adsorbents for the peptide NH2-Cys-Thr-Trp-Trp-COOH (CW-4). To validate the SPR technique, several linear polymers containing amino acid residues were synthesized as models of their corresponding adsorbents. SPR screening of all the linear polymers demonstrated that the linear polymer containing phenylalanine residues (PPhe) exhibited the highest affinity for CW-4 among the polymers tested. In accordance with the screening results from SPR, the adsorbent containing phenylalanine (APhe) exhibited the highest adsorption capacity for CW-4. An interesting observation was that the amounts of CW-4 adsorbed on 3 adsorbents were quite small, even though both SPR and isothermal titration calorimetry (ITC) experiments indicated the presence of interactions between CW-4 and the three polymers. A kinetic analysis performed using SPR technology suggested such a phenomenon was ascribed to the poor stability of the CW-4/polymer complexes; that is, CW-4 associates with the polymers quickly, but it also dissociated quickly. The combined results suggested that SPR was a promising tool to identify the optimal adsorbent for peptides, analyze the interactions contributing to adsorption and explain adsorption phenomena using polymer models.
