Fabrication Of Polymer-grafted Anion Exchangers For Protein Chromatography

The research about ion exchange chromatography mainly focused on the adsorption and mass transfer.In order to further reveal the adsorption and mass transfer of proteins onto polymer-grafted ion-exchange chromatography resin,dimethylamino propyl acrylamide(DMAPAA)and 2-aminoethyl methacrylate(AEM)were initiated to polymerized on the surface of Sepharose FF separately by atom transfer radical polymerization(ATRP),and the AEM-grafted resin with an ion exchange capacity(IC)of 513 mmol/L was modified with sodium acetate.A variety of anion exchange resins were prepared and their physical properties and adsorption performance were systematically studied.Firstly,18 DMAPAA-grafted anion exchangers of four grafting densities and various chain lengths were prepared and systematically characterized.It was found that an optimal IC existed at each grafting density to present a maximal capacity or uptake rate.Of the four optimal-IC resins,FF-Br3-p DMAPAA587 showed the highest capacity(377 mg/m L),but the protein uptake rate was smaller than the resin of a similar ionic capacity but lower grafting density(FF-Br2-p DMAPAA592).Consequently,the dynamic binding capacity(DBC)of FF-Br2-p DMAPAA592 was higher than that of FF-Br3-p DMAPAA587 at flow velocities higher than 450 cm/h.Moreover,FF-Br3-p DMAPAA587 showed higher adsorption capacity than FF-Br2-p DMAPAA592 at 0-150 mmol/L Na Cl,leading to its higher DBC values as compared to FF-Br2-p DMAPAA592 in the same salt concentration range.Taken together,DMAPAA-grafted resins of different grafting densities would be useful for purifying feedstocks of different ionic strengths.Then,a series of AEM-grafted resin with different chain lengths and sodium acetate-modified AEM-grafted resin were prepared.It was found that the static adsorption capacity increased with the increase of the p AEM chain length(IC),but the uptake rate decreased after reaching a peak value at IC?300 mmol/L.It is considered that the excess charged ligands caused uptake rate decline.In order to eliminate this effect,the AEM-grafted resin with the highest IC was neutralized with sodium acetate to prepare 3 AEM-grafted resin of reduced charge density.It's found that when the charge density was gradually reduced,the adsorption capacity was unchanged-then-decreased,but the uptake rate was always increased.The protein adsorption results showed that FF-p AEM513-R339 was more sensitive to IS.Chromatographic results showed that FF-p AEM513-R339 was most suitable for high-flow rate protein chromatography at low salt concentrations.This study shows that both grafting density and chain length significantly affect the protein adsorption performance of the grafted resin.Reduction of the charge on the resin could increase the uptake rate,but it will lead to the decrease on the salt tolerance of the resin.