High uptake rate and extremely salt-tolerant behavior of protein adsorption to 900 kDa poly(allylamine)-modified Sepharose FF

This work reports poly(allylamine) of 900 kDa (PAA-L) as a polymeric ligand for protein ion-exchange chromatography. PAA-L-modified Sepharose FF with 9 ionic capacities (ICs) from 80 to 880 mmol/L were prepared and bovine serum albumin adsorption and chromatography were investigated. With increasing IC, protein adsorption capacity increased somewhat in the IC range of 80-420 mmol/L, and then increased twice in the IC range of 420-740 mmol/L, and finally kept unchanged till 880 mmol/L; the uptake rate (De/D0) increased about 14 times (from 0.029 to 0.42) in the IC range of 420-700 mmol/L, and finally kept almost unchanged till 880 mmol/L. The maximum adsorption capacity and uptake rate of the resins reached 336 mg/mL and 0.42, which were 24% and 2.5 times respectively larger than those of 17.5 kDa PAA-grafted resins. The selected PAA-L resin of IC = 740 mmol/L was salt-tolerant up to 750 mmol/L NaCl. The dynamic binding capacity (DBC) of this resin showed a maximum of 142 mg/mL at 350 mmol/L NaCl, and kept over 90 mg/mL in the range of 150-500 mmol/L NaCl. Linear gradient elution on the column of this resin proved high protein recovery (>97%) and stability of the column. Taken together, the results indicate that the PAA-L resin was a promising anion exchanger for high-performance protein chromatography for use at extended ionic strengths.