High-resolution plasma protein fractionation using ultrafiltration

The effects of pH and ionic strength (salt concentration) on transmission of single protein human serum albumin (HSA) and human immunoglobulins (HIgG) through a 100 kDa molecular weight cut-off (MWCO) polyethersulfone membrane have been studied using a pulsed sample injection technique. Experimental results obtained clearly demonstrate the effectiveness of changing solution pH and ionic strength optimisation for selective transmission of HSA or HIgG. These also demonstrate the usefulness of pulsed injection experimental technique for the optimization of ultrafiltration processes. A pulse input carrier phase ultrafiltration (CPUF) was employed to fractionate a binary protein mixture of HSA and HIgG at low NaCl concentration, showing that it is feasible to separate the binary protein at optimised conditions.

The pulsed sample injection technique can facilitate rapid determination of conditions optimal for UF and protein fractionation and provide a more complete picture about the behavior of protein transmission under different solution environments. This technique requires only small quantities of protein. Using pulse input CPUF, a selectivity of more than 300 has been observed for fractionation of HSA/HIgG with the Omega 100 kDa PES membrane at pH 4.7 and a salt (NaCl) concentration of 1.5 mM. Acknowledgment This work is supported by the Engineering and Physics Science Research Council (EPSRC), UK. The authors would like to thank Dr. Q.Y. Li of the Scottish national Blood Transfusion Service, UK, for donating the HIgG used in the experiments.