The sieving characteristics of bovine serum albumin (BSA) deposits formed during microfiltration were studied using polydisperse dextrans with gel permeation chromatography. The actual sieving coefficients for the BSA deposit were calculated from observed sieving data using a stagnant film model to account for bulk mass transfer effects. The data confirm that the protein deposit is compressible, with the sieving coefficients decreasing with increasing applied pressure. The sieving coefficients and hydraulic permeability were both maximum at the BSA isoelectric point. The sieving coefficients decreased with increasing ionic strength at pH above and below the isoelectric point and were also a function of the ionic composition (Na+ vs Ca2+) of the solvent. These results, in combination with independent measurements of the hydraulic permeability, were used to obtain insights into the pore structure of these BSA deposits. The data suggest that the BSA deposit has a bimodal pore size distribution, with the effective size of these pores determined by the intermolecular electrostatic interactions between BSA molecules in the deposit in combination with conformational changes in the individual BSA molecules.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Surfaces, Coatings and Films
- Colloid and Surface Chemistry