Protein transport, aggregation, and deposition in membrane pores

Protein deposition on membrane surfaces and in pores can be probed using constant flux filtration experiments and electron microscopy. Protein precipitation near membrane pores are the result of preexisting aggregates, shear enhanced multilayer protein adsorption, and aggregate formation and growth. To determine what hydrodynamic conditions and solution conditions are required to create protein aggregates in situ, fluxes were incrementally raised until a critical threshold was reached and membrane permeability suddenly decreased. Addition of electrolytes was also used to change the protein interactions. Filtration below the critical threshold allows only low amount of protein adsorption to be maintained. Above this threshold, multilayer protein growth is rapid and sufficient to reduce the pore size ten fold. Protein aggregates do not appear to occur until after the rapid rise in transmembrane pressure is observed, and the effect of added electrolyte did not appear until a time period for protein rearrangement during filtration.