4.2. Biomolecules characterization
Before biomolecules immobilization on the functionalized membrane surface, BSA, protein G and lipase were characterized by DLS and electrophoresis measurements. These measurements were mandatory to understand the aggregation phenomena which take place at the solid-liquid interface during the immobilization step. Different reports in literature describe aggregation phenomena in relation to several bulk properties, such as protein concentration, ionic strength, pH and temperature [31]. In this paper, the possible aggregation phenomena were studied in relation to biomolecules concentration and their particle size distribution under the operating conditions used during the immobilization step. Therefore, pH, ionic strength and temperature were fixed at 7, 0.11 and 25 °C, respectively, to carry out the immobilization reaction in mild conditions. For all the biomolecules, the particle size distribution and the native electrophoresis are shown as a function of protein concentration