ADSORBED LAYERS OF HUMAN SERUM-ALBUMIN INVESTIGATED BY THE SURFACE FORCE TECHNIQUE

The interactions between human serum albumin (HSA) layers adsorbed from solution onto muscovite mica have been investigated by means of surface force measurements. The effects of varying the ionic strength and the serum albumin concentration have been studied at pH = 5.5. The negatively charged protein cannot be desorbed from the negatively charged mica surface by dilution with water. The thickness of the (compressed) adsorbed layer is small compared to the dimension of HSA, except at the highest concentration used (1 mg/ml). Hence, under a compressive load at low packing densities the protein conformation on the surface is different from that in bulk solution. No adhesion was observed when the amount adsorbed was large. However, an attractive interaction occurs at low and intermediate surface packing densities. At high ionic strength (0.15 M NaCl) some HSA molecules adsorb end-on to the surface.