ENERGY-DISSIPATION KINETICS FOR PROTEIN AND ANTIBODY-ANTIGEN ADSORPTION UNDER SHEAR OSCILLATION ON A QUARTZ-CRYSTAL MICROBALANCE

A new quartz crystal microbalance instrument, allowing simultaneous fr equency (f) and dissipation factor (D) measurements, has been used to study protein adsorption kinetics by measuring time-resolved data of b oth the D-factor, measuring the energy dissipation due to the added ov erlayer, and the f-shift, measuring the effective mass load on the sen sor. Four model proteins (myoglobin, hemoglobin, human serum albumin ( HSA), ferritin) and one antibody-antigen reaction (antibody against HS A) were studied on a hydrophobic, methyl-terminated (-CH3) gold surfac e. In all five cases system-specific, positive D-shifts and negative f -shifts were observed, revealing different adsorption phases. The D-fa ctor measurements provide new information about protein adsorption and improve the interpretation of the frequency shift in terms of mass up take. Possible mechanisms. for the adlayer-induced dissipation are dis cussed.