The direct determination of protein concentration for proteins immobilized on polystyrene microspheres

In this paper we show how the Lowry method, designed for the determination of proteins in solution, can be used for the determination of proteins immobilized on the surface of microspheres (for protein concentrations higher than 10 micrograms/ml). Measurements were made for human serum albumin (HSA) and for immunoglobulins [rabbit immunoglobulins--antibodies against human fibrinogen (IgGF) and against fragment D of human fibrinogen (IgGFgD)] immobilized on the surface of polystyrene microspheres.