Ultrafiltration of molecules through deposited protein layers.

A naturally deposited protein layer is shown to be highly compressible as witnessed by its resistance to the passage of both water and dissolved molecules. This protein layer can easily be much more important than the underlying membrane. Hydrodynamic methods can be employed to control this protein layer, even to the extreme of its extinction in a continuous flow system. The rejection properties are shown to be a function of both the tracer molecular weight and type. Some of the physical property variations are reviewed for plasma amd serum as a function of protein concentration.