Deformability and viscoelasticity of human erythrocyte membrane.

The human red cell membrane behaves as a viscoelastic solid material. Since the concentrated haemoglobin solution within the red blood cell is a Newtonian liquid, it is not surprising that the cell's shape (its memory) and its resistance to deformation comes from the elastic, solid membrane. What is surprising is that the cell's resistance to an imposed rate of deformation also comes almost entirely from the membrane. That is, thermodynamically irreversible (rapid) deformation processes are dominated by dissipation in the membrane rather than that in the cytoplasm. Since experimental measurements indicate that the membrane has a characteristic response time of 0.1 s, rapid cellular deformation processes (those that occur within 0.1 s or less) will be strongly resisted by membrane dissipation. Such a situation can occur in the cell filtration experiment when a cell rapidly moves from a large reservoir to a small pore.