A new material concept for the red cell membrane.

The proposition is made that the red cell membrane is a two-dimensional, incompressible material and a general stress-strain law is developed for finite deformations. In the linear form, the character of such a material is analogous to a two-dimensional Mooney material (e.g., rubber), indicating that the molecular structure in the plane of the membrane would consist of long chains, randomly kinked and cross-linked in the natural state. The loose network could be provided by the protein component and the lipid phase could exist interstitially as a liquid bilayer, giving the membrane its two-dimensional incompressibility. The material provides the capability of large deformations exhibited by the discocyte and yet the rigidity associated with the osmotic spherocyte state. It is demonstrated that a membrane of this type can form a sphere at constant area. An illustrative example of the application to single cell discocyte-to-osmotic spherocyte transformations is presented.