| Human erythrocytes (red blood cells, RBCs) have a biconcave shape with an average diameter of ∼8microm. During their 120-day life span, flowing through the human blood circulation system half a million times, RBCs experience large deformations in order to pass through capillaries as small as 3 microm in diameter. This implies that RBCs have an excellent deformability. If this high deformability is impaired, they either can not fulfill their biological functions or will have a shorter life. The origin of this excellent deformability lies in the structure of the RBC membrane. The RBC membrane has a tri-layer structure, where the spectrin skeletal network is anchored to the lipid bilayer of the cell membrane via physical linkages, such as integral proteins band 3 and ankyrin. The composition and architecture of the membrane play key roles in determining the shape and deformability. In this paper, a new structural micromechanical model is developed to investigate the structure-function relationship of RBC membranes. Unlike previous models on the RBC deformation where a RBC membrane is considered as a continuum one-layer shell with effective properties, this new model includes the detailed RBC membrane structures, such as the tri-layer structure, integral proteins and the connections between these component iv proteins. Simulations of some representative loading cases predict the area dilation modulus, shear modulus and bending stiffness on the same orders of literature values, confirming the accuracy and predictability of the model. Simulations of hereditary spherocytosis show the promise that the model provides a new way to investigate the structure-function relationship of RBCs and how the structure proteins can influence the phenotype of RBCs. |
