Coarse-Grained Molecular Dynamics Simulation of a Red Blood Cell

attened and depressed in the center, with a dumbbell-shaped cross section. Its average diameter is about 8 m. The membrane of RBCs is composed of a lipid bilayer, cholesterol molecules, transmembrane proteins, and an underlying cytoskeleton, which is tethered to the membrane. The cytoskeleton is built mainly by spectrin proteins, which consist of intertwined �� and �� polypeptide chains running anti-parallel to one another. [1] The human erythrocyte can squeeze through narrow capillaries much smaller than its own diameter and then recover its biconcave shape. Its remarkable mechanical properties originate from the unique architecture of its cell membrane, while the properties of a cell membrane’s deformation are attributed largely to its cytoskeleton. [2] Studies of the deformation of the human RBC have been going on for many years. Interest in the mechanical properties of the RBC can be attributed to several factors. [3] First, erythrocytes in mammals are non-nucleated. This means that they possess a relatively simple subcellular structure. With a nearly two-dimensional spectrin cytoskeleton network, these cells make it possible for us to establish an analytical and computational model. [4] Second, the progression and consequences of some hereditary hemolytic disorders such as spherocytosis, ovalocytosis, sickle cell disease, [5−8] and infectious diseases such as malaria [8,9] are strongly linked to the deformation characteristics of erythrocytes. It is of great importance therefore to understand the mechanical properties of erythrocytes. Many experimental, theoretical, and computational studies are motivated by Refs. [10{ 13] and aimed at the explanation of the deformation characteristics of RBCs. In this Letter, we use the worm-like chain (WLC) theory and a coarse-grained molecular dynamics (CGMD) model to develop a spectrin-based network model that is intermediate between the continuum and atomic scales. Simulation results show that the average bending modulus and the persistence length are very important factors of the mechanical properties of RBCs.