Simulation of shape changes and adhesion phenomena in an elastic model of erythrocytes.

We present simulations of a model of a closed membrane that shares important features with erythrocytes: resistance to bending and shear, membrane asymmetry, and an osmotic pressure difference between the interior and exterior. By varying a few parameters we obtain several realistic (e.g., biconcave and cup-like) shapes whose fluctuations, analogous to flickering of erythrocytes, and mutual transformations are studied in thermal equilibrium. Our simulations form a basis for quantitative analysis of recent experiments done on erythrocytes and artificial bilayer vesicles. They also predict effects that could be observed in experiments such as an "'unbinding" phenomenon, i.e., a separation of adhering cells induced by thermal fluctuations.