SPECTRIN PROPERTIES AND THE ELASTICITY OF THE RED-BLOOD-CELL MEMBRANESKELETON

Two models of spectrin elasticity are developed and compared to experi mental measurements of the red blood cell (RBC) membrane shear modulus through the use of an elastic finite element model of the RBC membran e skeleton, The two molecular models of spectrin are: (i) An entropic spring-model of spectrin as a flexible chain, This is a model proposed by several previous authors, (ii) An elastic model of a helical coile d-coil which expands by increasing helical pitch, In previous papers, we have computed the relationship between the stiffness of a single sp ectrin molecule (K) and the shear modulus of a network (mu), and have shown that this behavior is strongly dependent upon network topology. For realistic network models of the RBC membrane skeleton, we equate m u to micropipette measurements of RBCs and predict K for spectrin that is consistent with the coiled-coil molecular model, The value of spec trin stiffness derived from the entropic molecular model would need to be at least 30 times greater to match the experimental results. Thus, the conclusion of this study is that a helical coiled-coil model for spectrin is more realistic than a purely entropic model, (C) 1997 Else vier Science Ltd.