Affiliations: [a] Department of Bioengineering, Division of Mechanical Engineering, University of California, San Diego, La Jolla, California, USA | [b] Department of Applied Mechanics and Engineering Sciences, Division of Mechanical Engineering, University of California, San Diego, La Jolla, California, USA
Note: [*] R. Skalak died August 17, 1997.
Note: [**] Reprint requests to: Dr. Anne Hoger, Department of Applied Mechanics and Engineering Sciences, University of California, San Diego, La Jolla, CA 92093-0411, USA; Fax: 619-534-7078; E-mail: [email protected].
Abstract: Two models of spectrin elasticity are developed and compared to experimental measurements of the red blood cell (RBC) membrane shear modulus through the use of an elastic rmite element model of the RBC membrane 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 coiled-coil which expands by increasing helical pitch. In previous papers, we have computed the relationship between the stiffness of a single spectrin molecule (K) and the shear modulus of a network (µ), and have shown that this behavior is strongly dependent upon network topology. For realistic network models of the RBC membrane skeleton, we equate µ to micropipette measurements of RBCs and predict K for spectrin that is consistent with the coiled-coil molecular model. The value of spectrin 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.
