The erythrocyte's spectrin-actin membrane skeleton is directly shown to be capable of sustaining large, anisotropic strains. Photobleaching of an ~1-μm stripe in rhodamine phalloidin-labeled actin appears stable up to at least 37°C, and is used to demonstrate large in-surface stretching during elastic deformation of the skeleton. Principal extension or stretch ratios of at least ~200% and contractions down to ~40%, both referenced to an essentially undistorted cell, are visually demonstrated in micropipette- imposed deformation. Such anisotropic straining is seen to be consistent at a qualitative level with now classic analyses (Evans. 1973. Biophys. J. 13:941- 954) and is generally nonhomogeneous though axisymmetric down to the submicron scale. Local, direct measurements of stretching prove quantitatively consistent (within ~10%) with integrated estimates that are based simply on a measured relative density distribution of actin. The measurements are also in close agreement with direct computation of mean spectrin chain extension in full statistical mechanical simulations of a coarse-grained network held in a micropipette. Finally, as a cell thermally fragments near ~48°C, the patterned photobleaching demonstrates a destructuring of the surface network in a process that is more readily attributable to transitions in spectrin than in F-actin.
Lee, J. C. M., Wong, D. T., & Discher, D. E. (1999). Direct measures of large, anisotropic strains in deformation of the erythrocyte cytoskeleton. Biophysical Journal, 77(2), 853–864. https://doi.org/10.1016/S0006-3495(99)76937-7