Biophys J, December 1999, p. 3096-3107, Vol. 77, No. 6

The Deformation of Spherical Vesicles with Permeable, Constant-Area Membranes: Application to the Red Blood Cell

Physiological Flow Studies Group, Department of Biological and Medical Systems, Imperial College of Science, Technology and Medicine, London SW7 2BY, U.K.

The deformation of an initially spherical vesicle of radius a with a permeable membrane under extensive forces applied at its poles is calculated as a function of the in-plane shear modulus, H, and the out-of-plane bending modulus, B, using an axisymmetric theory that is valid for large deformations. Suitably nondimensionalized, the results depend upon a single nondimensional parameter, C  a²H/B. For small deformations, the calculated force-polar strain curves are linear and, under these conditions, the slope of the curve determines only C, not the values of H and B separately. Independent determination of H and B from experimental measurements require deformations that are large enough to produce nonlinear behavior. Simple approximations for large and small C are given, which are applied to experimental measurements on red blood cell ghosts that have been made permeable by treatment with saponin.

Biophys J, December 1999, p. 3096-3107, Vol. 77, No. 6
© 1999 by the Biophysical Society   0006-3495/99/12/3096/12  $2.00