Measurement of the extensional and flexural rigidities of a subcellular structure: marginal bands isolated from erythrocytes of the newt.

The elastic properties of marginal band, a microtubular structure isolated from the newt (notophthalmus viridescens) have been measured. Bands were isolated using Triton X-100 and pepsin at pH 6.8 according to the method of Cohen (1978). Isolated bands were manipulated with a glass microhook in a buffer-filled chamber under the microscope. Single bands were stretched between the hook and a thin glass fiber. The fiber was calibrated so that the force on the band could be calculated from the displacement of the fiber. The data pairs of force versus band deflection were analyzed according to the theoretical work of Libai and Simmonds (1983) to obtain the flexural and extensional rigidities of the band. Band dimensions calculated from the data were consistent with microscopically determined values. The average flexural rigidity of the bands (EI) was 5.3 X 10(-13) dyn X cm2 and the average extensional rigidity (EA) was 0.017 dyn. Compared to the cell membrane, the marginal band is nearly inextensible and has a much greater resistance to bending, indicating that the band makes an important contribution to the deformability of the circulating cell.