Elastic modulus of viral nanotubes.

We report an experimental and theoretical study of the radial elasticity of tobacco mosaic virus (TMV) nanotubes. An atomic force microscope tip is used to apply small radial indentations to deform TMV nanotubes. The initial elastic response of TMV nanotubes can be described by finite-element analysis in 5nm indentation depths and Hertz theory in 1.5nm indentation depths. The derived radial Young's modulus of TMV nanotubes is 0.92+/-0.15GPa from finite-element analysis and 1.0+/-0.2GPa from the Hertz model, which are comparable with the reported axial Young's modulus of 1.1GPa [Falvo, Biophys. J. 72, 1396 (1997)].