Maxime Clusel sent me a link to this paper, “Elasticity of Globular Proteins Measured from the ac Susceptibility,” by Y Wang and G Zocchi.  It details a beautiful experiment in which they measure the linear visco-elastic response of glubular proteins and short DNA molecules.  They use the molecules to tether electrically charged gold nanoparticles to a surface and then excite the molecules by applying an electric potential and inducing movement of the nanoparticles.  The resulting change in particle-surface distance (i.e. the amount that the molecule has stretched) is measured by evanescent wave scattering, which ends up with a resolution on the average extension of many molecules of ~ 0.1 Å!  Incredible!