Mechanical properties of crescentin and its eukaryotic counterparts in vitro.

Elasticity, G′, and phase angle, δ, were measured using a cone-and-plate strain-controlled rheometer, which applied oscillatory shear deformations of small 1%-amplitude and a frequency of 1 rad/s. Rheological parameters G′ and δ were measured at steady state, i.e. after these parameters had reached a steady state after onset of assembly. The phase angle measures the delay in the response of the stress induced in the filament networks by the rheometer. An elastic solid shows no delay (phase angle of 0°); a viscous liquid without elasticity like glycerol shows a maximum delay (phase angle of 90°). The mechanical resilience of cytoskeleton proteins is defined as the shear amplitude at which the elastic modulus started to fall (e.g. Fig. 3). Protein concentration for measurements of G′, δ, and resilience was 1 mg/ml. For the range of concentrations for the concentration-dependent elasticity, G′(c), see text and references.