AFM Indentation of Nuclei Elasticity: Effective Measurement Methods

1. Supplemental figure 2 Effective elasticity measured by AFM indentation of immobilized nuclei. Nuclei in the unswollen, swollen, and shrunken state were allowed to adhere to and spread on poly-l-lysine coated glass (A). A sphere-tipped AFM cantilever was then used to indent a given nucleus, yielding force-indentation curves. A height-corrected Hertz sphere model was fit to each curve, giving an apparent elastic modulus for the nucleus (B). Tip indentation speed was increased over 2 orders of magnitude to vary the AFM probe’s contact time with the nuclei (black squares). Tip indentation speed was then reduced to determine the reversibility (i.e. – no plastic deformation) of AFM indentation (gray squares). A  z AFM indentation B 10 unswollen 8 6 4 2 increasing indentation speed decreasing indentation speed apparent elastic modulus, E (kPa) 10 shrunken 8 6 4 2 0.01 0.1 1 contact time (s)