increasing indentation speed

AFM indentation

z

2

810

4

6

0.01 0.1 1

2

810

4

6

app

aren

t el

astic

mod

ulus

, E

(kP

a)

contact time (s)

unswollen

shrunken

decreasing indentation speed

A

B

Supplemental figure 2Effective 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).