Nanomechanical properties of α-synuclein amyloid fibrils: a comparative study by nanoindentation, harmonic force microscopy, and Peakforce QNM

Table 1 Overview of results from different methods

Method	Environment	Operation frequency (Hz)	Uncorrected modulus of elasticity (GPa)	Modulus of elasticity (GPa)
Nanoindentation	Liquid	1	-	1.3 ± 0.4
Peakforce QNM	Liquid	10³	1.0 ± 0.2	1.6 ± 0.3
Peakforce QNM	Air	10³	1.3 ± 0.3	2.1 ± 0.5
HarmoniX	Air	10⁵	1.2 ± 0.2	1.9 ± 0.3

Overview of results from different methods under different environmental conditions, 4th column represents the corrected values for modulus of elasticity. This correction is the same as done in the analysis of the indentation measurements; the contact area is changed to a spherical indenter on an infinite cylinder (average fibril height of 9.0 ± 0.4 nm, measured in AFM tapping mode) and is corrected for the finite sample thickness as described in the "Methods" section.