Figure 5.
Position-dependent event amplitudes and frequencies. The apparent
working stroke or mean bound level (a) and event
frequency (b) as a function of trap position
X (experimental points linked by dashed curve) for 15
100-s records at a combined trap stiffness of 0.08 pN/nm (no positive
feedback), together with the fitted curve
(X) predicted by the target
function A(U − X +
Xo) (Eqs. 2 and 4).
The abscissa X is determined as the mean displacement of
free periods after event detection in the chosen channel. The smooth
curve in a was obtained by least-squares fitting
(χ2/n = 0.9), giving
S = 8.2 nm, working stroke h = 5.2 nm,
α = 3.05, b = 36.5 nm, and
Xo = 4.4 nm, which sets the phase of
the target function in Eq. 4. The theoretical curve in
b is derived from the fit to the data of a.