Biomolecular Recognition: Analysis of DFS Data - Dynamic Force Spectroscopy and Biomolecular Recognition - page 180

Bell-Evans plot

F * (pN)

In(r e )=9.5

0.16
0.14
0.12
0.10
0.08

0.06
0.04
0.02
0.00 0

50 100 150 200 250
Force (pN)

300 350 400

F = 0

In (loading rate pN/s)

Value proportional to k off

Force (pN)

y = ar + F r =0

0.08 nm

k B T = 4.1 pN.nm

300

50

y

200

x
β

(nm) = k B T/slope

x

100

F = 0

2 3 4 5 6

r F =0

In (loading rate pN/s)

k off = r F= 0 x / k BT 0.025

β

FIGURE 5.8 (See color insert.) Theoretical Bell-Evans plot. The upper graph indicated
how the Bell-Evans plot is built from the most probable rupture forces ( F* ). These forces
are obtained from a Gaussian fit of the force distribution obtained at a given effective loading
rate. The lower graph indicates how to extract the energy barrier properties: the width ( x β in
nm) and the kinetic dissociation rate ( k off in s − 1 ). The width x β is obtained from the slope:
x β k B T/slope. The k off value is obtained by extrapolating the loading rate value at F ∗ = = 0:

k off = r F = 0 x β /k B T.

is still under intense debate and several explanations have been proposed to explain
this apparent nonlinearity of data (Dudko et al. 2003; Williams, 2003; Derenyi et al.
2004; Neuert et al. 2006; Li et al. 2010). In several studies of our group, such as
antibody-hapten (Odorico et al. 2007a; Teulon et al. 2007; Teulon et al. 2008) and
avidin-biotin (Teulon et al. 2011), such nonlinearity has been observed (Figure 5.9).
In these cases, two loading rate regimes were demonstrated to indicate two differ-
ent structural events in the dissociation pathway (Teulon et al. 2008; Teulon et al.