Biomedical Engineering Reference
In-Depth Information
(a)
Δ
z
Cantilever
Tip
γ
Biomolecular
partners
O
O
O
O
O
O
OH
OH
O
O
O
OH
O
O
OH
O
OH
OH
OH
OH
OH
OH
OH
OH
C
C
C
C
C
C
C
C
C
C
C
C
Substrate
(b)
F
40
200
C
150
30
100
50
E
65
20
G
0
70 75 80
Piezo displacement (nm)
10
0
A
G
E
d
D
-10
F
L
-20
0
50
100
150
Piezo displacement (nm)
FIGURE 6.2
(a) Sketch of the experimental setup commonly used to investigate by DFS the
unbinding process of two interacting molecules; Δ
z
is the cantilever deflection, and γis the
piezo displacement. Both the partners are immobilized to the surfaces (tip or substrate) by
linkers. (b) Representative experimental force curve (approach and retraction) for a specific
unbinding event of a biomolecular complex. The unbinding event occurs at the jump-off (FG
path); the corresponding unbinding force can be derived from
F
k
cant
d
,where
d
is the
cantilever deflection and
k
cant
is the effective cantilever spring constant.
L
is the unbinding
length given by the piezo displacement encompassing the nonlinear portion of the retraction
curve before the unbinding event. For other details, see the text.
Inset:
A zoom of the region
of the retraction curve corresponding to the unbinding process where the force
F
is given by
F
=
−
k
cant
Δ
z
. The area underlying the force versus piezo displacement (dashed region) pro-
vides the work done by the applied force (see Subsection 6.3.3).
=
−
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