Chemistry Reference
In-Depth Information
Table 7.2
(Continued)
Immobilization
strategy
Properties of the binding/
unbinding process
Receptor
Ligand
Reference
LFA-1 in Tcell hybridoma
3A9
ICAM-1
A LFA-1 expressing 3A9 cell was
attached to the end of a cantilever
coated with Con A (successive
incubations with biotin-BSA,
streptavidin and biotin-Con A).
Adhesion between 3A9 cells and ICAM-1 is mainly due to the
formation of LFA-1/ICAM-1 complexes. Mg
2þ
and EGTA
strengthened the interactions.
[138]
The average unbinding forces of individual LFA-1/ICAM-1
complexes calculated at loading rates ranging from 60 to
>
10
4
pN s
1
led to a two-regime force spectrum.
Mg
2þ
-stabilized interactions resulted in higher
unbinding forces in the slow loading regime.
The energy landscape for the dissociation process
consists of two activation barriers. The outer energy barrier
was characterized at slow loading rates by k
d
(0)
A soluble form of ICAM-1 was
adsorbed onto a culture dish
4s
1
(in agreement with the value reported from equilibrium
experiments) and x
b
¼
¼
0.15 nm for resting cells, and k
d
(0)
¼
0.17 s
1
and x
b
¼0.21 nm for Mg
2þ
-activated cells.
The inner activation barrier was characterized at fast
loading rates by k
d
(0)
57 s
1
and x
¼
b
¼
0.018 nm for
40 s
1
and x
b
¼
resting cells, and k
d
(0)
¼
0.024 nm
for Mg
2þ
-activated cells.
