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Table 7.2 Single-molecule force spectroscopy experiments investigating ligand
-
receptor interactions in living cells.
Immobilization
strategy
Properties of the binding/
unbinding process
Receptor
Ligand
Reference
Enzyme-linked
a 5 b 1 integrin in
endothelial cells
Fibronectin
Fibronectin was cross-linked
onto the AFM probe with PEG
Cells were grown on
gelatin-coated dishes
The mean unbinding force of a single
[174]
integrin bound was about 34 pN at a
retraction speed of 0.8
bronectin
-
ms 1 . After histamine treatment,
the probability of adhesion increased and the mean
adhesion force increased to about 39 pN.
m
a 5 b 1 integrin
in
Fibronectin
(fragment FN7-
10)
A K562 cell was attached to
the end of an AFM cantilever
The mean unbinding force was 69 pN at loading rates of
about 2000 pN s 1 .
[175]
K562 cells
FN7-10 was adsorbed on Petri
dishes.
Force spectra were obtained at loading rates between
10 and 5
10 4 pN s 1 , which revealed a two-regime
unbinding dynamics. Bell model parameters were k d (0)
·
¼
0.13 s 1 and x b ¼
0.41 nm at slow loading rates (outer
energy barrier), and k d (0)¼33.5 s 1 and x b ¼0.09 nm at
fast loading rates (inner energy barrier). Mutations to the
synergy site of
0.85 s 1 and x
bronectin yielded k d (0)
¼
b ¼
25.0 s 1 and x b ¼
0.10 nm at fast loading rates. Deletion of the RGD loop of
0.37 nm at slow loading rates, and k d (0)
¼
0.13 s 1
bronectin resulted in a single regime with k d (0)
¼
and x
0.46 nm.
Activation of integrin by TS2/16 antibody involved interactions
with both the RGD and synergy sites of
b ¼
bronectin.
 
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