Biomedical Engineering Reference
In-Depth Information
OmpF in
o
-POE
o
-POE
10 6
10 5
10 4
10 3
rinsing
rinsing
0
500
1000
1500
2000
t
/ s
Figure 12. Time-resolved change of the magnitude of the impedance | Z | at a fixed
frequency of 1 Hz of a pore-suspending membrane after the addition of o -POE with
a final concentration of 0.0002 % ( v/v ) and rinsing with buffer, followed by the
addition of OmpF dissolved in o -POE to the cis side, leading to a final protein con-
centration of 0.5 nM in 0.0002 % ( v/v ) o -POE. Electrolyte: 0.1 M NaCl. 35
membrane, demonstrating that the proteins are functionally insert-
ed.
Based on this result, we raised the question of how many
OmpF molecules contribute to the decrease in membrane re-
sistance. In order to quantify this, the change in conductivity ǻ G is
calculated from the bilayer resistance before ( R 0 ) and after ( R m ) the
insertion of OmpF. According to Eq. (5):
11
'
G
G
G
(5)
m0
RR
m0
ǻ G equals 19.7 μS. Taking the conductivity of 535 pS of a
single OmpF trimer in 0.1 M NaCl into account, 18 approximately
10 6 proteins cause the monitored decrease in bilayer resistance.
This calculation demonstrates that a significant number of mole-
 
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