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-
Search WWH ::
Custom Search