Biomedical Engineering Reference
In-Depth Information
5·10
-9
S and 5·10
-8
S. All current traces are characterized by two
transient currents occurring when switching the light on and off.
Dependent on the chosen conductance value for
G
p
, a certain value
for the stationary current
I
stat
is reached. The maximum current of
the transient when switching the light on (
I
max,on
) is not influenced
by
G
p
, while
I
max,off
decreases with decreasing
G
p
. A change in the
capacitance of the bilayer would evoke significant changes in the
time constants
IJ
on
and
IJ
off
of the transient current. However, as the
bilayer capacitance does not vary considerably during the course
of a photocurrent experiment, we do not show the corresponding
current traces.
(
ii
)
bR Inserted in Pore-Spanning Membranes
In the second scenario, bR was assumed to be reconstituted in-
to pore-suspending membranes (model B) (
Fig. 17 B
). While the
bR-containing membrane is represented by the elements
C
p
,
R
p
and
I
p
, the underlying electrochemical system composed of the buffer-
filled porous alumina substrate is simply represented by an Ohmic
circuit, differential Eq. (18) is derived, which contains the electri-
cal properties of the pore-spanning bilayer,
C
p
and
G
p
, as well as
the conductance
G
el
of the electrolyte including the buffer-filled
pores:
V
§
·
x
p
¨
©
¸
¹
I
1
V
G
V
C
V
G
(18)
p,0
p
m
p
p
p
el
*
V
The conductance of the electrolyte
G
el
and the voltage gener-
ated by the active bR molecules determine the measured pump
current
I
(
t
) (Eq. 19):
I t
()
UG
(19)
p
el
Together with Eq. (19), the solution of differential Eq. (18) yields
the following expression for the light-activated process:
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