Biomedical Engineering Reference
In-Depth Information
(a)
AgA(15)
gA
-
(13)
10 s
(b)
(c)
AgA(15)
1.0
120
0.8
90
0.6
gA
-
(13)
60
0.4
AgA(15)
30
0.2
gA
-
(13)
0
0.0
0
1
2
3
4
0
200
400
600
800
Current transition / pA
Time / ms
Fig. 5.12 a
A 60 s current traces recorded from a
DC
18
:
1
PC
/
n
-decane bilayer that was doped
with gA
−
(13) and AgA(15) on both sides.
b
The current transition amplitudes for gA
−
(13) and
AgA(15) channels are 1
11 pA.
c
Lifetime histograms (and their exponential
fits) for gA
−
(13) channels and AgA(15) channels (for details see [
13
])
.
95
±
0
.
12 and 3
.
05
±
0
.
(a)
(b)
10000
10000
1000
1000
100
100
10
10
1
1
18
20
22
0.0
0.5
1.0
Acyl chain length
DOPE / (DC
18:1
PC+DOPE)
Fig. 5.13
Average
τ
(gA dimers of AgA(15) or gA-(13)) changes with
d
0
(A. squalene in bilayer
reduces
d
0
over
n
-decane,
τ
increases 35-fold) and
c
0
(B. introducing 1,2-dioleoyl-
sn
-Glycero-3-
phosphoethanolamine (DEPE) into membranes/
n
-decane). For experimental protocols and meth-
ods see [
13
]. Acyl chain lengths 18, 20, and 22 represent bilayer-constructing lipids
DC
18
:
1
PC
,
DC
20
:
1
PC
,and
DC
22
:
1
PC
, respectively. Trans-membrane potential 200 mV. Aqueous conditions
the channel stability increases approximately 13-fold (
τ
AgA
(
15
)
=
149
±
11 ms and
τ
gA
−
(
13
)
=
13). Under
identical conditions, if we replace the PC bilayer by a more negative curvature
bearing DOPE bilayer [
49
] with comparable thickness [
52
], we observe that both
short (
g
A
−
(
11
.
2
±
2
.
1 ms, consequently the ratio
τ
AgA
(
15
)
/τ
gA
−
(
13
)
≈
13
)
) and long (
A
g
A
(
15
)
) gA channels experience almost equal (
∼
2
.
5-
fold) destabilization (see Fig.
5.13
). Here, by using a shorter
g
A
−
(
13
)
monomer
over a longer
A
g
A
(
)
∼
3 Å) hydrophobic
mismatch between the bilayer thickness and the channel length. As a consequence,
15
monomer we have introduced a higher (
Search WWH ::
Custom Search