Biomedical Engineering Reference
In-Depth Information
Figure 17. The solid circles are experimental points on a Zcc vs. Zc plot for a tBLM
in a pH 5.3 aqueous solution of 0.05 M NaH
2
PO
4
at -0.500 V vs. Ag/AgCl(0.1M
KCl) in the absence of SLN (
a
), after incorporation of SLN from its 0.7 PM solu-
tion (
b
), and after subsequent additions of 0.1 (
c
), 0.3 (
d
) and 3 PM ATP (
e
). The
solid curves are fits of a series of four RC meshes to the solid circles. The values of
the resistance,
R
m
, of the lipid bilayer moiety resulting from the fits are: 0.90 (
a
),
0.70 (
b
), 0.53 (
c
), 0.42 (
d
) and 0.35 (
e
) M: cm
2
. The corresponding
C
m
values are
all close to 1 PF cm
-2
. Inset: Conductance, 1/
R
m
, normalized to its maximum value
equated to unity, as a function of the ATP concentration. The error bars denote
standard deviations. The solid curve is a fit of the Michaelis-Menten equation to the
experimental points.
195
in the lumen of the SR at high calcium ion concentrations. It con-
sists of a single D-helix that spans the whole membrane. It was
shown that SLN forms channels highly selective toward small in-
organic anions, such as chloride ion.
194
The resistance of the tBLM
immersed in a 0.05 M aqueous solution of the sodium salt of the
tetravalent anion adenosyntriphosphate (ATP), which does not
permeate biomembranes, does not change upon incorporating
SLN. This indicates that SLN does not allow the translocation of
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