Biomedical Engineering Reference
In-Depth Information
Figure 18. Single-channel traces of OmpF porin from
Escherichia coli
incorporated
in a mercury-supported tethered bilayer lipid micromembrane immersed in aqueous
0.1 M KCl, at different applied potentials measured vs. a Ag/AgCl(3M KCl) refer-
ence electrode. Potentials must be decreased by 50 mV to refer them to the SCE.
199
This micromembrane was also used to investigate the sponta-
neous formation of microdomains, when the distal monolayer is
made up of a lipid mixture. Microdomains are in the gel state when
they consist primarily of a lipid with a transition temperature from
the gel to the liquid crystalline state (also called melting tempera-
ture,
T
m
) higher than room temperature, such as sphingomyelin.
When these microdomains also contain cholesterol to an apprecia-
ble extent, they become fluid, albeit more ordered and tightly
packed than the surrounding lipid matrix, consisting primarily of
lipids with
T
m
lower than room temperature, such as DOPC. The
latter microdomains, called
lipid rafts
, are qualified as
liquid-
ordered
, to distinguish them from the
liquid-disordered
lipid ma-
trix. Lipid rafts are microdomains, composed of glycolipids,
Search WWH ::
Custom Search