E. Hayakawa et al., CHANGE OF MOTION AND LOCALIZATION OF CHOLESTEROL MOLECULE DURING L-ALPHA-H-II TRANSITION, Biophysical journal, 74(2), 1998, pp. 892-898
Formation of the inverted hexagonal (H-II) phase from the lamellar (L-
alpha) phase of bovine brain-extracted phosphatidylcholine (BBPC) and
phosphatidylethanolamine (BBPE) was investigated using P-31-NMR with o
r without cholesterol. When the ratio of BBPC to BBPE was 1:1, the H-I
I formation was observed in the presence of 33 mol% cholesterol (i.e.,
BBPC:BBPE:cholesterol = 1:1:1) at 47 degrees C. The fraction of the H
-II phase in the BBPC/BBPE/cholesterol system could be controlled by t
he addition of dioleoylglycerol. The change of molecular motion of cho
lesterol affected by the H-II formation was measured at various ratios
of the L-alpha to H-II phase with the time-resolved fluorescence depo
larization method, using dehydroergosterol as a fluorescent probe. It
is observed that the motion of cholesterol became vigorous in the mixt
ure state of the L-alpha, and the H-II phases compared to that in the
L-alpha or the H-II phase only. These facts show that cholesterol has
the strong ability to induce the H-II phase, probably by special molec
ular motion, which includes change of its location from the headgroup
area to the acyl-chain area.