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Roles of Sterol Derivatives in Regulating the Properties of Phospholipid Bilayer Systems
journal contribution
posted on 2016-05-09, 00:00 authored by Tham Thi Bui, Keishi Suga, Hiroshi UmakoshiLiposomes are considered
an ideal biomimetic environment and are
potential functional carriers for important molecules such as steroids
and sterols. With respect to the regulation of self-assembly via sterol
insertion, several pathways such as the sterol biosynthesis pathway
are affected by the physicochemical properties of the membranes. However,
the behavior of steroid or sterol molecules (except cholesterol (Chl))
in the self-assembled membranes has not been thoroughly investigated.
In this study, to analyze the fundamental behavior of steroid molecules
in fluid membranes, Chl, lanosterol, and ergosterol were used as representative
sterols in order to clarify how they regulate the physicochemical
properties of 1,2-dioleoyl-sn-glycero-3-phosphocholine
(DOPC) liposomes. Membrane properties such as surface membrane fluidity,
hydrophobicity, surface membrane polarity, inner membrane polarity,
and inner membrane fluidity were investigated using fluorescent probes,
including 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene,
8-anilino-1-naphthalenesulfonic acid, 6-propionyl-2-(dimethylamino)
naphthalene, 6-dodecanoyl-2-dimethylaminonaphthalene, and 1,6-diphenyl-1,3,5-hexatriene.
The results indicated that each sterol derivative could regulate the
membrane properties in different ways. Specifically, Chl successfully
increased the packing of the DOPC/Chl membrane proportional to its
concentration, and lanosterol and ergosterol showed lower efficiencies
in ordering the membrane in hydrophobic regions. Given the different
binding positions of the probes in the membranes, the differences
in membrane properties reflected the relationship between sterol derivatives
and their locations in the membrane.