Kinetic Process of Formation
and Reconstruction of
Small Unilamellar Vesicles Consisting of Long- and Short-Chain Lipids
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Abstract
Whereas the phase separation of normal phospholipids
induces formation
of microdomains on the surface of spherical vesicles, the separation
of a long- and short-chain lipids can induce perforation of small
unilamellar vesicles (SUVs) and transformation into bilayered micelles
(bicelles) because the edges of the bilayers are stabilized by the
short-chain lipid microdomain. In this study, the effect of the phase
separation of lipids on the transformation behavior of SUVs consisting
of a mixture of long- and short-chain lipids was investigated using
small-angle neutron scattering. At the temperature jump from below
to above the chain melting temperature of the long-chain lipid, <i>T</i><sub>c</sub>, bicelles fused together and transformed into
SUVs when their size reached a critical radius. In contrast, a sequential
transformation of small SUVs to small bicelles, small bicelles to
large bicelles, and large bicelles to large SUVs occurred when the
temperature jumped from a value far above <i>T</i><sub>c</sub> to one slightly above <i>T</i><sub>c</sub>. To the best
of my knowledge, this is the first report of such reconstruction of
vesicles. By considering the bending energy of the membrane, the line
tension of the rim, and the perforation due to the phase separation,
the mechanism of the transformation processes was clarified
