3,089 research outputs found
Fluctuations in mixtures of lamellar- and nonlamellar-forming lipids
We consider the role of nonlamellar-forming lipids in biological membranes by
examining fluctuations, within the random phase approximation, of a model
mixture of two lipids, one of which forms lamellar phases while the other forms
inverted hexagonal phases. To determine the extent to which nonlamellar-forming
lipids facilitiate the formation of nonlamellar structures in lipid mixtures,
we examine the fluctuation modes and various correlation functions in the
lamellar phase of the mixture. To highlight the role fluctuations can play, we
focus on the lamellar phase near its limit of stability. Our results indicate
that in the initial stages of the transition, undulations appear in the
lamellae occupied by the tails, and that the nonlamellar-forming lipid
dominates these undulations. The lamellae occupied by the head groups pinch off
to make the tubes of the hexagonal phase. Examination of different correlations
and susceptibilities makes quantitative the dominant role of the
nonlamellar-forming lipids.Comment: 7 figures (better but larger in byte figures are available upon
resuest), submitte
New mechanism of membrane fusion
We have carried out Monte Carlo simulation of the fusion of bilayers of
single chain amphiphiles which show phase behavior similar to that of
biological lipids. The fusion mechanism we observe is very different from the
``stalk'' hypothesis. Stalks do form on the first stage of fusion, but they do
not grow radially to form a hemifused state. Instead, stalk formation
destabilizes the membranes and results in hole formation in the vicinity of the
stalks. When holes in each bilayer nucleate spontaneously next to the same
stalk, an incomplete fusion pore is formed. The fusion process is completed by
propagation of the initial connection, the stalk, along the edges of the
aligned holes.Comment: 4 pages, 3 figure
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