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Molecular dynamics study of bipolar tetraether lipid membranes.

ABSTRACT: Membranes composed of bipolar tetraether lipids have been studied by a series of 25-ns molecular dynamics simulations to understand the microscopic structure and dynamics as well as membrane area elasticity. By comparing macrocyclic and acyclic tetraether and diether archaeal lipids, the effect of tail linkage of the two phytanyl-chained lipids on the membrane properties is elucidated. Tetraether lipids show smaller molecular area and lateral mobility. For the latter, calculated diffusion coefficients are indeed one order-of-magnitude smaller than that of the diether lipid. These two tetraether membranes are alike in many physical properties except for membrane area elasticity. The macrocyclic tetraether membrane shows a higher elastic area expansion modulus than its acyclic counterpart by a factor of three. Free energy profiles of a water molecule crossing the membranes show no major difference in barrier height; however, a significant difference is observed near the membrane center due to the lack of the slip-plane in tetraether membranes.

SUBMITTER: Shinoda W

PROVIDER: S-EPMC1366815 | biostudies-literature | 2005 Nov

REPOSITORIES: biostudies-literature

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Molecular dynamics study of bipolar tetraether lipid membranes.

Shinoda Wataru W Shinoda Keiko K Baba Teruhiko T Mikami Masuhiro M

Biophysical journal 20050812 5

Membranes composed of bipolar tetraether lipids have been studied by a series of 25-ns molecular dynamics simulations to understand the microscopic structure and dynamics as well as membrane area elasticity. By comparing macrocyclic and acyclic tetraether and diether archaeal lipids, the effect of tail linkage of the two phytanyl-chained lipids on the membrane properties is elucidated. Tetraether lipids show smaller molecular area and lateral mobility. For the latter, calculated diffusion coeffi ...[more]

PMID: 16100279

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Project description:Archaeal bipolar tetraether lipids (BTLs) are among the most unusual lipids occurring in nature because of their presumed ability to span the entire membrane to form a monolayer structure. It is believed that because of their unique structural organization and chemical stability, BTLs offer extraordinary adaptation to archaea to thrive in the most extreme milieus. BTLs have also received considerable attention for development of novel membrane-based materials. Despite their fundamental biological significance and biotechnological interests, prior studies on pure BTLs are limited because of the difficulty to extract them in pure form from natural sources or to synthesize them chemically. Here we have utilized chemical synthesis to enable in-depth biophysical investigations on a series of chemically pure glycerol dialkyl glycerol tetraether (GDGT) lipids. The lipids self-assemble to form membrane-bound vesicles encapsulating polar molecules in aqueous media, and reconstitute a functional integral membrane protein. Structural properties of the membranes were characterized via small-angle X-ray scattering (SAXS) and cryogenic electron microscopy (cryo-EM). SAXS studies on bulk aqueous dispersions of GDGT lipids over 10-90 °C revealed lamellar and non-lamellar phases and their transitions. Next we asked whether vesicles overwhelmingly composed of a single GDGT species can undergo fusion as it is difficult to conceptualize such behavior with the assumption that such membranes have a monolayer structure. Interestingly, we observed that GDGT vesicles undergo fusion with influenza virus with lipid mixing kinetics comparable to that with vesicles composed of monopolar phospholipids. Our results suggest that GDGT membranes may consist of regions with a bilayer structure or form bilayer structures transiently which facilitate fusion and thus offer insight into how archaea may perform important physiological functions that require dynamical membrane behavior.

Dataset Information

Molecular dynamics study of bipolar tetraether lipid membranes.

Publications

Molecular dynamics study of bipolar tetraether lipid membranes.

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