| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 2000: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1999: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
Archaea including methanogens, extreme halophiles, extreme thermophiles and thermoacidophiles grow under rather extraordinary conditions and have structurally unique membrane lipids to adapt the extreme environments. The lipids are consisted of hydrophobic isoprenoid chains linked to glycerol with the ether bonds, which are well contrast to the ester linkage of the eubacterial and eukaryotic membrane lipids. The most striking feature of the archaeal ether lipid is found in the macrocyclic (36-or72-membered) ring structures. These unusual lipids have been interested in connection with the physicochemical properties based on the lipid bilayer structure. Our interest in these lipids focuses on the biochemical significance of the macrocyclic molecular structures.
Some biophysical properties of synthetic 36-membered archaeal phospholipids were studied using differential scanning calorimetry, electron and optical microscopies, stopped-flow/light scattering and solid-state ^2H-NMR techniques.
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This phospholipid gave a variety of self-organized structures in water, in particular vesucles and tubules. Some specific membrane properties of this archaeal phospholipid were observed : they are in a liquid-crystalline state over a wide temperature range ; the dynamics of their polyprenyl chains is higher than that of n-acyl chains ; the water permeability of the membranes is lower than that of n-acyl phosholipid membranes. It was also found that macrocyclization improves remarkably the barrier proprtlies to water and the membrane stability. This may be related to the adaptation of Methanococcus jannaschii to the extreme conditions of the deep-sea hydrothermal vents.
Further, the self-assembly properties of 72-membered macrocyclic tetraether phosphates, the major phospholipid components of Sulfolobus, Thermoplasma and methanogenic Archaea, which were also synthesized, were observed by phase contrast and fluorescence. The 72-membered macrocyclic dipolar phosphates formed spontaneously vesicles. Less
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