1989 Fiscal Year Final Research Report Summary
Polymorphism and Phase Transition Behaviors of Lipids and Related Long-chain Compounds Containing Unsaturated Acyl Chains
| Project/Area Number |
63470010
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
構造化学
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| Research Institution | OSAKA UNIVERSITY |
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Principal Investigator |
KOBAYASHI Masamichi Osaka University, Faculty of Science, Professor, 理学部, 教授 (40028147)
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| Co-Investigator(Kenkyū-buntansha) |
KANEKO Fumitoshi Osaka University, Faculty of Science, Research Associate, 理学部, 助手 (70214468)
TASHIRO Kohji Osaka University, Faculty of Science, Research Associate, 理学部, 助手 (60171691)
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| Project Period (FY) |
1988 – 1989
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| Keywords | unsaturated fatty acids / unsaturated glycerides / polymorphism / polytypism / phase transition / molecular motion / vibrational spectroscopy / X-ray structural analysis |
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| Research Abstract |
Phospholipids and glycerides are important materials as main constituents of the cell membranes, bearing the biological functional activities. Naturally occurring lipid compounds consist of long acyl chains joined to a polar group and nearly half of the acyl chains are occupied by unsaturated ones which give the membranes fluidity and promote the biological activity.
The aim of this research project is to elucidate the molecular mechanism of the characteristic function of the unsaturated acyl chains. Polymorphic structures in relation to the thermodynamic stability and the behavior of solid-state phase transition for a series of cis-monounsaturated fatty acids as well as cis-unsaturated triglycerides were investigated by means of IR and Raman spectroscopy, X-ray analysis, DSC, etc.
Unsaturated fatty acids exhibit very complicated polymorphism. The crystal structures of the gamma and gamma_1 phases of erucic acid and the low-melting and high-melting phases of petroselinic acid were fully determined. The molecular and crystal structures of the alpha and alpha_1 phases of erucic acid were also studied. Conformation of the olefine group, subcell structure of the polymethylene chain segments, polytypic structure of the bimolecular layers, and chain mobility have been clarified as the keynote for understanding the physicochemical properties and the phase transition behaviors of the unsaturated lipid compounds. The order-disorder type thermoreversible gamma <double arrow>alpha and gamma_1<double arrow>alpha_1 transitions occurring in cis-monounsaturated fatty acids were recognized as a partial melting process of the methylsided alkyl chains constituting the lamellar interface. The polymorphism of triblycerides whose 2-position is occupied by an oleoyl chain have been investigated. It has been revealed that a large molecular displacement takes place in a coherent fashion during solid-state transitions in saturated fatty acids.
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