2004 Fiscal Year Final Research Report Summary
Hydration property of lipid bilayers composed of sphingomyelins having functional groups forming hydrogen bonds with water molecules.
| Project/Area Number |
15550133
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Functional materials chemistry
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| Research Institution | Okayama University of Science |
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Principal Investigator |
KODAMA Michiko Okayama University of Science, Professor, 理学部, 教授 (40101282)
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| Co-Investigator(Kenkyū-buntansha) |
OHIRA Susumu Okayama Uninersity of Science, Professor, 理学部, 教授 (10194284)
AOKI Hyrouki Okayama University of Science, Associate Professor, 理学部, 助教授 (80248202)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Sphingomyelins / lipid bilayer / lipid microdomein / interdigitation packing / interlamellar water / differential scanning calorimetry / X-ray diffraction |
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| Research Abstract |
Recently, a new concept has been proposed for a lipid bilayer structure in biomembranes. In this connection, much attention of many investigators has been paid to lipid rafts and/or lipid caveolas. In this accord, we started our studies of bilayer packing of sphingomyelins, the most typical sphingophospholipid in biomembranes. Naturally occurring sphingomyelins are characterized by a widely distributed chain-length for the amide-linked fatty acid. In this study, the hydration property of bovine brain sphingomyelin was investigated by a deconvolution method of ice-melting differential scanning calorimetry (DSC) curves of varying water contents. For comparison, N-palmitoylsphingomyelin (C16:0-SM) having a homogeneous amide-linked fatty acid chain was partially synthesized by deacylation-reacylation of naturally occurring brain sphingomyelin and the final product was purified with sillcic acid callum chromatography. For the semisynthetic sphingomyelin, the ice-melting DSC curves were meas
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ured with the same way as that for the naturally occurring brain sphingomyelin. Results obtained in the present study are as follows : (1)The number of nonfreezable interlamellar water molecules is the same, 6 H2O/lipid, for the naturally occurring brain and the semisynthetic sphingomyelins ; (2)The number of freezable interlamellar water molecules is larger by two times for the naturally occurring brain than for the semisynthetic sphingomyelins ; (3)the naturally occurring brain sphingomyelins, which have a longer amide-linked fatty acid chain compared with their sphingosine chain (C-18), pack in an interdigitation form in an intrabilayer, so that the surface of bilayers is not flat, thus, resulting in a concavo-convex surface forming a water pool between bilayers ; (4)The semisynthetic sphingomyelin forms a flat surface between bilayers ; and (5)On the basis of the flat and/or concavo-convex surface, the amount of water molecules incorporated into regions between bilayer becomes different and is larger for the naturally occurring brain sphingomyelin than for the semisynthetic sphingomyelin. Less
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