1991 Fiscal Year Final Research Report Summary
Dynamical Behaviors of Amphiphilic Molecules in Biological Membranes and Model Membranes As Studied by Deuterium Nuclear Magnetic Resonance
| Project/Area Number |
02650642
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
高分子物性・高分子材料（含機械材料）
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
SASANUMA Yuji Tokyo Institute of Technology Polymer Chemistry, Assistant, 工学部, 助手 (30205877)
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| Co-Investigator(Kenkyū-buntansha) |
ABE Akihiro Tokyo Institute of Technology Polymer Chemistry, Professor, 工学部, 教授 (50114848)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Biomembrane / Molecular Aggregate / Amphiphilic Molecule / Liquid Crystal / n-Alkane / Oxyethylene Chain / Deuterium NMR / Conformational Analysis |
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| Research Abstract |
In this project, we have attempted to perform the conformational analyses of molecular chains constrained in anisotropic environments, using the deuterium NMR data. The scope of this project may be divided into two main parts : the conformational analysis of flexible chains dissolved in nematic solvents and that of amphiphilic molecules incorporated in their aggregates.
Conformational anisotropy of n-alkane chains in nematic environment has been investigated. Experimental values of proton-proton dipolar couplings of n-hexane and deuterium NMR quardrupolar splittings of a series of n-C_2D_<2n+2> (n=5, 6, 7, 8, 10, and 16) were analyzed within the framework of the RIS approximation. As a result, n-alkane chains were shown to be highly anisotropic in the nematic media. The treatment was extended to oxyethylene chains CH_3[OCH_2CH_2]_xOCH_3 (x=1, 2, and 3) dissolved in a liquid crystal. Oxyethylene chains were found to cope with the anisotropic environment by selectively enhancing the trans
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fraction of the C-C bond (s).
The phase transitional behavior of a ternary system of sodium octanoate (C_8Na) - 1-decanol (C_<10>OH) - water has been extensively studied. This is because it exhibits a variety of liquid crystalline phases. We have analyzed the deuterium NMR quadrupolar splitting data observed for C_8Na and C_<10>OH molecules in the hexagonal (E), lambellar (D), and reversed hexagonal (F) phases. The following results were obtained.
C_8Na molecule. The trans fraction (f_t) of the C-C bonds tends to decrease gradually from the head group to the methyl end. The flexibility of the second bond from the polar head is characteristic of the C_8Na molecule in the E phase, while in the D and F phases the bond is rather rigid.
C_<10>OH molecule. In the D phase, the second bond is virtually fixed in the gauche state. The next C-C bond also shows a marked preference for the gauche conformation. In contrast, the f_t values of the other bonds are comparatively large. Then the distance from the head group to the methyl end is nearly equal to that of the C_8Na molecule in its stretched form. This suggests that the lamellae have flat surfaces. On the other hand, in the E and F phases, all the C-C bonds prefer to be in the trans state. The difference in the f_t value between the E and F phases can be found only in the eighth bond. In the E phase were the C_8Na concentration is high, the methyl end of the C_<10>OH chain is easy to move, whereas it is constrained in the F phase. Less
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