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Concentration Fluctuations and Phase Separations in Lipid Bilayers
http://hdl.handle.net/10748/5909
http://hdl.handle.net/10748/5909d161ddf7-ff0e-463c-a8c6-c619f5917f7b
| 名前 / ファイル | ライセンス | アクション |
|---|---|---|
10180-001.pdf (20.4 MB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||
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| 公開日 | 2013-10-16 | |||||
| タイトル | ||||||
| タイトル | Concentration Fluctuations and Phase Separations in Lipid Bilayers | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
| 資源タイプ | thesis | |||||
| 著者 |
Hirose, Yuichi
× Hirose, Yuichi |
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| 著者(ヨミ) |
ヒロセ, ユウイチ
× ヒロセ, ユウイチ |
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| 著者別名 |
廣瀨, 雄一
× 廣瀨, 雄一 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | In this thesis, we proposed a model for lipid bilayers, and discussed the mechanism of the finite-sized domain formation together with the effects of coupling of the two monolayers. A lipid monolayer consisting of saturated lipid, hybrid lipid and cholesterol was considered. We proposed a phenomenological Ginzburg-Landau model in which the coupling of the lipid composition and chain orientational vector field is considered. This coupling arises from the liquid crystalline nature of the hybrid lipid which adjusts its orientational order in the tails to reduce the line tension. As a result, finite-sized domains can be formed. The minimization of the free energy with respect to the vector field yields an effective free energy which is analogous to that of 3D microemulsions (above the transition temperature) and modulated structures (below the transition temperature). Then we considered the model for lipid bilayers comprised of two modulated monolayers which are coupled via interleaflet interactions. The structure and the dynamics of the coupled modulated bilayer are investigated theoretically. We first studied concentration fluctuations in bilayers occurring above the transition temperature. We have calculated the static structure factors, and obtained the bilayer phase diagrams close to the critical temperature. In both monolayers, fluctuations are induced due to the coupling, and the spectrum of the induced fluctuations is determined by the cross correlation of the structure factor. When the two monolayers having different preferred wavenumbers are coupled, the peak height at smaller wavenumber becomes larger, whereas that at a larger wavenumber remains the same. We studied the dynamics of concentration fluctuations by using the coupled time dependent Ginzburg-Landau equations, and calculated the intermediate structure factors of the bilayer. In general, concentration fluctuations exhibit a double-exponential decay. Due to the coupling, the time for the cross over of the two concentration fluctuations appears when the characteristic length scale of each monolayer is different. Then we discussed the phase separation of the coupled modulated bilayers. Within the mean field approximation, we constructed phase diagrams of the bilayer when the two monolayers have the same wavenumber of the modulations. The phase behavior of the bilayers is described by the combinations of the stripe and the hexagonal morphologies. Due to the coupling effect, one of the monolayers induces micro-phase separation in the other monolayer. As the coupling strength increases, the asymmetric phases tend to disappear. By performing numerical simulations, we obtained various phase separated patterns when the two monolayers have different modulations. The obtained patterns are approximately classified into “independent”, “intermediate” and “coincident” cases. The degree of the overlap between the two monolayers is characterized by the inter-leaflet correlation of the local compositions. We showed that the initial growth rates of the most unstable mode are essentially identical to the decay rates of the concentration fluctuations. We showed that the formation of the intermediate structures is related to the stability of the concentration fluctuations occurring above the transition temperature. Using the mechanism of finite-sized domain formation proposed above, we shall also discuss its relation to the biologically relevant context of lipid rafts. |
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| 内容記述 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 首都大学東京, 2011-03-25, 博士（理学） | |||||
| 書誌情報 | p. 1-153, 発行日 2013-10-06 | |||||
| 著者版フラグ | ||||||
| 出版タイプ | VoR | |||||
| 出版タイプResource | http://purl.org/coar/version/c_970fb48d4fbd8a85 | |||||
| 国立国会図書館分類 | ||||||
| 主題Scheme | NDLC | |||||
| 主題 | UT51 | |||||
| 資源タイプ | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | Thesis | |||||
