今井研究室

[これからのセミナー・研究会]

・---

[過去のセミナー・研究会]

講師：Sasa Svetina（Institute of Biophysics, Faculty of Medicine, University of Ljubljana and Jozef. Stefan Institute, Ljubljana, Slovenia）　集中講義　セミナー
集中講義

日時：2009年11月2日 16:30～
場所：お茶の水女子大学理学部１号館２４１室（定員　３０名）　[交通案内][構内図]

タイトル：Vesicle shape behavior and the origin of cellular life
要旨： Vesicles such as lipid vesicles are macroscopic entities involving a thin flexible membrane that separates their inner from the outer aqueous medium. A vesicle attains the shape that at given vesicle volume, membrane area and membrane asymmetry corresponds to the minimum of the membrane bending energy. Here we shall reveal the shape phase diagram which was predicted theoretically and subsequently confirmed experimentally. Classification of vesicle shapes with respect to their symmetry will be presented, together with describing the causes of vesicle budding. Then it will be shown how vesicle shapes depend on membrane inclusions. Finally, we shall discuss possible relationship between vesicle shape behavior and cellular processes that involve changes of membrane conformation, e.g. exocytosis, endocytosis and cytokinesis. It will be invoked that complex mechanisms causing shape transformations of cells and cellular organelles are the result of an evolutionary upgrading of processes occurring also at the level of simple vesicles. The idea will be substantiated by presenting a simple model of vesicle self- reproduction. It will be shown that this process can occur only at fulfilling a certain relationship between vesicle intrinsic properties and properties of the outside medium. Such a relationship implies a selectivity principle and indicates that a kind of Darwinian evolution process may have acted already at the level of simple vesicles.

講師：Dr. Primoz Ziherl（Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia）　集中講義　セミナー
集中講義

日時：平成21 年 7月21日(火)10時40分～14時30分／7月22日(火)10時40分～16時00分
場所：お茶の水女子大学理学部１号館2階241号室　[交通案内][構内図]

タイトル：Elasticity of phospholipid membranes
要旨： After a brief introduction of the phenomenology of amphiphile self-assembly, we focus on the phospholipid bilayer membrane as the basic structure that defines a cell and a cell organelle as a compartment. We first discuss the free energy of a membrane and its curvature elasticity from a microscopic perspective. Then we turn to the continuum description of membrane elasticity and we derive the Canham-Helfrich elastic energy consisting of the bending and the saddle-splay term. We also describe the spontaneous curvature, the bilayer couple, and the area-difference-elasticity model of closed bilayer membranes. Finally, we review selected theoretical vesicle shapes, compare them to experimental results, and discuss their relevance as models of simple animal cells.
References：
D. Boal, Mechanics of the Cell (Cambridge University Press, Cambridge, 2002), chapters 5, 6, and 7.
A. Ben-Shaul, Molecular Theory of Chain Packing, Elasticity and Lipid-Protein Interaction in Lipid Bilayers, in Structure and Dynamics of Membranes, R. Lipowsky and E. Sackmann (eds.) (North-Holland, Amsterdam, 1995).
U. Seifert and R. Lipowsky, Morphology of Vesicles, in Structure and Dynamics of Membranes, R. Lipowsky and E. Sackmann (eds.) (North-Holland, Amsterdam, 1995).
J. N. Israelachvili, Intermembrane and Surface Forces (Academic Press, London, 1991).

セミナー

日時：平成21 年 7月21日(火)　15時00分～
場所：お茶の水女子大学理学部１号館2階241号室　[交通案内][構内図]

タイトル：Mechanical models of simple cell aggregates
要旨： Many aspects of the shape of animal cell aggregates and tissues can be interpreted in terms of a theoretical model that includes membrane bending elasticity and intermembrane attraction. Using a combination of numerical and variational results, we show that this approach reproduces the morphology of linear aggregates of erythrocytes as well as the structure of epithelia and endothelia of several animals as examples of sheet-like and bulk cell aggregates, respectively. The insight provided suggests that the anisotropic, reduced-dimensionality aggregates are stabilized by the competition of membrane elasticity and adhesion. We discuss the implications of these results for two key stages of embryogenesis: i) formation of the blastula as a curved two-dimensional cell aggregate and ii) gastrulation whereby the invaginated part of the blastula exhibits directional growth. The theoretical framework based on membrane elasticity and adhesion can also be used to study the shape of the Golgi apparatus. We focus on the role of the non-trivial topology of the cisternae laden with openings called fenestrations, which may be responsible for the large effective bending rigidity of the cisternae.

講師：菅原正教授（東京大学大学院　総合文化研究科）　集中講義　セミナー
集中講義

日時：平成21 年 6月16日(火)10時40分～16時00分／6月17日(火)10時40分～16時00分
場所：お茶の水女子大学理学部１号館2階241号室　[交通案内][構内図]

タイトル：膜分子自己集合体の物理・化学
要旨：両親媒性分子が水中で形成する自己集合体の中でも主にジャイアントベシクルを対象として、膜分子のダイナミクスが引き起こす形態変化、自律的運動性、ベシクル内自己複製ダイナミクス、自己生産ダイナミクスとその集団計測などについて論ずる。

セミナー

日時：平成21 年 6月17日(火)　15時00分～
場所：お茶の水女子大学理学部１号館2階241号室　[交通案内][構内図]

タイトル：ソフトマターがつなぐ生命と無生命
要旨：我々は、この10年間、生命システムの示す生き物らしさ”自己複製する、自発的に動く、恒常性を示す、進化する”を理解するアプローチの一つとして、素性の知れた有機分子をシステムとして組み上げ、そこに、生命システムと相同のダイナミクスを見出す研究を展開してきた。両親媒性分子(膜分子)を水に溶かすと、ベシクルという袋状の構造体ができるが、この膜分子に工夫を加えることで、ベシクル型自己複製系を創ることに成功した。さらに、ベシクルの膜内で、鋳型DNAの複製も出来ることがわかった。このような研究を遂行する中で偶然見つかった、分子集合体が自発的に示すダイナミクスについても併せ紹介する。ソフトマターの典型である両親媒性分子システムで、いかにして生命システムの本質に迫れるかについて議論したい。

脂質膜ベシクルセミナー

日時：平成20年 3月21日(金)　15時～17時
場所：お茶の水女子大学理学部3号館２Ｆ会議室　[交通案内][構内案内]

講演者[1]：Dr. Sarah L. Keller(University of Washington,USA)
タイトル：Liquid domains in Lipid Membranes
要旨：We study giant lipid vesicles as a model of cell membranes. Much of our past work has focused on finding the minimum number of lipid types required to create liquid domains in a vesicle. We find that liquid domains appear on the surface of vesicles containing at minimum a high melting temperature lipid, a low melting temperature lipid, and cholesterol. These three components separate into two phases. This presents an interesting question of which components are in which phases,and in what amounts. I will review our work using fluorescence microscopy and NMR to determine the lipid composition of the liquid domains vs. the background, and to map phase diagrams and to quantify tie-lines. Our work in the past year has focused on two new projects. We study how domains in one leaflet of the membrane are induced in an opposite, initially uniform leaflet, or if the uniform leaflet suppresses domain formation in the first leaflet. We also study how composition fluctuations in the membrane vary with temperature near a miscibility critical point, and find a fit with the prediction of the 2D Ising model.

講演者[2]：Dr. Rumiana Dimova(Max Planck Institute of Colloids and Interfaces,Germany)
タイトル：Fusion of model lipid membranes: timescales and some applications
要旨：Membrane fusion is a vital process as it is involved in many cellular functions and stages of cell life like import of foodstuffs and export of waste, signaling between nerve cells, fertilization, and virus infection. In both, life sciences and bioengineering, controlled membrane fusion has many possible applications, such as drug delivery, gene transfer, chemical microreactors, or synthesis of nanomaterials. Fusion dynamics is intriguing but microscopy observations with time resolution higher than several milliseconds have not been achieved until recently. Using micromanipulation of giant unilamellar vesicles as model membranes one can directly observe membrane fusion. We induce the fusion of giant lipid vesicles in a controlled manner and monitor the fusion dynamics with a temporal resolution of 50 microseconds; see Proc. Natl. Acad. Sci. USA. 103, 15841�15846 (2006). Two different approaches of inducing directed fusion are used. In the first one, we employ synthetic fusogenic molecules incorporated in the membranes. As a second approach we use electrofusion. Some aspects on the effects of electric fields on vesicles will be presented. For both fusion protocols, the opening of the fusion necks is very fast, with an average expansion velocity of centimeters per second. This velocity indicates that the initial formation of a single fusion neck can be completed in a few hundred nanoseconds.

講師：Prof. Frederic Nallet　セミナー

日時：平成19 年 10月31日(水)　15時00分～
場所：お茶の水女子大学理学部１号館2階241号室　[交通案内][構内図]

講演者：Frederic Nallet教授　(Centre de Recherche Paul-Pascal, France)
タイトル：Defect-mediated phase transitions in the DMPC/C12E5 lamellar Pase
要旨： We study a lyotropic system, consisting of a lecithin (DMPC) and a non-ionic surfactant (C12E5) in water. The system exhibits a lamellar-to-nematic or, with appropriately chosen chiral components, a lamellar-to-cholesteric phase transition upon lowering the temperature. The structural properties of the lamellar phase have been studied by polarised light microscopy, small-angle x-ray scattering and freeze-fracture transmission electron microscopy, while fluorescence recovery after photo-bleaching on a confocal microscope is used for dynamic properties. All the observations are consistently described in terms of topological melting, with the proliferation of dislocations leading to at least one, and possibly two intermediate phases above the nematic (or cholesteric) low-temperature phase. Such a system could be of interest in drug-delivery applications using multi-lamellar vesicles.

講師：土井正男先生　セミナー

日時：平成18 年 7月31日(月)～8月 1日(火)　10時00分～
場所：お茶の水女子大学理学部１号館2階201号室　[交通案内][構内図]

講演者：土井正男教授　（東京大学）
タイトル：ゲルのダイナミクス
要旨：ゲルは弾性体のなかに溶媒が浸潤したものである。ゲルにおいては、弾性的な変形と溶媒の運動がカップルしている。レモンをしぼると果汁がでる、波の打ち寄せる砂浜をあるくと足のまわりが乾いて見える、などは弾性変形と溶媒の流れがカップルした現象である。この講義では、このような現象を記述する連続体的モデルについて述べる。
講義で使用したパワーポイント(pdf形式) 1 , 2 , 3

パワーポイントの改定版(pdf形式,10M) 改定版
レポート
内容：講義中で登場した論文又はゲルに関する事柄をA4用紙2枚程度にまとめること
提出：８月末までに今井研究室(理学部1号館139室)に用紙で提出すること

3rd Ochanomizu University International Workshop on Soft Matter Physics (OUSMP Ⅲ)

中止になりました。

Prof. Otto Glatterセミナー

日時：平成17 年 3月22日(火)　15時30分～
場所：お茶の水女子大学理学部１号館2階201号室　[交通案内][構内図]

講演者：Otto Glatter　教授　(University of Graz, Austria) email: otto.glatter@uni-graz.at
タイトル：Reversible Phase Transition of Nano-Structured Lipid Systems in Confined Geometry
要旨：Aqueous sub-micron sized dispersions of the binary monolinolein/water system, which are stabilized by means of a polymer, internally possess a nano-structure. Taking this as our starting point, we were able to demonstrate for the first time that this internal structure can be tuned bytemperature in a reversible way. Upon increasing the temperature, this internal structureundergoes a transition from cubic via hexagonal to a fluid isotropic, so-called L2-phase and viceversa. This means that upon cooling there is also a back transformation of the internal structure from L2 via hexagonal to cubic. We found that these internal structures depend only on the current temperature and there is no hysteresis or other change after such a heating/cooling cycle. Intriguingly, in addition to the structural changes in topology, the particles exhibit a “breathing mode”: they expel (take up) water to (from) the aqueous continuous phase when increasing (decreasing) the temperature in a reversible way. At each temperature, the internal structures of the dispersed particles correspond very well to those in non-dispersed binary monolinolein-water phase with excess water. This proves that they actually remain in thermodynamic equilibrium even though the particles themselves are kinetically stabilized. They are internally self-assembled (“ISASOMES”). Recently we were able to incorporate also additional oil into the system and thereby controlling the resulting structures at a given temperature. This finally led, for the first time, to the formation of emulisified micro-emulsions.

Toledano教授、D. Beysens博士セミナー

日：　平成17年年2月 24日(木)
時：13時30分～15時45分

場所：　お茶の水女子大学理学部1号館2階201号室　[交通案内][構内図]
（〒112-8610 東京都文京区大塚2-1-1）

講演者：P. Toledano教授　University of Picardie, Amiens (France)
　　　　D. Beysens博士　CEA-ESEME, ESPCI-PMMH (France)

プログラム

13：30-14：30　P. Toledano教授　" Theory of Reconstructive PhaseTransitions"
14：30-14：45　break
14：45-15：45　D. Beysens博士　" Phase transition on a superhydrophobic substrate"

連絡先

Toledano教授に関する問い合わせ；
今井正幸, お茶の水女子大学理学部物理学科,電話: 03-5978-5316 (直通), 電子メール: imai@phys.ocha.ac.jp
D. Beysens博士に関する問い合わせ；
奥村剛, お茶の水女子大学理学部物理学科, 電話＆FAX: 03-5978-5321 (直通), 電子メール: okumura@phys.ocha.ac.jp

Prof. Ligoureセミナー

日：平成16年12月03日（金）
時：15:00-16:00
場所：お茶の水女子大学理学部1号館2階201室（第１講義室）
タイトル：Sedimentation of strongly attractive particle gels

第５回関東ソフトマター研究会

日：平成16年8月20日（金）
時：10：00-
場所：お茶の水女子大学理学部3号館
詳細：HP参照

寺田弥生氏（東北大学流体科学研究所助手）セミナー

タイトル：希薄高荷電コロイド分散系の相図とダイナミクス
日：平成16年1月15日（木）
時間：13時30分
場所：お茶の水女子大学理学部1号館2階241室
内容：近年、高荷電コロイド分散系では、同符号の荷電コロイド同士が凝集する現象などに興味が持たれ、様々な研究がなされている。その中で、最近、徳山は荷電コロイドと対イオンとの間に働くクーロン相互作用と多体効果から荷電コロイド同士に働く徳山有効引力ポテンシャルを提案した [1]。　そこで、この有効ポテンシャルを用いて、ブラウン動力学法による荷電コロイド分散系の計算機実験を行った。その結果、非常にコロイドの濃度が希薄な領域にもかかわらず、コロイドや対イオンの電荷数を変化させることによって、気体相に加えて、液滴相と固滴が見つかった [2]。さらに、固滴相と液滴相でのドロプレットの成長過程を調べたところ、固滴相と液滴相では、異なる成長則に従うことがわかった。
[1] M. Tokuyama: Phys. Rev. E　vol. 59, R2550 (1999)
[2] Y. Terada and M. Tokuyama: Physica A, (in Press)