Mini Conference on Physical Chemistry of Molecular Assembly (Jan. 12, 2019)
Mini Conference on Physical Chemistry of Molecular Assembly
Date: Saturday, January 12, 2019
Place: International House, Tokyo Metropolitan University
Program:
10:30 - 11:15 Ulf Olsson（Lund University）
On the kinetic stability of non-ionic surfactant vesicles
11:15 – 12:00 Tadashi Kato（Tokyo Metropolitan University）
Shear-induced structures in lyotropic phases of nonionic surfactants
13:30 – 14:15 Kazuya Saito（University of Tsukuba）
Liquid crystal study based upon entropy analyses
14:15 – 15:00 Toshiyuki Shikata（Tokyo University of Agriculture and Technology）
Structure and dynamics of chemically modified cellulose ethers in aqueous solution
15:30 – 16:15 Masayuki Imai（Tohoku University）
Morphology of vesicle aggregates
16:15 - 17:00 Shuji Fujii（Hokkaido University）
Rheology of cholesteric blue phase
Abstracts:
Ulf Olsson（Lund University）
On the kinetic stability of non-ionic surfactant vesicles
Surfactant/lipid vesicles are closed bilayer aggregates that are interesting to understand because of their importance in several biological processes. They are often surprisingly stable, partly because of an intriguing stability against Ostwald ripening. If, in addition, fusion events are rare, a vesicle dispersion may retain its size distribution for weeks and months. For this reason, kinetic stability of vesicles is sometimes misinterpreted as thermodynamic stability. Here we will focus on vesicle (membrane) fusion and how its kinetics depends on the surfactant monolayer spontaneous curvature, H0. As model system we have studied the binary water-C10E3 (CH3(CH2)9(OCH2CH2)3OH) system, where H0 of the non-ionic surfactant monolayer can be conveniently tuned by varying the temperature.(We use the convention that curvature away from water is counted as positive, thus, H0 decreases with increasing temperature, H0≈10-3(T0-T) where T0 is the “balanced temperature” where H0=0). In the vicinity of H0=0 (here, T≈26 °C), the surfactant may form two different bilayer phases. A lamellar phase, when H0>0 (T<26 °C) and a sponge phase when H0<0 (T>26 °C). Interestingly, it is found that the lamellar phase can in excess water be fragmented into kinetically stable uni-lamellar vesicles, while the sponge phase can not. Above 26 °C vesicles spontaneously fuse and the rate increases with increasing temperature. The fact that vesicle fusion typically requires H0<0 is consistent with membrane fusion models involving the so-called stalk intermediate structure. Vesicle fusion was also studied with giant uni-lamellar vesicles using rapid confocal laser scanning microscopy.
Tadashi Kato（Tokyo Metropolitan University）
Shear-induced structures in lyotropic phases of nonionic surfactants
In the past two or three decades, much attention has been paid to shear effects on the structure of the lyotropic phase composed of amphiphiles. Among them, the most striking result may be the transition from the lamellar phase to the "onion phase" composed of multilamellar vesicles alone without excess water. Although the onion formation has been found more than 20 years ago and reported for many systems after the first report by the French group, conditions and mechanism for the transition have not yet been fully understood. In this symposium, first I will talk about our discovery of the lamellar-to-onion transition with increasing temperature and also the re-entrant (lamellar-onion-lamellar) transition with temperature variation under a constant shear rate in nonionic surfactant systems based on experiments of rheo-SALS and rheo-SAXS. Then, I will propose a theoretical expression for deformation energies stored in polyhedral onions whose temperature dependence at rest is considered to dominate the re-entrant transition. Finally, I would like to demonstrate that intermediate structures may exist between lamellar and onion not as transient but as steady states depending on temperature and shear rate based on the results of rheo-SAXS experiments.
I will briefly mention another shear effects on the inverse bicontinuous cubic phase of a nonionic surfactant which suggests possibility to control the grain refining and grain growth by changing the amplitude of oscillatory shear without using the transition from other phases.
Kazuya Saito（University of Tsukuba）
Liquid crystal study based upon entropy analyses
Expected roles of entropy, one of most macroscopic quantities, are discussed in the scope of modern material research. Analyses of entropy attributable to alkyl chains attached to hard core of liquid crystalline molecules are utilized as case studies, which give new insights about stabilization of liquid crystalline phases and aggregation modes of layered smectics.
Toshiyuki Shikata（Tokyo University of Agriculture and Technology）
Structure and dynamics of chemically modified cellulose ethers in aqueous solution
Cellulose is abundant natural resources generated by plants. Many kinds of chemically modified celluloses have been supplied. We pay attention to hydroxypropylated and methylated cellulose ethers (HpMCs) which possess high solubility in cold water such as at 10 ºC, but lose it at higher temperatures than e.g. 50 ºC. Here, we report linear viscoelastic behaviours of aqueous solutions of HpMCs and discuss the configuration of HpMC molecules in aqueous solution.
Series of HpMC samples, which have the average substitution numbers of hydroxypropyl and methyl groups of 1.9 and 0.25, respectively, for 3 hydroxy groups in each glucose unit and have the weight average molecular weights: Mw/103=20, 75, 150, 215 and 300, were dissolved into pure water over a wide concentration (c) range. Dynamic viscoelastic measurements were carried out for aqueous HpMC systems, and storage and loss moduli, G’ and G”, were determined in a frequency range: ω=10-2−102 s-1 at 10 ºC.
Although the viscoelasticity of the systems became pronounced with increasing concentrations and molecular weights as usually observed in polymeric solutions, the determined viscoelastic parameters did not show that HpMC molecules behave as flexible polymeric chains. The c and Mw dependencies of the average modulus and relaxation time for the system were fairly corresponds to the theoretical prediction for rigid rod like particles.
Masayuki Imai（Tohoku University）
Morphology of vesicle aggregates
In this study we show the morphology transitions of adhering giant unilamellar vesicles (GUVs) induced by the changing the reduced volume of vesicles. The GUV is homogeneous single component vesicle composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). First we adhered two spherical GUVs by controlling the inter-vesicle interactions. Thereafter we decreased the reduced volume of the adhering vesicles by using thermal expansion of membranes. Depending on the reduced volume, the doublet deformed its shape and showed a unique morphology transitions. We describe the observed morphology transitions based on the competition among the bending elasticity, the surface tension, and the adhesion.
Shuji Fujii（Hokkaido University）
Rheology of cholesteric blue phase
Structure of the cholesteric blue phase is characterized by ordered alignment of the disclination lines. Numerical simulations have suggested that the alignement of the ordered disclination networks is disturbed by shearing, and break and annihilation of the disclination lines under shear induces anomalous rheological behavior. In this talk, experimental rheology on the cholesteric blue phase is presented, and we discuss how the blue phase rheology is correlated with the disclination networks.
２０１８年１２月１４日 Prof. Amy Shen
日時：２０１８年１２月１４日（金） １６：２０〜１７：５０
場所：首都大学東京 １１号館１０３号室
講師：Prof. Amy Shen (OIST)
題目：Novel nano- and microfabrication techniques for micro/nanofluidics and biosensing applications
要旨：Micro/nanofluidics has emerged in recent years as a powerful method of manipulating fluids at small length-scales. To highlight their versatility and great potentials, I present 3 micro/nanofluidic platforms with applications in enhanced micromixing, nanofluidic immunoassay, and localized surface plasmon resonance (LSPR) sensing.
(a) Enhanced micro-mixing: we present a summary of our recent results examining flow instabilities arising in stagnation point flows generated in cross-slot-type geometries. Our studies span purely inertial flows of simple Newtonian fluids, through inertio-elastic flows of highly dilute polymer solutions, to purely-elastic instabilities in more concentrated polymeric systems [1,2].
(b) Making Waves in a Total Capture Nanofluidic Immunoassay: understanding nanoconfinement phenomena is necessary to develop nanofluidic technology platforms. We demonstrate a convection limited nanofluidic immunoassay that achieves total capture of a target analyte, and an apparent shift in the reaction equilibrium due to nanoconfinement [3].
(c) We introduce a new nanofabrication procedure for localized surface plasmon resonance (LSPR) sensing with applications in sensitive bioassays and long term live-cell biosensing [4.5].
References:
[1] N. Burshtein, K Zografos, A. Q. Shen, R. J. Poole, and S. J. Haward, Inertioelastic flow instability at a stagnation point, Physical Review X, 7, 041039-18, 2017.
[2] S. J. Haward, R. J.Poole, M. A. Alves, P. J. Oliveira, N. Goldenfeld, A. Q. Shen, Tricritical spiral vortex instability in cross-slot flow, Physical Review E, 93: 031101, 2016.
[3] C. J. Galvin, K. Shirai, A. Rahmani, K. Masaya, and A. Q. Shen, Total Capture, Convection-Limited Nanofluidic Immunoassays Exhibiting Nanoconfinement Effects, Analytical Chemistry, 2018. DOI: 10.1021/acs.analchem.7b04664
[4] N. Bhalla, S. Sathish, A. Sinha, and A. Q. Shen, Large-scale nanophotonic structures for long-term monitoring of cell proliferation, Advanced Biosystems, 1700258, 2018.
[5] N. Bhalla, S. Sathish, C. J. Galvin, R. A. Campbell, A. Sinha, and A. Q. Shen, Plasma assisted large-scale nanoassembly of metal insulator bioplasmonic mushrooms, ACS Applied Materials & Interfaces, 2017.
２０１８年９月２５日 植松祐輝氏
日時：２０１８年９月２５日（火） １４：００〜１７：００（基礎＋研究の二部構成）
場所：首都大学東京 ８号館３００号室
講師：植松祐輝氏 (九州大学)
題目：空気水界面における不純物効果
要旨：まず、界面物理化学の大きな問題の一つである空気水界面の電荷問題について紹介し、界面の熱力学を使って電解質溶液の表面張力とジョーンズ・レイ効果（表面張力の塩濃度に関する極小）について説明する。次にポアソン・ボルツマン方程式を用いた空気水界面の一次元平均場理論を使って電解質溶液の表面張力変化の計算をし、微量の電荷を帯びた不純物により、ジョーンズ・レイ効果を定量的に説明できることを示す [1]。この理論の帰結として、意図的にイオン性界面活性剤を加えると、表面張力の極小の大きさをコントロールできることがわかる。そこで、意図的にカチオン性界面活性剤を加え、NaCl溶液の表面張力測定の実験をした。その結果、マイクロモーラー程度の界面活性剤の添加で、NaCl濃度10mMから100mM程度に極小が現れた。イオンの表面活性パラメータはすべて実験結果と矛盾ない理論となっており、ジョーンズ・レイ効果がコントロールできないほど希薄な不純物により引き起こされていた可能性が非常に高い。このことを踏まえて、空気水界面の電荷問題に戻ると、この不純物が重要な役割を果たしていると考えられる。そこで、まったく同じモデルで濡れ膜の分離圧と疎水性表面のゼータ電位の実験結果の理論的説明を試みる。最後に、不純物の正体と、関連するであろう空気水界面の他の異常性について展望する。
[1] Yuki Uematsu, Douwe J. Bonthuis, and Roland R. Netz, J. Phys. Chem. Lett. 9, 189–193 (2018).
２０１８年９月１１日 Hsuan-Yi Chen氏
日時：２０１８年９月１１日（火） １１：００〜１２：３０
場所：首都大学東京 ８号館３０４号室
講師：Hsuan-Yi Chen氏 (National Central University, Taiwan)
題目：Minimal model for epithelia steady state
要旨：The steady state of a epithelium is maintained by carefully regulated cell division, cell differentiation and cell apoptosis. The result is a robust spatial distribution of niches of proliferative cells and precisely regulated tissue size. We propose a minimal general model using least assumptions from empirical observations and conservation laws to study the properties of the steady states in epithelia. In a stratified epithelium we also compare the degree of stratification of two cell lineage models and compare to experimental observation on mouse olfactory epithelia. The main results are (i) for a stratified steady state to exist, the cells in a tissue need to know their distance from the basal membrane by some long range interaction such as mechanical stress or morphogen density, (ii) interaction due to direct cell-cell contacts tend to drive the tissue to a homogeneous state, therefore when both long-range interaction and interactions due to direct cell-cell contact are present, it is possible for the tissue to have two steady states. The relation between multistability and wound healing, tissue development are discussed. At the end of this talk, further generalization of our model to other types of epithlia will be discussed.
２０１８年９月３日 Yael Avni氏
日時：２０１８年９月３日（月） １１：００〜１２：３０
場所：首都大学東京 ８号館３０４号室
講師：Yael Avni氏 (Tel Aviv University, Israel)
題目：Charge-regulated macro-ions in ionic solutions
要旨：Macromolecules in aqueous environment often carry a self-regulating and non-constant charge due to dissociation/association of their ionic groups. The degree of dissociation/association depends on the local electrostatic potential, allowing for Charge-Regulation (CR) to occur, and modifying the present electrostatic interactions. In this talk, I will review the mean-field formalism used to describe CR phenomena, applying it first to the well-studied case of two interacting CR surfaces. I will then present an extension of the theory, which describes a system of many mobile CR macro-ions, and explore the resulting interesting behavior by studying the effective screening length [1].
[1] Y. Avni, D. Andelman, T. Markovich and R. Podgornik, Soft Matter 14, 6058 (2018).
