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Membrane fluctuation and static structure-dependent ordering of stacked structures in phospholipid bilayers.


脂質膜同士の膜間距離はいくつかの相互作用のバランスによって決まる。特に中性のリン脂質の場合、引力はvan der Waals相互作用、斥力は水和斥力と呼ばれる短距離斥力と膜の揺らぎに起因した長距離斥力(ヘルフリッヒ斥力)が提案されている。しかし我々はいくつかの系ではこの三つの相互作用の足し合わせだけでは理解できないような現象が存在することを示してきた。一点目はリン脂質とアルコールの混合系における異常膨潤相の存在、もう一点はリン脂質のゲル層と液晶層の相転移点近傍で起こるAnomalous Swellingである。



Anomalous Swellingと膜揺らぎダイナミクスの関係について

H. Seto et al., The Euro. Phys. J. E., 26, 217-223, (2008).



H. Seto et al., J. Phys. Soc. Jpn., 76, 054602, (2007).

The intermembrane distance between lipid membranes is determined by the balance of several interactions. In particular, in the case of neutral phospholipids, the van der Waals interaction has been proposed as the attractive force, and the short-range repulsion (hydration repulsion) and the long-range repulsion (Helfrich repulsion) due to membrane fluctuations have been proposed as the repulsive forces. However, we have shown that there are some phenomena in some systems that cannot be understood only by the addition of these three interactions. The first is the existence of anomalous swelling phase in the mixture of phospholipids and alcohols, and the other is anomalous swelling near the phase transition between the gel layer and the liquid crystal layer of phospholipids.


 We have shown that these phenomena (both of which appear to be caused by an increase in the long-range repulsion) are not caused by a change in the Helfrich repulsion by observing the interlayer distance in detail by X-ray and small-angle neutron scattering and the fluctuation dynamics of the membrane by neutron spin echo. Furthermore, since both of these phenomena occur near the transition point between the ripple gel layer and the liquid crystal layer, we proposed a model in which the poor matching of the static jagged structure of the membrane causes this abnormal swelling state.


Relationship between Anomalous Swelling and Membrane Fluctuation Dynamics

H. Seto et al., The Euro. Phys. J. E., 26, 217-223, (2008).


Anomalous swelling phase in phospholipid-ethanol mixtures

H. Seto et al., J. Phys. Soc. Jpn., 76, 054602, (2007).

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