Dynamical Structure of Nano-Meter-Sized Domains on a Vesicle

摘要

In recent years, lateral phase separation in cell membranes so-called lipid raft has gathered much attention. The lipid rafts are liquid domains rich in cholesterol, sphingolipid and specific proteins and responsible for the important biochemical reactions. In order to understand the roles of phospholipids and cholesterol in the lipid raft formation, the model biomembrane vesicles composed of saturated phospholipid, unsaturated phospholipid and cholesterol have been investigated extensively. The giant vesicles with micro-meter length scale show the phase separation and form micro-meter-sized liquid domains below a miscibility temperature. The behavior of the micro-meter-sized liquid domains on the model biomembranes is well understood by fluorescence microscope investigations, while that of the nano-meter-length scale domains is poorly understood due to the optical resolution limit of the microscopy. In this study we have investigated the dynamical nature of the nano-meter-sized domains on the model vesicles using a small unilamellar vesicles having nano-meter length scale and a contrast matching technique of a neutron scattering.%飽和リン脂質、不飽和リン脂質、コレステロールの3成分からなるモデル生体膜は、脂質アシル基の無秩序-秩序転移温度以下で相分離し、膜面上にドメイン構造を形成する。ナノメートルサイズのべシクルを用いることにより膜面上でのナノメートルスケールのドメインのダイナミクスを中性子スピンエコー法により調べた。臨界サイズに近い大きさを持つナノドメインはベシクル上で熱揺らぎにより融合・分裂を繰り返し、安定なモノドメイン構造にまで成長できない状態であると考えられる。