リピッド膜の相転移における臨界揺動に伴う圧縮率と比容 II.

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An automatic measuring system of ultrasonic velocity V and density ρ at high pressure was applied to a study of the phase transition of unilamellar liposomes consisted of dimyristoylphosphatidylcholine (DMPC) in distilled water. The compressibility B was obtained from the relation B=1/ρ V2. With raising the temperarure at the atmosphere, the limiting density number [ρ]=lim (ρ-ρ0)/ρ0c decreased largely and the intrinsic compressibility [B]=lim (B-B0)/B0c had a break at 25°C. Such a transition was also observed at constant temperatures with varying the pressure. The temperature dependence of the transition pressure determined from the break pressure of [B] was ca. 50 atm/K, that agrees with the value of 49 atm/K referred in a paper of the quasielastic light scattering measurement. With the increase of the temperarure, the change in [ρ] associated with the transition slightly increased and the value of [B] at the break point decreased, which suggests that the second order transition could not be caused by the pressure increase. These experimental results agree semi-quantitatively with the calculated phase transition behavior reported in the preceding paper by using the phenomenological theory proposed by Sugár.
特定非営利活動法人日本バイオレオロジー学会の論文